Title of Invention	ELECTRICALLY CONDUCTIVE COMPOSITIONS AND METHODS FOR PRODUCING SAME
Abstract	An electrically conductive composition and a method for producing same, for example by injection molding. The composition includes a matrix comprising substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make said network an electrically conductive network within the matrix.

Title of Invention

ELECTRICALLY CONDUCTIVE COMPOSITIONS AND METHODS FOR PRODUCING SAME

Abstract

An electrically conductive composition and a method for producing same, for example by injection molding. The composition includes a matrix comprising substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make said network an electrically conductive network within the matrix.

Full Text	FIELD OF THE INVENTION The present invention relates to electrically conductive composites based on a mixture of two thermoplastic compounds having different polarity with glass fibers and carbon black and or carbon fibers and to methods for producing same. BACKGROUND OF THE INVENTION Electrically conductive polymer based compositions are used in many industrial applications, such as for dissipating electrostatic charge from plastic parts and plastic boxes for shielding electronic components from electromagnetic interference (EMI). Examples for electrostatic discharge (ESD) applications are electronic packaging, clean room installations, storage trays, water carriers, chip carriers and construction components for explosion-proof environments. - 1A - Compounds tailored for dissipating static electricity having a typical surface resistivity of 102to 1013 ohm/square and compounds specified for EMI shielding applications typically exhibit volume resistivity of 10-2 to 102 ohm-cm. There are known in the art polymer based compounds having appropriate resistivity for both static electricity dissipation and EMI shielding. One class of compounds known in the art is based on polypropylene (PP) or polyethylene (PE) with high carbon loading levels up to 40 to 60% by weight characterized by surface resistivity of about 103 - 108 ohm/square. For applications requiring EMI shielding, weight loading levels of 30 to 50 % PAN carbon fibers, 40 % aluminum flakes, 15 % nickel-coated carbon fibers or 5 to 10 % stainless steel fibers have been used for the same class of polymers. The method currently used to increase the electrical conductivity of polymers is to fill them with specific conductive additives, such as metallic powders, metallic fibers, carbon black, carbon fibers and recently by intrinsically_conductive polymeric powders. The characteristic behavior of these materials is the existence of a strongly non-linear relationship between the electrical conductivity and the filler concentration. At low filler loading, the electrical conductivity of the polymeric compound is generally quite low; its magnitude is similar to that of the ? polymer matrix (10-16 to 10-11 ohm-1 cm-1). As loading is increased, the conductivity increases sharply by several orders of magnitude over a narrow concentration range, then slowly increases towards the conductivity of the condensed filler powder of the order of 10-4 to 10-1 ohm-1cm-1. This behavior describes an insulator-conductor transition occurring at a critical volume fraction (percolation threshold). This threshold is due to the formation of a chain-like network of particles extending throughout the entire specimen volume and allowing electrical current to flow. US Patent No. 4.169.816 describes an electrically conductive single thermoplastic material composition with a high carbon content, the composition including for each 100 parts of polypropylene-ethylene copolymer 15-30 parts of carbon black. 0.25 to 1 part of silica and 1-10 parts of a fiber reinforcing agent selected from carbon fibers or a mixture of carbon fibers and glass fibers. US Patent No. 5,004,561 describes another single thermoplastic based electrically conductive composition with a high carbon content, the composition including for each 100 parts of thermoplastic resin selected from the group of polyolefin, polystyrene and acrylonitrite/styrene/butadiene (ABS) copolymer resin, polybutylene terephthalate (PBT) resin, polyphenylene ether and polyamide (PA) resin, 3 30 - 300 parts of electrically conductive glass fibers, 5-40 parts of carbon black and 5-40 parts of graphite. Russian Patent No. SU 1,643,568 describes a high carbon based electrical conductive thermoplastic compostion in which electrical conductivity is achieved from the dispersion of carbon in the matrix. The composition includes 20-35 weight percent polypropylene, 10-20 weight percent polyamide, 20-30 weight percent carbon black, 10-20 weight percent graphite and 15-20 percent glass fibers. There are generally two methods for producing electrically conductive thermoplastic articles known in the art. In the slow production rate compression molding method less filler (e.g. carbon black) is required to achieve a desired conductivity, however the mechanical properties of the composition are usually deficient. In the fast production rate injection molding method better mechanical properties are achieved and articles having complex geometry can be produced but the amount of conductive filler required is high. One deficiency of compression molding of electrically conductive compounds is that the relatively slow processing is expensive. A major disadvantage of prior art polymer based compounds for electrostatic dissipation and EMI shielding applications is the high percentage of conductive additives required to form the conductive A polymer compounds resulting in high cost and deficient processability and mechanical properties and also high carbon contamination which is adverse in particular for clean room applications. c SUMMARY OF THE INVENTION The present invention provides an improved thermoplastic electrically conductive composition. According to an aspect of the present invention, the electrically conductive composition includes a first thermoplastic component forming a continuous matrix and a second thermoplastic component having a polarity larger than the polarity of the matrix. The composition also includes fibers being encapsulated in-situ by the second thermoplastic component and forming a network within the matrix and also a carbon black component which is preferentially attracted to the second component due to its higher polarity. The in-situ formation of an encapsulated network, including carbon black, in preferred locations of particles provides an electrically conductive composition. According to a further aspect of the present invention, the ratio between the conductive carbon filler and the second component is sufficiently high so that a substantial part of the carbon filler is located at the interface between the second component and the matrix to provide the electrical conductivity. Nevertheless, the overall concentration of carbon is at least an order of magnitude smaller than in the prior art electrically conductive compositions, thus making the compositions of the present 6 invention advantageous in many applications including clean room applications. Another object of the present invention is to utilize a fast processing method for producing the thermoplastic electrically conductive compositions of the present invention. Injection molding is used for producing the electrically conductive thermoplastic compositions of the recent inventions while using very low carbon black concentrations and improving the mechanical properties of the composition. The electrically conductive composition of the present invention includes a matrix including substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make the network an electrically conductive network within the matrix. In one embodiment of the present invention, the first thermoplastic component is a polyolefin compound with or without an added elastomer component. The polyolefin is selected from the group of polypropylene which may be a homopolymer or a copolymer and polyethylene. The second component is polyamide or EVOH. In a 7 preferred embodiment, the composition includes less than 20 parts per hundred polyamide or EVOH. In another embodimemt, the first component is acrylonitrite/ butadiene/styrene and the second component is polyamide, or EVOH. In yet another embodiment, the first component is selected from polystyrene, high impact polystyrene and polyphenyleneoxide/ polystyrene and the second component is polyamide or EVOH. The fibers of the compositions of the present invention may be glass fibers. In a preferred embodiment, the composition includes less than 55 parts per hundred glass fibers. The carbon component of the compositions of the invention of the present invention may be carbon black. Alternatively, or in combination, the carbon component may be carbon fibers. In a preferred embodiment, the composition includes less than 10 parts per hundred carbon black. In another preferred embodiment, the composition includes less than 30 parts per hundred carbon fibers. In a preferred embodiment, the composition has one or more of a volume resistivity from about 0.1 to about 109 ohm-cm, a flexural modulus of up to about 11,000 MPa and a tensile strength of up to 60 MPa. 8 BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which: Fig. 1 is a schematic illustration of the morphology of the electrically conductive thermoplastic compositions of the present invention; Figs. 2A-2C are nonlimiting exemplary SEM micrographs (at different magnifications) of freeze fractured surfaces of an injection molded composition of the present invention; Fig. 3 is a schematic block diagram illustration of a method for producing the electrically conductive thermoplastic compositions of the present invention; Figs. 4A - 4D are schematic block diagram illustrations of fouralternative preferred methods for producing the electrically conductive thermoplastic compositions of the present invention wherein carbon black is the carbon compound; and Figs. 5A - 5C are schematic block diagram illustrations of three alternative preferred methods for producing the electrically conductive thermoplastic compositions of the present invention wherein the carbon compound is both carbon black and carbon fibers. 9 DETAILED DESCRIPTION OF THE PRESENT INVENTION Reference is now made to Fig. 1. Figure 1 is a schematic illustration of the electrically conductive multi-component thermoplastic compositions of the present invention. The electrically conductive multi-component thermoplastic composition, generally referenced 10, includes a matrix 12 formed substantially of a first thermoplastic compound, glass fibers 14 encapsulated with a second thermoplastic compound 16 having therein and thereon carbon black shown in the SEM micrographs of Fig. 2. As illustrated in Fig. 1, glass fibers 14 encapsulated with second thermoplastic composition 16 with carbon black thereon form a conductive network within polypropylene matrix 12. In the preferred embodiments, the first thermoplastic component is a polyolefin based component, polystyrene (PS) based component or acrylonitrile/styrene/butadiene (ABS) terpolymer based compound, with or without an added elastomer component and the second thermoplastic component is polyamide (PA) or Polyethylene Vinyl Alcohol (EVOH) copolymer. Preferably, the elastomer component is a combination of elastomers. The addition of the elastomer component to 10 the compound changes the composition's mechanical properties without significantly affecting its electrical conductivity. Since the affinity of polyamide or EVOH 16 to glass fibers 14 is much stronger than to any of the first thermoplastic components , during the melt blending of composition 10, the second thermoplastic component) preferentially encapsulates, in situ, glass fibers 14 as described in detail with reference to Fig. 3 hereinbelow, thereby producing a network of encapuslated fibers within matrix 12. Moreover, carbon black particles are preferentially attracted to the second thermoplastic component phase and located at the second thermoplastic component (polyamide or EVOH) matrix interfaces as indicated by reference numeral 15, thereby making the network of encapsulated fibers electrically conductive using a much smaller content of carbon black than in the prior art and improving the mechanical properties of composition 10 as described hereinbelow. Referring to the three Scanning Electron Microscope (SEM) micrographs of Figs. 2A - 2C which differ in their magnification, the network of encapsulated fibers and the preferential distribution of carbon black 18 in the second thermoplastic component phase 16 is clearly seen. A particular feature of the present invention is that composition 10 includes much lower concentrations of carbon black than in the prior art for similar levels of electrical conductivities. This is since 1 1 the electrically conductive carbon black particles form continuous pathways along the interfaces between the second thermoplastic component phase and the matrix, (first level of percolation). Moreover, the