AI 中文总结
研究长链支化、短链支化和多分散性对聚乙烯熔体压敏流变学的影响，用高压滑动板流变仪表征四种聚乙烯熔体，发现分子支链是控制流变响应的主要结构参数，为高压聚合物加工预测模型提供见解。
AI 中文摘要
聚合物熔体在高压下的流变行为是注塑和挤出等许多工业过程中的关键因素，但往往表征不足。在超过100MPa的操作压力下，粘度会增加几个数量级，使得大气压数据不足以进行精确的过程模拟。这种压力引起的粘度增加高度依赖于材料的分子结构。本研究旨在解构短链支化（SCB）、长链支化（LCB）和多分散性等特定结构特征对聚乙烯粘度压敏性的影响。利用高压滑动板流变仪（HPSPR）在均匀剪切和压力下进行精确测量，我们对四种不同的聚乙烯熔体进行了表征。所有样品，无论其结构如何，都表现出压流变性简单的行为，允许在整个剪切速率范围内应用时间-压力叠加。一个关键发现是，文献中已知的热流变复杂的长链支化样品在压流变学上是简单的。这种二分法由温度和压力的不同物理机制解释。通过压力-粘度系数量化的粘度压敏性被发现强烈依赖于分子支化。SCB和LCB都显著增加了压敏性，而多分散性的影响可以忽略不计。这些结果表明，分子支链是控制聚乙烯对压力流变响应的主要结构参数，为开发更准确的高压聚合物加工预测模型提供了关键见解。
英文摘要
The rheological behavior of polymer melts under high pressure is a critical factor in many industrial processes like injection molding and extrusion, yet it is often inadequately characterized. At operating pressures that can exceed 100 MPa, viscosity can increase by orders of magnitude, making atmospheric-pressure data insufficient for accurate process simulation. This pressure induced viscosity increase is highly dependent on molecular architectures of the materials. This study aims to deconstruct the influence of specific structural features such as short-chain branching (SCB), long-chain branching (LCB), and polydispersity on the pressure sensitivity of the viscosity of polyethylene. Utilizing a high-pressure sliding plate rheometer (HPSPR) to ensure accurate measurements under uniform shear and pressure, we characterized four distinct polyethylene melts. All samples, regardless of their structure, exhibited piezorheologically simple behavior, allowing the application of time-pressure superposition over the entire shear rate range. A key finding is that the long-chain branched sample, known from the literature to be thermorheologically complex, was found to be piezorheologically simple. This dichotomy is explained by the different physical mechanisms of temperature and pressure. The pressure sensitivity of the viscosity, quantified by the pressure-viscosity coefficient, was found to be strongly dependent on molecular branching. Both SCB and LCB significantly increase the pressure sensitivity while polydispersity had a negligible effect. These results demonstrate that molecular branches are the dominant structural parameter controlling the rheological response of polyethylene to pressure, providing crucial insights for the development of more accurate predictive models for high-pressure polymer processing.
CommentsPublished in Transport Phenomena; 19 pages; 7 figures
Journal refTransport Phenomena 2026; 1(1): 20260007
