Research On Supercritical CO₂ Assisted Grafting Modification Of Polypropylene

Polypropylene (PP) is a widely used general-purpose thermoplastic. Polypropylene has many advantages such as: low density, good molding process property, excellent mechanical properties and heat resistance, which make it has a wider field of application in daily necessities, construction and packaging. However, it is a non-polar material and presents chemical inertness, which make it has poor compatibility with othe polar materials, inorganic fillers and reinforcing fibers. Graft modification is the samplest, the most economical and practical approach to overcome these limitations.In this paper, we use the supercritical CO₂ as swelling agent and carrying agent to assist acrylic acid/maleic anhydride/styrene (AA/MAH/St) to graft modification of PP. Soaking time, pressure and temperature; monomer and initiator concentration; grafting reaction temperature and time on the grafting process are investigated. The results show that grafting percentage can reach 8.49% when swelling pressure and temperature, reaction temperature and time are 8MPa, 41℃, 100℃and 2h respectively and PP/monomer/initiator is 10/0.6/0.03. At the same time, we used the same method to magnify the grafting reaction, the FTIR shows the monomers have grafted onto PP backbone; The contact angle and MFR measurements indicate the hydrophily and polarity had been improved obviously.Single monomer, bi-monomer and ternary-monomer are grafted onto PP backbone by solid-state grafting method. The effects of reaction temperature and time, initiator dosage, interface dosage and monomers were investigated in details. The products were characterized by FTIR and contact angle measurement, which shows that monomers were grafted onto the PP backbone and the polarity of the products was increased.Impregnation assisted modification of polypropylene by solid-state is used in the magnification research. The stirring rate was investigated. The results show the optimum agitation rate was 90 r/min. The products were characterized by FTIR, contact angle measurement, MFR and mechanical properties. The results show that the polarity of the grafted PP and mechanical properties were greatly improved.