Mechanism of Polymer Crystallization and Control of Fine Structure under Molecular Orientation

物理性质的分子量（MW）依赖性是聚合物材料中最常见的特性之一。例如，聚合物的熔体粘度显示出显著的MW依赖性，并且可以缩放并表示为缠结聚合物链的MW的3.4次幂。分子量对聚合物结晶速率的影响也一直是人们最感兴趣的课题。研究了不同聚合物的成核速率和晶体生长速率与分子量的关系。I和G的温度依赖性呈钟形曲线，显示出Imax和Gmax的明显最大点。Imax和Gmax具有明显的分子量依赖性。降低的生长速率（G/Gmax）和降低的成核速率（Inmax）的曲线图显示了没有MW依赖性的单个主曲线。Imax和Gmax分别是成核和晶体生长速率行为的特征参考。Imax和Gmax对MW的依赖性按比例缩放，并分别表示为I和MW的-0.5次幂， ...更多信息 聚碳酸酯（PC）的结晶速率一般很慢，而聚环氧乙烷（PEO）的加入可以加快PC的结晶速率。PC/PEO共混物中PC的结晶在几秒钟内完成。在结晶过程中，共混物的失稳分解和PC的球晶中观察到PC富相。在不同的应变速率和温度下，对聚对苯二甲酸乙二酯（PET）和聚2，6萘二甲酸乙二酯（PEN）进行了双轴和单轴拉伸，并对拉伸后的PET和PEN的结晶行为进行了研究。在几种拉伸条件下进行了拉伸应力和双折射的在线测量。应力光学定律（SOR）适用于低双折射，拉伸过程中得到的应力光学系数与文献值相近。PET和PEN的流动拉伸是在较高的拉伸温度和较低的应变速率下进行的。SOR也适用于流动拉伸条件。为了分析具有低结晶度和低双折射的每个样品的网络结构，应用高斯链的橡胶弹性理论，从热收缩和收缩应力的测量分析拉伸膜的缠结密度Nc。在笔会上。拉伸温度越高，应变速率越低，拉伸试样的Nc值越低。研究了高速熔融纺丝及后续拉伸退火工艺对聚乳酸立体复合（外消旋）纤维结构形成的影响。当纺丝速度大于4km/min时，纤维的WAXD衍射图出现明显的晶体反射。晶体结构的变化是α型和立体复合晶体共存，且立体复合晶体的反射强度随纺丝速度的增加、纺丝速度的降低和纺丝温度的降低而增加。退火高速纺纤维的结晶反射比拉伸和退火低速纺纤维得到的纤维显示出更高的取向和更丰富的立体复杂的微晶。通过对纺丝线直径分布的测量，发现纺丝过程中较高的结晶温度有利于立体复合晶体的形成。少

Molecular weight (MW) dependence of physical properties is one-of the most common characteristics in polymeric materials. For example, melt viscosity of polymer shows remarkable MW dependence and can be scaled and expressed as a 3.4 power of MW for entangled polymer chains. Also the influence of MW on polymer crystallization rate has been the most interesting subject. We studied on molecular weight dependence of crystal nucleation rate (I) and crystal growth rate for various polymers. The temperature dependence of I and G showed bell-shaped curves showing clear maximum points of Imax and Gmax. Imax and Gmax showed remarkable MW dependence. The plots of the reduced growth rate (G/Gmax) and the reduced nucleation rate (Inmax) showed a single master curve without MW dependence. Imax and Gmax are characteristic references to nucleation and crystal growth rate behaviors, respectively. The MW dependence of Imax and Gmax are scaled and expressed as I and -0.5 power of MW, respectively for a c … More hain folding crystallization.Crystallization rate of Poly(carbonate) (PC) in general is very slow, however its rate is accelerated by polymer blending with poly(ethylene oxide) (PEO). The crystallization of PC in the PC/PEO blends is completed within several seconds. During crystallization of the blends, spinodal decomposition was observed and spherulite of PC was observed in PC rich phase. The crystallization of PC was controlled by up-hill diffusion during liquid-liquid phase separation in the polymer blends.Bi-and uni-axial drawing of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6 naphthalene dicarboxylate) (PEN) were performed at various strain rates and temperatures. On-line measurements of drawing stress and birefringence were carried out under several drawing conditions. The stress-optical rule (SOR) was applicable at low birefringence, and the stress-optical coefficient obtained for drawing process was similar to the reported values. Flow drawings of PET and PEN were caused at relatively high drawing temperature and low strain rate. The SOR was also applicable in flow drawing conditions. To analyze the network structure of each sample that has low crystallinity and low birefringence, the entanglement density Nc of drawn films was analyzed from the measurement of heat shrinkage and shrinkage stress applying the rubber elasticity theory for Gaussian chain. In the drawing of PEN. Nc value of drawn sample was lower when the drawing temperature was higher and strain rate was lower.Structure formation of stereo complex (racemate) polylactides fibers by high-speed melt spinning and subsequent drawing and annealing process was investigated. Distinct crystalline reflections appeared in WAXD patterns of as-spun fibers above 4 km/min. The crystal modification was co-existence of alpha-form and stereo complex crystals, and reflection intensity of stereo complex crystal increased with an increase in the take-up velocity and a decrease in the throughput rate and spinning temperature. The crystalline reflections of annealed high-speed spun fibers showed higher orientation and richer stereo complex crystallites than the fibers obtained by drawing and annealing low-speed spun fibers. From the diameter profile measurement of the spin-line, it was found that higher crystallization temperature in the spinning process leads to the preferred formation of stereo complex crystals. Less