5. Surface aging

5.1 Photoaging

The phenomenon of photoaging is a very important problem in practice for certain parts such as unpainted automobile bumpers. It first induces a difference in appearance (whitening) and then, with further degradation, brittleness and premature failure. Aging kinetics depend on injection conditions and semi-crystalline surface organization. To demonstrate this, various plates were injected from a material comprising a polypropylene matrix and EPR (Ethylene Propylene Rubber) nodules, and subjected to accelerated aging. To understand the effect of skin structure, the surface and internal structure were subjected to the same accelerated photoaging tests. The core area was cleared by removing half a thickness by polishing. Photoaging kinetics were monitored by photoacoustic...