Phase Behavior of Polymer Blends

The present report deals with some results on phase behavior, miscibility and phase separation for several polymer blends casting from solutions. These blends are grouped as the amorphous polymer blends, blends containing a crystalline polymer or two crystalline polymers. The blends of PMMA/PVAc were miscible and underwent phase separation at elevated temperature, exhibited LCST behavior. The benzoylated PPO has both UCST and LCST nature. For the systems composed of crystalline polymer poly(ethylene oxide) and amorphous polyurethane, of two crystalline polymers poly(-caprolactone) and poly[3,3,-bis-(chloromethyl) oxetane], appear a single T_g, indicating these blends are miscible. The interaction parameter B's were determined to be –14 J cm^–3, –15 J cm^–3 respectively. Phase separation of phenolphthalein poly(ether ether sulfone)/PEO blends were discussed in terms of thermal properties, such as their melting and crystallization behavior.This revised version was published online in November 2005 with corrections to the Cover Date.     

Effect of Polydispersity on the Phase Behavior of Polymer Blends

Summary: The effect of polydispersity on polymer blend phase behavior is studied by in situ small‐angle X‐ray scattering. In a polydisperse polyethylene (PE)/isotactic poly(propylene) (iPP) blend, the enthalpic portion of the interaction parameter is greater than that of a corresponding blend with lower polydispersity. This is attributed to the presence of long chains, which provide a higher interaction energy and packing constraint, reducing the system miscibility. As expected, the radius of gyration is higher in the system with higher polydispersity.

Comparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals.     

填料对聚合物共混物相分离行为的影响

近年来,由于粒子填充聚合物共混物的广泛运用,复合材料的结构研究具有重要意义.除了研究粒子在聚合物中的分散外,关于粒子对聚合物共混物的相分离影响也做了大量工作.研究结果表明粒子的尺寸,粒子的表面处理以及粒子含量对聚合物共混物相分离热力学以及动力学有重要影响.由于粒子对聚合物组分的选择吸附、聚合物分子对粒子的润湿作用、填料对聚合物相区生长的阻碍导致了聚合物共混物-填料体系相行为的复杂性.本文扼要地综述了聚合物共混物-填料体系相分离的理论基础以及实验结果,介绍了粒子对相分离的影响因素,并展望了该领域的研究趋势和前景.     

Monte Carlo Simulation of Phase Behavior of Polymer Blends with Special Interactions

The phase behavior of A–B-random copolymer/C-homopolymer blends with special interaction was studied by a Monte Carlo simulation in two dimensions. The interaction between segment A and segment C was repulsive, whereas it was attractive between segment B and segment C. The simulation results showed that the blend became two large co-continuous phase domains at lower segment-B component compositions, indicating that the blend showed spinodal decomposition. With an increase of the segment-B component, the miscibility between the copolymer and the polymer was gradually improved up to being miscible. In addition, it was found that segment B tended to move to the surface of the copolymer phase in the case of a lower component of segment B. On the other hand, it was observed that the average end-to-end distances (h) for both copolymer and polymer changed slowly with increasing segment-B component of the copolymer up to 40%, thereafter they increased considerably with increasing segment B component. Moreover, it was found that the h of the copolymer was obviously shorter than that of the homopolymer for the segment-B composition region from 0% to 80%. Finally, a phase diagram showing I phase and II phase regions under the condition of constant temperature is presented.     

剪切流动对共混物相行为影响的研究进展

介绍了国外８０年代以来开展的剪切流动对聚合物共混物相容性影响的研究概况，并着重介绍了采用最新的二维小角激光散射流变仪和光学显微流变仪对共混物体系在剪切应力作用下相行为的研究结果，反映了该前沿领域的最新进展。     

聚合物共混物的相容性及相分离

综述了聚合物共混物相容性和相分离的研究现状。介绍了聚合物共混物的相容性理论,影响相容性的因素及改善和相容性的方法和表征相容性的手段。聚合物共混物的相分离机理制约着材料的性能,旋节分离和成核－增长相分离分别形成不同的形态结构。旋节分离和成核－增长相分离所对应的动力学过程是不同的,散射光强与相分离时间分别满足指数和幂指数关系。     

剪切流动对聚合物共混物相行为影响的研究进展

剪切流动对聚合物共混物相行为影响的研究进展;综述     

二元共混聚合物的热诱导周期性相分离

Simulations were carried out for studying the periodic phase separation of a symmetric binary polymer blend on the basis of Cahn-Hilliard-Cook theory. The time dependent interaction parameter ?(?) was assumed to undergo a step-wise oscillation. The hierarchic structures composed of both large and small domains were obtained. The mechanism of the periodic formation of hierarchic structures was also demonstrated.     

