Phase Morphology And Mechanism Of The Synergy Of Nanoparticles And Reactive Compatibilization On Strengthening And Toughening PLA/PBAT Immiscible Blend

Polylactic acid(PLA)is a renewable biodegradable polyester material with excellent mechanical properties and biocompatibility,making it the best substitute for traditional petroleum-based polymer materials.However,the poor ductility and low impact strength of PLA limited its application and development.Reactive blending mainly adds a chain extender and a crosslinking agent to react the functional groups on the molecular chains with these agents to form a branched copolymer enhancing interfacial adhesion and improving compatibility,which is an effective strategy to greatly improve the toughness of PLA materials.In this paper,a biodegradable poly(butylene adipate-co-terephthalate)(PBAT)with excellent flexibility was selected to toughen PLA,and reactive blending was initiated by using a multifunctional epoxy oligomer(ADR)as a reactive compatibilizer to improve the interface compatibility of PLA/PBAT blending system to improve the toughness of the blends.During the blending process,the epoxy group of ADR can react with the terminal carboxyl group and/or hydroxyl group of the PLA and PBAT chains to generate PLA-g-PBAT branched copolymer,which improves the compatibility,melt strength and viscoelasticity of the system.The interface adhesion of the PLA/PBAT blend was enhanced by in-situ compatibilization,and the phase morphology of changed from a"sea-island"structure to a bi-continuous structure,which was beneficial to the energy dissipation of the material during the stress process.The impact strength and elongation at break of PLA/PBAT(60/40)blends reached 15.3 kJ/m~2 and 421.2%,and the tensile strength decreased to 33.2 MPa.The phase morphology of PLA/PBAT blending system was adjusted and toughened by the in situ reactive blending.In order to increase the compatibilization efficiency,carboxylated multi-walled carbon nanotubes(CNTs)were introduced to undergo ring-opening reactions with ADR,PLA,and PBAT molecular chains and generate PLA-g-PBAT branched copolymers based on CNTs.The branched copolymers tend to disperse at the interface of PLA/PBAT due to thermomechanical effect,which improves the melt strength and viscoelasticity of the system.The blend after compatibilization obtains stronger interfacial layer strength,further enhancing interfacial adhesion to improve compatibilization efficiency and energy dissipation during stress;The connected CNTs by ADR induced the uninvolved CNTs to form a NPs-NPs network in the continuous phase PBAT,which hindered the development and diffusion of cracks.The strong synergistic enhancement and toughening effect of the two types of CNTs with different dispersion was verified by quantitative characterization of the synergy effect(the synergy efficiency reached 3.05).The impact strength and elongation at break of the material reach 35.3 kJ/m~2 and 498%,which were 15.5 times and 38.0 times higher than that of neat PLA while the tensile strength is increased to 42.8 MPa.The compatibilizing efficiency of the reactive blend in the PLA/PBAT blend was improved,and the synergistic enhancement and toughening effect of nanoparticle/reactive compatibilization was realized.