Preparation,characterization And Properties Of Cellulose And Lignin Biomass-based Reinforced Polylactic Acid 3D Printing Materials

With the development of energy industry and the attention paid to environmental problems in various countries,Due to rich content and renewability biomass reinforced composites have attracted more and more attention for researchers,Natural cellulose and lignin are the two most abundant natural polymers in nature.As biomass materials,cellulose and lignin are in line with the social trend of green development.3D printing is one of the main drivers of innovation in smart manufacturing technologies,development of 3D printing technology is a great achievement in fabrication industry in recent years.It shows great potential in many fields such as food,daily commodity,medical instruments,electronic components and industrial apparatuses due to it can used to fabricate materials to various shapes.It can be said that the application of biomass materials in the field of 3D printing is also one of the development trends in the future.In this paper,polylactic acid(PLA)was used as the matrix of 3D printing materials.Microcrystalline cellulose(MCC)and lignin reinforced PLA composite 3D printing materials were prepared by melt blending extrusion and 3D printing technology.The mechanical properties of the 3D printing products of the composites were tested,and the micro-morphology of the frozen fracture surface of the composite wire was observed by scanning electron microscopy(SEM).Thermal properties of composite 3D printing materials were also analyzed by thermogravimetric analysis(TG)and differential scanning calorimetry(DSC).In order to further increase the cellulose reinforcing 3D printing materials and lignin reinforcing 3D printing materials,silane coupling agent and nano cellulose were used to modify it to form nano cellulose/microcrystalline cellulose(NCMC)and lignin/microcrystalline cellulose(LMC).High performance 3D printing materials were prepared via NCMC and LMC.The main research contents and results are as follows:(1)The compatibility between MCC and polylactic acid is weak lead to a small amount of MCC will affect the arrangement of PLA polymer chains and destroy the regularity of internal structure,resulting in a decline in performance.Excess microcrystalline cellulose is easy to agglomerate,which also destroys the regularity of the internal structure of PLA.When the ratio of MCC to total mass is 3%,the appearance and properties of the material are better.Generally speaking,the addition of MCC with high molecular rigidity decreases the mechanical properties and thermal stability of the 3D printing materials.At the same time,the nozzle of 3D printer is easily blocked during the process of 3D printing,and the printing products also have warping and expansion.Unmodified microcrystalline cellulose is not suitable for reinforcing PLA 3D printing materials.(2)Lignin has good compatibility with PLA,excessive lignin is easy to agglomerate lead to a large number of defects within the material,which result in a decline in the performance of the corresponding material.When the ratio of lignin to lignin is 2%,the mechanical properties of 3D printing materials are the best.Unmodified lignin decreases the elasticity of materials,and other highly active groups in lignin also lead to poor thermal stability.Lignin/PLA 3D printing materials have high gloss,but high lignin viscosity will affect the printing accuracy of 3D printing,which is not conducive to continuous production.(3)Different NCMC were prepared and their special surface morphology was observed by SEM,it was found that NCMC was cellulose with towards hierarchical structure.The functional groups of the composite were measured by infrared spectroscopy(IR),and the relative crystallinity of the composite was measured by X-ray diffraction(XRD).It is also found that the NCMC prepared by different methods have great differences.The properties of PLA 3D printing for reinforced by different acid,silane coupling agent and different quantity of nano cellulose treated NCMC were studied.It was found that a very small amount(0.5% of the mass)of the composite can significantly improve the printing performance of the material,and significantly improve the printing accuracy and appearance of the finished product.The tensile strengthand flexural strength of 3D printing materials can be increased by 40% and98%,respectively.The elongation at break also increased to more than 10%.Observing its 3D printing process,it was found that there was no blocking phenomenon in the continuous printing process,which indicated that NCMC/PLA can act as ideal 3D printing materials.(4)The functional groups and dissolution experiments of LMC showed that it was stable compound.In order to compare the effect of the composite on reinforcing PLA,lignin/MCC/PLA for 3D printing with the same proportion of lignin,MCC and PLA were prepared,it was found that the mechanical properties of PLA reinforced by LMC were better.The thermal stability of the composites decreases due to the presence of active groups.LMC can effectively reduce the glass transition temperature and improve the crystallinity of PLA,the presence of LMC can make the crystallinity of PLA reach 46.60%.Lignin/MCC/PLA for 3D printing has a high gloss,and appearance is similar to that of lignin/PLA 3D printing materials.LMC reinforced PLA for 3D printing has greasy gloss,hard texture,good toughness,repeated bending is not easy to break;the printed product has a strong woodiness,is a better 3D printing material.