Research On High-Melt-Strength Polypropylene Via Solid Phase Grafting

Polypropylene (PP) is one of the most commonly used plastics because of its good properties, wide applicability, and low cost. However, PP is limited in its application in several technological1y important fields, because of its low surface energy, lack of reactive sites, difficulty to dye, extremely poor hygroscopicity, low impact strength, and poor compatibility with synthetic polar polymers. So modification of PP through solid-phase grafting was researched.The isotactic polypropylene (PP) was modified by solid phase grafting copolymerization with maleic-anhyfride (MAH) and styrene (St), using benzoyl peroxide (BPO) as the initiator and xylene as the interfacial agent. The influence factors including the reaction time, the reaction temperature, the concentration of initiator and monomer and monomer ratio were systematically investigated. The optimum reaction contidions were ascertained. The grafting product was measured by melting point, melting flow rate, mechanics capability, FTIR spectra were employed to characterize the structure. Finially, the grafted PP were used in PP/PA6 blends system as compatilizer. The content of grafted PP for MFR and mechanics capability is investigated.The FTIR spectra indicated that MAH and St has grafted on PP forming PP-g-(St-MAH). The results show that the optimum condtions of solid pahse grafting are as follows: solvent xylene; reaction temperature 125℃; reaction time 1h; concentration of BPO 2wt% of PP; molar ration of St to MAH 1.2:1; concentration of MAH 10wt% of PP.The results of capability tests show that the melting point and MFR decrease while the melting range and the density and tensile strength intensity as well as notched impact strength increase.Finially, the grafted PP were used in PP/PA6 blends system as compatilizer. We found that the MFR decrease a lot while the tensile strength intensity as well as notched impact strength increase.