Theoretical And Experimental Studies On The Extruding Foaming Of Photooxidation Polypropylene

Nowadays, problems on the environment pollution and the lack of resources we are facing with become very serious. More and more people are focusing on developing new technology and new products which can save energy sources and protect environment. Polypropylene Foams have gradually become the substitute for other thermoplastic foams because of their outstanding performance and the applications of this new technology in national economy and daily Life become more and more comprehensive.Basing on the former research achievments, I united the foaming process and degradation study to discovery and discuss the relationship between foam structure and photo-degradation in this work. Meanwhile, the effects of all kinds of factors in one step extrusion foaming process on foaming properties and photo-degradation properties were examed profoundly. The changes of surface and microstructure of foamed and solid PP samples were systematically investigated in experiments and theory before and afterthey were degraded by photo-oxidation.The main achievements and conclusions are as follows:1. Based on the analysis of degradation process and theory on the foamed and solid PP samples, the crystallinity and the parameter of foam structure were introduced into the mathematic model of the heterogeneous photo-oxidation spreading in solid and foamed PP samples. It can be analyzed and obtained that the larger crystallinity is, the slower the rate of degradation is; and the larger expansion ratio is, the quicker the rate of degradation is. And the model was validated primarily by experiments.2. It was found that there were great differential of the disruption mode between foamed and solid PP samples by observing and comparing the appearance and microscopic changes in photo-oxidation between the solid and foamed PP samples. The former is "single-direction" disruption, while the latter is "multi-direction" disruption. With the results of DSC analyses and FTIR spectra, it was further confirmed that the degradation degree of the foamed PP was greater than that of the solid PP after the same exposure time.3. The blending modification has negative effect slightly on degradation, while the crosslinking modification has a larger bad influence on the property of photo-degradation by the comparing experiments of different modification methods. Comparing the blending samples with crosslinking samples, it can be found that the degradation degree of the former is greater...