Study On Pla Toughened By Polyethylene Glycol-polydimethylsiloxane

The continuous growth of plastic consumption has caused increasingly serious environmental pollution.While people are consuming a lot of petroleum resources,they are also looking for biodegradable plastics that can replace petroleum based materials.Polylactic acid(PLA)is one of them.PLA is a kind of polyester made from renewable natural plants through chemical synthesis.It has great application potential in food packaging,agricultural construction,biomedicine and other fields.However,PLA has some limitations in industrial processing and application due to its brittleness,poor toughness and slow crystallization speed.Therefore,the study of toughening modification of PLA is of great significance.In this paper,polyethylene glycol polydimethylsiloxane copolymer(PEG-PDMS)was used as a toughening agent to toughen PLA.Furthermore,hexamethylene diisocyanate(HDI)was used as reactive blending compatibilizer.The effect of HDI on the toughening of PLA/PEG-PDMS was studied.Use silane coupling agent KH550 to modify halloysite nanotubes(HNTs),cooperate with PEG-PDMS to toughen and strengthen PLA.Explore the toughening modification effect and draw the following conclusions:PLA/PEG-PDMS composites were prepared by melt blending.The effects of PEG-PDMS content on the mechanical properties and thermal stability of the composites were studied.The results show that PEG-PDMS improves the toughness of PLA.When the content of PEG-PDMS was 10%(mass fraction,the same below),the elongation at break of PLA/PEG-PDMS composites reached 106%,17 times that of pure PLA.XRD and DSC results showed that the crystallinity of PLA was enhanced,and the crystallinity of PLA/20%PEG-PDMS composites was 10.4% higher than that of pure PLA.Rheological tests show that PLA/PEG-PDMS is a shear thinning fluid,and the storage modulus(G)and complex viscosity of PLA/PEG-PDMS composites(η*)are directly proportional to the load of PEG-PDMS.In addition,the transmittance of PLA/10%PEG-PDMS is 76.7%.PLA/10%PEG-PDMS composites with good toughness was selected as the research object,and hexamethylene diisocyanate(HDI)was used as the reactive blending modifier to modify the PLA/10%PEG-PDMS system.The results showed that the addition of HDI made the PLA/PEG-PDMS system react and cross link.With the increase of HDI content,the breaking strength and Young’s modulus of the compatibilizer system increase.When loading 1wt%HDI,the breaking elongation of the compatibilizer system reaches 126%,which is 21 times that of pure PLA.The initial decomposition temperature of the compatibilized system was increased by 2-6℃,and the thermal stability of the system was improved.The interface of the two phases tends to be fuzzy and the compatibility increases.The halloysite nanotubes(HNTs)were grafted with silane coupling agent KH550.PLA/PEG-PDMS/K-HNTs composites were prepared by melt blending.The results showed that the tensile strength of the composites containing 3%K-HNTs nano filler was 8% higher than that of the composites without nano filler(PLA/10%PEG-PDMS),reaching 42 MPa.The crystallinity of PLA/PEG-PDMS/5%K-HNTs composites was 36.1%.At the same time,the thermal stability is improved.The barrier performance of ultraviolet and visible light is also improved.