SAXS study on the crystallization of PET under physical confinement in PET/PC multilayered films

The present work is concerned with the study of the development of the crystalline structure of poly(ethylene terephthalate) in multilayered films of poly(ethylene terephthalate)/polycarbonate (PET/PC) prepared by means of layer multiplying coextrusion. Small angle X-ray scattering patterns were recorded during isothermal crystallization experiments and evaluated by means of Ruland's interface distribution function. Thus, structural parameters describing the thickness distribution of crystalline and amorphous layers were determinated. It is shown that the crystallization of PET is delayed with increasing confinement. However when the crystallization process comes to an end, the values of the nanostructural parameters of the lamellar system are nearly the same for the confined and non-confined PET.     

拉伸下PET的取向诱导结晶

综述了PET在3种拉伸方式(单轴拉伸、平面拉伸和双轴拉伸)下的取向诱导结晶的最新进展。拉伸温度、应变速率和拉伸比是常用的3个宏观参数，它们对取向诱导结晶等微观参数有着最直接的影响。     

Confined crystallization in end-linked PEO network under uniaxial extension

In this work extension induced crystallization of end-linked polyethylene oxide (PEO) network was investigated with in-situ small angle X-ray scattering (SAXS) and rheological measurement. The coupling between crystallinity and stress of crosslinked network makes the morphology time dependent. With a large strain the structure evolution in the stretched network is found to follow a two-stage process: i) crystals with high numerical density and small dimension form first, which laterally correlate with adjacent ones; ii) continuous melting and fusing of adjacent crystal happen after the first nucleation stage, leading to increase of crystal dimension and stability. Decreasing strain a gradual transformation to normal lamellae formation is found. Strain tuned confinement and crystallization induced confinement release is supposed to induce the structural change.     

Microindentation technique as a tool for investigating the development of order in PET under uniaxial stress

The development of microhardness during annealing was used as a tool to follow the development of the liquid crystalline transient mesophase during the crystallization of uniaxially oriented polyethylene terephthalate (PET). 2D X-ray diffraction was used to characterize the different stages of the crystallization process. We were able to separate those stages by quenching into air. Microindentation hardness experiments were done in real time where samples were heated with their ends fixed on a specially developed stage and microhardness was measured simultaneously. The oriented samples examined exhibit a clear difference in behavior from isotropic samples that mainly lack the existence of such an ordered mesophase. The mesophase clearly has a reinforcement effect on the whole polymer matrix that leads to an increase in hardness value with annealing of the oriented PET films. Microindentation hardness is shown to be a versatile tool to detect the existence of the liquid crystalline transient mesophase. It is also efficient in comparing and explaining results obtained by wide angle X-ray scattering.     

Chain confinement in electrospun nanofibers of PET with carbon nanotubes

Composite nanofibers of poly(ethylene terephthalate), PET, with multiwalled carbon nanotubes (PET/MWCNT) were prepared by the electrospinning method. Confinement, chain conformation, and crystallization of PET electrospun (ES) fibers were analyzed as a function of the weight fraction of MWCNTs. For the first time, we have characterized the rigid amorphous fraction (RAF) in polymer electrospun fibers, with and without MWCNTs. The addition of MWCNTs causes polymer chains in the ES fibers to become more extended, impeding cold crystallization of the fibers, resulting in more confinement of PET chains and an increase in the RAF. The fraction of rigid amorphous chains greatly increased with a small amount of MWCNT loading: with addition of 2% MWCNTs, RAF increased to 0.64, compared to 0.23 in homopolymer PET ES fibers. Spatial constraints also inhibit the folding of polymer chains, resulting in a decrease in crystallinity of PET. For fully amorphous PET/MWCNT composites, MWCNTs do not affect the chain conformation of PET in the ES fibers. For cold crystallized PET/MWCNT composite nanofibers, more trans conformers were formed with the addition of MWCNTs. The increase of RAF (chain confinement) is associated with an increase of the concentration of the trans conformers in the amorphous region as the MWCNT concentration increases in the semicrystalline nanofibers.     

