Preparation And Properties Of Poplar Powder/PLA Composites For FDM

Poplar powder/poly-lactic acid(PLA)composite is a new kind of degradable environmentally friendly materials.In recent years,fused deposition modeling(FDM)technology has been popularized and developed rapidly in China as a kind of additive manufacturing technologies.On the basis of related researches all over the world on wood powder/PLA composites,the preparation of poplar powder/PLA composites for FDM was proposed.The rheological behavior,crystallization,impact strength and the printing parameter of the composite were studied and discussed.The main contents are as follows:(1)Determining the optimal ratio of raw materials and the extrusion temperature by investigating the effect of raw material content and temperature on torque rheology.The orthogonal test was carried out with five levels of three factors:poplar powder content,toughening agent content,and lubricant content with torque rheometer.And the equilibrium torque and peak torque were analyzed by means of range analysis.When the wood flour content of poplar was 10wt%,the toughening agent content was 20wt%,and the lubricant content was 4wt%,the fluidity is the best,and the force of the melt system on the rotor is the least of the composite in the mixing process.Studies on different test temperatures showed that when the test temperature is 180?,the torque value of the composite was the lowest,which was suitable for the highest temperature in the extrusion process.The single factor test was carried out at the above formula and temperature and the test results showed that the peak torque decreased first and then rose with the increase of poplar powder content,and when the poplar flour content was 10 wt%,the peak torque could reach the minimum value of 5.7N·m.(2)A twin-screw extruder was used to prepare poplar powder/PLA composite filament and the melt flow rate was analyzed.The optimum raw material ratio was obtained by orthogonal test,and the single factor experiment was carried out under the optimum ratio.The results showed that the fluidity of silk increased first and then decreased with the addition of poplar powder and toughening agent,and the fluidity of silk was greatly improved by lubricant.When the lubricant content was 4wt%,the melt flow rate of the material became 31.622g/10 min,which was nearly twice as high as that without lubricant.(3)The pure PLA and different samples with additives were tested by Fourier transform infrared spectroscopy,scanning electron microscope and differential scanning calorimetry.The FTIR showed that the main functional groups of the composites did not change in comparison compared with pure PLA,but the toughness of the composites was improved by the addition of the toughening agent.The SEM showed that the surface of PLA became rough with the addition of poplar powder and the compatibility between poplar powder and PLA was poor;the mixture of poplar powder and PLA was more uniform because of the toughening agent.Non-isothermal crystallization test showed that lower cooling rate was more conducive to the crystallization of composites.(4)The melt deposition type 3d printer was used to print the extrusion wire under the orthogonal test and the impact strength of the samples was tested.The results showed that the order of the main and secondary effects of each factor of the impact strength was as follows:toughening agent>lubricant>poplar powder,and the effect of toughening agent was very significant.When the content of poplar powder was 15wt%,the content of toughening agent was 20wt%and the content of lubricant was 1wt%,the impact strength of the samples was the best which could reach 31.224kj/m~2.The size of the print spline was measured and the results showed that the deviation of the length and width direction of the spline was small with different contents of poplar powder,toughening agent and lubricant,but the deviation of the thickness direction was larger.(5)The different printing parameters of the silk under the optimal impact strength were tested.The effects of different printing speeds on the density and time of printing samples,the effects of different printing temperature on feed speed,sample density and bonding force between sample and bottom bond and the effect of different thickness of printing layer on printing time and sample density were investigated.The surface quality of printed samples with different poplar powder content was compared and analyzed.The results showed that when the temperature was above 200?,it was not good for the printing of the sample;when the printing speed was 70mm/s-90mm/s,the wire extrusion was more stable,and the printing sample density was better;when the thickness of the printed layer is below 0.15mm,better samples can be obtained.When the content of poplar powder was 15 wt%,the poplar powder could be combined with PLA well,and the impact strength,color and surface quality of the sample were better.