Slow elastic modulus changes in plasticised poly (vinyl chloride)

✍ Scribed by Leharne, Stephen A. ;Park, Geoffrey S. ;Norman, Ronald H.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1979
• Tongue: English
• Weight: 506 KB
• Volume: 11
• Category: Article
• ISSN: 0007-1641
• DOI: 10.1002/pi.4980110103

✦ Synopsis

Abstract

The Young's Modulus of PVC plasticised with various dialkylphthalates at concentrations from 40–120 phr that has been subject to a short heat treatment at 100°C, increases linearly with the logarithm of the time of storing at temperatures from 20–100°C. Both the Young's Modulus and its rats of increase with time is found to increase with increasing size of plasticiser to increase with decreasing concentration of plasticiser and to pass through a maximum with changing temperature of storage at a temperature of about 38°C. These effects can be explained if it is assumed that the elasticity results from a network linked by crystallites that can be melted on heating and reformed on storing at a lower temperature. The density of the plasticiser compositions is found to increase with time and this together with the development of endothermic DSC peaks support the hypothesis that changes in rigidity result from changes in crystallinity. The endothermic peak occurs at an almost constant temperature independent of plasticiser concentration or the size of the plasticiser molecule. It is suggested that the effect of these variables on the the melting point is nullified by the changes they also produce in crystallite size.