Stress cracking of rigid polyvinyl chloride by plasticizer migration

Abstract

Environmental stress cracking (ESC) (failure caused by crack and craze formation at a stress less than the yield stress) reduces the service life of many plastic products. This paper is concerned with ESC of rigid PVC products which are in contact with a plasticized PVC material. The ESC affect (as measured by elongation to break) is reduced at faster strain rates and by higher plasticizer viscosity, which suggests a mechanism requiring flow of plasticizer into a growing craze. Well fused (gelled) PVC made at a higher melt temperature slowed but did not eliminate environmental stress cracking. Rubber impact modifier added to the rigid PVC had no effect on ESC. Environmental stress cracking can be avoided by using flexible PVC that has a non-migrating plasticizer or by designing the Droduct so that rigid PVC is not stressed while in contact with plasticized -PVC.

A new/old material as an engineering thermoplastic—PVC

“…Short term moduli vs. temperature are plotted in Fig. 6. From this plot we see that the modulus increases somewhat with the molecular weight of the PVC and, of course, the used in designing snap-fit joints to avoid permanently damaging snap-fitting cantilever by avoiding yielding during joining.…”