embedded part of carbon black particles is located within the amorphous phase of the second thermoplastic 16 (second level of percolation), thereby the formation of the conductive pathways is facilitated. This is further facilitated by the network formed of second thermoplastic component encapsulated glass fibers (third level of percolation). Reference is now made to Figs. 3 through 5C which illustrate preferred methods for producing the electrically conductive thermoplastic compositions of the present invention. Fig. 3 illustrates the method in general and Figs. 4A - 4D and Fig 5A - 5C illustrate, respectively, alternatives of the method for two nonlimiting exemplary compositions. The method of Fig. 3 illustrated in a time sequence from left to right comprising the steps of compounding 32, the step of pelletizing 34 and the step of injection molding 36. In one preferred embodiment the step of compounding 32 includes the steps of dry blending of polypropylene with second thermoplastic component indicated by reference numeral 31 followed by melting and melt mixing with the glass fibers as indicated by 33 and subsequent melt mixing with carbon fibers, carbon black or both. In the non limiting examples described below, the 12 compounding step 32 is conducted on a twin-screw compounder (Berstorf, Germany), at processing temperatures in the range of 200-285 °C (corresponding to the melting point of the polymer components) and a screw speed of 55 rpm. The resulting compounds are pelletized (step 34) and then injection molded (step 36) at 200-285 °C on a Battenfeld injection molding machine equipped with a three_cayity American Standard Testing Material (ASTM) mold (tensile bar, flexural bar and falling dart impact disc). Figs. 4A - 4D illustrate four preferred alternatives of the method for producing composition 10 whereas the composition includes carbon black as the carbon compound. Figs. 4A - 4D are illustrated for the nonlimiting example of a composition 10 comprises 100 parts by weight polypropylene, 12 parts by weight polyamide, 30 parts by weight glass fibers, and 2 parts by weight carbon black. In the embodiment illustrated in Fig. 4A, carbon black concentrate is added in the injection molding stage as indicated by reference numeral 37 rather than in the compounding step 32 resulting in a resistivity of 537 Ohm-cm and flexural modulus of 4819 ± 161 MPa. Fig. 4B illustrates the alternative wherein the carbon black concentrate is dry blended with the polypropylene and polyamide resulting in a resistivity of 432 Ohm-cm and flexural modulus of 4649 ± 32 MPa. 13 Fig. 4C illustrates the alternative wherein the carbon black concentrate is added during compounding resulting in a resistivity of 214 Ohm-cm and flexural modulus of 4491 ±51 MPa. In the embodiment of Fig. 4D glass fibers are dry blended with the polypropylene and polyamide while carbon black concentrate is added during compounding resulting in a resistivity of 431 Ohm-cm and flexural modulus of 3790 ± 63 MPa. Figs. 5A - 5C illustrate three preferred alternatives of the method for producing composition 10 whereas the composition carbon fibers or carbon black and carbon fibers as the carbon compound. Figs. 5A - 5C are illustrated for the nonlimiting example of a composition 10 comprises 100 parts by weight polypropylene, 12 parts by polyamide , 30 parts by weight glass fibers, and 2 parts by weight carbon black and 20 parts by weight carbon fibers. In the alternative of Fig. 5A both carbon black and carbon fibers are added during the injection molding step resulting in high conductivity (Resistivity of 0.465 Ohm-cm) and high flexural modulus (9770 ± 428 MPa). In the alternative of Fig. 5B carbon black is dry blended with the polyolefin and polyamide as indicated by step 39 instead of the dry blending indicated by step 31 of the other alternatives while carbon fibers 14 are added (step 35) during compounding resulting in a resistivity of 2 Ohm-cm and flexural modulus of 9550 ± 350 MPa. In the alternative of Fig. 5C, carbon fibers are added in the compounding stage resulting in resistivity of 8 Ohm-cm illustrates and flexural modulus of 8931 ± 267 MPa. It will be appreciated that the specific method used to prepare the compounds forming composition 10 for injection molding can be selected from the nonlimiting' embodiments described hereinabove and from many other variations thereof, thereby varying the specific electrical conductivity and mechanical properties (illustrated by the flexural modulus above) of composition 10. In all methods, the present invention provides an electrically conductive thermoplastic composition which provides high electrical conductivity and strong mechanical properties after injection molding. The following examples illustrate without limitation certain aspects of the present invention. In all examples, injection molded composite samples (12.6cm x 1.27cm x 0.32cm) were characterized for electrical properties by measuring volume resistivity, according to ASTM D 257 - 93 and ASTM D 4496 - 87, using Keithley instruments.Silver paint was used to eliminate the contact resistance between samples and electrodes. 15 The corresponding ASTM test methods were used for the mechanical properties evaluation. Specifically, ASTM D 0638 was used for measuring tensile properties, ASTM D 790 was used for measuring flexure, ASTM D 256 was used to measure IZOD impact and ASTM D 570 was used to measure water absorption. The glass fiber content and the carbon black content in each specimen was determined by using ASTM D 5630 - 94 and ASTM D 1603 - 94, respectively. The composites morphology was studied using JEOL 5400 scanning electron microscope. Freeze fractured surfaces were studied. In the experiments, commercial grades of PP (homopolymer and copolymer), ABS, PS, HIPS, NORYL (described in detail with reference to Tables 10-13), PE (high and low density grades), elastomer, PA (PA6, PA66, PA 11, PA 12, PA 6/6.9, PA 6/12), EVOH, glass fibers (chopped strands, 3.2-6.3 mm length, 10-13 micrometer diameter), conductive carbon black and carbon fibers (chopped fibers, 6mm length, 7-8 microns diameter) have been used in this study. Five types of carbon black were studied. Their properties are shown in Table 1 below. 16 Table 1 Property Ketjen EC 300J (AKZO) Ketjen EC 600JD (AKZO) Vulcan XC-72 (Cabot) Corax L6 (Degussa) Conductex 975 (Columbian Chemicals) Surface area BET, m2/g 1000 ? 180 265 250 Particle size, nm 30 ? 29 18 22 Porevolume DBP,ml/100g 350 480 178 123 165 Surface area CTAB, m2/g 480 0 86 150 153 Iodine absorption, mg/g 900 1000 293 260 Volatilities, % 0.5 0.6 1.0 1.5 1.0 pH 8 8 7 7.5 7 All blend ratios described relate to parts by weight, in each case based on 100 parts by weight of the first compound. An electrically conductive polyolefin composites comprise: 100 parts by weight polymer matrix, 4 to 20 parts by Polyamide, 10 to 55 parts by weight glass fibers, 0.5 to 10 parts by weight carbon black, 0 to 30 parts by weight carbon fibers. The electrical and mechanical behavior of compositions 10 was studied for different polyamide mixtures ratios as a function of glass fiber concentration, polyamide/glass fiber ratio and carbon black concentration. The resistivity and the mechanical properties as a function 17 of composition are summarized in Tables 2A and 2B. It will be appreciated that the samples produced were in accordance with the processing method of the present invention i.e., injection molding. 18 Table 2A Compostion 1 2 4 5 6 7 8 9 10 polypropylene (MFI 12) 100 100 100 100 100 100 100 100 100 100 Polyamide 6 5 5 5 5 5 8 8 10 12 10 Glass Fiber (Vetro tex) 12 12 20 20 20 20 30 30 30 30 Carbon Black (EC 600) 1 3 0.5 1 3 3 1 1.5 2 3 Property Flexural Modulus, MPa 3044"* 3849 3041 3945 4104 4366 5003 4655 4941 515: Izod Impact, notched, J/m 69 64 33 83 60 57 76 75 79 65 Volume Resistivity ohm-cm 9 0.1 - 10 >108 3.3x105 108 104 1.6x105 8.6xl03 6.6x103 3xl03 1.4xl03 6.5x 19 Table 2B Composition 1 2 3 4 5 6 7 Polypropylene (MFI 25)." 100 100 100 100 100 100 100 Polyamide 6 4 5.3 6.6 8 8 8 12 Glass fiber (Vetrotex) 20 0.67 20 0.88 20 1.1 20 1.5 20 2 30 30 2 Carbon black (EC 600) 1.3 Property Specific Gravity, Kg/dm3 1.02 1.01 1.02 1.02 1.02 1.06 1.06 Water Absorption, % 0.04 0.06 0.06 0.04 0.05 0.08 0.08 Flexural Modulus, MPa 3984 3958 3954 3941 3936 4866 5039 Tensile Strength, MPa Elongation at Break, % 54 2.8 58 3.1 52 2.7 52 2.8 58 2.8 63 2.5 63 2.6 Izod Impact, notched, J/m 68 85 66 63 71 85 76 Melt Flow Rate, 5.2 4 6 2.8 3 3.3 3.2 230°C,2.16Kg Heat Distortion Temp, °C 161 163 161 162 163 164 163 Volume Resistivity, ohm-cm 3.24x105 2.5x103 3.2x104 1.3xl03 7.9x103 3.4xl03 1.2x!03 Tables 3A and 3B illustrate the dependence of resistivity and physical properties on glass fiber concentration in compositions 10 for different polypropylene/ polyamide mixtures. The increase of tensile strength, modulus and flexural modulus with increasing glass fiber content is clearly appreciated. 20 Table 3A Composition 1 2 3 4 5 Polypropylene (MFI 12) Polyamide 66 100 5 12 1 100 8 20 1.5 100 12 30 2 100 16 40 100 16.5 50 Glass Fiber (Vetrotex) Carbon black (EC600) 2.8 2.8 Properly Tensile Strength, MPa Elongation at break, % Tensile Modulus, MPa Flexural Modulus, MPa Izod Impact, notched, J/m Water Absorption, % Specific Gravity, kg/dm3 Volume Resistivity, ohm-cm 39.4 3.2 1771 3054 44 2.6 2030 3801 56.2 2.3 2634 4684 58 2.1 3133 47.4 2 2406 5394 5576 64 0.02 0.981 >108 69 0.03 1.025 9.4x104 77 0.04 1.082 850 71 0.06 1.122 440 57 0.07 1.145 2.3xl04 21 Table 3B Composition I 2 3 4 5 6 7 8 9 Polypropylene (MFI 25) Polyamide 66 100 100 100 100 100 100 100 100 100 4 5.3 6.6 8 8 6 8 10 12 Glass fiber (Vetrotex) 20 0.67 20 0.88 20 1.1 20 1.5 20 2 30 30 30 2 Carbon black (EC 600) 1 1.3 1.6 Property Specific Gravity, Kg/dm3 1.02 1.00 1.01 1.04 1.02 1.05 1.06 1.05 1.06 Water Absorption, % 0.04 0.04 0.07 0.04 0.05 0.05 0.07 0.1 0.05 Flexural Modulus, MPa 3917 3804 3858 373 3936 4815 4640 4732 4856 Tensile Strength, MPa 52 53 53 53 56 57 59 57 61 Elongation at Break, % 2.7 3.1 3.0 3.0 3.0 2.6 2.4 2.9 2.0 Izod Impact, notched, J/m 64 71 76 66 67 75 75 77 62 Melt Flow Rate, 18 12 11 8.6 11 8 8.8 8 6 275°C, 2.16Kg Heat Distortion Temp. °C 161 163 163 162 162 164 165 165 163 Volume Resistivity, ohm-cm 2x 10 4 9.9x103 4xl01 490 7.9xl03 650 814 241 175 Table 4 illustrates the dependency of electrical resistivity of PP/PA/GF/CB systems (100/12/30/4 phr ratio respectively) on the type of second thermoplastic component (polyamide) used. It is clearly seen that any type of polyamide can be used for composition 10 and that their electrical conductivity can be determined by selecting the degree of crystalinity of the polyamide. Lower values of resistivity were obtained for compositions 10 based on PA 66 and PA 6, PA11, PA 12 (semicrystalline polyamide) than for those based on PA 6/6-9 and PA 6-12 (amorphous polyamide). Given the same concentration of conductive additive, a higher 22 level of conductivity was achieved in PA 66 (the most crystalline polyamide studied) based compound. Table 4 Property PA 66 PA 6 PA12 PA11 PA 6-6/9 PA 6-12 Tensile Strength, MPa 58.4 54.2 51.9 49.6 58.5 56.6 Elongationat break,% 2.1 1.9 2 3 2.3 1.9 Tensile Modulus, MPa 3256 3030 2541 1868 3074 3160 Flexural Modulus,MPa 4850 4699 4592 3899 4650 4890 Izod Impact, notched, J/m 72 70 68.8 58.9 61 62 Specific gravity, kg/dm3 Volume Resistivity, ohm-cm 1.086 700 1.092 3.3x103 1.081 1.079 1.076 3.3xl05 1.069 1.3x105 2.3x103 5.4xl03 It will also be appreciated that any type of carbon black can be used with compositions 10. Resistivity and mechanical properties of composites with Five CB grades, at two loading levels, for composites based on Polypropylene (100 parts), PA 66 (12 parts) and glass fibers (30 parts) are presented in Table 5. Inspection of this table reveals that Ketjenblacks EC 300 and EC 600, the most conductive carbon blacks used provide the highest electrical conductivity. 23 Table 5 Property EC600 EC 300 XC 72 CORAX L6 CONDU CTEX 2 phr 2 phr 4 phr 2 phr 4 phr 2 phr 4 phr 2 phr 4 phr Tensile Strength, MPa 56.2 52.1 57.7 45.9 54 44.2 45.1 43.9 58.4 Elongation at break, % 2.1 2.5 2.3 2.6 2.3 2.6 2.2 3.1 2.1 Tensile Modulus, MPa 3133 2776 2911 2087 2933 2291 2147 2193 3194 Flexural Modulus, MPa 4684 4898 4803 4968 4747 5108 4335 4948 4638 Izod Impact,notched, J/m 77 72 70 58 74 66 79 72 Specific gravity, kg/dm3 1.082 1.072 1.079 1.079 1.079 1.074 1.076 1.069 1.074 Volume Resistivity, ohm-cm 850 1560 789 >108 4110 >108 852 >108 4x104 Yet another factor which determines the resistivity and mechanical properties of compositions 10 is the flowability (MFI) of the polymer matrix used. As clearly seen from Table 6 below, significant lower resistivities are obtained using for example polypropylene with higher MFI. Table 6 is provided below. 