Study On The Preparation And Crystallization Kinetic Of Low Density Polyethylene-Grafted-Acrylic Acid

In this thesis, the aqueous suspension graft polymerization method was used to modified low density polyethylene (LDPE) with benzoyl peroxide (BPO) as the initiator, toluene as the swelling agent, op-10as the surfactant and acrylic acid(AA) as the grafted monomer. By adjusting the process conditions of grafting, low density polyethylene-grafted-acrylic acid (LDPE-g-AA) with different degree of grafting were synthesized.Orthogonal experiment was designed to investigate the effects of the amount of monomer and initiator, reaction temperature and reaction time on the degree of grafting, and the optimum conditions for this grafting reaction was determined.LDPE and LDPE-g-AA were characterized by FTIR and TGA to discuss their changes of chemical composition and thermal stability after grafting.The DSC was used to test the isothermal and non-isothermal crystallization behaviors of the above products, and their equilibrium melting temperatures (Tm0) were calculated from the Hoffman-Weeks equation. The Avrami equation was used to explore the isothermal crystallization kinetic of LDPE and LDPE-g-AA, the results showed that the grafted polar AA branched chain acted as nucleating agent during its isothermal crystallization process, promoted the heterogeneous nucleation of LDPE-g-AA, lastly accelerated their isothermal crystallization rate, and the crystallization rate of LDPE-g-AA increases with increasing of degree of grafting. The Jeziorny method and Mo method were used to describe their non-isothermal crystallization behaviors, and the results showed that Jeziorny method can describe the initial non-isothermal crystallization process of LDPE and LDPE-g-AA, and Mo method can describe the whole non-isothermal crystallization process of LDPE and LDPE-g-AA. With increasing cooling rates, the non-isothermal crystallization rate of LDPE-g-AA increased and the non-isothermal crystallization rate of LDPE-g-AA also increased with increasing of degree of grafting.Meanwhile, we explored the bond behaviors of the above products on non-woven fabric, and the peel strength tests showed that LDPE-g-AA have good bonding properties for non-woven fabrics.