PET结晶行为改进的研究进展

综述并分析了影响PET结晶行为的因素、改进措施及评价结晶行为参数的研究进展。     

Molecular morphology of petaloid bases of PET bottles: A small‐angle X‐ray scattering study

Small‐angle X‐ray scattering (SAXS) studies were undertaken to explore possible morphological explanations for poor mechanical strength in the petaloid bases of poly(ethylene terephthalate) (PET) bottles. The bottles were manufactured using a two‐stage injection stretch blow molding process. Splitting of PET bottle bases under load is both inconvenient and expensive. In this study, SAXS data were collected with a 100 μm square X‐ray beam to establish the molecular morphology as a function of position across the base topology. An amorphous region was identified in the base center (i.e., close to the injection gate of the preform) with biaxially orientated, semicrystalline regions in the feet and valleys of the bottle bases. For bottles that had split under load, the transition between these two regions displayed uniaxial orientation that would lead to reduced mechanical strength in the circumferential direction. Reasons for this effect are explored. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3328–3335, 2006     

PET/分子筛复合材料的非等温结晶性能

采用原位聚合法制备了PET／分子筛复合材料并研究了其非等温结晶性能。结果表明：分子筛的加入有明显的异相成核效应,加快了结晶速度,增加了结晶度,减小了晶粒粒径分布;PET及PET／分子筛体系的热结晶峰温随着降温速率的增加而移向低温,半结晶时间、结晶度随降温速率的增加而减小,晶粒粒径分布则增大;分子筛的加入降低了降温速率对PET半结晶时间的影响;随着分子筛用量的增加,半结晶时间t1／2、结晶热焓ΔH、结晶峰半峰宽ΔW都能达到一个较佳值。     

Formation of lamellar structure by competition in crystallization of both components for crystalline-crystalline block copolymers

Crystallization and structure formation of poly(ethylene oxide)-poly(?-caprolactone) block copolymers (PEG-PCL) in which the melting temperatures of the components are close to each other were elucidated using differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) techniques. The diblock copolymers with 33, 46 and 59 wt% of PEG composition formed ordinary single spherulites similar to those of PCL homopolymers, while concentric double-circled spherulites appeared for the PCL-PEG-PCL triblock copolymer with 66 wt% PEG composition as observed previously. For the diblock copolymers, despite of the ordinary appearance of the single spherulites, the DSC thermograms and the WAXD patterns indicated the crystallization of PEG as well as PCL. The time-resolved SAXS profiles for the diblock copolymers showed that long spacings of the crystal lamellae decreased stepwise in the crystallization process. Synthesizing these results for the single spherulites, it was concluded that PCL crystallized first followed by the crystallization of PEG with preservation of the PCL crystal lamellar structure. This means that PEG must crystallize within confined space between the formerly formed PCL crystal lamellae. Such confined crystallization of PEG caused the suppressed melting temperature, crystallinity and crystallization rate especially in the smaller PEG compositions. In the melting process of the diblock copolymers, it was observed that the PEG component first melted with a stepwise increase in the long spacing.     

高阻隔性PET的现状与发展趋势

对高阻隔性PET的国内外市场现状与技术开发趋势作了系统介绍。     

Morphology development in immiscible polymer blends during crystallization of the dispersed phase under shear flow

Crystallization under shear of dispersed polybutylene terephthalate (PBT) fibers in copolymer polyethylene-methyl acrylate matrix (EMA) was investigated using a hot optical shear device. Crystallization during isotherm and cooling process was studied. Static crystallization experiments were carried out for comprehension purpose. Differential scanning calorimetry (DSC) analysis was performed in order to predict the crystallization behavior of PBT. Shear enhancement of its crystallization was thus demonstrated from rheological experiments. Interfacial tension of EMA/PBT blend was experimentally measured using the hot optical shear device. Theoretical break-up times of PBT fibers were also calculated. Control of the morphology through shear rate and crystallization time balance was demonstrated. Static crystallization experiments show that decreasing crystallization time favor fibrillar morphology. Breaking up of fibers was brought to the fore during dynamic crystallization experiments due to heterogeneous development of the crystallization along the fiber. During the dynamic crystallization, rapid quenching enables fibrillar morphology. Long crystallization times associated with low shear rates allow nodular morphology.     

