Research On Synthesis And Performances Of Polypropylene Composite

Polypropylene(PP) as a common polymer materials has been widely applicated in many fields. It developed so rapidly that makes it be the third largest general plastics next to polyethylene and polyvinyl chloride. As usual, polypropylene has the characteristics of poor toughness and easy embrittlement under low temperature, the compatibility to inorganic materials and other porlar polymers is poor due to the contribution of its nonpolar linear chains and high crystallinity. Modification of polypropylene to prepare alloys and composites is a promosing way to improve its performance.In this paper, the preparation, application and research progress of PP alloy and composites were summarized. The research progress of PP alloy catalyst has also been reviewed. PP alloys with excellent properties have been prepared through in-situ solid-phase graft acrylic acid (AA) and supercritical carbon dioxide (SC CO2) assisted grafting of multi-monomer onto PP backbone in solid-phase. The PP/nano-montmorillonite and PP/nano-montmorillonite/calcium carbonate composites were prepared in blending process with core-shell structure of nano-montmorillonite and calcium carbonate, using the GPP as the compatilizer and PP (T30S) as the raw material.The results showed that the process to make polypropylene alloys via in-situ solid-phase graft AA onto PP can effectively increase the polarity and hydrophilicity of PP, and is easy to carry out. The original properties of polypropylene were reserved. The grafting percentage was a function of polymerization temperature, time and initiator concentration, amount of free radical tapping agent and other factors. There was no significant degradation in the process of polymerization. No obviously change in molecular weight can be detected. Spherulite was refined. The most properties of alloys were almost the same as original polypropylene, but surface resistance decreased evidently, tensile and impact strength was improved. The contact angle of water drop to 80°for the product with grafting percentage of 1.6%.PP alloy were prepared by modification of PP with multi-monomer in solid-phase assisted with supercritical CO2 (SC CO2). The results indicated that monomers distribute on the surface equalitily and the polarity and hydrophilicity of PP increased effectively. The method of grafting soft-hard monomers onto PP, via solid-phase grafting with assistance of SC CO2, is practicable. Maximum grafting efficiency was more than 70%, grafting percentage was about 4.29%, in the condition that swelling time is 4h, reacting time is 2h and temperature is 80℃. PP was swelled in this process. With the increase of reacting time, temperature, initiator concentration and monomer concentration, the grafting percentage increase firstly and then drop. The reacting time for solid-phase grafting assisted with SC CO2 was shorter than normal solid-phase grafting. Melting point of the grafting product decreaseed, crystalline temperature, thermal stability and the polarity increased, the contact angle of water droped from 98°to 72°. After grafting, morphology of inner and surface of PP had been changed notable, and grafted molecules had been uniformly distributed in the PP substrate. Combination of soft monomer and hard monomer can counteract decreasing of mechanical properties caused by introducing side-chains. The tendency of main chain breaking decrease and toughness of product has been improved obviously.Based on the preparation and evaluation of PP composite, the montmorillonite was treated with a self-made organic tractive agent (Q) and activator (H) to form organic non-montmorillonite with core-shell structure. Using the GPP as the compatilizer, the PP/nano-montmorillonite composite was prepared by melt extrusion through blending process with core-shell structure nano-montmorillonite and PP. The results showed that the mechanical properties of the composite have been improved greatly for the addition of GPP. GPP can help nano-montmorillonite disperse in the composite, that is for GPP can combine with organic non-montmorillonite, and also combine with PP. the composite tractive agent (FQ) worked better than single tractive agent. When the H/FQ/GPP were used together, the nano-montmorillonite were dispersed beter that makes extrusion pressure decreased obviously. The modulus of product reached 2100MPa, the impact strength was 53J/m, the head shrinkage was 0.52% and the proper processing temperature was 180-190℃。The dispersion of montmorillonite in PP showed a laminated structure which was formed by 2-3 sheets overlapping with lamellar spacing of 3-4nm. The agglomeration tendency montmorillonite was neglectable. The adition of e GPP can promote the combination between montmorillonite and PP, the best properties of composite were achieved at the content of GPP was 5%. The polarizing microscope images indicated that the growth pattern of the composite's crystal increased the impact property. The composite is thermal stable and can meet theneeds in many application fields.The experimental data was lower than the value of the Halpin-Tsai equation, which suggested that the stripping layer of montmorillonite was insufficient.The feasibility of two kinds of inorganic filler was investigated as to further improve the performance of the composite. In the same way, calcium carbonate particles were actived, and the core-shell construction of calcium carbonate rigid particles was formed. GPP-4.3 was used as compatilizer, then PP/rigid particles composite were prepared. The kind of surface agent, activator and compatibilizer and concentration that effect extrusion pressure and product of performance were studied by screen experiment and performance test. The result indicated that dispersion of calcium carbonate particles highly disperse in composite and the property of composite further improve through synergistic effect of surface agent, activator and compatibilizer. Inorganic rigid particles using as grafting PP have been prepared through compound use of calcium carbonate particles and nano-montmorillonite. Then PP/Inorganic rigid particles composite have been prepared through they mixed with PP. The modulus of product reached 2300MPa, the impact strength was 60J/m, the head shrinkage was 0.5%.