24 Table 6 Composition 1 2 3 4 5 6 7 8 9 Polypropylene (MFI 3) 100 Polypropylene (MFI 12) 100 100 100 100 Polypropylene (MFI 25) 5 100 5 12 12 100 12 16 100 16 16.5 100 15 Polyamide 66 Glass fiber (Vetrotex) 12 12 30 30 30 40 40 50 50 Carbon black (EC 600) 1 1 2 2 2 2.8 2.8 2.8 2.5 Property Flexural Modulus, MPa 3054 3037 4168 4684 4450 5812 5515 5576 6249 Volume Resistivity, ohm-cm 107 2863 1100 850 290 565 405 2.3xl04 543 Table 7 Composition 1 2 3 4 5 6 7 8 9 10 Polypropylene (MFI 25) 100 12 30 2 0 100 12 30 2 6 100 12 30 2 10 100 12 30 2 20 100 12 30 2 30 100 14 40 2.8 0 100 14 40 2.8 6 100 14 40 2.8 10 100 14 40 100 14 40 Polyamide 66 Glass Fiber (Vetrotex) Carbon Black (EC 600) Carbon Fiber 2.8 14 2.8 20 Property Flexural Modulus, MPa Volume Resistivity, ohm-cm 4850 344 6264 7.2 7910 2 9770 0.465 10514 0.168 5964 425 6675 12.2 8129 1.2 9641 0.96 10495 0.32 It will be appreciated that the compositions of the present invention, in particular the ones including carbon fibers and having a resistivity of less than 1 Ohm-cm provide improved Electro Magnetic Interference (EMI) shielding with a lower content of carbon black and carbon fibers. Therefore, they are superior to prior art electrically conductive plastics in a wide range of applications, such as clean room applications where the amount of carbon is important for the cleanliness of the process. It will be appreciated that the present invention is not limited by what has been described hereinabove and that numerous modifications, all of which fail within the scope of the present invention, exist. For 26 example, while the present invention has been described with reference to polypropylene, the present invention is equally applicable to other polyolefins such as polyethylene and to polyethylene-polypropylene mixtures. Polyethylene based compositions were prepared using LDPE and HDPE grades in a generally similar manner to that of polypropylene. As an example, a polyethylene based composition (100 parts on a similar weight basis) blended with 11 parts of polyamide (PA6), 20 parts of glass fibers and 4.4 parts of carbon black (EC-300) exhibit volume resistivity of 105- 106 ohm-cm. Table 8 illustrates two further examples of polyethylene based compositions. 27 Table 8 Composition 1 2 PE 800 (MFI 20) 100 PE600(MFI7) 100 Polyamide 66 12 12 Glass fiber (Vetrotex) 30 30 Carbon black (EC 600) 2 2 Property Specific Gravity, Kg/dm3 1.07 1.07 Water Absorption, % 0.06 0.06 Flexural Modulus, MPa 1663 1622 Tensile Modulus, MPa 746 678 Tensile Strength, MPa 19.3 17.1 Elongation at Break, % 3.0 3.3 Izod Impact, notched, 80 81 J/m Melt Flow Rate, 275°C, 33.2 18.8 2.16Kg Heat Distortion Temp, °C 96 96 Volume Resistivity, ohm-cm 1x106 2x106 In other alternative embodiments, the polyolefin component is replaced by another thermoplastic compound as the first component forming matrix 12. In four preferred embodiments, the first component forming matrix 12 was acrylonitrile/butadiene/styrene (ABS), polystyrene 28 (PS), high impact polystyrene (HIPS) and polyphenyleneoxide/polystyrene (NORYL). Table 9 illustrates two examples of polyethylene-polypropylene based compositions. Table 9 Composition 1 2 PE 800 (MFI 20) PE 600 (MFI 7) Polypropylene (MFI 25) Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600) 100 100 24 24 8 8 20 20 1.5 1.5 Property Specific Gravity, Kg/dm3 Water Absorption. % Flexural Modulus. MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 275°C, 2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm 1.03 1.02 0.05 0.05 1975 2117 1246 1176 27 27.4 2.3 2.5 68 70 24.7 14.2 101 102 3x105 3x105 Table 10 illustrates a nonlimiting example of compositions 10 formed with ABS, PS, HIPS and NORYL with different second thermoplastic component ( different types of polyamide compositions, different glass fiber content and different low amounts (less than or equal to 3 phr) of carbon black. Table 10 Composition 1 2 3 4 5 6 ABS 100 100 100 PS 100 HIPS 100 NORYL 100 Polyamide 6 12 12 Polyamide 12 8 12 12 Polyamide 66 12 Glass fiber (Vetrotex) 20 30 30 30 30 30 Carbon black (EC 600) 1.2 3 3 2 3 3 Property Volume Resistivity,ohm-cm 108 104 103 105 104 103 Tables 11, 12 and 13 provide further examples of PS, HIPS and Noryl based compositions, respectively, and their mechanical properties. Table 11 illustrates the dependence of resistivity and physical properties on glass fiber concentration in a PS/PA/GF/CB compound. 30 Table 11 Composition 12 3 4 PS (GP) Polyamide 6 Polyamide 12 Glass fiber (Vetrotex) Carbon black (EC 600) 100 100 100 100 5 8 12 12 12 20 30 30 1.5 2 3 3 Property Specific Gravity, Kg/dm1 Water Absorption, % Flexural Modulus. MPa Tensile Modulus,. MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 230°C,2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm 1.09 1.17 1.22 1.2 0.12 0.12 0.13 0.07 4850 5830 7100 7000 2740 3130 3650 3290 56 70 66 59 2 2 2 2 43 52 51 38 8.2 5.7 3.7 3.0 82 84 - 86 4.5xl05 7.5xl04 3.8xl04 2.2xl04 Table 12 illustrates the dependence of resistivity and physical properties on glass fiber concentration in HIPS/PA/GF/CB compound. 31 Table 12 Composition 1 2 3 4 HIPS Polyamide 6 Polyamide 12 Glass fiber (Vetrotex) Carbon black (EC 600) 100 100 100 100 5 8 12 12 12 20 30 30 1.5 2 3 3 Property Specific Gravity, Kg/dm3 Water Absorption, % Flexural Modulus, MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 230°C,2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm 1.12 1.16 1.21 1.19 0.13 0.14 0.14 0.07 3600 4560 6410 6050 1800 2050 2630 2050 43 51 61 46 2 2 2 2 46 46 47 34 2.3 1.7 1.9 1.7 97 92 93 9xl06 7xl04 7xl03 1.5x104 Table 13 illustrates the dependence of resistivity and physical properties on glass fiber concentration in Noryl/PA66/GF/CB compound. 32 Table 13 Composition 1 2 Noryl Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600) 100 100 12 16 30 40 3 4 Property Specific Gravity, Kg/dm3 Water Absorption, % Flexural Modulus, MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 275°C, 2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm 1.24 1.28 0.17 0.20 6501 7193 3382 4361 64.1 79.2 2.0 1.8 38 42 1.0 0.5 122 124 5x105 1.8xl04 Table 14 illustrates compositions 10 wherein the second thermoplastic component is EVOH and notpolyamide. The table illustrates the dependence of resistivity on glass fiber concentration in PP/EVOH/GF/CB compound. 33 Table 14 Composition 1 2 3 Polypropylene (MFI 25) 100 100 100 EVOH 8 10 12 Glass fiber (Vetrotex) 20 30 30 Carbon black (EC 600) 2 2.5 3 Property Specific Gravity, Kg/dm3 1.03 1.07 1.07 Water Absorption, % 0.03 0.03 0.05 Flexural Modulus, MPa 4530 5697 5529 Tensile Modulus, MPa 2475 2572 2670 Tensile Strength, MPa 59.7 62.1 61.8 Elongation at Break, % 2.7 2.5 2.4 Izod Impact, notched, J/m 69 66 58 Melt Flow Rate, 230°C, 5.0 4.5 3.2 2.16Kg Heat Distortion Temp, °C 160 160 160 Volume Resistivity, 1.7xl05 1.6x105 1.2xl03 ohm-cm Table 15 illustrates the dependence and resistivity and physical properties on glass fiber concentration in PP/PA/GF/CB (PP: Elastomer 60:40) compound containing elastomer. It is clearly shown that the compounds containing elastomer offer higher impact than the compounds summarized in Table 3B. 34 Table 15 Composition 1 2 3 4 Polypropylene Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600) 100 100 100 100 5 8 8 10 12 20 25 30 1 1.5 1.5 2 Property Flexural Modulus, MPa Izod Impact, notched, J/m Surface Resistivity, ohm/sq. 1500 1900 2000 2300 134 120 107 100 107 106 105 105 It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention is defined only by the claims that follow: 35 We claim: 1. An electrically conducive composition comprising: a matrix comprising substantially a first thermoplastic component; a second thermoplastic component having a higher polarity than that of said first thermoplastic component, said second component encapsulating a plurality of fibers forming a network of encapsulated fibers within said matrix; and a carbon component preferentially attracted to said second component so as to make said network an electrically conducive network within said matrix, said carbon component located at the interface between said second thermoplastic component and said matrix wherein said carbon component is carbon black and is present in an amount less than 10 parts per hundred. 2. A composition as claimed in claim 1 wherein said first thermoplastic component is a polyolefin compound with or without an added elastomer component. 3. A composition as claimed in claim 2 wherein said polyolefin is selected from the group consisting of polypropylene and polyethylene. 4. A composition as claimed in claim 3 wherein said polypropylene is a homopolymer or a copolymer. 5. A composition as claimed in claim 1 wherein said second component is polyamide or EVOH. 6. A composition as claimed in claim 5 wherein said composition comprises less than 20 parts per hundred polyamide or EVOH. 7. A composition as claimed in claim 1 wherein said fibers are glass fibers. 8. A composition as claimed in claim 7 wherein said composition comprises less than 55 parts per hundred glass fibers. 9. A composition as claimed in claim 1, wherein said carbon component further comprises carbon fibers. -36- 10.A composition as claimed in claim 1 wherein said carbon component is a mixture of carbon black and carbon fibers. 11. A composition as claimed in claim 9, comprising less than 30 parts per hundred carbon fibers, 12. A composition as claimed in claim1, having a volume resistivity from 0.1 to 109 ohm-cm. '13. A composition as claimed in claim 1 having a flexural modulus of up to 11, 000 Mpa. 14. A composition as claimed in claim 1 having a tensile strength of up to 60 Mpa. 15. A composition as claimed in claim 1 wherein said first component is selected from acrylonitrite/butadiene/styrene, polystyrene, high impact polystyrene and polyphenylene oxide /polystyrene. 16. A composition as claimed in claim 15 wherein said second component is polyamide or EVOH. 17. A composition as claimed in claim 2 wherein said elastomer component comprises a combination of elastomers. 18. A composition as claimed in claim 17 wherein said combination of elastomers affect the mechanical properties of said composition without significantly affecting its electrical conductivity. 19. A method for producing an electrically conductive composition comprising the step of compounding a matrix comprising substantially a first thermoplastic component with a second thermoplastic component having a higher polarity than that of said first thermoplastic component, said second component encapsulating a plurality of fibers forming a network of encapsulate fibers within said matrix; and a carbon component preferably attracted to said second component so as to make said network an electrically conducive network within said matrix, said carbon component located the interface between said second thermoplastic component and said matrix wherein said carbon component is carbon black and is present in an amount less than 10 parts per hundred. -37- 26. -A method as claimed in claim 19 further comprising the step of forming said first thermoplastic component from a polyolefin compound with or without an added elastomer component. 21. A method as claimed in claim 20 wherein said polyolefin is selected from the group consisting of polypropylene and polyethylene. 22. A composition as claimed in claim 21 wherein said polypropylene is a homopolymer or a copolymer. 23. A composition as claimed in claim 19 further comprising the step of forming said second thermoplastic component from polyamide or EVOH. 24. A method as claimed in claim 23 wherein said composition comprises less than 20 parts per hundred polyamide. 25. A method as claimed in claim 19 wherein said fibers are glass fibers. 26. A method as claimed in claim 25 wherein said composition comprises less than 55 parts per hundred glass fibers. 27. A method as claimed in claim 19 wherein said carbon component further carbon fibers. 28. A method as claimed in claim 19 wherein said carbon component is a mixture of carbon black and carbon fibers. 29. A method as claimed in claim 27 wherein said composition comprising less than 30 parts per hundred carbon fibers. -38- 30. A method as claimed in claim 19 wherein said composition has a volume resistivity from 0.1 to 109 ohm-cm. 31. A method as claimed in claim 19 wherein said composition has a flexural modulus of up to 1,000 Mpa. 32. A method as claimed in claim 19 wherein said composition has a tensile strength of up to 60 Mpa. 33. A method as claimed in claim 19 comprising the step of forming said first component from acrylonitrite/butadiene/styrene, polystyrene high impact polystrene and polyphenyleneoxide/polystyrene. 34. A method as claimed in claim 33 wherein said second component is polyamide or EVOH. 35. A method as claimed in claim 19 wherein said elastomer component comprises a combination of elastomers. 36. A method as claimed in claim 35 wherein said combination of elastomers affect the mechanical properties of said composition without significantly affecting its electrical conductivity. 30. Dated this 22nd day of September 97 OF L.S.DAVAR & CO. APPLICANTS' AGENT. -39- An electrically conductive composition and a method for producing same, for example by injection molding. The composition includes a matrix comprising substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make said network an electrically conductive network within the matrix.

