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  • 1
    Electronic Resource
    Electronic Resource
    Morphology and electric conductivity of cross-linked polyethylene–carbon black blends prepared by gelation/ crystallization from solutions (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 669-679 
    Details
    ISSN: 1435-1536
    Keywords: Key words UHMWPE ; CB blends ; gelation/crystallization ; cross-linking ; thermal stability ; electric conductivity ; PTC effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Ultra-high-molecular-weight polyethylene (UHMWPE) – carbon black (CB) blends were prepared by gelation/ crystallization from PE dilute solutions containing CB particles. The UHMWPE/CB composition chosen were 1/0.15, 1/0.25, 1/0.5, 1/0.75, 1/1, 1/3, 1/5, and 1/9, etc. The cross-linking of PE chains was performed by chemical reaction of dicumyl-peroxide at 160 °C. X-ray diffraction patterns indicate that the crystallinity of PE within the blends decreased drastically through the chemical reaction at high temperature. The sample preparation method by gelation/crystallization provided the UHMWPE–CB system with various CB contents up to 90% and the conductivities for the resultant specimens were in the range from 10-9 to 1 Ω-1 cm-1 corresponding to the electric conductivity range of semiconductors. The blends assured thermal stability of electric conductivity by cross-linking of PE chains, although the mechanical property such as the storage and loss moduli were very sensitive to temperature. The conductivity of the blends with CB content ≥20% were almost independent of temperature up to 220 °C and the values in the heating and cooling processes were almost the same. On the other hand, for the UHMWPE–CB blends with 13% CB content corresponding to the critical one, temperature dependence of electric resistivity showed positive temperature coefficient (PTC) effect. The PTC intensities for non-cross-linked and cross-linked materials were lower than that of the corresponding low-molecular-weight-polyethylene (LMWPE)–CB blend but the maximum peak appeared at 160 °C which is higher than the peak temperature of LMWPE–CB blend.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050296
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  • 2
    Electronic Resource
    Electronic Resource
    Morphology and electrical conductivity of ultrahigh-molecular-weight polyethylene–low-molecular-weight polyethylene–carbon black composites prepared by gelation /crystallization from solutions (1999)
    Springer
    Colloid & polymer science 277 (1999), S. 452-461 
    Details
    ISSN: 1435-1536
    Keywords: Key words UHMWPE-LMWPE-CB composite ; electrical conductivity ; PTC effect ; gelation/crystallization ; kneading ; heat treatment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Composite materials based on ultrahigh-molecular-weight polyethylene (UHMWPE)–low- molecular-weight polyethylene (LMWPE) and carbon black (CB) particles were prepared by a gelation/crystallization process from dilute solution. The method was developed to obtain composite materials with an improved and reproducible positive temperature coefficient (PTC) effect. Drastic improvement of the PTC effect was achieved when specimens with a LMWPE/UHMWPE composition of 9/1 containing 13 wt% CB were treated at 170 °C without restraint before measurement. The maximum PTC intensity, defined as the ratio of the maximum resistivity to the resistivity at room temperature, was about 5 orders of magnitude, which equals that of the LMWPE-CB system prepared by a kneading method. Interestingly, electrical resistivity during the heating-cooling process showed good reproducibility in the temperature range 30–190 °C, but has never been reported before even for cross-linked LMWPE-CB compostie. Scanning electron micrographs revealed that CB particles were dispersed in the LMWPE matrix, but not on the UHMWPE fibrils. It turns out that the network structure of UHMWPE, with a very low melt index, plays an important role in removing the negative temperature coefficient effect usually observed for the LMWPE-CB system and in ensuring the quality and the reproducibility of the PTC effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003960050408
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal conductivity of a polymer composite filled with mixtures of particles (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 34 (1987), S. 1429-1437 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new thermal conduction model is proposed for a polymer system filled with a mixture of several types of particles. Predicted values by the new model are compared with experimental data. The model is derived by extending a model that was previously proposed for a two-phase system. The following equation is derived from the new model: log λ = V · (X2 · C2 · log λ2 + X3 · C3 · log λ3 + (1 - V) log (C1 · λ1. When the thermal conductivities of polymer and particles (λ1, λ2, λ3, …) and a mixing ratio of particles (X2, X3, …) are known, thermal conductivity of the filled polymer (λ) with several types of particles can be estimated from the equation, with any volume content of particles (V). Furthermore, from each polymer-filler composite (two-phase system) data, the thermal conductivity of a composite filled with different filler particles can be estimated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1987.070340408
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal conductivity of poly(vinyl chloride)/polycaprolactone blends (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 59-62 
    Details
    ISSN: 0887-6266
    Keywords: thermal diffusivity ; heat capacity ; PVC/PCL blends ; laser flash method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermal diffusivity, heat capacity, and density of polyvinyl chloride/polycaprolactone (PVC/PCL) blends were measured by the laser flash method, DSC, and pycnometry, respectively. The thermal conductivity of the PVC/PCL blends was determined from the results. The miscibility of the blend and crystallinity of PCL were determined by DSC. The effect of blend structure on thermal conductivity is discussed. The phase compositions of the PVC/PCL blends are of three types depending on PCL content: i.e., up to 33%, from 33 to 70%, and above 70% PCL by weight. Thermal conductivity, thermal diffusivity, and heat capacity of the PVC/PCL blends are strongly affected by the phase composition of the blend, which changes in a complicated way with PCL content. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320108
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement of thermal diffusivity and specific heat capacity of polymers by laser flash method (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 33-42 
    Details
    ISSN: 0887-6266
