Preparation And Properties Of Polypropylene Powders Applied To Selective Laser Sintering

Selective laser sintering(SLS)uses the principle of layered stacking.During the sintering process,the laser beam is scanned on the powder material so that the powder material is bonded and solidified,and then the next layer is scanned and sintered,eventually generate needed 3D parts.It is one of the most important means of 3D printing rapid prototyping technology,which contains many advanced technologies such as CAD,mechanical engineering,numerical control technology,laser precision servo drive,new materials science,etc.The powder materials can be used for SLS include:polymer powder,ceramic-based composite powder,metal-based composite powder,casting sand and so on.The sintering temperature of polymer material is low,the laser energy is small,the sintering process is simple,high precision parts,and it is currently the most widely used and most successful material.This paper studies the polypropylene(PP)powder materials for SLS.The application of the solvent precipitation method in the preparation of polypropylene(PP)powders was investigated,including the influence of various technological conditions,such as the melt flow rate(MI)of PP,dissolution temperature,solute content,packing pressure,stirring speed and dissolution time.The experimental data shows that the solvent method can effectively produce PP powder,and the optimal technological conditions are:the MI-value of PP approximately 17.8g/10min,dissolution temperature being about 170°C,solute content being about15ml/g,the packing pressure being approximately 1.2MPa,stirring speed being about600r/min and dissolution time being about 30min.Under these technological conditions,the apparent density of PP powder is 0.36g/cm~3,the average particle size is 63.2?m,the minimum particle size is 20?m,the maximum particle size is 100?m,the particle size distribution is narrow,the powder has good spherical shape,smooth surface,in addition to the existence of a very small number of potholes,there is no obvious cracks and cracks.Using solvent precipitation method can prepare PP/aluminum composite powder,and the use of silane coupling agent KH570 on the aluminum surface treatment effect is the best,after the treatment of aluminum powder and PP resin has good compatibility.After dissolution of the resin can be well wrapped in aluminum surface,forming a composite system is more uniform;and then prepared five composite powders with content of aluminum with 0wt.%,5wt.%,10wt.%,15wt.%,20wt.%.Through the analysis of the mechanical properties of the composite powder,it can be seen that when the content of aluminum powder is 10%(wt%),the tensile strength of the prepared composite powder is the largest,which can reach 33.5MPa,compared with the pure PP powder,the tensile strength increased by 16.7%;The impact strength of 5.3KJ/m~2,compared with pure PP powder slightly lower,but the overall mechanical properties of the best.The preparation of pure PP powders can meet the requirements of the parts by SLS sintering in this paper,and when the processing temperature of 150?,powder thickness of 0.12mm,laser power 20W,the sintered spline appearance smooth,accurate size,no warping deformation,and the tensile strength reaches 27.9MPa,the impact strength is 6.3KJ/m~2.