Full Text

FIELD OF THE INVENTION
The present invention relates to electrically conductive composites based on a mixture of two thermoplastic compounds having different polarity with glass fibers and carbon black and or carbon fibers and to methods for producing same.
BACKGROUND OF THE INVENTION
Electrically conductive polymer based compositions are used in many industrial applications, such as for dissipating electrostatic charge from plastic parts and plastic boxes for shielding electronic components from electromagnetic interference (EMI). Examples for electrostatic discharge (ESD) applications are electronic packaging, clean room installations, storage trays, water carriers, chip carriers and construction components for explosion-proof environments.
- 1A -

Compounds tailored for dissipating static electricity having a typical surface resistivity of 102to 1013 ohm/square and compounds specified for EMI shielding applications typically exhibit volume resistivity of 10-2 to 102 ohm-cm.
There are known in the art polymer based compounds having appropriate resistivity for both static electricity dissipation and EMI shielding. One class of compounds known in the art is based on polypropylene (PP) or polyethylene (PE) with high carbon loading levels up to 40 to 60% by weight characterized by surface resistivity of about 103 - 108 ohm/square. For applications requiring EMI shielding, weight loading levels of 30 to 50 % PAN carbon fibers, 40 % aluminum flakes, 15 % nickel-coated carbon fibers or 5 to 10 % stainless steel fibers have been used for the same class of polymers.
The method currently used to increase the electrical conductivity of polymers is to fill them with specific conductive additives, such as metallic powders, metallic fibers, carbon black, carbon fibers and recently by intrinsically_conductive polymeric powders. The characteristic behavior of these materials is the existence of a strongly non-linear relationship between the electrical conductivity and the filler concentration. At low filler loading, the electrical conductivity of the polymeric compound is generally quite low; its magnitude is similar to that of the
?

