Application Of Tetrafunctional Peroxide In The Preparation Of High Impact Polystyrene

In order to improve the impact properties of polystyrene,rubber is added to produce high impact polystyrene(HIPS).Free radical polymerization is the most widely used method,and the initiator usually added to the reaction system to control the molecular weight well.The industrial production of HIPS has been initiated by thermal or monofunctional initiator,but there is less research on the effect of the initiator types on the mechanical properties of HIPS.It has very important academic significance and application to study the effect of tetrafunctional initiator.HIPS was prepared with bulk grafting polymerization method and tetrafunctional initiator was used as the initiator.The effect of reaction temperature,stirring conditions,initiator type and concentration on the reaction kinetics,phase inversion and the properties of the HIPS were studied.Firstly,the kinetics of bulk graft polymerization of HIPS was studied.The kinetic curve of polymerization was "S" type,which was a typical free radical polymerization reaction kinetic curve.The addition of rubber slowed down the polymerization rate,and the reaction rate was low at the constant stirring speed of 130 r·min-1,and was rather different from the reaction kinetic curves of constant stirring speed 30,50,70 and 90 r·min-1.After phase inversion,the effect of decreasing the latter stirring speeds on the reaction kinetics is very small.With the same concentration of peroxide group,the kinetic curves of polymerization initiated by the monofunctional initiator and the tetrafunctional initiators were basically coincident.The phase inversion was analyzed with the changes of the particle structure and viscosity of the polymerization system by transmission electron microscope and the change of relative torque.The results obtained from these two analysises are similar,and the conversions at phase inversion increased with the increase of the temperature and reduced with the increase of the constant stirring speed.With the staged stirring method,the conversions at phase inversion increased when stirring speeds reduced before the phase inversion.The corresponding stirring speeds to the phase inversion was what exactly influenced the phase inversion which could be called "effective stirring speeds".With the same concentration of peroxide group,the conversions at phase inversion initiated by tetrafunctional initiators were similar,and higher than that of the monofunctional initiator.The morphology of rubber particles in HIPS was observed by transmission electron microscope,and the mechanical properties of HIPS were analyzed in terms of the relative molecular weight,graft ratio,rubber particle size and distribution.The elongation at break and impact strength of the final products of the HIPS synthesized by using the tetrafunctional initiators were higher than those of the final product synthesized by using the monofunctional initiator.With the increase of the constant stirring speed,the mechanical properties of the final products of HIPS firstly increased and then reduced,and the mechanical properties of HIPS synthesized at constant stirring speed 90 r·min-1 were the best.With the former stirring speed 90 r·min-1,tensile properties and impact properties of HIPS reduced on condition of decreasing the stirring speed before the phase inversion but unchanged on condition of changing the stirring speed after the phase inversion.The corresponding stirring speed at the phase inversion was what exactly influenced the mechanical properties of HIPS which could be called "effective stirring speeds".No matter what the stirring conditions were,the tensile and impact properties of HIPS synthesized at the same effective stirring speed were the same.