Abstract
The thermal shrinkage of drawn PVC filaments has been studied in the range of 20°C to 150°C. The effects of plasticizer (DOP) on the dimensional change of those filaments have been investigated as second order transion phenomena.
In reversible process, as typical runs are shown in Fig. 11, the slopes of length-temperature curves vary considerably at a constant temperature Tg. The first portion up to Tg shows the characteristic of simple thermal expansion, the second portion above Tg shows that of rubber-like state in which segmental motion may occur. The transition temperature is dependent on the content of plasticizer, and Boyer-Spencer's plot, as shown in Fig. 15, permits an evaluation of relative activation energy. Also the linear expansion coefficient defined as the gradient of slope, depends upon the content of plasticizer Fig. 13, suggests that the additiones of small amounts (5phr.) of plasticizer contribute to increase the cohesive force between PVC segments, and otherwise at higher amounts (50phr.) plasticizer itself behaves as a diluent.
In irreversible process, the shrinkage at selected temperature are shown in Fig. 3 to Fig. 9. The amounts of contraction due to the the thermal relaxation of segmental motoion depend upon plasticizer content and draw ratio of filaments. Considering the temperature dependence of Young's modulus, the observed stress-temperature curves are estimated from the load-elongation curves and thermal shrinkage curves, as shown in Fig. 16.
