Preparation And Compatibilization Modification Of Poly(Lactic Acid)Blends Toughened By Polycaprola Ctone And Thermoplastic Polyester Elastomer

PLA,a linear aliphatic thermoplastic polyester with good biodegradability,biocompatibility,high strength and modulus,can be manufactured by a ring-opening polymerization of a monomer(lactic acid)derived from renewable resources such as starch or sugarcanes.PLA is used not only in medicine and tissue engineering,but also in manufacturing of everyday items such as food packaging,flatware or bottles.However,its inherent brittleness limits significantly the applications of PLA materials.POM,as a non-reactive compatibilizer,is used to improve the compatibility of the PLA/PCL blends.ADR,as a reactive compatibilizer,is used to in-situ compatibilize the PLA/TPEE blends,and the compatibilization effect of adr was further studied by changing the loading of ADR and the way of adding ADR.In addition,the improvement of the heat resistance was studied by means of annealing.In this experiment,the PLA blends with good toughness were prepared by two different compatibilization methods,which is PLA/PCL/POM,PLA/TPEE/ADR(one-step method,two-step method)blends,respectively.The main contents are as follows:(1)The PLA/PCL blends were prepared through melt blending and compatibilized using POM resin.Characterizations by tensile testing,SEM,FTIR,DSC,and WAXD were performed to understand the relationship between micro and macroscopic properties of the PLA/PCL blends with and without POM.It is found that the tensile ductility of the blends significantly improves with POM loadings.Compared with the PLA/PCL/POM(80:20:x)samples,the PLA/PCL/POM(70:30:x)samples show a better tensile ductility.The SEM observations indicate that the average size of PCL domains decreases and the interfacial adhesion within the blends increases with the incorporation of POM.The incorporation of POM significantly improves the PLA/PCL interface compatibility due to the hydrogen bonding interaction between POM macromolecules and PLA/PCL macromolecules.In addition,the nonisothermal and isothermal crystallization behaviors of PLA/PCL/POM(70:30:x)samples were investigated by using DSC and WAXD measurements.The results indicate that the crystallization dynamic of PLA matrix increases with POM loadings.It can be attributed to the fact that POM crystals have a nucleating effect on PLA.The optimal Tc leading to a minimized ti/2 is 100? for all the PLA/PCL samples regardless of POM loadings.While Tc is 100 ?,t1/2 reduces from 9,4 min to 2.0 min with increasing POM loading from zero to 3 phr.(2)Effects of the loading of ADR and the way of adding ADR on rheological properties, crystallization behaviors,microstructure,tensile properties and heat resistance of the PLA/TPEE/ADR(one-step method,two-step method)blends was studied by MFR,DSC,SEM,VST,WAXD.The chain-extending reaction between PLA,TPEE and ADR with one-step method and two-step method was studied by the torque and MFR resules.And the the compatibilization mechanism of one-step method and two-step method was proposed.In the one-step method,the multi-epoxy group on the ADR dispersed in the blends can react with the terminal carboxyl group and hydroxyl group of the PLA,PCL.The in situ of the macromolecule PLA-ADR-TPEE can improve the compatibilization of the PLA/TPEE blends.In the two-step method,TPEE and ADR were melt blended firstly to prepare the TPEE-ADR preepoxided,then it were blended with PLA.By this way,PLA-ADR-TPEE was produced more at the phase interfaces of the PLA and TPEE.The compatibilization effect was further improved.It was also proved that the viscosity of the blends could be significantly increased with the addition of adr,and the viscosity of the two-step blend was lower than that of the one-step method at the late stage of reaction.The crystallization and melting behavior were studied by the DSC.It was proved that the viscosity influenced by the loading of ADR and the way of adding ADR affects further the crystallization behavior.With the viscosity increases,the random chain segments of PLA in the blends were easily arranged to form the primary crystal nuclei.The growth of PLA crystal was restricted and the crystallization rate of the PLA was reduced because the poor mobility of PLA molecular chain and the kinetic hindrance of viscosity.The heat resistance(VST)improves with the increase of the crystallinity of the samples.Improve the crystallinity of the materials by annealing and study the changes of mechanical properties,micromorphology,heat resistance and crystal structure of PLA/TPEE/ADR blends prepared by one-step method and two-step method annealing at 90? for 30min.The results show that the sample prepared by two-step method has better compatibilization and refinement effect.The samples with high crystallinity still maintain good tensile toughness(elongation at tensile break 282.45%,and high VST of 160?).It is also proved that the addition of ADR and the way of adding ADR to the PLA matrix did not change the crystal shape and grain size.