Studies On Heterogeneous Grafting Of Maleic Anhydride Onto PP Powder In Water Solution And Product Applications

Polypropylene (PP) is one of five general purpose plastics and its application field isvery wide. PP has many merits such as lower price, big volume of production, water andchemicals resistance and simple technological process. However it is a nonpolar andcrystalline polymer, so it is difficult to blend it with other polymers, fillers and reinforcingmaterials because of poor interfacial adhesion. So it is hard to develop the novel polymeralloys.Maleic anhydride (MAH) is a polar ramification with many functional groups. Itsstructure and unsaturated double bond make it easy to react and connect with otherpolymers. The active anhydride groups react with hydroxy, carboxy and amimo groupseasily, so as to improve the interphase adhesion and compatibility of the two polymers.In this paper, the heterogeneous grafting of MAH onto PP powder was initiated byammonium persulfate (APS) in water solution. The functionalization of PP isaccomplished by this method.First, the MAH-g-PP was prepared through the heterogeneous grafting reaction. Thegrafting rate was determined by titration. The effects of the concentration of MAH andASP at the beginning of the reaction, and reaction temperature and time on the graftingreaction were investigated. Furthermore, the attempt of promotion of higher efficiency ofMAH was conducted. The result is shown as follow:1. The grafting degree of over 1.10% could be achieved under certain condition in theexperiment.2.The efficiency of original MAH was increased to as high as 3 times by circularlyusing of MAH solution.Second, characterization and property test of the reaction product gave the followingconclusions:1. The IR spectra showed that MAH was successfully grafted onto PP backbone forsome new distinct absorption peaks.2. The melting flow rate of the PP-g-MAH was decreased and the mechanical properties was improved due to the intermolecular action of PP-g-MAH wasenhanced by the polar groups grafted onto PP chain. And the peel strength betweenthe aluminum sheets was improved obviously.And third, the application of PP-g-MAH product as an interfacial improver in theblend of PP/PA6 alloy was experimentally studied. The result is as following:1.PP-g-MAH could perform well in the PP/PA6 composites as the interfacialcompatibilizer. The mechanical properties of the alloy had been improved obviously.2.The level of the PP-g-MAH in the composites should be optimized for specialcomposites.3. The previous conclusions were supported by the SEM analysis of the fracturesurface.4. Cocrystallization can take place in PP/PA6 blends for adding PP-g-MAH, and itsprocess property has improved too.