A Study On The Preparation Of Polystyrene Microspheres With Controllable Glass Transition Temperature For Selective Laser Sintering

In this paper, the polystyrene micro spheres, which would be used for the selective laser sintering (SLS), were prepared from polystyrene powder with irregular paticle shape through induced sphericallization. After the surface modification (copolymerization), polystyrene powder becomes the PS microspheres with controllable glass transition temperature (Tg). The distribution of copolymer inside the microspheres can be imagined through the result of atomic force microscope about the height distribution of the microsphere section plane, elasticity modulus distribution, and adhesion distribution of cryo-cut surface across the polystyrene microsphere.Induced sphericallization is a new way to prepare the polymer powder with spherical particles. According to the principle of lowest energy, the ploymer particles trend to become spherical shape under sufficient conditions, those include stirring, solvent, surfactant, temperature, etc. The product of spherical particles getting from this way have regular shape and good uniformity. The average grain size reduces from 24.6 microns of the row powder to 16.5 microns, the apparent density rises from 0.475 g/cm3 to 0.613 g/cm3, melt flow rate rises from 13.6 g/10min to 15.4 g/10min, and the accumulation angle reduces from (46.3±1.4)°to (32.0±0.7)°.The uniform powder does not form sharp angle and overall collapse in the course of accumulation, and the angle of corn is full.After that, the Tg controllable powder was prepared though the copolymerization of the above product with different monomers. Copolymerizing with acrylic monomer, the products with Tg varied from 61.2℃ to 81.2℃ can be prepared. On the other hand, copolymerizing with divinyl benzenne and divinyl-POSS, products with higher Tg from 98.1 ℃ to 104.2℃ can be prepared.Finally, the morporlogy of polystyrene microspheres containing copolymer of butyl acrylate (BA) is studied by atomic force microscope (AFM). The height profile distribution, elasticity modulus distribution, and adhesion distribution across the sphere particle were investigated. It was imagine from above contributions that the copolymer molecules contribute inside the overall sphere and copolymer and polystyrene molecules formed a structure something like the interpenetrating network. However, in this interpenetrating network structure, the copolymer molecules did not penetrate beside the polystyrene molecules uniformly. The concentration of copolymer decreased from edge to internal part of the sphere. In the middle of microspheres, copolymer molecular phase separating from the polystyrene matrix was observed.