Reinforcement And Toughen Modification Study Of Polypropylene

Polypropylene (PP) is a nonpolar resin which own the properties of good chemical stability, high crystallization, easy processing, low cost etc..making it be widely used in household appliances, packing materials, auto industries and so on. But polypropylene has some disadvantages such as high shrinkage, low melting point, poor dimensional stability, fragile at low temperature etc. These disadvantages limit the application of PP as force bearing materials. It’s necessary to modify polypropylene to extend the application of PP. This paper studied the reinforcement and toughening of PP.Raw materials were mixed in high speed mixer prior to extruding in twin-screw extruder. Injection molding the dried pellets and tested the mechanical properties, the melt flow property, morphology of modified PP samples. In the study of PP/wollastonite composite, we found mechanical properties of composites produced by one-step and two-step mixing are almost equal, but taking account of the cost, we chose one-step mixing process. Among different contents of W needle-like shaped wollastonite in polypropylene, there are almost no differences between modified PP and PP in tensile strength when the content of wollastonite was20%-25%while the elongation at break increased dramatically. The maximum impact strength of modified PP appeared when the content of wollastonite was25%. The tensile strength, elongation at break and impact strength decreased with the content of W needle-like shaped wollastonite increase. Add W needle-like shaped wollastonite, W800wollastonite and W1250wollastonite into PP to make composites respectively, it showed that W needle-like shaped wollastonite has the best enhancement while W1250has the best toughen effect. Results from POM and SEM showed that the sizes of different types of wollastonite are different and disperse uniformly in PP matrix forming tough morphology when broken.When study the system of PP/W needle-like shaped wollastonite/Glass fiber, added NJGF(made in Nanjing),DLGF(made in Dalian) and JLGF(made in Shenyang) respectively with the same content of W needle-like shaped wollastonite. It showed that JLGF has the best reinforcement effect while DLGF has the best toughen property. Observation from POM and SEM indicated different types of glass fibers have diversified sizes but all of them dispersed uniformly in PP matrix. Lap-rivet occurred between long fibers. Tensile strength and modulus of polypropylene increased but elongation at break decreased and no obvious change of impact strength with the increasing content of GF when the content of GF was10%-25%. It showed that from POM and SEM different contents of GF dispersed uniformly in matrix and both the lap-rivets and holes in composite increased with the increasing amount of GF.In PP/CaCO3composite system, compare with micron CaCO3nano-CaCO3has better effect on reinforcement and toughening. POM of PP/CaCO3indicated that the introduce of CaCO3minished the crystal size. The study of the influences of brightener, compatibilizer and lubricant on modification of PP showed that brightener can well modify tincture of PP, interface combination of PP and inorganic filler was improved by compatibilizer, of which LWPE-g-MAH was better than PE-g-MAH. As a lubricant, silicone masterbatch can better improve melt flow property of PP than methyl silicone oil.