The Effect Of Peroxide On Structure And Properties Of Copolypropylene

Due to excellent balance of rigidity and toughness, co-polypropylene has been wildly used in electric appliances and automobiles etc. As the products become thinner and more complex, the fluidic property of co-polypropylene is becoming more important. There are two ways to produce high flowing co-polypropylene. One is hydrogen modulation method using hydrogen as molecular regulator in advanced catalyst system, where the strict controlling on polymerization parameter is necessary; its product is called HM-PP. The other method is controlled degradation by peroxide initiating, its product is called controlled-rheology polypropylene (CR-PP). Because of simple production process and being easy to change product grades, the later is widely applied. In our earlier research, it was found that the flow ability of product modified with CR-PP is different from the prospective value. The fundamental purpose of this paper is to study the effect of main technological parameters in producing process of CR-PP on the properties of the final product CR-PP, the effect of remaining peroxide on the properties of CR-PP will also be investigated. To compare the difference in structures and properties between HM-PP and CR-PP, the mechanical propertis, rheological behaviors, processing stabilities and thermal-oxidative ageing properties were determined. The effects of extrument technological parameters in producing CR-PP on the properties of CR-PP were also examined. The results showed that in the same MFR, CR-PP has higher impact strength and HM-PP has higher elongation. Added peroxide make rubber particle assemble and the impact strength of PP was improved. On the other hand, because the viscosity ratio between plastics phase and rubber phase was enhanced, so the elongation of CR-PP was declined. The structure of CR-PP was affected by the content of peroxide, when the content of peroxide is less than 0.4‰,cross linking reaction is dominant, and when the content of peroxide is more than 0.4‰, degraded reaction is dominant. Meanwhile, high shear rate during the production process is favorable for peroxides to initiate degradation reaction of PP.