Studies On The Properties Of PLA Blends Compatibilized By Reactive Extrusion Induced By Ultraviolet Irradiation

Polylactic acid(PLA)is a kind of biodegradable plastic,which is made from starch extracted from crops by fermentation into lactic acid,and then polymerized.PLA has excellent physical and mechanical properties and good machinability,which makes it an ideal substitute for petroleum-based polymers.However,PLA has poor toughness and slow crystallization rate,which restrict the application of PLA in foaming,blow molding and other processing methods.To solve the problem of slow crystallization rate of PLA,PLA/ trimethylpropane triacrylate(TMPTA)/ polypropylene(PP)blend was prepared by reactive extrusion induced by ultraviolet irradiation.PP was used as heterogeneous nucleation site to improve the crystallization performance of PLA,and TMPTA was added as reactive compatibilizer,as the improvement of compatibility of PLA/TMPTA/PBAT blend,the crystallization property of PLA was improved.Due to the poor toughness of PLA,this paper added polyadipic acid/butyl terephthalate(PBAT)in PLA to improve the toughness of PLA,using the same processing method to prepare PLA/TMPTA/PBAT blend,PLA/TMPTA/PBAT blend film was prepared.After in-situ reactive compatibilization of PLA/TMPTA/PBAT blend,and the crystallization property and toughness of PLA were improved.The specific research contents and results are as follows:(1)The effect of in-situ reactive compatibilization on the properties of PLA/TMPTA/PP blends was investigated.After the in-situ reaction,the graft copolymer of PLA-g-TMPTA-g-PP was formed at the phase interface between PLA and PP.The compatibility of the blend was improved,and the dispersion of PP was smaller and more uniform.The formation of copolymer at the interface increases the degree of entanglement of molecular chains at the interface,which increases the apparent viscosity,storage modulus and complex viscosity of the blend,and enhances the elasticity of the melt.After PP was added into PLA,the crystallinity and nucleus density of PLA in blends were increased,indicating that PP could be used as a heterogeneous nucleation site of PLA to promote the crystallization of PLA.After the reaction increased,the crystallization properties of PLA in blends were further improved.(2)The effect of TMPTA content on the properties of PLA/TMPTA/PBAT blends after insitu reaction compatibilization was investigated.After the in-situ reaction,due to the formation of PLA-g-TMPTA-g-PBAT copolymer at the interface,the molecular weight of the blend was increased,the compatibility was improved,and the crystallization property of PLA was significantly improved.With the increase of TMPTA content,the reaction degree of the two phases at the interface was improved,the compatibility of the blends was continuously improved,the apparent viscosity,modulus,complex viscosity,melt elasticity were also improved,and the crystallinity was continuously improved.(3)The effect of PBAT content on the properties of PLA/TMPTA/PBAT blends after insitu reaction compatibilization was investigated.With the increase of PBAT content,the compatibilization effect of in-situ reaction decreased,and the toughness of the blend increased.When the content of PBAT was 10%,the crystallinity of PLA in the blend was the highest.The effect of in-situ reaction compatibilization on the properties of PLA/TMPTA/PBAT blended films was investigated.After the reaction capacity increase,the tensile strength and tear strength of the blend film were improved,the oxygen barrier performance was improved,and the light transmittance was decreased.The SEM image of the tear section of the film shows that after the reaction capacity increase,the blend film presents more obvious ductile fracture.