涤纶短纤维标准样品研制

探讨了涤纶短纤维标准样品研制方法及其应用 ,为今后的研制提供依据     

聚酯自伸长纤维的研究发展

介绍了聚酯自伸长纤维的发展历史、不同的制备技术和应用 ,简略论述了自伸长纤维的机理 ,并对自伸长纤维在国内的发展作了回顾和展望。     

中国再生聚酯行业的发展与再生行业的平台/体系建设

从产业地位、应用领域及竞争格局上分析了国际聚酯产业发展态势,介绍了国内再生聚酯的发展情况,分析了再生行业面临的有利及不利因素,探讨了再生行业发展与行业平台/体系建设的关系。     

抗静电聚酯的研制及性能分析

归纳分析国内外聚酯抗静电方法,采用复合抗静电剂（SRA）研制抗静电聚酯（SRPET）及纤维,探讨SRA的添加量、合成及纺丝工艺。纤维碱减量处理后,抗静电性能和手感均有所改善。     

浅谈我国再生PET短纤维工业的发展历程和前景

回顾了我国再生聚酯(PET)短纤维工业的发展历程及近年来太平洋成套公司在再生PET短纤维成套设备和工艺研发方面的主要成果,分析了目前我国在该行业中存在着高物耗、高能耗、高污染,设备运转率低、劳动生产率低、产品品质低的三高三低的现象,就我国瓶料回收和再生纤维行业存在的问题提出了建议。     

水刺非织造布专用涤纶短纤的开发及应用

介绍了水刺非织造布的发展现状及其对原料的要求,并通过对聚合及纺丝工艺的设 计与优化,在普通棉型涤纶短纤生产设备上成功开发出更加适合水刺非织造专用的涤纶短纤。     

“环境友好型”聚酯纤维的产品开发

聚酯纤维从工业化生产至今经历了大规模生产期,差别化、功能化改性期和新时期备受关注的“环境友好”期几个阶段。相对其它合成纤维,聚酯纤维在生产过程、使用过程、资源重复利用以及回归自然界等各阶段具有所谓“环境友好”的特点。近期的聚酯纤维产品开发更关注如何简化纤维原料的合成过程,降低加工过程的能耗和物耗;通过非石油资源得到合成纤维的原料,并可以使纤维制成的织物包括非织造布能够有效降解;纤维加工业从纺织加工链的角度为下游加工的环境保护、降低能耗和提高织物的功能性等诸方面不懈努力,无论经济效益和社会效益都取得实质性的进展。     

PET/纳米SiO2复合材料的制备(Ⅱ):纳米SiO2在PET中的分散性研究

研究了分散方法、纳米材料的加入体系、分散时间、分散剂的种类及SiO2 的加入量对纳米SiO2 在PET/纳米SiO2 中分散性的影响 ,用TEM对其分散情况进行表征 ,并对其分散机理进行探讨与研究。其结果表明 :采用球磨分散法并以氨基硅烷A1 1 2 0分散剂时分散效果最佳 ;当分散时间达 7 5h时 ,分散液中SiO2 基本以纳米尺寸存在 ;将分散液加入对苯二甲酸二甲酯熔体中并在球磨状态下进行酯交换SiO2 的分散效果最好 ,1 0 0nm以下的SiO2 达 95 0 7% ;体系中随SiO2 量的增加 ,其分散性变差 ,当纳米SiO2 的加入量为 1 %～ 4 %时 ,粒径在 1 0 0nm以下的SiO2 由 88%下降到 61 %。     

Studies of nylon 6/PET polymer blends: Structure and some physical properties

The structure, morphology, and some physical properties of nylon 6/polyethylene terephthalate (PET) blends (PET varying from 10 to 50%) have been reported here. Various techniques such as SEM, X-ray diffraction, birefringence, density, DTA, and DSC have been used. SEM studies revealed that in the blend PET is dispersed as spheres in the nylon 6 matrix. On melt spinning these are elongated in the form of rods and a fibril matrix-type morphology is developed. PET reinforces the (202, 002) lattice planes of nylon 6 up to a certain composition, resulting in increased crystallinity. Both nylon 6 and PET aid each other in mutual nucleation. The highly oriented and extended PET chains hold the nylon 6 molecular chains along their length resulting in increased orientation of the blend fiber system. All these studies further revealed that the improvement in some of the observed properties is due to the fibril-reinforced morphology and the crystallization behavior of the two components, especially that of nylon 6 in the presence of PET.