Research On Grafting Modification Of Polypropylene In Solid-phase Method

Polypropylene (PP) has outstanding application value and versatility, and it has been widely used in various industrial fields. There is no polar group on PP that cause obvious performance defects. The modification studies of grafting polar group onto PP are emerging at the right moment.In this paper, effects of experimental conditions were investigated by means of solid-state grafting on PP, such as different type of monomer and initiator system, ratio of binary or ternary composite monomer, reaction temperature and time, usage of initiator and monomer, dosage of interfacial agent and dispersant agent. Some effects of swelling process were studied in solid-state grafting on PP with supercritical CO₂ (SC-CO₂) assisted technology. The structure and thermal property of grafted polymers were characterized through FTIR, DSC, contact-angle and melting flow rate (MFR).The optimum grafting condition is that, PP 20.00g, monomer 1.20g and initiator 0.06g, w(MAH):w(St)=2:3 of binary-monomer, interfacial agent xylene 1mL, dispersant agent ether 2mL, reaction 2h at 90℃(AIBN) and 100℃(BPO). PP 20.00g, monomer 1.60g, initiator 0.06g (AIBN-BPO) and initiator 0.12g (BPO-DCP), and w(AIBN):w(BPO)=1:1 and w(BPO):w(DCP)=1:2 of the composite initiator system, w(MAH):w(St)=1:1.05 of binary- monomer, w(MAH):w(St):w(MBA)=6:9:5 of ternary-monomer, interfacial agent xylene 2mL, dispersant agent ether 1mL (AIBN-BPO), reaction 2h at 100℃(AIBN-BPO) and 3h at 120℃(BPO-DCP).The optimum condition of swelling process is swelling at 40℃and 8.0MPa for 4h. The swelling condition at rather high temperature and low pressure than critical point, could make solvation ability of SC-CO₂ under reasonable control, and to lower the destruction on rigid structure of PP, while improving depth and uniformity of grafting process.FTIR results of grafted products indicate that all monomers were indeed grafted onto PP backbone; DSC results show that melting point (Tm) and apparent crystallinity (Xc) decrease as GP increase; MFR and mechanical analysis results show that degradation is inevitable during the grafting process; contact-angle results show that solid-state grafting with SC-CO₂ assistance could significantly improve hydrophilicity.The products by grafting with SC-CO₂ assistance could raise GP markedly. Controlling GP by changing experimental conditions, can stabilize physical property of grafted product.