polymer matrix (10-16 to 10-11 ohm-1 cm-1). As loading is increased, the conductivity increases sharply by several orders of magnitude over a narrow concentration range, then slowly increases towards the conductivity of the condensed filler powder of the order of 10-4 to 10-1 ohm-1cm-1. This behavior describes an insulator-conductor transition occurring at a critical volume fraction (percolation threshold). This threshold is due to the formation of a chain-like network of particles extending throughout the entire specimen volume and allowing electrical current to flow.
US Patent No. 4.169.816 describes an electrically conductive single thermoplastic material composition with a high carbon content, the composition including for each 100 parts of polypropylene-ethylene copolymer 15-30 parts of carbon black. 0.25 to 1 part of silica and 1-10 parts of a fiber reinforcing agent selected from carbon fibers or a mixture of carbon fibers and glass fibers.
US Patent No. 5,004,561 describes another single thermoplastic based electrically conductive composition with a high carbon content, the composition including for each 100 parts of thermoplastic resin selected from the group of polyolefin, polystyrene and acrylonitrite/styrene/butadiene (ABS) copolymer resin, polybutylene terephthalate (PBT) resin, polyphenylene ether and polyamide (PA) resin,
3

30 - 300 parts of electrically conductive glass fibers, 5-40 parts of carbon black and 5-40 parts of graphite.
Russian Patent No. SU 1,643,568 describes a high carbon based electrical conductive thermoplastic compostion in which electrical conductivity is achieved from the dispersion of carbon in the matrix. The composition includes 20-35 weight percent polypropylene, 10-20 weight percent polyamide, 20-30 weight percent carbon black, 10-20 weight percent graphite and 15-20 percent glass fibers.
There are generally two methods for producing electrically conductive thermoplastic articles known in the art. In the slow production rate compression molding method less filler (e.g. carbon black) is required to achieve a desired conductivity, however the mechanical properties of the composition are usually deficient. In the fast production rate injection molding method better mechanical properties are achieved and articles having complex geometry can be produced but the amount of conductive filler required is high. One deficiency of compression molding of electrically conductive compounds is that the relatively slow processing is expensive.
A major disadvantage of prior art polymer based compounds for electrostatic dissipation and EMI shielding applications is the high percentage of conductive additives required to form the conductive
A

polymer compounds resulting in high cost and deficient processability and mechanical properties and also high carbon contamination which is adverse in particular for clean room applications.
c

SUMMARY OF THE INVENTION
The present invention provides an improved thermoplastic electrically conductive composition.
According to an aspect of the present invention, the electrically conductive composition includes a first thermoplastic component forming a continuous matrix and a second thermoplastic component having a polarity larger than the polarity of the matrix. The composition also includes fibers being encapsulated in-situ by the second thermoplastic component and forming a network within the matrix and also a carbon black component which is preferentially attracted to the second component due to its higher polarity. The in-situ formation of an encapsulated network, including carbon black, in preferred locations of particles provides an electrically conductive composition.
According to a further aspect of the present invention, the ratio between the conductive carbon filler and the second component is sufficiently high so that a substantial part of the carbon filler is located at the interface between the second component and the matrix to provide the electrical conductivity. Nevertheless, the overall concentration of carbon is at least an order of magnitude smaller than in the prior art electrically conductive compositions, thus making the compositions of the present
6

invention advantageous in many applications including clean room applications.
Another object of the present invention is to utilize a fast processing method for producing the thermoplastic electrically conductive compositions of the present invention. Injection molding is used for producing the electrically conductive thermoplastic compositions of the recent inventions while using very low carbon black concentrations and improving the mechanical properties of the composition.
The electrically conductive composition of the present invention includes a matrix including substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make the network an electrically conductive network within the matrix.
In one embodiment of the present invention, the first thermoplastic component is a polyolefin compound with or without an added elastomer component. The polyolefin is selected from the group of polypropylene which may be a homopolymer or a copolymer and polyethylene. The second component is polyamide or EVOH. In a
7

preferred embodiment, the composition includes less than 20 parts per
hundred polyamide or EVOH.
In another embodimemt, the first component is acrylonitrite/ butadiene/styrene and the second component is polyamide, or EVOH.
In yet another embodiment, the first component is selected from polystyrene, high impact polystyrene and polyphenyleneoxide/ polystyrene and the second component is polyamide or EVOH.
The fibers of the compositions of the present invention may be glass fibers. In a preferred embodiment, the composition includes less than 55 parts per hundred glass fibers.
The carbon component of the compositions of the invention of the present invention may be carbon black. Alternatively, or in combination, the carbon component may be carbon fibers. In a preferred embodiment, the composition includes less than 10 parts per hundred carbon black. In another preferred embodiment, the composition includes less than 30 parts per hundred carbon fibers.
In a preferred embodiment, the composition has one or more

of a volume resistivity from about 0.1 to about 109 ohm-cm, a flexural modulus of up to about 11,000 MPa and a tensile strength of up to 60 MPa.
8

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the appended drawings in which:
Fig. 1 is a schematic illustration of the morphology of the electrically conductive thermoplastic compositions of the present invention;
Figs. 2A-2C are nonlimiting exemplary SEM micrographs (at different magnifications) of freeze fractured surfaces of an injection molded composition of the present invention;
Fig. 3 is a schematic block diagram illustration of a method for producing the electrically conductive thermoplastic compositions of the present invention;
Figs. 4A - 4D are schematic block diagram illustrations of fouralternative preferred methods for producing the electrically conductive thermoplastic compositions of the present invention wherein carbon black is the carbon compound; and
Figs. 5A - 5C are schematic block diagram illustrations of three alternative preferred methods for producing the electrically conductive thermoplastic compositions of the present invention wherein the carbon compound is both carbon black and carbon fibers.
9

DETAILED DESCRIPTION OF THE PRESENT INVENTION
Reference is now made to Fig. 1. Figure 1 is a schematic illustration of the electrically conductive multi-component thermoplastic compositions of the present invention.
The electrically conductive multi-component thermoplastic
composition, generally referenced 10, includes a matrix 12 formed
substantially of a first thermoplastic compound, glass fibers 14
encapsulated with a second thermoplastic compound 16 having therein and
thereon carbon black shown in the SEM micrographs of Fig. 2. As
illustrated in Fig. 1, glass fibers 14 encapsulated with second thermoplastic
composition 16 with carbon black thereon form a conductive network
within polypropylene matrix 12.

In the preferred embodiments, the first thermoplastic component is a polyolefin based component, polystyrene (PS) based component or acrylonitrile/styrene/butadiene (ABS) terpolymer based compound, with or without an added elastomer component and the second thermoplastic component is polyamide (PA) or Polyethylene Vinyl Alcohol (EVOH) copolymer. Preferably, the elastomer component is a combination of elastomers. The addition of the elastomer component to
10

the compound changes the composition's mechanical properties without significantly affecting its electrical conductivity.
Since the affinity of polyamide or EVOH 16 to glass fibers 14 is much stronger than to any of the first thermoplastic components , during the melt blending of composition 10, the second thermoplastic component) preferentially encapsulates, in situ, glass fibers 14 as described in detail with reference to Fig. 3 hereinbelow, thereby producing a network of encapuslated fibers within matrix 12. Moreover, carbon black particles are preferentially attracted to the second thermoplastic component phase and located at the second thermoplastic component (polyamide or EVOH) matrix interfaces as indicated by reference numeral 15, thereby making the network of encapsulated fibers electrically conductive using a much smaller content of carbon black than in the prior art and improving the mechanical properties of composition 10 as described hereinbelow.
Referring to the three Scanning Electron Microscope (SEM) micrographs of Figs. 2A - 2C which differ in their magnification, the network of encapsulated fibers and the preferential distribution of carbon black 18 in the second thermoplastic component phase 16 is clearly seen.
A particular feature of the present invention is that composition 10 includes much lower concentrations of carbon black than in the prior art for similar levels of electrical conductivities. This is since
1 1

the electrically conductive carbon black particles form continuous
pathways along the interfaces between the second thermoplastic
component phase and the matrix, (first level of percolation). Moreover, the
embedded part of carbon black particles is located within the amorphous
phase of the second thermoplastic 16 (second level of percolation), thereby
the formation of the conductive pathways is facilitated. This is further
facilitated by the network formed of second thermoplastic component
encapsulated glass fibers (third level of percolation).
Reference is now made to Figs. 3 through 5C which illustrate

preferred methods for producing the electrically conductive thermoplastic compositions of the present invention. Fig. 3 illustrates the method in general and Figs. 4A - 4D and Fig 5A - 5C illustrate, respectively, alternatives of the method for two nonlimiting exemplary compositions.
The method of Fig. 3 illustrated in a time sequence from left to right comprising the steps of compounding 32, the step of pelletizing 34 and the step of injection molding 36. In one preferred embodiment the step of compounding 32 includes the steps of dry blending of polypropylene with second thermoplastic component indicated by reference numeral 31 followed by melting and melt mixing with the glass fibers as indicated by 33 and subsequent melt mixing with carbon fibers, carbon black or both.
In the non limiting examples described below, the
12

compounding step 32 is conducted on a twin-screw compounder (Berstorf, Germany), at processing temperatures in the range of 200-285 °C (corresponding to the melting point of the polymer components) and a screw speed of 55 rpm. The resulting compounds are pelletized (step 34) and then injection molded (step 36) at 200-285 °C on a Battenfeld injection molding machine equipped with a three_cayity American Standard Testing Material (ASTM) mold (tensile bar, flexural bar and falling dart impact disc).
Figs. 4A - 4D illustrate four preferred alternatives of the method for producing composition 10 whereas the composition includes carbon black as the carbon compound. Figs. 4A - 4D are illustrated for the nonlimiting example of a composition 10 comprises 100 parts by weight polypropylene, 12 parts by weight polyamide, 30 parts by weight glass fibers, and 2 parts by weight carbon black.
In the embodiment illustrated in Fig. 4A, carbon black concentrate is added in the injection molding stage as indicated by reference numeral 37 rather than in the compounding step 32 resulting in a resistivity of 537 Ohm-cm and flexural modulus of 4819 ± 161 MPa.
Fig. 4B illustrates the alternative wherein the carbon black concentrate is dry blended with the polypropylene and polyamide resulting in a resistivity of 432 Ohm-cm and flexural modulus of 4649 ± 32 MPa.
13

