Study On Preparation And Properties Of Poly(Lactic Acid)/Wood Flour Composites Modified With Cyanuric Chloride-Oil-based Amine

Wood flour is a kind of renewable biomass and poly(lactic acid)(PLA)is a kind of green polymer material.The preparation of composites with wood flour and PLA have good environmental and economic benefits.However,PLA/wood flour composites have some problems,such as poor compatibility,melt flow difficulty and greater brittleness,which have become the problems the research and application of PLA/wood flour composite will have to revisit.In this article,raw poplar wood flour(RWF)was modified with cyanuric chloride(2,4,6-Trichloro-1,3,5-triazine,TCT),and the modified wood flour(TWF)and Oil-based amine compounds were used to prepare composites with the high reactivity between TCT and amine compounds.TWF and oleyl amine(OAM)were used to prepare compatibilization composites by solution grafting and reactive extrusion,respectively.Poly(ethylene imine)(PEI)and castor oil(CO)were used to prepare CO-based polymeric amine(PC)by aminolysis reaction.PLA/TWF/PC composites which had good effects of compatibilization,toughening and plasticization were prepared by reactive extrusion.RWF was modified with TCT which depends on gradient temperature of reactivity.The modified wood flour(TWF)was attached active chlorine on the surface of RWF.FT-IR spectra indicated that triazine structure of TCT was attached on RWF.Elemental analysis and titration analysis measured the increment of nitrogen and chlorine.TWF-grafted-OAM(TWF-g-OAM)was prepared with the grafting reaction between OAM and TWF in solvent.FT-IR spectra indicated that the surface of TWF-g-OAM had a structure of long-chain alkyl of OAM.PLA/TWF-g-OAM composites presented better mechanical strength than PLA/TWF composites which revealed the good compatibility between TWF-g-OAM and PLA.Melt flow property test showed PLA/TWF-g-OAM composites had lower melt mass-flow rate(MFR)than PLA/RWF composites and PLA/TWF composites.Contact angle test indicated the grafting between OAM and TWF was good for surface hydrophobic property of the composites.TWF and OAM were used to prepare composites with poly(lactic acid)by reactive extrusion.FT-IR spectra indicated that OAM was grafted onto TWF in the progress of reactive extrusion.PLA/TWF/OAM composites presented better tensile strength and flexural strength than PLA/RWF/OAM composites under the same dosage of OAM,which revealed the compounding system of TWF and OAM improved the compatibility between PLA and wood flour.PLA/TWF/OAM composites had a greater melt flow rate than PLA/TWF composites under the same dosage of wood flour,which indicated the processability of composites was improved.DMA and DSC showed that PLA/TWF/OAM composites had a higher glass transition temperature than PLA/RWF/OAM composites under the same dosage of OAM.In the test of hydrophobic property,PLA/TWF/OAM composites had higher contact angle towards water than PLA/TWF/OAM composites under the same dosage of OAM,and the value had a significant increase comparing with PLA/TWF composites and PLA/RWF composites.PEI and CO were used to prepare PC by aminolysis reaction which was confirmed by FTIR analysis.PLA/wood flour composites were modified by PC.The mechanical properties,melt flow property and hydrophobic property of modified composites were compared with composites modified by CO,epoxidized soybean oil(ESO),di-n-octylo-phthalate(DOP)and polycaprolactone(PCL),respectively.The composites modified by PC-8 had better mechanical properties than the composites with other modifiers.The composites modified by PC-8 had higher MFR and lower torque of blend melt than composites with other modifiers,which mean that the composites had better processability.The composites modified by PC-8 had a significant increase of contact angle towards water,which indicated the modified composites had good surface hydrophobic property.TWF and PC were used to prepare composites with poly(lactic acid)by reactive extrusion.FT-IR spectra indicated that PC was grafted onto TWF in the progress of reactive extrusion.PLA/TWF/PC composites had better integrate mechanical properties and hydrophobic property than PLA/RWF/PC composites,while PLA/TWF/PC composites had lower MFR than the latter.DMA showed the composites modified by PC had lower storage modulus at glass state than composites without modifiers.Under the same content of PC-8,PLA/TWF/PC-8 composites had higher storage modulus than PLA/RWF/PC-8 composites.With the increase content of PC-8 in the composites,storage modulus decreased and tan ? increased,which mean the increase of internal friction and the improvement of toughness.DSC showed glass transition temperature and melting temperature all decreased with the addition of PC-8.