Effects of a small amount of poly(ethylene glycol) on the non-isothermal cold crystallization of uniaxially oriented poly(ethylene terephthalate) fibers

The kinetics of non-isothermal crystallization of uniaxially oriented poly(ethylene terephthalate) fibers modified by poly(ethylene glycol)(PET-co-PEG) was investigated by using a DSC heating scanning method and analyzed by using a new non-isothermal equation. Two crystallization peaks appeared for PET and PET-co-PEG fibers. The kinetics parameters, such as the Avrami exponent, the activation energies of diffusion, and the weight fractions per sub-process, were obtained. Based on the Avrami exponent, peak position, and crystallization rate, the crystallization mechanism was proposed.     

Kinetics of non-isothermal cold crystallization of uniaxially oriented poly(ethylene terephthalate)

The non-isothermal equation was extended to describe non-isothermal cold crystallization kinetics of oriented polymers. The validity of the equation was examined by using a DSC crystallization curve of oriented poly(ethylene terephthalate) (PET) fibers with a constant heating rate. The double cold crystallization peaks appeared in the DSC curve. The relative degrees of crystallinity at different temperatures were analyzed by using the equation. The results show that the value of the Avrami exponent near to 1 at lower temperatures implies the bundle-like crystal growth geometry and the value of the Avrami exponent near to, 2, at higher temperatures implies the higher dimension crystal growth geometry. The first crystallization process crystallizes at faster rate than that of the isotropic sample, while the second process crystallizes at slower rate than that of isotropic sample. If a simple single process model was used, the value of the Avrami exponent, 0.77, was obtained. The result shows the simple single process model cannot describe the processes of crystallization of oriented PET fibers satisfactorily.     

氧化铁包覆云母对聚对苯二甲酸乙二醇酯非等温结晶动力学的影响

以氧化铁包覆云母为成核剂,对聚对苯二甲酸乙二醇酯（PET）进行成核改性,采用差示扫描量热法分别研究了不同降温速率下PET和PET/氧化铁包覆云母复合材料的非等温结晶行为,用Jeziorny法和莫志深法对非等温结晶过程进行了分析,并用Flynn-Wall-Ozawa法计算其活化能。结果表明：氧化铁包覆云母对PET具有异相成核的作用,可明显提高PET的结晶速率;与Jeziorny法相比,莫志深法可较好描述PET和PET／氧化铁包覆云母复合材料的非等温结晶过程。进一步分析表明,氧化铁包覆云母的加入并没有明显改变PET基体的成核机理和生长方式,但降低了PET的结晶活化能,从而提高了PET的结晶性能。     

水溶性聚酯的结晶性能研究

研究了水溶性聚酯(W SPET)切片的结晶性能,并与常规聚酯(PET)切片相对比。结果表明W SPET切片与PET切片具有相同的非等温结晶行为,在非等温条件下的结晶机理以异相成核为主,在有限的三维体积中生成球晶,但W SPET切片的结晶速率明显慢于PET切片,结晶能力明显弱于PET切片。     

聚乳酸/环氧化聚丁二烯抗冲树脂结晶性能的研究

采用差示扫描量热仪(DSC)对聚乳酸/环氧化聚丁二烯抗冲聚乳酸树脂(PLA/PB(EPB))的结晶性能进行了考察,并与纯聚乳酸(PLA)的结晶行为进行了对比,研究了环氧化聚丁二烯(EPB)对PLA等温/非等温条件下结晶行为的影响规律。结果表明:聚丁二烯橡胶(PB)对PLA的结晶行为影响较小,而EPB对PLA的晶体完善程度影响较为明显。PLA和PLA/PB更倾向于在低温条件下结晶,而PLA/EPB20.9%和PLA/EPB46.5%更倾向于在高温条件下结晶。抗冲聚乳酸树脂的结晶速率高于纯PLA,并且随着EPB环氧化度的增大,抗冲聚乳酸树脂的结晶速率呈逐渐增大的趋势。     

Investigations of the Non-Isothermal Crystallization Behavior of Polyamide 6/Polyethylene-Octene/Organomontmorillonite Nanocomposites

The crystallization behavior of polyamide 6/polyethylene-octene/organomontmoril- lonite (PA 6/POE/OMMT) nanocomposites fabricated via melting intercalation route was investigated using differential scanning calorimeter (DSC). The crystallization kinetics under non-isothermal conditions was analyzed by Jeziorny method and Mo method, and the crystallization kinetics parameters were obtained. It was found that nano-clay acted as a heterogeneous nucleation agent and the semi-crystallization time was prolonged with the OMMT loading increasing. The activation energy for non-isothermal crystallization of such nanocomposites was calculated according to the Huffman-Lauritzen theory. The average size of the composite nanocrystals was reduced with introduction of OMMT to the synthetic system.     