Polymer Blends

The concept of appropriately combining two or more different polymers to obtain a new material system with the desirable features of its constituents is not new. Over the years, numerous systems based on the chemical combination of different monomers through random, block, and graft copolymerization methods have been developed with this goal in mind. For similar reasons, the coatings and rubber industries have long blended together different polymers, and particularly over the last decade the interest in polymer blend systems as a way to meet new market applications with minimum development cost has rapidly increased. This approach has not been without its difficulties and has not developed as rapidly as it might have, in part because most physical blends of different high molecular weight polymers prove to be immiscible. That is, when mixed together, the blend components are likely to separate into phases containing predominantly their own kind. This characteristic, combined with the often low physical attraction forces across the phase boundaries, usually causes immiscible blend systems to have poor mechanical properties. Despite this difficulty, a number of physical blend systems have been commercialized, and some of these are discussed later. However, there are ways around this problem of compatibility. Much research has shown that there are many truly miscible polymer pairs that can lead to significant opportunities for new products. Even for immiscible pairs, proper control of phase morphology during processing and/or the addition of “compatibilizing” agents can improve the interfacial situation mentioned above.     

Stabilized Polymer Blends

Abstract

Today, producers of plastics are expected to tailor very different properties on request, without much financial and technical effort. But since the costs and the risks of newly developed polymers are high, the interest of industries has turned to combinations of polymers that are already available: 1) In blends [l, 2], different polymers are simply mixed; 2) in copolymers [3], different polymer segments or blocks are chemically tied together. Both principles are combined in blends with copolymer components.     

含无规共聚物三元共混体系SMMA-PMMA-SAN相行为

含无规共聚物共混体系的相容性研究正在成为近年来的研究热点 ,因为相容的驱动力来自共聚物分子内不同单体链段间的排斥性相互作用 [1～ 3] .目前研究这类体系还主要采用过份简化的 F- H平均场理论 ,用旨在克服平均场理论缺陷的 Flory状态方程 ( EOS)理论仅局限于研究二元共聚物共混体系[4～ 8] .与三元共混体系相比 ,用 EOS理论预测含两个无规共聚物三元体系相行为尚需确定共聚物 -共聚物间的二元参数 sj/si,Xij和 Qij.若用 Ax B1- x和 Cy D1- y分别代表共聚物 1和 2 ,则 A,B,C,D代表相应共聚物中的单体单元 ,x,y分别是 1和 2的共…     

高分子混合物薄膜的相分离行为

从高分子混合物薄膜的相分离行为的机理，相分离后期粗化动力微区尺寸与时间的标度关系，影响高分子混合物薄膜表面形态形成的因素等几个方面对近年来高分子混合物薄膜相行为的研究进展进行总结，概述了今后可能的发展趋势。     

流变学方法测定共混物相图及其分辨尺度探讨

应用小振幅振荡剪切(SAOS)和小角激光散射(SALS)测定了苯乙烯-马来酸酐共聚物/聚甲基丙烯酸甲酯(SMA/PMMA)共混体系相分离温度,并分析了动态储能模量对频率响应的敏感程度以及不同测试方法在相分离判据方面的差别.认为前者是造成由不同的测试频率得到的相边界之间存在差异的原因,而SAOS与SALS得到的相边界不同则缘于后者;通过评估不同温度下分散相的尺度,发现选择合适的测试频率进行SAOS测试可以得到比SALS法更小的分辨尺度.     

