Research On Interfacial Properties Modification Of Wood Flour/PLA Composites

With the requirement of sustainable de velop ment of soc iety and the improvement of environmental protection conscious ness,the green envi ronmental protection compo site has gain more and more attention because of its low price,biodegradable,easy recovery and so on.But owing to its own characteristics,the nature fiber as the reinforcement material has poor dispersion in the matrix resin and easy to agglomerate,which makes the interface compatibility of the composites is poor.Aiming at the above problems,the poplar wood flour was chosen as the filling materials to study the preparation and interfacial mod ification of po ly?lactic acid?composites.In this paper,WF was pretreated by sodium hydroxide,titanate coupling agent and grafted monomer methyl methacrylate?MA?and PLA was pretreated with po lyethylene glycol?PEG?in order to change the surface properties of WF and increase the surface polarity of matrix resin,thereby reducing the repulsion between polar WF and weakly polar PLA and improving the interface compatibility.Through the test of contact angle,XRD,IR,further characterize the performance of the mod ified fiber and matrix.It was opt imized by orthogonal test to study on the various properties of PLA composites through the single factor experiment such as the alkali concentration,content of titanate,MA,BPO and PEG,which included the mechanical properties,crystallinity,fluidity,water resistance and thermal stability.The results ind icated that:alka li treatment decreased the content of cellulose and improved the crystallinity and thermal stability of WF.With the increase of the concentration of NaOH,the mechanical properites,fluidity,thermal stability and water resistance of PLA compos ites were improved significantly.And the op timum processing of alka li treatment at concentration of NaOH 3%were obtained.Based on alkali pretreatment,the addition of titanate coupling agent further improved the properties of composites.Taking into account the effect of coupling agent modification was not good,the changes of properties after grafting mod ification on the compos ites was further studied.When the dos age of monomer MA was3phr and initiator BPO was 0.8phr,the mechanical strength of composites increased most while the interface compatibility was good and no visible fiber and holes were observed in the cross section.Addition of plasticizer PEG reduced the glass transition temperature?T_g?and surface free energy of PLA system,and improved the mechanical strength,water resistance and thermal stability of WF/PLA compo sites to some extent.The formula of WF/PLA compos ites was further studied by or thogonal experimentation,an or thogonal test table L₉?3⁴?was used with the factors of alkali concentration,content of MA and PEG.The mechanical properties were determined by experimentation.When the ratio was NaOH concentration 5%,MA 2%,PEG2000 1%,WF/PLA composites have the best integrated performance through the orthogonal ana lysis of the inde x.