Study On Preparation And Properties Of Biodegradable Poly(Butylene Adipate-co-terephthalate) Nanocomposites

Plastics have been widely adopted into humans'lifestyles,but their inability to biodegrade will leave the plastic waste accumulating in nature,causing a devastated"white pollution" crisis.Using biodegradable polymer as an alternative material is a critical remedy to alleviate the situation.Poly(butylene adipate-co-terephthalate)(PBAT)has excellent biodegradability but low crystallinity and intermediate mechanical strength,significantly limiting its wide application.As such,focusing solely on the mechanical properties of PBAT,we developed a series of PBAT composite by different approaches involving either surface modified nanofillers or via in-situ copolymerization.The strategy employed includes the incorporation of nanofillers such as organically modified nanosilica(SiO2),SiO2 and surface-functionalized cellulose nanofiber(CNF)with covalently interaction,and in-situ copolymerization to graft cellulose nanocrystalline(CNC)onto PBAT.The obtained composite films were observed with good nanofillers dispersion and characterized with improved mechanical properties.Meanwhile,the incorporation of double-ring structured biomass monomer enhanced its compatibility with PBAT chain and increased PBAT's mechanical properties.Also,2,3:4,5-diisopropylidene-galactitol(Galx)monomer was prepared and copolymerized with PBAT to synthesis copolyester(PBGAT),which was later used as a compatibilizer for PBAT and xylan(Xln).The main conclusions are shown below:(1)The epoxy-modified SiO2(SiO2-EO)is well compatible with PBAT.The blown film with 1 wt.%SiO2-EO showed an increase in Young's modulus,tensile strength,and elongation at break by 94%,75%,and 65%,respectively,when compared to neat PBAT film.(2)Uniform dispersion of amino-modified CNF(CNF-NH2)within PBAT was assisted by SiO2-EO.A simultaneous enhancement in both strength and toughness for PBAT was attributed to the filler network,formed by covalent interaction between the surface functional group of the two homogeneously dispersed fillers.(3)CNC/PBAT nanocomposites(PfgCNC)were prepared by in-situ copolymerization.Compared with pure PBAT film,the film containing 0.02 wt%CNC shown a concurrent increase in Young's modulus,tensile strength,elongation at break,and toughness by 26%,27%,37%,and 56%.(4)PBGAT copolyester was synthesized with biomass monomer Galx through separate esterification and co-polycondensation.The introduction of 1-4 wt%Galx in PBGAT improves the mechanical properties and hydrolysis rate of PBAT.(5)PBGAT with branch structure is used to improve the compatibility of PBAT and Xln biomass.The film containing 3 wt%Xln and 1 wt%PB95G5AT demonstrated a synergistic increase in Young's modulus,tensile strength,and elongation at break by 17%,35%,and 13%,respectively.The main innovations are as follow:(1)Nanoparticles of good compatibility with PBAT can act as a compatibilizer to modify the dispersion of incompatible nanoparticles through their synergistic chemical reaction,promoting homogeneous distribution and achieving simultaneous strengthening and toughening of PBAT.(2)Grafting PBAT with CNC via in-situ copolymerization renders its composite with a superior strengthening effect,even at a very low dosage of CNC.(3)Mechanical properties and hydrolysis of PBAT can be improved by incorporating biomass monomers with a double ring structure,enhancing the compatibility between PBAT and hemicellulose,thereby expanding biomass application in PBAT.