Study On Preparation And Printing Parameters Of PLA/Wheat Straw Powder Composites For Fused Deposition Modeling

In recent years,the technology of 3D printing is widely used and fused deposition modeling(FDM)receives much concern from researchers for low cost and simple device as one of the way of 3D printing technology.However,the materials applied in 3D printing is limitted and cause pollution to environment.In order to broaden the kinds of avaliable materials for FDM,the paper study the process recipe and molding technology of the composites that polylactic acid(PLA)/wheat straw powder is preparaed with PLA as matrix and wheat straw powder as filling material.While the composites is used for 3D printing,it is inevitable to get aged like traditional materials of WPC,so it is necessary to add uv absorber and control its erosion by the natural environment.As the materials is used for FDM printing,its performance not only related to its nature but also related to its printing conditions.In the paper,the best proportion of raw materials is studied by orthogonal test and the effect of uv absorber to the property of PLA/wheat straw powder composites is discussed.In the end,the article investigates the effect of printing conditions and technical parameters to the property of composites.The main results of the research are concluded as follows:(1)The PLA/wheat straw powder composites is preparaed through the orthogonal test design table of four factors three levels that the factors and levels are the average particle size of wheat straw powder(70?m?120?m?170?m),the adding quantity of wheat straw powder(1%?3%?5%),the adding quantity of coupling agent(2%?5%?8%),the adding quantity of compatibilizer(0.5%?1%?1.5%),which study the effect of the factors and levels to the mechanical property.The results prove that:the increase of adding amount of wheat straw powder decrease the mechanical property of composites;the composites achieve optimum mechanical property when the addition of coupling agent is 8%;with the increase of the average particle size of wheat straw powder and adding amount of compatibilizer,the mechanical property of composites presents a tendency of first increase then decrease.(2)The uv absorber of UV531 is choosed to prepare PLA/wheat straw powder composites with different content from 0 to 1.5%and property is tested after the irradiation of ultraviolet.The results show that:with the increase of aging time,the lightness change value(?L~*)and the chromatism change value(?E~*)of composites expand and the amplitude is reduced when the addition of UV531 increases.Before aging,the mechnical property of composites get declined while the addition of UV531 increases.After aging,the mechnical strength of composites drops respectively and the loss rate presents a tendency of first decrease then increase.SEM analysis showes that aging makes the surface of composites apppear some crack.XPS analysis shows that the process of aging make the surface of composites get oxidized and the proportion of O/C increases.However,the addition of UV531 can effectively reduce the degree of oxidation.FTIR analysis showes that the intensity of C=O and C-O of composites get decreased after aging and the addition of UV531 is benefical to decrease the degree of aging.(3)The paper studys the effect of printing conditions to its performance such as fill density?layer height?printing speed?printing temperature.The results show that:the increase of fill density will make the composites achieve higher mechnical property.DMA proves that the raise of fill density make it increased for the storage modulus?the glass transition temperature and corresponding loss modulus.SEM analysis shows that increase of fill density reduce the hole of composites which is favorable to improve the bonding force;The enhancent of layer height make the mechanical property lower.DMA indicates that storage modulus?the glass transition temperature and corresponding loss modulus will drop when the layer height rises.SEM analysis showes that the increase of layer height is opposed to the combination of inner line;While the printing speed raises,the mechanical property of composites will drop.Rheological properties test proves that the enhancement of layer height is not conducive to the increase of storage modulus?loss modulus and viscosity.However,it has nothing to do with thermal stability.SEM analysis showes that the increase of layer height is easy to cause lack of materials during the printing;With the increase of temperature,the mechnical property of composites will get higher.SEM analysis showes that enhancing temperature will promote the fusion and is conducive to the combination of the composites.