The effect of the density fluctuations of amorphous polymer on the plastic region

It is generally known that amorphous polymers fracture with forming of the plastic region such as a crazing and shear yielding. To establish the fracture mechanism of amorphous polymer, it is very important to clarify how the plastic region was formed by deformation. Previous studies have been reported that forming plastic zone of Polycarbonate (PC) was influenced by amplifying the density fluctuations due to annealing below Tg. However, it is not clarified the relationship the density fluctuation and forming the plastic zone of Polymethylmethacrylate (PMMA) and Polystyrene (PS) with different fracture mode for PC. The purpose pf the study is to investigate how the change of the density fluctuations affect their plastic region. First, it was found that the plastic region obtained by polarized optical micrograph was different with the different fracture mode. Next, SAXS results show that the density fluctuations exist in PMMA and PS and its amplitude depend on each amorphous polymer. In addition, it was found that the density fluctuations induced by deformation, in case of PC and PMMA, while the fluctuations of PS did not change by deformation and appeared streak due to formed craze at just before at a break.