Fig. 4C illustrates the alternative wherein the carbon black concentrate is added during compounding resulting in a resistivity of 214 Ohm-cm and flexural modulus of 4491 ±51 MPa.
In the embodiment of Fig. 4D glass fibers are dry blended with the polypropylene and polyamide while carbon black concentrate is added during compounding resulting in a resistivity of 431 Ohm-cm and flexural modulus of 3790 ± 63 MPa.
Figs. 5A - 5C illustrate three preferred alternatives of the method for producing composition 10 whereas the composition carbon fibers or carbon black and carbon fibers as the carbon compound. Figs. 5A - 5C are illustrated for the nonlimiting example of a composition 10 comprises 100 parts by weight polypropylene, 12 parts by polyamide , 30 parts by weight glass fibers, and 2 parts by weight carbon black and 20 parts by weight carbon fibers.
In the alternative of Fig. 5A both carbon black and carbon fibers are added during the injection molding step resulting in high conductivity (Resistivity of 0.465 Ohm-cm) and high flexural modulus (9770 ± 428 MPa).
In the alternative of Fig. 5B carbon black is dry blended with the polyolefin and polyamide as indicated by step 39 instead of the dry blending indicated by step 31 of the other alternatives while carbon fibers
14

are added (step 35) during compounding resulting in a resistivity of 2 Ohm-cm and flexural modulus of 9550 ± 350 MPa.
In the alternative of Fig. 5C, carbon fibers are added in the compounding stage resulting in resistivity of 8 Ohm-cm illustrates and flexural modulus of 8931 ± 267 MPa.
It will be appreciated that the specific method used to prepare the compounds forming composition 10 for injection molding can be selected from the nonlimiting' embodiments described hereinabove and from many other variations thereof, thereby varying the specific electrical conductivity and mechanical properties (illustrated by the flexural modulus above) of composition 10. In all methods, the present invention provides an electrically conductive thermoplastic composition which provides high electrical conductivity and strong mechanical properties after injection molding.
The following examples illustrate without limitation certain aspects of the present invention.
In all examples, injection molded composite samples (12.6cm x 1.27cm x 0.32cm) were characterized for electrical properties by measuring volume resistivity, according to ASTM D 257 - 93 and ASTM D 4496 - 87, using Keithley instruments.Silver paint was used to eliminate the contact resistance between samples and electrodes.
15

The corresponding ASTM test methods were used for the mechanical properties evaluation. Specifically, ASTM D 0638 was used for measuring tensile properties, ASTM D 790 was used for measuring flexure, ASTM D 256 was used to measure IZOD impact and ASTM D 570 was used to measure water absorption.
The glass fiber content and the carbon black content in each specimen was determined by using ASTM D 5630 - 94 and ASTM D 1603 - 94, respectively.
The composites morphology was studied using JEOL 5400 scanning electron microscope. Freeze fractured surfaces were studied.
In the experiments, commercial grades of PP (homopolymer and copolymer), ABS, PS, HIPS, NORYL (described in detail with reference to Tables 10-13), PE (high and low density grades), elastomer, PA (PA6, PA66, PA 11, PA 12, PA 6/6.9, PA 6/12), EVOH, glass fibers (chopped strands, 3.2-6.3 mm length, 10-13 micrometer diameter),
conductive carbon black and carbon fibers (chopped fibers, 6mm length,
7-8 microns diameter) have been used in this study. Five types of carbon black were studied. Their properties are shown in Table 1 below.
16

Table 1

Property
Ketjen EC 300J (AKZO)
Ketjen EC
600JD
(AKZO)
Vulcan XC-72 (Cabot)
Corax L6 (Degussa)
Conductex 975
(Columbian
Chemicals)
Surface area BET, m2/g
1000
?
180
265
250
Particle size, nm
30
?
29
18
22
Porevolume DBP,ml/100g
350
480
178
123
165
Surface area CTAB, m2/g
480
0
86
150
153
Iodine absorption, mg/g
900
1000

293
260
Volatilities, %
0.5
0.6
1.0
1.5
1.0
pH
8
8
7
7.5
7
All blend ratios described relate to parts by weight, in each case based on 100 parts by weight of the first compound. An electrically conductive polyolefin composites comprise: 100 parts by weight polymer matrix, 4 to 20 parts by Polyamide, 10 to 55 parts by weight glass fibers, 0.5 to 10 parts by weight carbon black, 0 to 30 parts by weight carbon fibers.
The electrical and mechanical behavior of compositions 10

was studied for different polyamide mixtures ratios as a function of glass fiber concentration, polyamide/glass fiber ratio and carbon black concentration. The resistivity and the mechanical properties as a function
17

of composition are summarized in Tables 2A and 2B. It will be appreciated

that the samples produced were in accordance with the processing method of the present invention i.e., injection molding.
18

Table 2A

Compostion
1
2

4
5
6
7
8
9
10
polypropylene (MFI 12)
100
100
100
100
100
100
100
100
100
100

Polyamide 6
5
5
5
5
5
8
8
10
12
10
Glass Fiber (Vetro tex)
12
12
20
20
20
20
30
30
30
30
Carbon Black (EC 600)
1
3
0.5
1
3
3
1
1.5
2
3
Property

Flexural Modulus, MPa
3044"*
3849
3041
3945
4104

4366

5003
4655
4941

515:
Izod Impact, notched, J/m
69
64
33
83
60
57
76
75
79
65
Volume Resistivity ohm-cm 9
0.1 - 10
>108
3.3x105
108
104
1.6x105
8.6xl03
6.6x103
3xl03
1.4xl03

6.5x
19

Table 2B

Composition
1
2
3
4
5
6
7
Polypropylene (MFI 25)."
100
100
100
100
100
100
100
Polyamide 6
4
5.3
6.6
8
8
8
12
Glass fiber (Vetrotex)
20 0.67
20 0.88
20 1.1
20 1.5
20
2
30
30 2
Carbon black (EC 600)

1.3

Property

Specific Gravity, Kg/dm3
1.02
1.01
1.02
1.02
1.02
1.06
1.06
Water Absorption, %
0.04
0.06
0.06
0.04
0.05
0.08
0.08
Flexural Modulus, MPa
3984
3958
3954
3941
3936
4866
5039
Tensile Strength, MPa Elongation at Break, %
54 2.8
58 3.1
52 2.7
52 2.8
58 2.8
63 2.5
63

2.6
Izod Impact, notched, J/m
68
85
66
63
71
85
76
Melt Flow Rate,
5.2
4
6
2.8
3
3.3
3.2
230°C,2.16Kg

Heat Distortion Temp, °C
161
163
161
162
163
164
163
Volume Resistivity, ohm-cm
3.24x105
2.5x103
3.2x104
1.3xl03
7.9x103
3.4xl03
1.2x!03
Tables 3A and 3B illustrate the dependence of resistivity and physical properties on glass fiber concentration in compositions 10 for different polypropylene/ polyamide mixtures. The increase of tensile strength, modulus and flexural modulus with increasing glass fiber content is clearly appreciated.
20

Table 3A

Composition
1
2
3
4
5
Polypropylene (MFI 12) Polyamide 66
100
5 12
1
100
8
20
1.5
100 12 30 2
100
16
40
100 16.5 50
Glass Fiber (Vetrotex) Carbon black (EC600)

2.8
2.8
Properly

Tensile Strength, MPa Elongation at break, % Tensile Modulus, MPa Flexural Modulus, MPa Izod Impact, notched, J/m Water Absorption, % Specific Gravity, kg/dm3 Volume Resistivity, ohm-cm
39.4 3.2 1771 3054
44 2.6
2030 3801
56.2 2.3 2634 4684
58 2.1 3133
47.4
2
2406

5394
5576

64 0.02 0.981 >108
69 0.03 1.025 9.4x104
77 0.04 1.082 850
71
0.06 1.122 440
57 0.07 1.145 2.3xl04
21

Table 3B

Composition
I
2
3
4
5
6
7
8
9
Polypropylene (MFI 25) Polyamide 66
100
100
100
100
100
100
100
100
100

4
5.3
6.6
8
8
6
8
10
12
Glass fiber (Vetrotex)
20 0.67
20 0.88
20 1.1
20 1.5
20 2
30
30
30
2
Carbon black (EC 600)

1
1.3
1.6

Property

Specific Gravity, Kg/dm3
1.02
1.00
1.01
1.04
1.02
1.05
1.06
1.05
1.06
Water Absorption, %
0.04
0.04
0.07
0.04
0.05
0.05
0.07
0.1
0.05
Flexural Modulus, MPa
3917
3804
3858
373
3936
4815
4640
4732
4856
Tensile Strength, MPa
52
53
53
53
56
57
59
57
61
Elongation at Break, %
2.7
3.1
3.0
3.0
3.0
2.6
2.4
2.9
2.0
Izod Impact, notched, J/m
64
71
76
66
67
75
75
77
62
Melt Flow Rate,
18
12
11
8.6
11
8
8.8
8
6
275°C, 2.16Kg

