Effect of hollow glass microsphere on the processing and flame retardancy of intumescent flame retardant polypropylene composites prepared by selective laser sintering

In this article, flame retarding PP composite powder composed of commercial pure PP powder, intumescent flame retardant (IFR), and hollow glass microsphere (HGM) suitable for SLS was prepared successfully by mechanical blending, and the corresponding sintering process and flame retardancy were studied. The results showed that the HGM can improve the flowability of PP composite powder effectively and enlarged the sintering window, decreasing the warping phenomenon during printing. The flame-retardant tests showed that there was a synergistic flame-retardant effect between HGM and IFR. The LOI value and UL-94 grade reached 32.1 ± 0.5% and V-0 with the addition of 10 wt% HGM. SEM results showed that HGM improved the quality of char layer. Moreover, HGM could increase thermal stability and decreased the density to 0.712 g/cm3, the tensile strength and the elongation at break could reach 16.7 ± 0.2Mpa and 7.6 ± 0.1%, respectively. A new kind of PP composite powder with high flame retardancy suitable for selective laser sintering (SLS) was prepared successfully by mechanical blending. Hollow glass microsphere (HGM) can effectively enhance the flame retardancy and tensile strength.