Preparation Of IPP/sPS Alloy Using In-situ Supported Binary Catalysts

Demands on polymer properties have become more and more intense as its application has become wider and wider.In addition to synthesis of new polymers, modifications of existing polymer materials also provide practical ways to improve their properties,among which the technology of reactor alloy is one of the most effective methods to improve the performance of polymer materials.Using the in-situ supporting technology,Cp^*Ti(OMe)₃ for isotactic polyproplyene (iPP)or rac-Et-(Ind)₂ZrCl₂ for syndiotactic polystyrene(sPS)is supported onto the silica to form single supported catalyst.Cp^*Ti(OMe)₃ and rac-Et-(Ind)₂ZrCl₂ are simultaneously supported onto the silica to form binary supported catalysts.The same cocatalyst,methylaluminoxane(MAO),was used for all polymerization.It was found that polymers produced using single supported catalyst and binary supported catalysts have similar structure and proeprties.Secondly,the alloys of iPP/sPS were synthesized through a two-step metheod using the in-situ supported binary catalysts.In the first step,iPP was produced at 50℃.Then,all the toluene was removed and styrene was added to produce sPS through bulk polymerization at 70℃.In separated experiments,iPP and sPS were produce with the same binary supported catalysts individually and compared with corresponding component in the alloy.It was found that the activity,macrostructures and thermal properties of iPP were not significantly changed.However,iPP's crystallinity in the alloy is much higher due to the induce effect of sPS.On the other hand,due to the steric hindrance from the iPP,activity,Mw and crystalinity of sPS in the alloy were lower than that of sPS produced without iPP present.The effects of the ratio between titanium and zirconium were investigated.As this ratio was increased,the decrease in the steric hindrance from PP led to higher activity,Mw and crystallinity of sPS in the alloy.The melting point changes according to its crystallinity.Effects of the type of solvent on alloy were also investigated.Three solvents, toluene solvent,toluene and heptane mixture solvent and heptane solvent,were used for both isotactic polymerization of propylene and syndiotactic polymerization of styrene.It was found that crystallinity of iPP in the alloy was higher than that of iPP without sequential syndiotactic polymerization of styrene. Because crystal degree of sPS by solvent polymerization is higher than that by bulk polymerization,crystalinity of sPS in the alloy was higher than that of sPS which was polymerized without perious isotactic polymerization of proplyene. The activity,isotacticity and crystalinity of iPP in the alloy were decreased following the order of toluene solvent,mixture solvent and heptane solvent.The same tendency has been found for the activity and crystalinity of sPS in the alloy. The melting point changes according to its crystallinity.However,the highest syndiotacticity of sPS was found when the toluene and heptane mixture solvent was used.Molecular weight of sPS with toluene solvent polymerization is lower than that with sPS bulk polymerization.The morphology of alloy were also investigated.Effects of solvent type were considerable.Using heptane solvent added,iPP and sPS in alloy cannot be mixed at the micro-scale,which was achieved with bulk polymerization and toluene solvent polymerization.This point of view was also validated by the trend of the change in melting temperature of alloys.