Study On Properties And Crystallization Behaviors Of S–MA Random Copolymer Compatibilized Polylactide/SBS Blends

Polylacide(PLA)is a renewable polymer with biodegradability,biocompatibility,and good mechanical properties.It is a potential substitute for perroleum-based polymers.However,the disadvantages of poor toughness and slow crystallization rate limit the application of PLA in the engineering fields.Blending with other polymers is a cost-effective way to adjust the properties of PLA materials.However,the compatibility of PLA with most polymers is poor,so compatibilization is required.In the currently commonly used compatibilization methods,the remaining reactive groups in the reactive compatibilization may affect the safety of the blended materials,and the preparation of block and graft copolymers requires a large amount of solvents.Therefore,it is of great significance to develop greener compatibilizers for compatibilizing PLA blending systems.Our group used low-cost and simple surfactant-free emulsion polymerization to obtain poly(styrene-ran-methyl acrylate)(S–MA)to compatibilized PLA/polystyrene and PLA/high impact polystyrene blending systems,and achieved good compatibilization effect.However,since PS and HIPS are relative rigid plastics,they cannot effectively absorb the ground stress transmitted by the matrix during impact,so the toughness of PLA materials need to be further improved.In order to further improve the toughness of PLA,we select polystyrene-b-polybutadiene-b-polystyrene(SBS)thermoplastic elastomer as the toughening agent,and use S–MA(nSt : n MA = 75 : 25)as the compatibilizer for them.A series of PLA/SBS/ S–MA blends were preperd by melting and solution blending.The influence of S–MA content on the compatibility of blends of was studied by scanning electron microscope(SEM),universal testing machine,Charpy impact tester,and rotational rheometer.The influences of S–MA compatibilization on the crystallization behaviors of PLA/SBS blends were studied using differential scanning calorimeter(DSC),polarizing microscope(POM)and thermogravimetric analyzer(TGA).Analysis of mechanical properties showed that the tensile strength,modulus,and elongation at break increased with the increase of S–MA content,and the notched impact strength was the maximum when the addition amount of 1 wt%.SEM results show that the particle size of the SBS dispersed phase decreases as the S–MA content increases.Dynamic rheological analysis showed that the complex viscosity,storage modulus and loss modulus of PLA matrix also increase with the addition of S–MA;Han curves and Cole–Cole curves showed that the addition of S–MA increases compatibility of PLA/SBS blends.The DSC non-isothermal test showed that the addition of S–MA resulted in a decrease in the melt crystallinity of PLA and SBS blends at the same scan rate for melt crystallization and cold crystallization.The results of isothermal crystallization of DSC and POM indicate that the addition of S–MA leads to a decrease in the rate of PLA nucleation and spherulite growth in the PLA/SBS blend.TGA results indicate that the addition of S–MA causes a convergence of the maximum decomposition-rate temperatures of PLA and SBS.The above results show that the addition of S–MA increases the compatibility of PLA and SBS,and S–MA has the best toughening effect at a moderate content(1 wt%);S–MA acts as a compatibilizer,which leads to PLA/SBS The crystallization ability of the mixture is reduced.