聚酯/热致液晶聚合物体系的非等温结晶动力学研究

热致性液晶共聚酯PET／60PHB组分对PET及PBT在两种共混体系中的非等温结晶行为的影响用DSC方法进行了研究，并用Ozawa方法处理了动力学数据。随共混体系中LCP含量的增加，PET的Avrami指数值n趋于降低而PBT的n值趋于增加，表明在非等混结晶条件下．对不同组成的共混物体系有着不同的成核和晶体生长的机理．     

成核剂对PET结晶行为及形态结构的影响

系统地研究了四种成核剂:N-A、液晶VectraA950、滑石粉(Talc)、乙撑双硬脂酰胺(EBS)对聚对苯二甲酸乙二醇酯(PET)的结晶行为的影响。采用差式扫描量热仪(DSC)研究了PET/成核剂复合体系的非等温结晶行为,通过小角激光散射(Sals)、X衍射(XRD)对PET/成核剂复合体系的晶体尺寸和晶体结构进行了研究。结果表明,引入成核剂后,PET的结晶行为有较大改善,结晶峰向高温方向移动,且变尖锐,结晶尺寸变小,结晶度提高,除EBS外,均使PET结晶诱导时间减少。在这四种成核剂中,离子聚合物成核剂N-A成核效果最好。     

成核剂对不同特性粘数PET结晶性能的影响

研究了新型复合成核剂水滑石(HT)／离聚物(Surlyn8920)／聚乙二醇(PEG)对不同特性粘数聚对苯二甲酸乙二醇酯(PET)非等温结晶性能的影响。通过差示扫描量热仪测试了PET的结晶峰温度T_(mc)和熔融峰温度(T_m)。结果表明,复合成核剂各组分及PET的质量比为0.5:3.0:3.0:100.0时,各种PET的过冷度(T_m-T_(mc))均显著减少．半结晶时间(1gt_(1／2))也明显降低。而且,复合成核剂对不同特性粘数PET结晶性能的改善是一致的。     

Effects of talc orientation and non-isothermal crystallization rate on crystal orientation of polypropylene in injection-molded polypropylene/ethylene-propylene rubber/talc blends

The effects of talc orientation and non-isothermal crystallization rate on the crystal orientation of polypropylene in the injection-molded PP/EPR/Talc blends were studied by using AFM, DSC, SEM and XRD. Polypropylene was transcrystallized on the talc surface and the polypropylene crystal was oriented perpendicular to the talc surface. Therefore, the crystal orientation was affected by the talc orientation. At the surface of injection-molded specimens, the crystal orientation increased with decreasing the molecular weight of EPRs and increasing the talc content. Because talc particles were nearly oriented parallel to the flow direction in the skin layer of the specimens, the crystal orientation was amplified by the increased crystallization rate. The non-isothermal crystallization behavior of PP/EPR/Talc blends was investigated in terms of the molecular weight of EPRs and the talc content. Non-isothermal crystallization rate increased with decreasing the molecular weight of EPRs due to the plasticizing effect of EPRs and increasing the content of talc which acts as nucleating agent.     

锦纶6/聚偏二氟乙烯共混纤维的非等温结晶行为

采用差示扫描量热法(DSC)研究了熔融纺丝法制备的锦纶6(PA6)/聚偏二氟乙烯(PVDF)共混纤维的非等温结晶行为,并利用修正Avrami方程的Jeziorny法和R-t法对其结晶动力学进行分析。结果表明,由于PVDF的黏度大,且PVDF中的氟原子能与PA6的酰胺键形成氢键,阻碍了PA6分子链在结晶过程中的运动,导致共混纤维的结晶温度和结晶速率比纯PA6纤维低,半结晶时间比PA6大,且随着PVDF含量的增加,其变化更为明显。     

正弦脉动挤出流场对聚合物熔体分子链的解缠结效应——动态流变行为与非等温结晶过程

将松弛时间较长的聚对苯二甲酸乙二醇酯（PET）动态挤出后淬火“冷冻”其熔体的分子链缠结状态，然后在差示扫描量热仪（DSC）上升温到玻璃化转变温度以上进行结晶。通过分析PET熔体的动态流变参数和结晶动力学过程的变化，间接证实动态挤出聚合物熔体分子的解缠结作用。结果发现，正弦脉动挤出流场对聚合物分子链造成的解缠结效果不仅可以降低聚合物熔体的加工黏度，还可以明显降低PET的结晶温度，结晶峰向低温移动且次峰强度明显增大，低温结晶峰含量随振幅和频率的增加而增大，在振幅为0．3mm、频率为12Hz时达到60.7％，成为主结晶过程。     

湿度对单轴取向PET纤维结晶过程的影响

采用DSC研究了不同拉伸比的单轴取向PET纤维在不同湿度下的冷结晶过程。发现湿度可以诱导纤维双重结晶峰的出现。从DSC图可以看出,随着湿度的提高,结晶峰向低温移动,且分化成两个较小的结晶峰,结晶可在玻璃化转变温度之下发生。DSC数据处理结果表明,所得Avrami指数呈规律变化,由于湿度的影响,单轴取向PET纤维在低温时的结晶机理发生变化。     

