Selective Laser Sintering of Polystyrene: Preserving Mechanical Properties without Post-processing

This study investigated the possibility of improving strength and density of polystyrene (PS) parts produced by selective laser sintering (SLS) without additives or post-processing. Post-processing methods are used by researchers to achieve optimal mechanical properties. An efficient method was proposed to systematically evaluate the PS powders and optimize the SLS process, in order to overcome the challenges of sintering the PS parts. The tailored SLS powder was produced from PS granule, and its properties including particle size and particle morphology, powder bed density and Hausner ratio (HR) were analyzed in order to evaluate powder quality. The FT-IR test was also utilized to investigate the possible effects of cryogenic milling and SLS processes on the material's chemical compounds. Then, the effects of input parameters, including powder bed temperature as well as power and speed of the laser on the parts' mechanical properties, were investigated. The sample's maximum tensile strength and elongation were, respectively, 17.06 +/- 0.9 MPa and 2.75% +/- 0.55. The results revealed that it is possible to strengthen PS samples without additives and post-processing. However, due to the powder particle burning and confinement in the molten pool, the increase in energy density beyond the optimum level created spherical pores in the structure that weakened the sample's strength. It is indicated that the energy density of the laser can be increased to achieve higher strength of specimens and dimensional accuracy can be controlled. TGA analysis of the SLS samples demonstrates when the energy density exceeds 0.4 J/mm(2), degradation and decomposition take place in the specimens.