热历史对聚醚醚酮及其碳纤维复合材料——Ⅱ.熔融行为的影响

THE STUDY ON THERMAL BEHAVIOR OF POLY(ETHER- ETHER-KETONE) (PEEK) AND ITS CARBON FIBER COMPOSITES II. Effect of Thermal History on Melting Behavior

本文利用差示扫描量热仪(DSC)研究了聚醚醚酮(PEEK)和以PEEK为基体的碳纤维复合材料(APC-2)的热历史对它们熔融行为的影响。在200—315℃结晶并退火热处理后,试样的DSC曲线上出现了两个吸热峰。低温吸热峰(峰温T′_m)较小,并与结晶和退火温度(T_c)有关;高温吸热峰(峰温T_m)较大,几乎不受T_n的影响。T′_m的出现与在不同T_c下生成的不完整晶体的熔融和重结晶过程有关,而T_m的出现则与完整晶体的熔融过程有关。实验结果表明,T′_m与T_c之间呈线性关系。按文献报道的方法,将T′_m与T_c的直线外推至与T′_m=T_c直线相交,其交点温度即为平衡熔点.结果表明,PEEK和APC-2试样的“平衡熔点”受不同热历史条件下生成晶体的完整程度的影响。当结晶并退火时间越长,求出的“平衡熔点”值越低,并与理论值接近。实验结果还表明,碳纤维表面具有促进PEEK树脂基体晶体完整化的作用,因而导致APC-2试样中PEEK树脂基体的熔点高于纯PEEK树脂。

A study has been made of the effect of thermal history on melting behavior of poly (ether-ether-ketone) (PEEK) and its carbon fiber composites (APC-2) by using differential scanning calorimeter (DSC).The two samples crystallized and annealed between 200 and 315℃ from the rubbery state or from the melt state exhibited a small endotherm peak (T'm) at approximate 10 to 20℃ above the crystallization and annealing temterature (Tl) and a large endotherm peak (Tm) at 335 to 345℃. The small endotherm peak was attributed to the melting and recrystallization of the unperfect crystals formed at the Tc. The large endotherm peak was attributed to the melting of the perfect crystals. The results of our study showed that the T'm depended linearly on Tc. The 'thermodynamic equilibrium melting point' calculated according to the literature which is defined by the intersection temperature of T'm as a function of Tc with the T'm = Tc line. The results of our study demonstrated also that carbon fiber in the composites has a strong effect of perfection on the crystals of PEEK matrix, so that the melting point of composites is higher than that of PEEK resin itself.