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Electrothermal study of carbon loaded ethylene‐vinylacetate copolymer
Author(s) -
Sircar A. K.,
Wells J. L.
Publication year - 1981
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760211302
Subject(s) - carbon black , materials science , porosity , differential scanning calorimetry , composite material , electrical resistivity and conductivity , temperature coefficient , carbon fibers , copolymer , volume fraction , polymer , scanning electron microscope , conductivity , polymer chemistry , thermodynamics , natural rubber , chemistry , physics , composite number , electrical engineering , engineering
Temperature dependence of resistance of carbon black loaded ethylene‐vinylacetate (EVA) copolymer was studied from −100 to 250°C in a modified differential scanning calorimeter (DSC) apparatus. Both room temperature resistivity and positive temperature coefficient of resistance (PTC) effects can be correlated with carbon black parameters (structure, surface area, porosity). Room temperature resistivity and the degree of increase of resistivity, (ratio of maximum to minimum) progressively decrease with carbon black structure if occlusion of polymer by carbon black is considered in calculating the volume fraction. An integrated surface areastructure‐porosity equivalence of the carbon black is derived by introducing factors proportional to the volume and porosity of the black used. Any black parameter that increases conductivity (loading, surface area, structure, porosity) decreases the PTC effect. A cable compounder can therefore minimize the undesirable impact of PTC by suitable choice of black‐parameters. The necessary considerations for other uses, where PTC effect is used for microswitches, heaters, etc., will be just the opposite. The modified DSC method provides a quick scanning tool for determining the suitability of semicrystalline polymer recipes, either for cable or for any other material using the PTC effect.