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

物理性质的分子量依赖性是高分子材料最常见的特性之一。例如，聚合物的熔体粘度表现出明显的分子量依赖性，对于纠缠的聚合物链，熔体粘度可以按比例表示为3.4倍的分子量。此外，微波对聚合物结晶速率的影响一直是人们关注的课题。我们研究了不同聚合物晶体成核速率(I)和晶体生长速率的分子量依赖性。I和G的温度依赖性呈钟形曲线，Imax和Gmax的最大值点明显。Imax和Gmax表现出显著的MW依赖性。还原生长速率（G/Gmax）和还原成核速率（Inmax）曲线均为一条主曲线，与分子量无关。Imax和Gmax分别是表征成核和晶体生长速率行为的特征参数。Imax和Gmax的毫瓦依赖性分别按比例表示为1和-0.5毫瓦的幂次，用于c…More链折叠结晶。摘要聚碳酸酯（PC）的结晶速率一般较慢，但与聚环氧乙烷（PEO）共混可加快结晶速率。PC/PEO共混物中PC的结晶在几秒钟内完成。在共混结晶过程中，观察到自发分解，在富PC相中观察到PC的球晶。聚合物共混物液-液分离过程中，PC的结晶受上坡扩散控制。在不同的应变速率和温度下，对聚对苯二甲酸乙酯（PET）和聚乙烯2,6萘二羧酸酯（PEN）进行了双轴拉伸和单轴拉伸。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-光学规律（SOR）在低双折射条件下适用，拉伸过程得到的应力-光学系数与文献报道值相近。PET和PEN在较高的拉伸温度和较低的应变速率下形成流动图。SOR也适用于流程图条件。为了分析低结晶度和低双折射样品的网络结构，应用高斯链橡胶弹性理论，从热收缩和收缩应力的测量出发，分析了拉伸膜的缠结密度Nc。在绘图的笔。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后拉伸退火法制备立体配合物（外消旋体）聚乳酸纤维的结构。当纺丝速度超过4 km/min时，在WAXD图中出现明显的晶体反射。晶体改性为α型和立体复合晶体共存，立体复合晶体的反射强度随吸丝速度的增加、吞吐率的降低和纺丝温度的降低而增加。退火高速纺丝纤维的晶体反射比拉伸退火低速纺丝纤维的取向更高，立体络合物晶体更丰富。通过对自旋线直径剖面的测量，发现纺丝过程中较高的结晶温度有利于立体络合晶体的形成。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