    Keywords: thermal diffusivity ; heat capacity ; polymers ; laser flash method ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We measured thermal diffusivity and heat capacity of polymers by laser flash method, and the effects of measurement condition and sample size on the accuracy of the measurement are discussed. Thermal diffusivities of PTFE films with thickness 200-500 μm were the same as those data that have been reported. But, the data for film thickness less than 200 μm have to be corrected by an equation to cancel thermal resistance between sample film and graphite layers for receiving light and detecting temperature. Thermal diffusivity was almost unaffected by the size of area vertical to the direction of laser pulse, because heat flow for the direction could be negligible. Specific heat capacity of polymer film was exactly measured at room temperature, provided that low absorbed energy (〈 0.3 J) and enough sample mass (〉 25 mg) were satisfied as measuring conditions. Thermal diffusivity curve of PS or PC versus temperature had a terrace around Tg, whereas that of PE decreased monotonously with increasing in temperature until Tm. Further, we estimated relative specific heat capacity (RCp) by calculating ratios of heat capacities at various temperatures to the one at 299 K. RCp for PS obtained by laser flash method was larger than that obtained by DSC method, whereas the RCps for PE obtained by the both methods agreed with one another until Tm (305 K). RCp for PS decreased linearly, with increase in temperature after it increased linearly until Tg (389 K), showing similarity to temperature dependency of thermal conductivity. RCp for PE also decreased until Tm, similar to thermal conductivity. ©1995 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1995.090330104
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal conductivity of a polymer filled with particles in the wide range from low to super-high volume content (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 929-941 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyethylene and polystyrene composites filled with high-volume content of filler particles (quartz or Al2O3) were prepared by ordinary melt-casting method to effectively increase the thermal conductivity. The result, however, suggested that fractional void volume cssentially occupied by filler particles is left unfilled when high or super-high content of filler is used. After investigating the relation between the mixing ratio of different sized filler particles and the fractional voidage under various compression intensities, a mixture of filler was found to give minimum fractional voidage. Polymers filled with such an optimum mixture of fillers for minimum fractional voidage were then prepared under compression. Thus, expected monotonous increases in thermal conductivity in the wide range from low to super-high filler content were obtained. Further, it was confirmed that a predictive model proposed by us agreed quite satisfactorily with the experimental data in comparison with many other models.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400526
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal conductivity of a polymer composite (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 49 (1993), S. 1625-1634 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A prediction equation for thermal conductivity of polymer composites reported in our previous papers has been revised in terms of two view points: (1) estimation of thermal conductivity of a composite using an idea of reduced thermal conductivity; and (2) the effect of ease in forming conductive filler chains on thermal conductivity is related to the CVF value in electric conductivity of the composite. The new equation was confirmed to be adaptable to thermal conductivities of varieties of polymer composite systems filled with spherical or irregular fillers. The equation was also considered to explain thermal conductivity of polymer composites filled with fibers. Further, it was found that thermal conductivities of fiber composites can be estimated by introducing a factor of the CVF value or aspect ratio (L/D) into the new equation. © 1993 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070490914
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal conductivities of composites in several types of dispersion systems (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1665-1669 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We measured thermal conductivities as well as electric conductivities of some composites in several types of dispersion systems. The dispersion state, that is, the ease in forming conductive chains in these composites, was estimated by the characteristic electric conductivities and compared with the thermal conductivities. Thus, it became clear that thermal conductivity of a composite was significantly affected by the dispersion state in the composite. Further, it was confirmed that the predictive model proposed in the previous report was adaptable to the thermal conductivity of the composites in several types of dispersion systems. It was made clear that the dispersion state of a composite affected the values C1 and C2 in the previous model.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1991.070420621
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  • 9
    Electronic Resource
    Electronic Resource
    Thermal conductivity of polyethylene/polystyrene blends containing SEBS block copolymer (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1957-1965 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We measured the thermal conductivity of a polyethylene/polystyrene blend containing SEBS block copolymer, which has two components of polystyrene block and hydrogenated polybutadiene block, and discussed the effect of phase inversion on the thermal conductivity by observing the morphorogy of the blend. Further, we examined the applicability of the thermal conduction model for composites, which was proposed in our previous reports, to this blend system. By plotting the logarithm of the thermal conductivities of the blends vs. the weight content of polyethylene, it was found that the experimental data lie approximately on a straight line with an increase in polyethylene until the range of dual-phase continuity (phase inversion), and then the data move on another straight line beyond the range of dual-phase continuity. Thus, our model to explain the thermal conductivity of the polymer blend was proved. Further, both coefficients A and B in our model took linear relations with the weight content of the block copolymer, and the model was, thus, more strongly confirmed to be applicable to thermal conductivity of polymer blends.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070451110
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  • 10
    Electronic Resource
    Electronic Resource
    Electrical and thermal conductivities of polyethylene composites filled with biaxial oriented short-cut carbon fibers (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 52 (1994), S. 1223-1231 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyethylene composites filled with various types of carbon fiber were prepared for electrical and thermal conductivity measurements. By estimation of the anisotropic parameter (Hermans' parameter), the fibers were confirmed to be significantly biaxially oriented in the composites. The critical volume fractions in the electrical conductivity of these composites for the two oriented directions (X and Y) were equal to each other and smaller than that for a direction (Z) vertical to the above. The electrical anisotropy, i.e., ratio of electrical conductivity of the composite for the Z direction to the X and Y directions varied drastically with increase in filler content. The longer the length of carbon fiber was, the higher became the electrical conductivity of the biaxially oriented carbon fiber composites for all directions. But, the thermal conductivity of the composite was almost unchanged for the Z direction, even if fiber length was sufficiently long. Our equation, previously proposed, proved adaptable to these thermal conductivities. The factors of Cp and Cf in the equation are kept unchanged, in spite of increasing fiber length. © 1994 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1994.070520907
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