Preparation And Properties Of PLA Based 3D Printing Wood Plastic Composites

As 3D printing materials,polylactic acid(PLA)has been paid highly valued by academic researchers because of its fully biodegradable properties.At the same time,it also has some disadvantages such as high production cost,brittleness,poor heat resistance and poor tensile.Mixture of plant fiber and PLA can not only synthesize the advantages of both,but also make up for the deficiency of single material and realize the complementary advantages,so it has good practical value.However,there are still many deficiencies in the application of plant fiber/PLA wood-plastic composite in 3D printing at present.The main problem lies not only the limited kinds of PLA-based wood-plastic composites that can be used in 3D printing,but also in the application of the new composite materials in 3D printing is seldom studied.In order to solve these problems,the paper used bleached pulp fiber,mechanical pulp fiber,newspaper pulp fiber,eucalyptus powder,pine powder,lignin and other plant fibers as raw materials,silane coupling agent(KH550)and maleic anhydride grafted polylactic acid(PLA-g-MAH)was used as the compatilizer to prepare PLA-based wood-plastic composites which could be used for 3D printing.Firstly,the fiber was modified by KH550 before the preparation of wood-plastic composite material.Investigate the effects of different kinds and contents of modified plant fibers on the comprehensive performance of the composite.The results showed that the water absorption,apparent density and tensile strength of the composite were all improved with the increased of the fiber content,and the melt flow rate of the melt decreased as a whole.And the lignin/PLA composite had the best comprehensive properties under the same amount of fiber.What’s more,the lignin was used to strengthen PLA,and the results of SEM showed that the compatibility between lignin and PLA was the best when the content of lignin was15%.It can be seen from the DSC curve that lignin can improve the crystallinity of pure PLA,ameliorate the crystallization temperature of PLA,and promote the formation of a melting peak.When 15% lignin was added,the crystallization temperature of the composite was high at 102.36℃,which was 51.71% higher than that of pure PLA.Secondly,the PLA-based wood-plastic composite material with the lignin content of15% was prepared by using the KH550 and the PLA-g-MAH as compatibilizers.The results showed that the addition of the KH550 and the PLA-g-MAH can improve the properties of the composites such as water absorption,apparent density,tensile strength,melt flow rate andcompatibility.When 3% KH550 and 3% PLA-g-MAH worked together,the distribution of lignin was uniform and the comprehensive performance of the composite was the best.At last,the prepared lignin/PLA wood-plastic composite material with the best comprehensive performance was used for 3D printing,which showed a good printing effect.The effects of filling rate,layer thickness and printing temperature on the mechanics properties of new material were investigated by orthogonal experiment.Through the combination of intuitionistic analysis,range analysis and variance analysis,it was found that the influence of filling rate on the performance of the mechanical properties was great,the thickness of the layer was the next,and the printing temperature had little effect on it.It was also determined that the optimal combination of 3D printing process parameters of the new material was 80% filling rate,0.3mm layer thickness and 200℃ printing temperature,which solved the problem of the selection of process parameters in the printing process of new composite materials.