Preparation Of Biodegradable Elastomer And Study On Toughening Plastics

The extensive use of traditional non-degradable plastics has caused serious“white pollution”.In order to solve this knotty problem,the use of biodegradable materials is one of the effective ways to solve this problem.Traditional thermoplastic polyester elastomer（TPEE）has the characteristics of thermoplastic processing of plastic and high elasticity and toughness of rubber.It has been widely used in many fields,but it still has the disadvantages of poor biodegradability,low tensile strength and tensile recovery.Biodegradable plastics such as polylactic acid（PLA）and polyglycolic acid（PGA）have good mechanical properties and biodegradability.However,the poor toughness of PLA and PGA limits their further application.To solve these problems,a biodegradable thermoplastic polyester elastomer（PBATE）with excellent mechanical properties was synthesized by condensation polymerization,and the effects of monomer ratio on the mechanical,crystalline and thermal properties of PBATE were investigated.Furthermore,PLA and PGA were toughened by PBATE to prepare blends with excellent comprehensive properties.This study is carried out mainly from the following three aspects,and the specific contents are as follows:1.A biodegradable thermoplastic polyester elastomer（PBATE）was synthesized by transesterification and melt polycondensation with terephthalic acid,adipic acid,butanediol and ethylene glycol as reaction monomers,and the effect of the molar ratio of terephthalic acid to adipic acid on the properties of the material was investigated.The studies of FTIR and¹H NMR showed that the polyester elastomer PBATE was successfully synthesized.The results of acid value test and GPC test showed that the conditions of high temperature and high vacuum were conducive to the increase of PBATE molecular weight and the decrease of acid value.The mechanical property results showed that the maximum tensile strength of PBATE was 31 MPa,the elongation at break was 1186%,and the low strain tensile（100%、200%、300%）showed high recovery performance.XRD and DSC tests showed that PBATE had weak crystallinity,and the maximum crystallinity was 5.7%.The thermal performance study found that PBATE had excellent thermal stability,and the thermal decomposition temperature(T_5%)exceeded 380℃.The degradation test results showed that the degradation rate of PBATE decreased the fastest under alkaline conditions,and the mass loss rate of samples in 3 months under composting conditions exceeded 65%.In conclusion,PBATE was a thermoplastic polyester elastomer with excellent mechanical properties and rapid biodegradation rate.2.The polyester elastomer PBATE was used to toughen PLA.The results showed that the elongation at break of pure PLA was only 7.9%and the impact strength was 3.1 k J/m².When the content of PBATE was 20 wt%,the elongation at break of PLA/PBATE blend reached 510%and the impact strength exceeded 52 k J/m².It could be seen that the addition of PBATE greatly improved the toughness of PLA.SEM and TGA test showed that PLA and PBATE had good compatibility,which was conducive to the improvement of thermal stability of PLA/PBATE blends.DSC test showed that the addition of a small amount of PBATE was conducive to the crystallization of PLA.Using 2 wt%compatibilizer ADR4370s and adding10 wt%PBATE,the toughness of PLA/PBATE/ADR4370s blends was greatly improved,the tensile strength reached 55 MPa,the elongation at break reached 427%,and the thermal decomposition temperature(T_5%)was also increased to 360℃.In conclusion,the addition of PBATE improved the brittleness of PLA and endowed PLA with high toughness.3.PBATE was used to improve the poor toughness and thermal stability of PGA.Under the condition of adding 2 wt%ADR4370s and 30 wt%PBATE,the elongation at break of PGA/PBATE blends was 41%,and the impact strength also reached 19 k J/m² by using the two-step processing method.Compared with pure PGA,the toughness was significantly improved,and the tensile strength exceeded 40 MPa,which still maintained a high level.Meanwhile,the T_5%of PGA increased by more than 50℃,and the thermal stability was further improved.DSC and SEM results showed that reactive compatibilization enhanced the interfacial adhesion between PGA and PBATE and decreased the crystallinity of PGA.Different reaction types of compatibilizers such as dicumyl peroxide（DCP）,4,4-methylene diphenyl isocyanate（MDI）,1,6-hexanediol diglycidyl ether（HDE）,oxazoline and phthalic anhydride complex compatibilizer（BOZ-PA）were used to compatibilize PGA/PBATE blends.It was found that MDI had an obvious effect on improving the mechanical properties and thermal stability of PGA/PBATE blends.