Polymer and Materials Science
Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Dc conductivity measurements were performed as a function of temperature on unplasticized poly(vinyl chloride) and on PVC plasticized with various amounts of dioctylphthalate. The conductivity curves consist of two or three straight-line segments denoted I, II, and III with increasing of temperature. The intersection of segments I and II occurs at the glass-transition temperature Tg. The slope in region I is independent of the DOP concentration, while the slope in region II decreases slowly with an increase in the amount of DOP. No dependence of the conductivity on the molecular weight was found. From the conductivity curves, activation energies were evaluated below and above Tg. These satisfactorily coincide with those determined by dielectric loss or by electrical transient phenomena. A dc conduction mechanism is proposed based on electronic hopping favored by the micro-Brownian motions responsible for dielectric losses. These motions involve smaller chain lengths below than above Tg. The experimental results are discussed and interpreted in terms of the proposed mechanism.
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