Effect of solid‐state shearing of poly(ethylene terephtalate) on isothermal crystallization and fiber structure formation

Solid‐state shearing was applied on recycled poly(ethylene terephtalate) (PET) using twin‐screw extruder. The shearing effect on isothermal crystallization was investigated by DSC. Structure formation in melt spinning was also studied by characterizing the spun fibers. It was found that the solid‐state shearing imposes a great influence on its crystallization behavior. Crystallization peak temperature of the sheared PET (199°C) was much higher than that of the PET without shearing (188°C). Overall isothermal crystallization rate was found to be accelerated to more than 50 times by the shearing. The shearing effect remained even after fiber spinning (melt processing). Differences in crystallization behavior, fiber structure formation, and tensile properties of the fibers were found. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 787–791, 2007     

纤维增强PET复合材料非等温结晶行为的研究

用差示扫描量热法 (DSC)研究了 PET及增强 PET的非等温结晶动力学 ,结果表明 ,增强纤维的加入能促进 PET的结晶 ,且 Kevlar浆粕和碳纤维的效果较好。玻纤和碳纤维经等离子处理后 ,前者的成核效果下降而碳纤维的成核效果得以提高 ;在体系中加入成核剂能进一步促进 PET的结晶。另外还用偏光显微镜研究了体系的结晶形态 ,发现没有形成横穿晶 ,增强纤维的加入只是起了成核位的作用。     

结晶成核剂对PET／PE-HD共混物非等温结晶性能与力学性能的影响

研究了水滑石（HT）等四种结晶成核剂对聚对苯二甲酸乙二醇酯（PET）倩密度聚乙烯（PE-HD）共混物结晶性能和力学性能的影响。结果表明，加入HT，不仅可以提高PET／PlE—HD共混物中PET的结晶性能，而且还有助于改善共混物的力学性能；而添加离聚物（Surlyn 8920）或复合成核剂，PET结晶性能改善显著，但力学性能下降较多。     

DSC studies on the crystallization characteristics of poly(ethylene terephthalate) for blow molding applications

The crystallization behavior of blow-molded PET bottles, which helps determine the product's transparency, was investigated by DSC dynamic cooling experiments that simulated the cooling that occurs in the injection blow-molding manufacturing process. Dynamic cooling crystallization of PET optimized the conditions for keeping crystallinity to a minimum during the production of PET bottles. The kinetic parameters of non-isothermal crystallization behavior were determined, which indicate that the competing processes of nucleation and the growth of PET spherulites during the cooling process are the controlling factors for the degree of crystallinity in the final product. In addition, DSC measurements were employed to obtain information on related aspects, such as the ease of crystallization from glassy and molten states and the crystallinity in the products. An Avrami equation was used for the calculations of the crystallization kinetic parameters.     

水性聚氨酯的结晶动力学参数及其在鞋用胶黏剂的应用

以聚己二酸1,4-丁二醇酯（PBA）、六亚甲基二异氰酸酯（HDI）和异佛尔酮二异氰酸酯（IPDI）为主要原料,制备了不同软段分子量和不同硬段含量的水性聚氨酯（WPU）乳液。采用DSC技术表征了WPU胶膜在非等温和等温条件下的结晶行为,并以莫志深方程和Avrami方程为模型,对WPU胶膜的结晶行为进行了研究。WPU胶膜的非等温结晶动力学分析结果表明,随着WPU相对结晶度的增加,非等温结晶动力学参数F（T）增大,说明适当提高活化温度可提高WPU胶黏剂的结晶速率和初黏强度;WPU胶膜的等温动力学分析结果表明,不同软段分子量和不同硬段含量的WPU胶膜的等温结晶动力学参数t_1/2与相应WPU胶黏剂的开放时间存在对应关系,即t_1/2较大者,相应WPU胶黏剂的开放时间较长。     

取向PET/PEG共聚酯纤维的非等温结晶动力学

研究了取向ＰＥＴ／ＰＥＧ共聚酯纤维的非等温结晶动力学，提出了解析结晶动力学参数的新方法。结果表明，随ＰＥＧ含量的增加共聚酯纤维的结晶扩散活化能降低，结晶速率加快。与各向同性试样比较，取向试样的结晶峰明显向低温方向扩散。取向试样在较低温度下的结晶速率高于各向同性试样，而在较高温度下的结晶速率低于各向同性试样。     

PET/粘土纳米复合材料加工条件下结晶行为的研究

采用DSC手段测试了PET、PET／粘土纳米复合材料熔体降温时的结晶行为。结果表明，在PET中引入纳米粘土可提高PET基体的降温结晶峰峰温，并使结晶速率提高1倍以上。PET及PET／粘土纳米复合材料的结晶峰峰温随降温速率的增大而移向低温，半结晶时间及结晶度随降温速率的增大而减小。基于Avrami方程的动力学分析表明，PET／粘土纳米复合材料的非等温结晶过程是带有异相成核的三维增长过程。