Analysis of internal fine structures of high-speed-spun fibers of PET/PEN blends

1.建立了一种适合于高速纺丝纤维(HSS纤维)的结构分析技术，利用该技术可以直观地解释PET、PEN和PET/PEN共混物中HSS纤维某些性质的来源。(1)碱刻蚀后的PEN纤维(纺丝速度大于或等于4 km/mm)具有纤维状织构和由堆叠片层状结构组成的细小网状结构。(2)对熔体施加剪切应变，制备了PET和PEN的单轴取向薄膜，并用透射电子显微镜对薄膜进行了表征。PEN纤维的电子衍射(ED)表现出高度的单轴取向，与PEN高速钢纤维的广角X射线衍射(XD)一致。这种PEN薄膜被认为是高速钢纤维的模型样品。涤纶的透过率与涤纶高速钢纤维的透过率基本一致。(3)对于PET/PEN共混物的单轴取向薄膜，ED图由两个均聚物晶体的反射组成，也表现出高度的单轴取向。通过暗场成像发现，PEN可以在单轴取向的薄膜中形成片状晶体，这一趋势比在PET中更明显。随着PET含量的增加，聚对苯二甲酸丁二醇酯(PBT)的形态由PET型转变为PEN型，PEN抑制了PEN片层的形成，PEN也抑制了PEN的结晶。尽管它们的ED图由仅属于α形式的弧形反射组成，因此显示出不太发达的单轴取向，但在PBT中观察到的堆积层状结构比PEN中更清晰。结果表明，每个结构中堆积的片层形成了烤肉串结构。基于对所有聚酯取向薄膜的研究结果，我们提出了烤肉串结构的“高级”模型。

1.We tried to establish a suitable technique of structural analysis for the high-speed-spun fibers (HSS-fibers), with which the origin of some properties of the fibers can be straightfowardly elucidated for PET, PEN [poly(ethylene naphthalate)] and PET/PEN blends. (1)Fibrillar texture and a fine network structure consisting of stacked-lamella-like structures were recognized in the alkaline-etched HSS-fibers (spun at 4 km/mm or greater) of PEN. (2)Uniaxially oriented thin films of PET and PEN were prepared by applying shear-strain to the melt, and were examined by TEM. Electron diffraction (ED) of PEN showed a highly uniaxial orientation and was consistent with wide-angle x-ray diffraction (XD) of PEN HSS-fibers. Such thin films of PEN were regarded as a model specimen for the HSS-fibers. ED of PET is in good agreement with XD of PET HSS-fibers. (3)As for uniaxially oriented thin films of PET/PEN blends, ED patterns consisted of the reflections from both homopolymer crystals and also showed a highly uniaxial orientation. By dark-field imaging, it was recognized that PEN can form lamellar crystals in uniaxially oriented thin films and this tendency is more remarked than in PET. Morphology was changed from a PET-type to a PEN-type with increasing PET content, formation of PEN lamellae was depressed by PET, and to the contrary, crystallization of PET was suppressed by PEN.2.Oriented thin films of PBT [poly(butylene terephthalate)] were prepared and examined by TEM. Although their ED patterns consisted of the arc-shaped reflections attributed only to the α-form and accordingly showed a less-developed uniaxial orientation, stacked-lamellar structures were more clearly observed in PBT than in PEN. It was concluded that the stacked lamellae in each of the structures form a shish-kebab structure. Based on the results obtained from all the oriented thin films of polyesters used here, we proposed an "advanced" model of shish-kebab structure.