Synthesis Of Brominated Polystyrene With High Content Of Bromine And Excellent Thermal Stability

Brominated polystyrene (BPS) is a kind of polymeric brominated flame retardant, which possesses high efficiency, good heat resistance, and good compatibility with matrix, which has been a superior alternative for polybrominated diphenyl ether flame retardant to be used in engineering plastics. BPS have been commercialized under worldwide, however, domestic BPS products with low content of bromine and poor heat resistant property would be difficult to form industrial products. Therefore, it has practical significance to study the synthetic technology to produce BPS with high content of bromine, excellent heat resistance and considerable whiteness.In this paper, the influence of the amount of catalyst, brominating agent, reaction temperature and reaction time on the bromination of polystyrene was studied. BPS products were characterized by NMR, IR, TGA, potentiometric titration and gel chromatography. The optimal conditions to prepare BPS are as follows:In anhydrous conditions, the dosage of catalyst SbCl3was3%weight of polystyrene, and the ratio of BrCl to styrene was3,0:1. BrCl was dropped at10～15℃for3h. Then the obtained polymer was preserved at30℃for3h. The product BPS was precipitated by methanol. Bromine content, glass transform temperature,1%loss weight and5%loss weight of BPS were67.5%,173.2℃,316℃and376℃respectively. Yield and R457whiteness of polystyrene powder were90%and125respectively.SnCl4and TiCl4, as backbone halogenation suppressing additive (BHSA), were studied to avoid halogenation reaction in backbone of polystyrene. GPC, TGA, potentiometric titration and whiteness meter were used to test the molecular weight, heat stability, halogenation on backbone and whiteness of polystyrene respectively.1%SnCl4was selected to produce polystyrene with halogen on backbone lower than1200ppm. The bromine content,1%loss weight and R457whiteness of obtained product were68.4%,341℃and148respectively.In order to improve the practicality of BPS products, diphenyl sulfone as heat carrier was mixed with BPS under melting condition for2h. After cooling, diphenyl sulfone was extracted with hot alcohol, and then the granular BPS products were obtained. This method could further reduce halogenation on backbone of BPS, and increase the decompose temperature of BPS products.