Heat Distortion Temp. °C
161
163
163
162
162
164
165
165
163
Volume Resistivity, ohm-cm
2x 10
4
9.9x103
4xl01
490
7.9xl03
650
814
241
175

Table 4 illustrates the dependency of electrical resistivity of PP/PA/GF/CB systems (100/12/30/4 phr ratio respectively) on the type of second thermoplastic component (polyamide) used. It is clearly seen that any type of polyamide can be used for composition 10 and that their electrical conductivity can be determined by selecting the degree of crystalinity of the polyamide. Lower values of resistivity were obtained for compositions 10 based on PA 66 and PA 6, PA11, PA 12 (semicrystalline polyamide) than for those based on PA 6/6-9 and PA 6-12 (amorphous polyamide). Given the same concentration of conductive additive, a higher
22

level of conductivity was achieved in PA 66 (the most crystalline polyamide studied) based compound.
Table 4

Property
PA 66
PA 6
PA12
PA11
PA 6-6/9
PA 6-12

Tensile Strength, MPa
58.4
54.2
51.9
49.6
58.5
56.6
Elongationat break,%
2.1
1.9
2
3
2.3
1.9
Tensile Modulus, MPa
3256
3030
2541
1868
3074
3160
Flexural Modulus,MPa
4850
4699
4592
3899
4650
4890
Izod Impact, notched, J/m
72
70
68.8
58.9
61
62
Specific gravity, kg/dm3
Volume Resistivity, ohm-cm 1.086 700
1.092 3.3x103
1.081
1.079
1.076 3.3xl05
1.069 1.3x105

2.3x103
5.4xl03

It will also be appreciated that any type of carbon black can be used with compositions 10. Resistivity and mechanical properties of composites with Five CB grades, at two loading levels, for composites based on Polypropylene (100 parts), PA 66 (12 parts) and glass fibers (30 parts) are presented in Table 5. Inspection of this table reveals that Ketjenblacks EC 300 and EC 600, the most conductive carbon blacks used provide the highest electrical conductivity.
23

Table 5

Property
EC600
EC
300
XC 72

CORAX L6
CONDU
CTEX

2 phr
2 phr
4 phr
2 phr
4 phr
2 phr
4 phr
2 phr
4 phr
Tensile Strength, MPa
56.2
52.1
57.7
45.9
54
44.2
45.1
43.9
58.4
Elongation at break, %
2.1
2.5
2.3
2.6
2.3
2.6
2.2
3.1
2.1
Tensile Modulus, MPa
3133
2776
2911
2087
2933
2291
2147
2193
3194
Flexural Modulus, MPa
4684
4898
4803
4968
4747
5108
4335
4948
4638
Izod Impact,notched, J/m
77

72
70
58
74
66
79
72
Specific gravity, kg/dm3
1.082
1.072
1.079
1.079
1.079
1.074
1.076
1.069
1.074
Volume Resistivity, ohm-cm
850
1560
789
>108
4110
>108
852
>108
4x104

Yet another factor which determines the resistivity and mechanical properties of compositions 10 is the flowability (MFI) of the polymer matrix used. As clearly seen from Table 6 below, significant lower resistivities are obtained using for example polypropylene with higher MFI. Table 6 is provided below.
24

Table 6

Composition
1
2
3
4
5
6
7
8
9
Polypropylene (MFI 3)

100

Polypropylene (MFI 12)
100

100

100

100

Polypropylene (MFI 25)
5
100
5
12
12
100 12
16
100 16
16.5
100 15
Polyamide 66

Glass fiber (Vetrotex)
12
12
30
30
30
40
40
50
50
Carbon black (EC 600)
1
1
2
2
2
2.8
2.8
2.8
2.5
Property

Flexural Modulus, MPa
3054
3037
4168
4684
4450
5812
5515
5576
6249
Volume Resistivity, ohm-cm
107
2863
1100
850
290
565
405
2.3xl04
543

Table 7

Composition
1
2
3
4
5
6
7
8
9
10
Polypropylene (MFI 25)
100
12
30
2 0
100
12
30
2
6
100
12
30
2
10
100
12 30 2 20
100
12
30
2
30
100
14
40
2.8
0
100
14
40
2.8
6
100
14
40
2.8
10
100
14
40
100
14
40
Polyamide 66 Glass Fiber (Vetrotex) Carbon Black (EC 600) Carbon Fiber

2.8 14
2.8
20

Property

Flexural Modulus, MPa Volume Resistivity, ohm-cm
4850
344
6264
7.2
7910 2
9770 0.465
10514 0.168
5964
425
6675 12.2
8129 1.2
9641 0.96
10495 0.32
It will be appreciated that the compositions of the present invention, in particular the ones including carbon fibers and having a resistivity of less than 1 Ohm-cm provide improved Electro Magnetic Interference (EMI) shielding with a lower content of carbon black and carbon fibers. Therefore, they are superior to prior art electrically conductive plastics in a wide range of applications, such as clean room applications where the amount of carbon is important for the cleanliness of the process.
It will be appreciated that the present invention is not limited by what has been described hereinabove and that numerous modifications, all of which fail within the scope of the present invention, exist. For
26

example, while the present invention has been described with reference to polypropylene, the present invention is equally applicable to other polyolefins such as polyethylene and to polyethylene-polypropylene mixtures. Polyethylene based compositions were prepared using LDPE and HDPE grades in a generally similar manner to that of polypropylene. As an example, a polyethylene based composition (100 parts on a similar weight basis) blended with 11 parts of polyamide (PA6), 20 parts of glass fibers and 4.4 parts of carbon black (EC-300) exhibit volume resistivity of 105- 106 ohm-cm.
Table 8 illustrates two further examples of polyethylene based compositions.
27

Table 8

Composition
1
2
PE 800 (MFI 20)
100

PE600(MFI7)

100
Polyamide 66
12
12
Glass fiber (Vetrotex)
30
30
Carbon black (EC 600)
2
2
Property

Specific Gravity, Kg/dm3
1.07
1.07
Water Absorption, %
0.06
0.06
Flexural Modulus, MPa
1663
1622
Tensile Modulus, MPa
746
678
Tensile Strength, MPa
19.3
17.1
Elongation at Break, %
3.0
3.3
Izod Impact, notched,
80
81
J/m

Melt Flow Rate, 275°C,
33.2
18.8
2.16Kg

Heat Distortion Temp, °C
96
96
Volume Resistivity, ohm-cm
1x106
2x106

In other alternative embodiments, the polyolefin component is replaced by another thermoplastic compound as the first component forming matrix 12. In four preferred embodiments, the first component forming matrix 12 was acrylonitrile/butadiene/styrene (ABS), polystyrene
28

(PS), high impact polystyrene (HIPS) and polyphenyleneoxide/polystyrene (NORYL).
Table 9 illustrates two examples of
polyethylene-polypropylene based compositions.
Table 9

Composition
1 2
PE 800 (MFI 20) PE 600 (MFI 7) Polypropylene (MFI 25) Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600)
100
100
24 24
8 8
20 20
1.5 1.5
Property

Specific Gravity, Kg/dm3 Water Absorption. % Flexural Modulus. MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 275°C, 2.16Kg
Heat Distortion Temp, °C Volume Resistivity, ohm-cm
1.03 1.02
0.05 0.05
1975 2117
1246 1176
27 27.4
2.3 2.5
68 70
24.7 14.2
101 102 3x105 3x105

Table 10 illustrates a nonlimiting example of compositions 10 formed with ABS, PS, HIPS and NORYL with different second

thermoplastic component ( different types of polyamide compositions, different glass fiber content and different low amounts (less than or equal to 3 phr) of carbon black.
Table 10

Composition
1
2
3
4
5
6
ABS
100
100
100

PS

100

HIPS

100

NORYL

100
Polyamide 6

12

12

Polyamide 12
8

12
12

Polyamide 66

12
Glass fiber (Vetrotex)
20
30
30
30
30
30
Carbon black (EC 600)
1.2
3
3
2
3
3
Property

Volume Resistivity,ohm-cm
108
104
103
105
104
103
Tables 11, 12 and 13 provide further examples of PS, HIPS and Noryl based compositions, respectively, and their mechanical properties.
Table 11 illustrates the dependence of resistivity and physical properties on glass fiber concentration in a PS/PA/GF/CB compound.
30

Table 11

Composition
12 3 4
PS (GP) Polyamide 6 Polyamide 12 Glass fiber (Vetrotex) Carbon black (EC 600)
100 100 100 100
5 8 12
12
12 20 30 30 1.5 2 3 3
Property

Specific Gravity, Kg/dm1 Water Absorption, % Flexural Modulus. MPa Tensile Modulus,. MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 230°C,2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm
1.09 1.17 1.22 1.2
0.12 0.12 0.13 0.07
4850 5830 7100 7000
2740 3130 3650 3290
56 70 66 59
2 2 2 2
43 52 51 38
8.2 5.7 3.7 3.0
82 84 - 86 4.5xl05 7.5xl04 3.8xl04 2.2xl04

Table 12 illustrates the dependence of resistivity and physical properties on glass fiber concentration in HIPS/PA/GF/CB compound.
31

Table 12

Composition
1 2 3 4
HIPS
Polyamide 6 Polyamide 12 Glass fiber (Vetrotex) Carbon black (EC 600)
100 100 100 100 5 8 12
12 12 20 30 30 1.5 2 3 3
Property

Specific Gravity, Kg/dm3 Water Absorption, % Flexural Modulus, MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 230°C,2.16Kg Heat Distortion Temp, °C Volume Resistivity, ohm-cm
1.12 1.16 1.21 1.19
0.13 0.14 0.14 0.07
3600 4560 6410 6050
1800 2050 2630 2050
43 51 61 46
2 2 2 2
46 46 47 34
2.3 1.7 1.9 1.7
97 92 93 9xl06 7xl04 7xl03 1.5x104

