Preparation Of High Impact Polystyrene Resins Via In-Situ Bulk Polymerization

In this thesis, a series of high impact polystyrene (HIPS) resins were successfully prepared via in-situ bulk polymerization. That is, the prepolymer solution was prepared by the selective polymerization of conjugated dienes in styrene, then directly subjected to the radical copolymerization with styrene by radical initiator to produce HIPS. Compared with traditional productive technology, the rubber materials do not need being isolated from inert solvent, drying and redissolving in styrene, so this process is distinguished by particular economic viability and good environmental compatibility. The main contents and conclusions obtained are as follows:The selective polymerization of butadiene (Bd) in styrene (St) was achieved by using neodymium bis(2-ethylhexanol)phosphonate/diisobutyl aluminium hydride/diethylaluminum chloride (Nd(P507)3/AlH(i-Bu)2/AlEt2Cl) catalyst to give the prepolymer, which was situed to toughen polystyrene. The prepolymer had extremely low styrene mole content (1.01%) and high cis-1,4 content (96.6%). In addition, The selective copolymerization of butadiene and isoprene (Ip) in styrene was carried out with neodymium bis(2-ethylhexanol)phosphonate/ diisobutyl aluminium hydride/tertiary butyl chloride (Nd(P507)3/AlH(i-Bu)2/t-BuCl) catalyst. The effects of polymerization temperature and time, catalyst dosage, Al/Nd and Cl/Nd mole ratios, catalyst aging temperature and time and monomer ratio on the copolymerization of Bd and Ip were investigated. The results showed that the conversation of Bd and Ip were higher than 90% and 70%, respectively, at Al/Nd mole ratio of 15.0, Cl/Nd mole ratio of 3.0, Nd/(Bd+Ip) of 0.8 mmol/100g, Ip/Bd weight ratio of 1.0 and polymerization temperature of 70℃for 4 h. The St mole content in copolymer was lower than 7%, and both the 1,4 contents of Bd and Ip units of the copolymer were above 96%, regardless of the polymerization conditions.The prepared polybutadiene solution was further subjected to the radical copolymerization with styrene to produce HIPS by using 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane (TETMTPA) as initiator. The effects of reaction conditions on the polymerization process and the structure and properties of HIPS were investigated. The results showed that polymerization rate of styrene, phase transition, molecular weight and molecular weight distribution of polystyrene, grafting degree and mechanical properties of HIPS could be adjusted by changing polymerization temperature, rubber content, initiator concentration, stirring rate and ethylbenzene content. Rubber particles of the produced HIPS displayed well "salami" morphology and the impact strength of HIPS was up to 166 J/m. Compared with monofunctional benzoyl peroxide (BPO), bifunctional 1,1-di(tert-butylperoxy) cyclohexane (DP275B), and tetrafunctional 2,2,bis(4,4-di-(tert-butyl-peroxy-cyclohexyl)propane) (TBPP), trifunctional TETMTPA gave HIPS having the highest impact strength.