The Structural Design Of ACR And Research On Toughening Of PLA

Poly(lactic acid)or polylactide(PLA)is the most extensively researched and utilized biodegradable and renewable thermoplastic polyester,w ith potential to replace conventional petrochemical-basedpolymers.Unfortunately,PLA is a brittle material with only 2.6k J/m~2 of the impact strength,which has hindered the application and development of PLA.In order to better bring the effect of the practical value of PLA,it is necessary to modify PLA.That rubber blended with plastic is a common method to toughen PLA.Acrylic core-shell resin(ACR)is commonly used for toughening PLA.Its typical structure is a moderate crosslinking poly(butyl acrylate)(PBA)as the nuclear providing a degree of elasticity,and methyl methacrylate(PMMA)as the shell to help ACR disperse in matrix.In this paper,preformed ACR with controllable structure were synthesized.The influence of particle size,the content,mixed particle and structure of ACR on toughening PLA were investigated.The main research works and conclusions are as follows:1.Four core-shell acrylic copolymer(ACR)with different particle size,which the ratio of core and shell components of 75/25 and content of cross-linking agent of 5wt%are changeless,were synthesized by batch emulsion polymerization.The influence of particle size,the content and mixed particle of ACR on toughening PLA were investigated.The experimental results showed that small particle size and single particle size is more suitable for toughening poly lactic acid.The content of ACR is conducive to the toughening effect.When the dosage of ACR is 25wt%,the maximum impact strength of PLA/ACR blends can reach 43.7k J/m~2,which about 14times of pure PLA.SEM analysis showed that ACR debonding from PLA matrix under the external impact force leads to external cavitation and PIA matrix plastic deformation was the toughening mechanism for PLA/ACR blends.2.Five core-shell acrylic copolymer with different content of GMA(GACR),which the ratio of core and shell components of 75/25 and content of crosslinking agent of 5wt%are changeless,were synth esized by batch emulsion polymerization.The content of GACR is a constant of 20wt%.Then studied how the content of GMA effect on the toughening of PLA.The experimental results showed that The impact strength of the PLA/GACR blend is only 2-3 times higher than that of the pure PLA,while the impact strength of the PLA/ACR blend is about 11 times higher than that of the pure PLA.The introduction of GMA did not significantly improve the impact strength of PLA/ACR blends,and the impact strength of blends was not significantly changed by the change of grafting amount of GMA.It may be underwent crosslinking reaction in PLA.