Research On Preparation Technology Of Polarity Polypropylene

Modification of polypropylene(PP) was studied by two methods, which were Supercritical CO₂(SCCO₂)assisted modification of polypropylene by solid-state and impregnation assisted modification of polypropylene by solid-state. The two methods have similar grafting process, which pre-swelling and thermal induced free radical grafting modification.Using benzoylperoxide(BPO) as initiator, styrene (St) as comonomer, acrylic acid(AA) was grafted onto PP in the solid state with assistant of SC CO₂. Effects of experimental parameters such as swelling conditions, reaction conditions and subsequent processing for crude products on grafting reactions and properties of product were studied systematically. The grafting products were characterized by FTIR, TG and water contact angle. It was that AA and St were actually gartfed onto the PP backbone proved by FTIR.TGA results show that grafted products have a higher-onest thermal degradation temperature and a lower weight loss at a particular temperature than pure PP. DSC results show that the melting points (Tm) and apparent crystallinity (Xc) decrease with the grafting percentage increase. The contact angle with water decreased from 98°to 76°,indicating an enhanced hydrophilicity for the grafted PP.The maximum grafting degree can reach 3.98% when the reaction was operated under the optimal reaction conditions.Using BPO as initiator, styrene (St), acrylamide(AM)and maleic anhydride(MAH)were grafted onto PP in the solid state with assistant of impregnant. The effects of impregnant species, impregnant dosage, swelling conditions, reaction conditions and feed of monomers on grafting reactions were investigated in details. As a result the maximum gratfing degree can reach3.96% when with ether as swelling agent, ultrasonic assist swelling 15min after another, swelling 5 hours and the reaction was operated under 90℃, for 2h with PP:monomer:BPO=100:6:0.3. Microstructure, melt behavior, and mechanics properties of grafted PP were studied by FTIR, DSC, tensile strength, elongation at break and MFR. Grafting polar side chains decreased melting temperature and improved cooling temperature. After grafting, morphology of inner and surface of PP had been changed notable, and grafted molecules had been uniformly distributed in the PP substrate.