Toughening Modification Of PLA

In today’s world,the harm caused by petroleum products and their wastes is often ignored by people and has caused a lot of social problems,such as the abuse of petroleum resources,environmental pollution and global warming,which have begun to affect People’s Daily life.With the continuous attention to environmental problems and sustainable development,the importance of developing renewable resources has become increasingly prominent.Polylactic acid(PLA)is a new kind of biodegradable polymer,which shows a broad prospect in various fields,but its hard and brittle characteristics limit its wider application.In view of the poor toughness of PLA,the melt blending method was chosen to modify PLA.The main research contents and conclusions of this paper are as follows:(1)We synthesized poly(butylene succinate-co-butylene 2,5-thiophenedicarbo-xylate)(PBSTF25)and prepared PLA/PBSTF25 blends by melt blending with PLA.Since PBSTF25 has been reported in the literature as a potential bio-based and biodegradable polyester and has excellent ductility.Here,we examined the effect of PBSTF25 on various properties of PLA.The results of differential scanning calorimetry(DSC)analysis showed that PBSTF25 promoted the cold crystallization of PLA.Wide-angle X-ray diffraction(XRD)results showed that PBSTF25 underwent stretch-induced crystallization during the stretching process.Scanning electron microscopy(SEM)showed that the fracture surface of PLA was smooth,but the fracture surface of the blends was rough.PBSTF25 improved the ductility and processability of PLA.When PBSTF25 was added at 20 wt%,the tensile strength was 42.5 MPa and the elongation at break was 156.6%,which was about19 times that of PLA.The toughening effect of PBSTF25 was better than that of PBS reported in the literature.(2)We synthesized poly(pentylene furanyl dicarboxylate)(PPe F)and prepared PLA/PPe F blends by melt blending with PLA.The excellent toughness,degradability and barrier properties of PPe F have been reported in the literature.The effects of the PPe F content on the thermal,crystalline,mechanical,and rheological properties of the blends were investigated.The test results of thermal properties showed that the addition of PPe F did not adversely affect the thermal stability of PLA,and the cold crystallization of PLA was suppressed.From SEM plots,it can be seen that after the addition of PPe F,PLA changed from typical brittle fracture to ductile fracture,but the compatibility between PPe F and PLA was poor.From the tensile results,it can be seen that the elongation at break of the blend has reached160% when the addition of PPe F reaches 20 wt%,and the tensile toughness has been well improved.(3)We synthesized poly(butylene adipate?co?butylene furandicarboxylate)(PBAF70)and prepared PLA/PBAF70 blends by melt blending with PLA.The thermal,crystalline,mechanical and rheological properties of the blends were characterized.The results showed that the elongation at break was 222% when the addition of PBAF70 was increased to 30 wt%,indicating that PBAF70 increased the ductility of PLA.Meanwhile,the XRD results showed that PBAF70 underwent stretch-induced crystallization during the stretching process.The strong electronegative oxygen atoms on the furan ring may increase the interaction and compatibility of PBAF70 with PLA.Therefore,the glass transition temperature of PBAF70 was not obvious on the DSC curves of the blends.The rheological results showed that the complex viscosity of the blends was greater than that of PLA.due to the addition of PBAF70,the addition of PBAF70 hindered the cold crystallization of PLA.From SEM,it can be seen that the cross section of the blends is rough.The elongation at break of PLA/PBAF70 was better than PLA/PBAT when the amount of PBAF70 was the same as the amount of polybutylene terephthalate-adipate(PBAT)in other literature.