Control of Structural Morphology in Shear-Induced Crystallization of Polymers
Control of Structural Morphology in Shear-Induced Crystallization of Polymers
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DOI：
10.1021/ma902495z
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发表时间：
2010-03-09
期刊：
影响因子：
5.5
通讯作者：
Ryan, Anthony J.
中科院分区：
文献类型：
--
作者：
Mykhaylyk, Oleksandr O.;Chambon, Pierre;Ryan, Anthony J.
批判性的研究发现，最长的链发挥催化作用，在形成shish烤肉串招募其他链到这种形态的形成。所有系综中的最长链通过剪切流拉伸以形成“shish”，在其上大部分材料结晶为“串”。提供了一种用于形成串晶结构的通用参数，具体的机械功，以及一种方法，通过该方法可以测量任何给定的聚合物系综。在旋转平行板流动中，在取向和非取向材料之间观察到明显的边界，该边界取决于剪切速率和总应变。我们发现，形成取向核的必要条件是剪切速率应大于系综中最长链的反劳斯时间，并要求在临界阈值以上的机械功。进行这种测量所需的实验程序，以及必要的预防措施，以避免文物，如拉长球晶，弹性不稳定性和pholoelasticity，详细检查。作为一个控制参数的临界功的概念已被证明使用模型线性线性氢化聚丁二烯共混物，这一概念被扩展到工业聚合物，低密度聚乙烯和聚丙烯，使用小角度X射线散射和偏振光成像来测量取向。所提出的方法是简单的，是优雅的，并且可以很容易地在实验室中实施，以研究流动诱导结晶的基本过程，并在真实的应用中处理之前测试商业材料。
Critical examination finds that the longest chains play a catalytic role in the formation of shish kebabs recruiting other chains into the formation of this morphology. The longest chains in ail ensemble are stretched by shear flow to form the "shish" upon which the bulk of the material crystallizes as "kebabs". A universal parameter for the formation of shish kebab structures, the specific mechanical work, and a method by which it may be measured for any given ensemble of polymers is provided. In rotating parallel-plate flow a clear boundary is observed between oriented and unoriented material which is dependent on both the shear rate and the total strain. It has been found that the necessary conditions for the formation of oriented nuclei is that the shear rate Should be larger than the inverse Rouse time of the longest chain in the ensemble and that mechanical work above it critical threshold is required. The experimental procedure required to make such measurements, and the precautions necessary to avoid artifacts such as elongated spherulites, elastic instabilities and pholoelasticity, are examined in detail. The concept of the critical work being a control parameter has been previously demonstrated using model linear-linear hydrogenated polybutadiene blends and this concept is extended to industrial polymers, low-density polyethylene and polypropylene, using both small-angle X-ray scattering and polarized light imaging to measure orientation. The approach proposed is simple, is elegant, and can be easily implemented in the laboratory to study the fundamental processes of flow-induced crystallization and to test commercial materials before processing in real applications.