Table 13 illustrates the dependence of resistivity and physical properties on glass fiber concentration in Noryl/PA66/GF/CB compound.
32

Table 13

Composition
1 2
Noryl
Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600)
100 100 12 16
30 40 3 4
Property

Specific Gravity, Kg/dm3 Water Absorption, % Flexural Modulus, MPa Tensile Modulus, MPa Tensile Strength, MPa Elongation at Break, % Izod Impact, notched, J/m Melt Flow Rate, 275°C, 2.16Kg
Heat Distortion Temp, °C Volume Resistivity, ohm-cm
1.24 1.28
0.17 0.20
6501 7193
3382 4361
64.1 79.2
2.0 1.8
38 42
1.0 0.5
122 124 5x105 1.8xl04

Table 14 illustrates compositions 10 wherein the second thermoplastic component is EVOH and notpolyamide. The table illustrates the dependence of resistivity on glass fiber concentration in PP/EVOH/GF/CB compound.
33

Table 14

Composition
1
2
3
Polypropylene (MFI 25)
100
100
100
EVOH
8
10
12
Glass fiber (Vetrotex)
20
30
30
Carbon black (EC 600)
2
2.5
3
Property

Specific Gravity, Kg/dm3
1.03
1.07
1.07
Water Absorption, %
0.03
0.03
0.05
Flexural Modulus, MPa
4530
5697
5529
Tensile Modulus, MPa
2475
2572
2670
Tensile Strength, MPa
59.7
62.1
61.8
Elongation at Break, %
2.7
2.5
2.4
Izod Impact, notched, J/m
69
66
58
Melt Flow Rate, 230°C,
5.0
4.5
3.2
2.16Kg

Heat Distortion Temp, °C
160
160
160
Volume Resistivity,
1.7xl05
1.6x105
1.2xl03
ohm-cm

Table 15 illustrates the dependence and resistivity and physical properties on glass fiber concentration in PP/PA/GF/CB (PP: Elastomer 60:40) compound containing elastomer. It is clearly shown that the compounds containing elastomer offer higher impact than the compounds summarized in Table 3B.
34

Table 15

Composition
1 2 3 4
Polypropylene Polyamide 66 Glass fiber (Vetrotex) Carbon black (EC 600)
100 100 100 100
5 8 8 10
12 20 25 30
1 1.5 1.5 2
Property

Flexural Modulus, MPa Izod Impact, notched, J/m Surface Resistivity, ohm/sq.
1500 1900 2000 2300 134 120 107 100 107 106 105 105
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention is defined only by the claims that follow:
35

We claim:
1. An electrically conducive composition comprising: a matrix comprising substantially a first thermoplastic component; a second thermoplastic component having a higher polarity than that of said first thermoplastic component, said second component encapsulating a plurality of fibers forming a network of encapsulated fibers within said matrix; and a carbon component preferentially attracted to said second component so as to make said network an electrically conducive network within said matrix, said carbon component located at the interface between said second thermoplastic component and said matrix wherein said carbon component is carbon black and is present in an amount less than 10 parts per hundred.
2. A composition as claimed in claim 1 wherein said first thermoplastic component is a polyolefin compound with or without an added elastomer component.
3. A composition as claimed in claim 2 wherein said polyolefin is selected from the group consisting of polypropylene and polyethylene.

4. A composition as claimed in claim 3 wherein said polypropylene is a homopolymer or a copolymer.
5. A composition as claimed in claim 1 wherein said second component is polyamide or EVOH.
6. A composition as claimed in claim 5 wherein said composition comprises less than 20 parts per hundred polyamide or EVOH.
7. A composition as claimed in claim 1 wherein said fibers are glass fibers.
8. A composition as claimed in claim 7 wherein said composition comprises less than 55 parts per hundred glass fibers.
9. A composition as claimed in claim 1, wherein said carbon component further comprises carbon fibers.
-36-

10.A composition as claimed in claim 1 wherein said carbon component is a mixture of carbon black and carbon fibers.
11. A composition as claimed in claim 9, comprising less than 30 parts per hundred carbon
fibers,
12. A composition as claimed in claim1, having a volume resistivity from 0.1 to
109 ohm-cm.
'13. A composition as claimed in claim 1 having a flexural modulus of up to 11, 000 Mpa.
14. A composition as claimed in claim 1 having a tensile strength of up to 60 Mpa.
15. A composition as claimed in claim 1 wherein said first component is selected from acrylonitrite/butadiene/styrene, polystyrene, high impact polystyrene and polyphenylene oxide /polystyrene.
16. A composition as claimed in claim 15 wherein said second component is polyamide or
EVOH.
17. A composition as claimed in claim 2 wherein said elastomer component comprises a
combination of elastomers.
18. A composition as claimed in claim 17 wherein said combination of elastomers affect the
mechanical properties of said composition without significantly affecting its electrical
conductivity.
19. A method for producing an electrically conductive composition comprising the step of compounding a matrix comprising substantially a first thermoplastic component with a second thermoplastic component having a higher polarity than that of said first thermoplastic component, said second component encapsulating a plurality of fibers forming a network of encapsulate fibers within said matrix; and a carbon component preferably attracted to said second component so as to make said network an electrically conducive network within said matrix, said carbon component located the interface between said second thermoplastic component and said matrix wherein said carbon component is carbon black and is present in an amount less than 10 parts per hundred.
-37-

26. -A method as claimed in claim 19 further comprising the step of forming said first thermoplastic component from a polyolefin compound with or without an added elastomer component.
21. A method as claimed in claim 20 wherein said polyolefin is selected from the group
consisting of polypropylene and polyethylene.
22. A composition as claimed in claim 21 wherein said polypropylene is a homopolymer or a copolymer.
23. A composition as claimed in claim 19 further comprising the step of forming said second thermoplastic component from polyamide or EVOH.
24. A method as claimed in claim 23 wherein said composition comprises less than 20 parts per hundred polyamide.
25. A method as claimed in claim 19 wherein said fibers are glass fibers.
26. A method as claimed in claim 25 wherein said composition comprises less than 55 parts per hundred glass fibers.
27. A method as claimed in claim 19 wherein said carbon component further carbon fibers.
28. A method as claimed in claim 19 wherein said carbon component is a mixture of carbon black and carbon fibers.
29. A method as claimed in claim 27 wherein said composition comprising less than 30
parts per hundred carbon fibers.
-38-

30. A method as claimed in claim 19 wherein said composition has a volume resistivity from 0.1 to 109 ohm-cm.
31. A method as claimed in claim 19 wherein said composition has a flexural modulus of up to 1,000 Mpa.
32. A method as claimed in claim 19 wherein said composition has a tensile strength of up to 60 Mpa.
33. A method as claimed in claim 19 comprising the step of forming said first component from acrylonitrite/butadiene/styrene, polystyrene high impact polystrene and polyphenyleneoxide/polystyrene.
34. A method as claimed in claim 33 wherein said second component is polyamide or EVOH.
35. A method as claimed in claim 19 wherein said elastomer component comprises a combination of elastomers.
36. A method as claimed in claim 35 wherein said combination of elastomers affect the mechanical properties of said composition without significantly affecting its electrical conductivity.
30.

Dated this 22nd day of September 97
OF L.S.DAVAR & CO. APPLICANTS' AGENT.
-39-
An electrically conductive composition and a method for producing same, for example by injection molding. The composition includes a matrix comprising substantially a first thermoplastic component, a second thermoplastic component having a higher polarity than that of the first thermoplastic component, the second component encapsulating a plurality of fibers forming a network of encapsulated fibers within the matrix, and a carbon component preferentially attracted to the second component so as to make said network an electrically conductive network within the matrix.

Documents:

01749-cal-1997.abstract.pdf

01749-cal-1997.claims.pdf

01749-cal-1997.correspondence.pdf

01749-cal-1997.description(complete).pdf

01749-cal-1997.drawings.pdf

01749-cal-1997.form-1.pdf

01749-cal-1997.form-2.pdf

01749-cal-1997.form-3.pdf

01749-cal-1997.form-5.pdf

01749-cal-1997.pa.pdf

01749-cal-1997.priority document.pdf

1749-cal-1997-granted-abstract.pdf

1749-cal-1997-granted-claims.pdf

1749-cal-1997-granted-correspondence.pdf

1749-cal-1997-granted-description (complete).pdf

1749-cal-1997-granted-drawings.pdf

1749-cal-1997-granted-form 1.pdf

1749-cal-1997-granted-form 2.pdf

1749-cal-1997-granted-form 3.pdf

1749-cal-1997-granted-form 5.pdf

1749-cal-1997-granted-letter patent.pdf

1749-cal-1997-granted-pa.pdf

1749-cal-1997-granted-specification.pdf

1749-cal-1997-granted-translated copy of priority document.pdf

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Patent Number

194882

Indian Patent Application Number

1749/CAL/1997

PG Journal Number

30/2009

Publication Date

24-Jul-2009

Grant Date

01-Jul-2005

Date of Filing

22-Sep-1997

Name of Patentee

CARMEL OLEFINS LTD.

Applicant Address

P.O. 1468, HAIFA

Inventors:

#	Inventor's Name	Inventor's Address
1	MOSHE NARKIS	3 LAVON STREET, HAIFA 34951
2	ROSA TCHOUDAKOV	29/14 ABA HILLEL SILVER STREET, HAIFA 32693
3	ARNON SIEGMANN	6 AMNON VE TAMAR STREET, HAIFA 32545
4	ANITA VAXMAN	64 HANDKE STREET, HAIFA 34608

PCT International Classification Number

H01B 1/24,C04B 35/52

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	60/030,621	1996-11-07	U.S.A.