Study On The Structure And Property Of Polylactide/Non-Planar Ring Contained Polyesters Blends

Polylactide(PLA)is a biobased and biodegradable green material with high strength and modulus.It is also one of the most important materials for supporting the sustainable development in future polymer materials technology field.However,the toughness of PLA is poor,the elongation at break and the notch impact strength of PLA are much lower than those of common petroleum-based polymers,which severely limits its wide applications.So far,the reported toughening agents can not effectively implement green toughening without decreasing the high strength and modulus of PLA.And,the theory behind chosing toughening agents is not sufficient.Through adequate consideration of the structural characters and physicochemical properties of non-planar ring,in this study,a series of novel biodegradable non-planar ring contained polyesters on the basis of 1,4-cyclohexanedicarboxylic acid(CHDA)is synthesized by molecular structure design to modify PLA.Based on intensive discussion of the relationship between structures and properties,the effect and mechanism on toughening PLA with non-planar ring contained polyesters are systematically investigated.Firstly,a non-planar ring contained polyester named poly(butylene 1,4-cyclohexanedicarboxylate)(PBC)was synthesized from CHDA with high cis content and 1,4-butanediol(BDO).PBC is an amorphous polyester elastomer in room temperature.The PLA/PBC blends were obtained by melt blending.According to the mechanical analysis,the addition of PBC can significantly improve the impact strength of PLA.With the addition of 20% PBC,the impact strength increased to 6.3kJ/m2.To futher improve the toughening effect,a long chain aliphatic polyester unit was introduced into PBC.Another non-planar ring contained polyester named poly(butylene adipate-co-1,4-cyclohexanedicarboxylate)(PBAC)was synthesized from CHDA with high trans content,BDO,and adipic acid(AA).PBAC is a semicrystalline plastic polyester at room temperature with high strength and flexibility.The PLA/PBAC blends were obtained by melt blending.Study indicated that the compatibility between PBAC and PLA is good.Besides,the addition of PBAC can highly improve the toughness of PLA.The elongation at break reached its maximum 196% with the addition of 30% PBAC.And,the impact strength dramatically increased to 10.1kJ/m2 with the content of 40% PBAC.Comparing the effect of PBC and PBAC on toughening PLA,the two key factors to achieve high toughness of PLA with non-planar ring contained polyester can be obtained.They are about the aggregate structure of polyesters and the compatibility between polyesters and PLA.To obtain PLA/PBAC blends with controllable tensile toughness and impact toughness,four types of PBACx with different ratios of cis/trans-CHDA were synthesized by controlling the configurations of the non-planar ring.With lower cis-CHDA content,PBACx is the semicrystalline plastic polyester.While with higher cis-CHDA content,PBACx is the amorphous polyester elastomer.But,all of them are flexible.The PLA/PBACx blends were obtained by melt blending.Study showed that plastic PBACx has better compatibility with PLA.Through the comparison of tensile toughness and impact toughness of blends,the regulation effects on the toughness of PLA with different stereostructure of non-planar ring contained polyesters are discussed.Combining the study of the influence on toughening PLA by the addition of non-planar ring contained polyesters with different structures and properties,and the different toughening mechanisms between tensile toughness and impact toughness,this work provides a novel method for optimizing of toughening PLA,and building biodegradeble PLA materials with high performance.