Phase behavior in mixtures of a homopolymer and a block copolymer. 4. SALS and SAXS studies

Phase behavior of blends of poly(vinyl methyl ether) (PVME) with four styrene-butadiene-styrene (SBS) triblock copolymers, being of various molecular weights, architecture, and compositions, was investigated by small-angle light scattering. Small-angle X-ray scattering investigation was accomplished for one blend. Low critical solution temperature (LCST) and a unique phase behavior, resembling upper critical solution temperature (UCST), were observed. It was found that the architecture of the copolymer greatly influenced the phase behavior of the blends. Random phase approximation theory was used to calculate the spinodal phase transition curves of the ABA/C and BAB/C systems; LCST and resembling UCST phase behavior were observed as the parameters of the system changed. Qualitatively, the experimental and the theoretical results are consistent with each other. © 1996 John Wiley & Sons, Inc.     

PP/PS共混体系相结构形成与演变

以连续共混过程中间歇出料法研究了聚丙烯(PP)/聚苯乙烯(PS)体系共混过程中的扫描电镜图样演化过程,利用小角激光散射(SALS)证明了PP/苯乙烯-乙烯-丙烯嵌段共聚物(SEP)/PS体系的部分相容性,同时说明SALS研究聚合物熔体动态过程的有效性.针对扫描电镜图样,用重心粒径dg这一结构参数研究了PP/PS体系共混过程,利用分布函数求取了分散相PP分形维数,对共混过程中相分散进行了研究.     

环氧树脂/聚氨酯共混体系相行为研究

利用小角光散射 (SALS)技术实时记录了环氧树脂 聚氨酯共混体系在固化过程中的相行为发展情况 ,得到了表征共混体系相区结构尺寸大小的相关距离ac 和表征体系均匀程度的均方介电常数涨落 η2 ,讨论了等温固化条件下 ,环氧树脂 聚氨酯共混体系的相区大小随时间的变化规律 .实验结果表明 ,环氧树脂 聚氨酯共混体系的固化过程是典型的反应诱导相分离的过程 .相分离初期 ,符合Cahn的线性理论 ;随着固化时间的延长 ,相区由小变大 ,约至反应开始后 3 2 1 0s,相分离趋于平衡态 ,相区尺寸趋于稳定     

Crystallization behavior of some unimodal and bimodal linear low‐density polyethylenes at moderate and high supercooling

Effect of molar mass distribution (MMD) and composition distribution (CD) on crystallization behavior of linear low‐density polyethylene materials at moderate and high supercooling was studied using differential scanning calorimetry, hot‐stage polarized light microscopy, small‐angle light scattering, and chip nanocalorimetry methods. A set of uni‐ and bimodal materials having small variation in average molar mass, density, and melt flow rate, but large differences in MMD and CD, was investigated. The results indicate a clear effect of structural heterogeneity on morphology and crystallization behavior of the materials. Broader MMD and CD increased in average radius of superstructures, melting, crystallization temperatures, and isothermal crystallization rate at different supercoolings. Origin of such behavior is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1577–1588, 2008     

Small-Angle light scattering from an anisotropic sphere: Anisotropy and size effects

The recently developed theory of light scattering from an anisotropic sphere (taken as a model for a spherulite) summarizes all information obtainable from such scattering system when the Rayleigh-Gans-Debye approximation is appropriate. The commonly used procedure of size determination from the maximum of the H_v intensity is tested for a number of models differing in radius size, inherent anisotropy δn and mean refractive index ¯n. It has been confirmed, that the parameter (¯n - 1)/δn plays the decisive role in the angular dependence of the H_v intensity and the influence of that parameter on the size determination and resulting accuracy is specified. The results differ for positive and negative spherulites and the stabilizing role of increasing spherulite size in accuracy of procedure is demonstrated. It has been shown that the RGD approximation is appropriate especially for the case of homogeneous spherulite texture (thus implying, that the refractive index of the surrounding is close to the average refractive index of a single spherulite). The results extrapolated outside of the RGD approximation display invariable U_max position for isotropic contribution with increasing sphere size in contrast to the oscillatory character of U_max predicted by the LM solution. It is proposed to construct the anisotropic solution under an approximation recently suggested for thin anisotropic shell. © 1994 John Wiley & Sons, Inc.     

A Novel Approach for Observing Morphology of Polypropylene under Ultrasonic Vibration by SALS

In this paper, a set of ultrasonic vibration device connecting with small angle light scattering(SALS) for in-situ observing phase-transition of polymer under ultrasonic vibration was established. The experiments for verifying polypropylene(PP) indicated that ultrasonic vibration resulted in the decrease of the crystallization rate and made PP crystallizable at low temperature.     

阻燃聚丙烯共混体系结晶形态研究

本工作利用WAXD、DSC、PLM、PCM和SAIS等手段,对几种具有代表性的阻燃PP共混体系的结晶形态和结晶行为进行了研究。结果表明各种阻燃剂存在,对阻燃PP体系中PP的结晶形态和结晶行为有明显影响。其影响情况取决于这些阻燃剂自身的各种特性。另外,PP的结晶对某些阻燃剂的分散也有一定的影响,其结晶过程是体系中阻燃剂的一个再分散过程。     

STUDIES ON THE MORPHOLOGY OF THERMOTROPIC POLYESTER DURING TRANSITIONS BETWEEN ISOTROPIC AND ANISOTROPIC MELTS

The morphology of a thermotropic aromatic polyester during the transitions between isotropic and anisotropic melts was studied by means of polarizing microscopy and small angle light scattering techniques. Both transition processes were found to be composed of the initiation of a new phase at local places of the old phase matrix and the growth of the new phase domains. A change of Hv scattering patterns was observed in the transition temperature ranges and was explained as the result of heterogeneity of the mesophase system, but not the change in ordering of a homogeneous mesophase.     

用光散射研究部分相容聚合物共混物的相间过渡层(英文)

在光散射的理论中 ,密度均方起伏η2在两相完全不相容的体系中 (界面间也不存在相互粘附 )η2 =Φ1Φ2 (α1-α2 )。对于界面间有相互作用或形成一定的相容区时 ,η2将变小 ,则有η2 =(α2 -α1) 2 (φ1φ2 -φ3/6)。α1、α2 为两组元分别的极化率 ,φ1、φ2 为两组元的体积分数。本文根据部分相容的聚合物共混体系中的分散相尺寸γ和积分不变量θ,可计算出φ3,并提出相间弥散层的概念 ,进而计算出弥散层的厚度 d,从而发展了光散射理论。激光小角散射计算的弥散层厚度 d与 X光小角散射计算的界面层厚度σb是相对应的。在计算中应用相关距离 ac代替分散性尺寸γ是可行的 (也可用均方旋转半径 R2g代替 )。文中给出了 PA6/PP合金的弥散层厚度 d和界面层厚度σb的计算结果 ,同时给出了 HIPS/Pc BR合金在熔体动态过程中两相间弥散层厚度的变化