The synthesis of high impact polystyrene(HIPS)with the usage of a tetrafunctional peroxide initiator was investigated.The polymerization performance of a commercial initiator polyether poly-t-butylperoxy carbonate(JWEB50)was compared with that of its monofunctional counterpart

tert-butyl(2-ethylhexyl)monoperoxycarbonate(TBEC).It was shown that the polymerization kinetic curves completely overlapped at the same polymerization temperature when the molar concentrations of ［O-O］ were equal for these two initiators.And the higher the molecular weights

the equal polymerization rate could be obtained simultaneously by tetrafuctional JWEB50 compared to monofuctional TBEC under the same other conditions.The effect of polymerization temperature on molecular weight of HIPS prepared with JWEB50 or TBEC was investigated.It suggested that the molecular weight changed slower with the increase of polymerization temperature for JWEB50

compared to TBEC.That meant the molecular weight-increasing effect of JWBE50 would be more pronounced at high polymerization temperatures.The effect of initiator type on graft efficiency was also studied.At the same molar concentration of initiator

it was found that the graft efficiency was dramatically improved with the usage of JWEB50.It was also shown that the graft efficiency increased with the increase of polymerization temperature

but decreased with the increase of conversion.And the evolutions of viscosity during the preparation of HIPS recorded on-line by rotation rheometer(HAAKE RS6000)were very similar for these two initiators when the molar concentrations of ［O-O］ were equal.The two viscosity versus time curves completely overlapped with each other.And the phase inversion turned out to be flat in the curves.The phase inversion flats for both initiators were found to occur at a monomer conversion range around 18%—25%.