聚萘二甲酸丁二醇酯的“一步结晶”和“两步结晶”行为

Crystallization of“One-Stage Route”and“Two-Stage Route”of Poly(Butylene Naphthalate)

聚萘二甲酸丁二醇酯(PBN)在不同结晶条件下可能发生“一步结晶”和“两步结晶”,从而形成不同的晶型和结晶形态。文中采用差示扫描量热仪和快速扫描芯片量热仪研究了PBN熔体在不同降温速率下的结晶行为,并借助偏光显微镜和原子力显微镜观察了PBN熔体在不同过冷度条件下形成的晶型及形态。结果表明,随着降温速率的增加,PBN的结晶机理由“一步结晶”转变为“两步结晶”,其临界降温速率约为40 K/s。另外,PBN熔体在低过冷度下形成具有片晶结构的β'晶和α晶,在高过冷度下形成非片晶结构的粒状小晶块,同时证实PBN液晶中间相向α晶的转变是固固相转变。

The crystallization mechanism of“one-stage route”or“two-stage route”of poly(butylene naphthalate)(PBN)can occur under different cooling conditions,which lead to the formation of different kinds of crystal form and morphology.In this work,differential scanning calorimetry and fast-scanning chip-calorimetry were employed to investigate the crystallization behavior of the melt of PBN.Moreover,the resulting crystal forms and morphologies of the melt of PBN at different degrees of supercooling were observed through polarized-light optical microscopy and atomic force microscopy.The results indicate that the crystallization mechanism of PBN shifts from“one-stage route”to“two-stage route”with the increase of cooling rate and the critical cooling rate is about 40 K/s.Besides,β'andαcrystals with lamellae structure are formed at low supercooling of the melt,while small domains are formed at high supercooling.Meanwhile,it is confirmed that the transformation from liquid crystalline mesophase intoα-crystals is a solid-solid phase transformation.