Study On The Preparation Technology Of Toughened Polystyrene With In-situ Bulk Polymerization

Polystyrene(PSt) is widely used in many engineering fields due to its excellent mechanical property and good processability.PSt is often modified with rubber particles, leading to high-impact polystyrene(HIPS),acrylonitrile-butadiene-styrene(ABS).However, in the traditional process of high impact materials,the rubber materials need to be isolated from the polymer solution and renewedly dissolved in St.Thus,much labor and expensive apparatus are required for evenly dissolving the rubber material in the monomer.A considerable reduction of variable costs can be achieved by adopting the so-called in-situ bulk polymerization process in which a solution of butadiene preplolymer is produced through selective polymerization of butadiene(Bd) in styrene(St) and then the resultant prepolymer solution was further subjected to a copolymerization of St and acrylonitrile(AN) initiated by radical initiator to produce high impact materials directly.In this study,the solution polymerization of 1,3-butadiene(Bd) was investigated in styrene(St) with the catalyst system comprised of Nd(P₅₀₇)₃(Nd),Al(i-Bu)₂H(Al) and Et₃Al₂Cl₃(C1).The effects of solvent,catalyst components and polymerization temperature on polymerization of Bd were examined.Meanwhile,the effects of aging methods and the kinds of cocatalyst on the molecular weight(M_W) and molecular weight distribution(M_W/M_n) of prepolymer were investigated.The results indicated that the selective polymerization of Bd was achieved in St by the above catalyst.The polymer yield was up to 90%at 50℃,Al/Nd molar ratio of 10 and CI/Nd molar ratio of 2.The produced polymer had extremely low content of St content(＜3%),high cis-1,4 content of 90%and 1,2 content of 2%.Relative narrow M_W/M_n of polymer can be obtained when the catalyst was aged in the presence of Bd. Butadiene prepolymers with different M_w and M_w/M_n were synthesized using different Al/Nd molar ratios and aging methods.And then produced high impact materials directly (HIPS and ABS).Furthermore,the effects of rubber content,molecular weight(M_W) and molecular weight distribution(M_W/M_n) of prepolymer,the amounts and kinds of initiators on the microstructure,kinetics of polymerization and the proprieties of final products were investigated.It is shown that as the rubber content increase,both impact strength of HIPS and ABS increased,the tensile strength decreased gradually and the elongation at break increased. The impact strength of resin toughed by prepolymer with broad M_W/M_n was higher than that of roughed by prepolymer with narrow M_W/M_n.As the amounts of initiator increased,both GD and RPVF slightly increased.The impact strength of HIPS obtained with TETMTPA as initiator was 147.7 J/m.Due to a more effective craze formation induced by fine particles with regular stereo network,the ABS obtained with DP275B displayed high impact strength, whose value reached 333.5 J·m^-1.