Halogen-free Flame Retardant Polystyrene By Novel Suspension Polymerization Process

In this thesis, the suspension polymerization of styrene in the absence of extrasurfactant was carried out, in which the ammonia persulfate/tricalcium phosphate(APS/TCP) was used as stabilizer. The effects of APS/TCP on the polymerizationstability and the particle size and its distribution were investigated. The results showthat, TCP is the key factor of the polymerization stability and particle size and theparticle size will become smaller with increasing the TCP content in thepolymerization; APS also plays important role to the polymerization stability,especially for the particle size distribution. In order to ensure the polymerizationstability and narrow particle size distribution, the minimum content of TCP and APSshould be0.8%and0.05%to total monomer weight, respectively. For preparing theparticles in the range of1.2mm to2.0mm, the optimal content of TCP and APSshould be1.0%and0.01%to total monomer weight, respectively. Under the optimalcondition mentioned above, the average particle size is about1.35mm, the particlesize dispersion index is about1.04and the yield of the particles is higher than97%.In order to prepare the flame-retardant polystyrene with halogen-free flameretardants, the surface modification of ammonium polyphosphate with silane couplingagent KH-550and KH-792and oleic acid was carried out. The modified APP wascharacterized by FTIR, TEM and TGA. The modified APP was directly used in thesuspension polymerization to prepare the PS particles. The encapsulation ratio of APPparticles in PS was tested. The results show that APP modified by KH-550andKH-792is effective, the modified APP is surface-adsorbed by organic groups and thethermal stability is improved, while the modification by oleic acid is not very obvious.The encapsulation ratio of the modified APP in PS is improved, which means that theoleophilic of the modified APP is enhanced; but there is still a relatively large amountof APP cannot be coated by PS, which indicate that the further research on themodification of APP is needed.