Morphology, Cocontinuity and Conductive Properties of Anisotropic Polymer Blends
Morphology, Cocontinuity and Conductive Properties of Anisotropic Polymer Blends
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DOI：
10.1021/ma981476u
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发表时间：
1999
期刊：
影响因子：
5.5
通讯作者：
C. Arns;M. Knackstedt;A. Roberts;V. Pinczewski
中科院分区：
文献类型：
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作者：
C. Arns;M. Knackstedt;A. Roberts;V. Pinczewski
聚合物共混是制备具有新型性能的工程材料的常用方法。众所周知，性能主要取决于形态，而形态又取决于混合和后续加工过程中的流动条件。了解形态对聚合物共混性能的影响是通过聚合物共混技术提供更好的框架来预测、控制和改变宏观性能的主要因素。在聚合物共混物的加工中，涉及两个步骤：第一步是使用间歇混合器或连续挤出机对两种聚合物进行熔体共混，第二步是使用注塑成型机等制造设备进行成型。最终共混物的形貌总是受到加工条件的影响；特别是，由于熔体混合和最终成型过程中的剪切作用，共混物呈现出各向异性结构。许多聚合物共混物的研究已经解决了形态发展的问题，重点是流变学和热力学方面的考虑（例如，utrack1）。相比之下，聚合物共混体系的性能仅与组分选择和组成比变化有关，而与形态特征无关。其中一个原因是缺乏合适的混合形态模型表示。在最近的一篇论文2中，我们表明，最初由于Cahn3及其扩展的方法4提供了各向同性共连续共混物的形态和连续共混相的界面膜的自然描述。在本文中，我们将之前的工作扩展到生成现实的各向异性混合形态。我们报告了渗透阈值，并评估了模型两相共混物的各向异性导电性能作为组分体积分数的函数。我们证明了从二维图像中解释双相连续性是有缺陷的。我们展示了一个简单的导电性能理论，它提供了一个很好的近似观察到的共混形态的行为。卡恩的方法最初是用来描述与spinodal分解相关的形态学。因此，描述由相分离产生的聚合物共混物的形态是一个自然的选择。在卡恩提出的原始方案中，人们将密度均匀的两种材料相之间的界面与由N个正弦波组成的随机驻波y (r)的水平集（或等值面）联系起来
Blending of polymers is a common method to produce engineering materials with novel property profiles. It is well-established that properties depend crucially on morphology, which in turn depends on flow conditions during blending and subsequent processing. An appreciation of the influence of morphology on polymer blend properties is a major element in providing a better framework within which to predict, control, and change macroscopic properties via polymer blending technology. In the processing of polymer blends, two steps are involved: the first step is melt blending of the two polymers using a batch mixer or continuous extruder, and the second step is shaping using fabrication equipment such as an injection moulding machine. Invariably, the morphology of the resultant blend is effected by the processing conditions; in particular, the blend exhibits an anisotropic structure due to shear during the melt mixing and final moulding. Numerous studies of polymer blends have addressed the problem of morphology development, with emphasis on rheological and thermodynamic considerations (see eg, Utracki1). In contrast, the properties of polymer blend systems have been correlated simply with component selection and composition ratio variation rather than morphological features. One reason for this has been the lack of a suitable model representation of blend morphology. In a recent paper, 2 we showed that an approach originally due to Cahn3 and its extensions4 provides a natural description of the morphology of isotropic cocontinuous blends and for interfacial films contiguous to the blend phases. In this paper, we extend our previous work to the generation of realistic anisotropic blend morphologies. We report the percolation thresholds and evaluate the anisotropic conductive properties of model two-phase blends as a function of component volume fraction. We show that the interpretation of dual-phase continuity from two-dimensional images is flawed. We show a simple theory for conductive properties which provides a good approximation to the observed behavior for blend morphologies.Cahn’s approach3 was originally developed to describe the morphologies associated with spinodal decomposition. It is therefore a natural choice for describing the morphology of polymer blends generated by phase separation. In the original scheme due to Cahn, 3 one associates an interface between two material phases of uniform density with a level set (or isosurface) of a random standing wave y (r), composed of N sinusoids