Study On Functionalized Graphene Toughening PLA And The Related Mechanism

Polylactic acid(PLA),as a biodegradable,plant-derived and recyclable green polymer material,is indispensable in medical fields,daily disposables and electronic appliances,etc.However,due to its inherent brittleness,low crystallization rate,poor heat resistance and other issues,its application field is limited.Graphene are widely used to prepare high-performance PLA nanocomposites because of its high Young's modulus,great specific surface area,and two-dimensional layered structure.However,the related mechanism is still under investigation.Therefore,this subject proposes to design and prepare novel GO derivatives,and then to adjust its compatibility and the interaction with the PLA matrix,thereby realizing the improvement in mechanical properties and crystallization behavior,and thus contributing to revealing the toughening mechanism of the composite material.The research mainly includes the following two aspects:Preparation and characterization of alkylamine-modified-GO/PLA composites.The functional GO was prepared with different alkyl chain structures of 2-octyldodecylamine(ODDA),dodecylamine(DDA)and octadecylamine(ODA),and then was blended with PLA by the combination of solution blending and melt blending.The structures of all GO/PLA composite were characterized.The results show that ODDA-GO with the branch structure in the alkyl chain can effectively elevate the tensile toughness of PLA.Especially,at the loading of 0.3 wt% in ODDA-GO,the tensile toughness of PLA is increased by 4 times.Secondly,compared with pure PLA,its thermal stability and crystallinity property are also significantly improved.These results suggest that as a two-dimensional material,functional GO bearing swallowed tailed chains is able to interact with PLA molecules tightly,thus remarkably suppress the molecular slipping during the fracture.Preparation and characterization of functional GO/EBA-GMA/PLA composites.3-mercaptopropylethoxysilane was utilized to modify GO to form CSH-GO,and additionally elastomer-ethylene butyl acrylate was grafted to glycidyl methacrylate(EBA-GMA)as an interface compatibilizer to adjust interface interaction between PLA and CSH-GO.CSH-GO/EBA-GMA/PLA composite material was prepared by the combined solution-melt blending strategy.The results show that the ternary system composite material shows a toughening effect at a filler content of 0.2 wt% CSH-GO.Especially at the filler content of 0.4 wt% CSH-GO,the elongation at break of the composite material is increased by 3.2 times compared with pure PLA.This phenomenon was speculated to originate from the fact that EBA-GMA adjusts the compatibility between inorganic fillers and polymers through its three-dimensional crosslinking structure,which is consistent with the results from pinning effect.The above research provides new ideas for us to design new molecules and improve the dispersion characteristics of GO,and provides a new way to further clarify the mechanism of functionalized GO toughening PLA.In particular,the strategy of introducing EBA-GMA to adjust the compatibility of inorganic fillers with PLA has formed a three-dimensional cross-linked network in this system.On the one hand,it suppresses the stacking of CSH-GO sheets,on the other hand,it strengthens the interaction between each other,providing relevant theoretical basis for designing high-performance nanocomposites.