The Fracture Behavior Investigation Of Co-polypropylene With Annealing And Modification

The influence of annealing conditions, blending and chemical modification on the fracture behaviors of the co-polypropylene (PP) sheets at low cross-head speed was investigated by means of the essential work of fracture (EWF) method.It was shown that annealing has great effects on the crystal structures and properties of PP, moreover, remarkable variations of fracture properties can be observed for PP treated under different annealing conditions. With the increase of annealing temperature, the displacement to failure of double edge-notched tension (DENT) specimens decreased gradually. It was also found that with increasing annealing temperature, the specific essential work of fracture (w_e) increased, while the specific plastic work item (βw_p) decreased gradually. For all specimens before and after annealing, the variation of w_p was almost similar to that of βw_p. At lower annealing temperature, the effect of prolonged annealing time on the fracture parameters was similar to that of increasing annealing temperature.To study the influence of chemical modification on the fracture behaviors, PP was reacted with divinylbenzene (DVB), in the presence of dicumyl peroxide (DCP) and Antioxidant (1010) by a reactive extrusion process. It was found that with increasing DVB content, the Melt Flow Rate (MFR) of PP decreased, while the amount of macrogel in the samples and Vicat Softening Point of the samples increased. In addition, the crystallization temperature of modified PP was higher than that of pure PP, which moved to high temperature with the increase of DVB content.The crystallization morphology changed a lot and the size of spherocrystal refined.