Functionalization Of Green Elastomer And Its Application In The Modification Of Polylactic Acid

In recent years,with the attention of the international community to issues such as the energy crisis,ecological environment deterioration,the development and utilization of sustainable polymers are gradually attracting attention.Eco-environmental polymer has become a hotspot in the field of polymer science because of its advantages of low environmental load.As an important branch of ecological environment polymer,the development of bio-based elastomer is conducive to alleviating or solving the current environmental crisis.Therefore,the development of recyclable elastomers with high added value,such as commercial and renewable epoxy natural rubber(ENR)and chloroether rubber(ECO),has important practical significance.At present,self-healing materials represented by ionomers or polyionic liquids have received extensive attention.At the same time,it is a cost-effective method to construct efficient self-healing materials based on commercialized elastomers.Therefore,by combining the high-efficiency self-repairing efficiency of ionic groups and the low cost of ENR,the introduction of imidazole,hydroxyl and other functional groups into ENR is expected to prepare cost-effective new bio-based self-repairing materials,thereby prolonging the service life of rubber products,and expand its wide application in the fields of electronics and aerospace.In addition,some commercial elastomers,such as bromobutyl rubber,natural rubber,chloroether rubber,etc.,are also widely used in the toughening modification of brittle polylactic acid(PLA).However,PLA has poor compatibility with most elastomers,which largely limits the toughening effect of elastomers.Therefore,the graft modification of the elastomer can be used to improve the interface bonding between the toughening phase and the PLA matrix,thereby improving the mechanical properties of PLA and broadening its application range.This thesis focuses on the post-chemical treatment of bio-based elastomers to broaden its application in self-healing materials and PLA blending modification.The main research results are as follows:1.Using 1-ethylimidazole,1-butylimidazole and newly designed synthetic 1-octylimidazole and 1-dodecylimidazole as reactive monomers,through the ring-opening reaction of bromoacetic acid with ENR25 and subsequent reaction with imidazole monomers,a series of new bio-based ionomers with excellent self-repair properties were synthesized by quaternization reaction,and their structure and performance were characterized in detail.The effects of imidazole group content and alkyl chain length on the mechanical properties and self-healing efficiency of the self-healing materials were systematically studied.2.Through the ATRP polymerization method,we prepared a series of ECO-g-PMMA copolymers with different grafting ratios,and studied the reaction time(5 h,10h,20 h)to the molecular weight and mechanical properties of the graft copolymer.At the same time,the influence of the graft copolymer on the mechanical properties,compatibility and phase morphology of PLA was also deeply explored.The results showed that when the reaction time is 10 h,the graft copolymer can obtain the best elasticity and graft efficiency,and it can become the best toughening modifier for PLA.In the PLA/ECO-g-PMMA binary blend,due to the rigidity of the PMMA side chain in ECO-g-PMMA and good compatibility with PLA,when the addition amount is only 5wt%,PLA based material with high strength and high tensile toughness can be obtained:tensile strength up to 60 MPa,elongation at break up to 251%.3.Aiming at the poor impact strength of the PLA/ECO-g-PMMA binary blend,we designed ECO as the toughening agent and ECO-g-PMMA as the compatibilizer to synergistically improve the impact toughness of PLA.The results of the study show that ECO-g-PMMA is an efficient compatibilizer for PLA/ECO blends.When the addition amount is 15 wt%,the material can obtain the best mechanical properties,and the elongation at break and impact strength can reach 285%and 96.9 k J/m~2,repectively,which makes up for the lack of impact toughness of binary blends.The characterization of rheology,SEM,and TEM reveals the toughening mechanism of the excellent mechanical properties of the blend:the graft copolymer can be accurately distributed at the PLA/ECO phase interface,so that the sea-island structure of the blend is transformed into a quasi-continuous.It can not only improve the compatibility,but also hinder the premature development of microcracks during the stress loading,thereby absorbing a large amount of energy and obtaining higher impact strength.