间规聚苯乙烯同质多晶现象的研究

间规聚苯乙烯(ｓＰＳ)是由日本出光公司在1985年首先合成,由于其优良的耐热性(熔点高达270℃),立刻被认为有可能或为下一世纪最重要的工程塑料.独特的分子结构,使间规聚苯乙烯具有密度低、尺寸稳定、耐热性、耐溶剂性好等诸多优点,因而引起研究人员的广泛重视.同时,间规聚苯乙烯存在复杂的同质多晶现象,共有α、β、γ和δ四种晶型.以不同的条件从熔体结晶,间规聚苯乙烯可形成平面锯齿结构的α晶和β晶.其中,α晶属六方晶系,晶胞参数为:ａ=263ｎｍ,ｃ=078ｎｍ;β晶是斜方晶,晶胞参数为:ａ=088ｎｍ,ｂ=263ｎｍ,ｃ=078ｎｍ.与传统的全同聚丙烯…

STUDY ON POLYMORPHISM OF SYNDIOTACTIC POLYSTYRENE

The crystallization of the α \|and β \|form crystals of syndiotactic polystyrene ( s PS) is determined by the crystallization temperature. Being crystallized at various temperatures from the melt, sPS forms the β form crystal at high temperatures above about 230℃, α form crystal at low temperatures below about 170℃ and a mixture of the α and β form at intermediate temperatures. The effect of different cooling rates is considered in more details. Since the β form crystallizes at high temperature from the melt.It will first crystallize during cooling.At low cooling rates,the crystalline phase of the β form has almost reached the maximum crystallinity of the sample by cooling to 230℃.So even the temperature for the α form formation is reached,there is no more crystallizable s PS portion remaining for the α form formation.That is the reason why the β form is always obtained by cooling at a slow or moderate rate.If cooling rate is high enough that the β form has almost no time to crystallize at high temperature,only the α form can crystallize at low temperature.That is the reason why only the α form crystal is obtained under quenching conditions.It clearly indicates that the crystallization temperature is the intrinsic factor controlling the formation the α \| and β \|form crystals.