DSC Studies of Thermally Induced Phase Separation of Hydrogen Bonded Polymer Blends

The thermally induced phase separation behavior of hydrogen bonded polymer blends, poly(n-hexyl methacrylate) (PHMA) blended with poly(styrene-co-vinyl phenol) (STVPh) random copolymers having various vinyl phenol contents, was studied by temperature modulated differential scanning calorimetry (TMDSC).The enthalpy of phase separation was determined to be about 0.5 cal g^–1 for one of the blends. A phase diagram was constructed from the TMDSC data for one of the blends. The kinetics of phase separation was studied by determining the phase compositions from the glass transition temperatures of quenched samples after phase separation. Subsequently, the phase separated samples were annealed at temperatures below the phase boundary to observe the return to the homogeneous state.This revised version was published online in November 2005 with corrections to the Cover Date.     

Shear‐induced Apparent Shift of Phase Boundary of Binary Polymer Blends

Summary: The combined influence of the thermodynamical and hydrodynamic effects of shear was tentatively considered for the first time, in the modeling of the shear‐induced phase behavior of binary polymer blends in this paper. In this model, the original “two‐fluid” model proposed by Onuki 1 , 2 was modified by replacing the quiescent thermodynamical term with the one defined in the frame of extended irreversible thermodynamics (EIT). 3 - 5 The stress term of the polymer blend was determined by using the mixing rule of “Double Reptation” 6 , 7 along with the Graessley's 8 functions to make the model applicable in both linear and weak non‐linear regions. Then the apparent shift of phase boundary of a model blend system was computed by using this theory. It's found that this modified theory can predict both the “miscibility gap” and anisotropical phase separation of the polymer blend, while the two different previous theories, that is the pure thermodynamical one and hydrodynamic one, could only predict one but not both of them. For example, this modified “two‐fluid” model predicts that the miscibility gap can be observable not only in vorticity direction but also in the velocity gradient direction.

The calculated reduced stored energy F_s/RT as a function of Φ_A and the temperature T (shear rate: 0.5 s⁻¹).     

温度梯度引起的聚合物共混物梯度相形态的研究

研究了两相不相容聚合物共混物在静态退火时,由温度梯度引起的分散相尺寸的空间分布梯度相形态,讨论了分散相体积分数和两相之间界面张力对梯度形态形成的影响.应用接触凝聚模型计算了在温度梯度作用下,分散相粒子的粗化过程.计算结果表明,界面张力越大,或者分散相体积分数越大,形成的梯度相形态越明显;并且在温度梯度存在下,分散相粒子粗化的速度加快.     

Polymer Blends Modified Asphalt

Asphalt is an important low-cost thermo-plastic material which is widely used for construction, in particular as road-paving. Therefore it is exposed to a wide range of load and weather conditions. Increasing traffic factors, such as heavier loads, higher traffic volume and higher tire pressure demand higher performance pavements. However, this kind of materials does not have good mechanical properties because it is hard and brittle in cold weather, and soft and fluid in a hot environment.     

聚合物共混：Ⅰ.聚合物共混物的制备方法

本讲主要介绍聚合物共混物的制备方法,其中包括熔融共混、溶液共混、胶乳共混、冷冻干燥共混、接技共聚共混、互穿聚合物网络、就地反应型共混、分子共混等.     

Effect of Nanoclay on the Phase Separation Behavior of Poly（methyl methacrylate）/Poly（vinyl acetate） Binary Polymer Blends

The effect of nanoclay on the phase-separation behavior of poly（methyl methacrylate）/poly（vinyl acetate）（PMMA/PVAc） blends has been mainly investigated by small-angle laser light scattering. It is found that the effect of clay on the thermodynamics and kinetics of phase-separation for PMMA/PVAc blends seems inconsistent. The kinetics phaseseparation rate decreases, while the thermodynamics parameters, cloud points Tc and delay time tD of isothermal phaseseparation also decrease, and the variation amplitude depends on the matrix composition. The affinity of clay to PMMA results in the composition difference between the border layer and the polymer matrix and further causes the concentration fluctuation at the early stage of phase separation to reduce Tc and tD. On the other hand, the decrease of phase-separation rate is caused by the mechanical barrier effect of clay on the macromolecular diffusion of blend matrix. Hence, such seemingly counterintuitive results on the thermodynamics and kinetics of phase-separation are attributed to different dominant factors.     

Influence of the Phase Distribution of Filler on the Viscosity of Heterogeneous Polymer Blends

The influence of the distribution of carbon black between phases of binary heterogeneous blends of polyethylene with elastomers on the viscosity of their melts was studied.