Melt Fracture in Soft Solid-Like Polymeric Materials

【摘要】本项目将研究一大类工程材料的非线性力学，即每年生产数千亿磅的纠缠聚合物液体。具体来说，拟议的研究将探索在这些材料加工过程中发生的不同类型的类断裂失效（技术上称为熔体断裂）的分子机制。基于分子工程的策略将被开发，以减少或消除熔体断裂，以提高这些材料的机械性能。各种实验方法将应用于阐明断裂类破坏的真正物理根源：1)屈服和简单剪切破坏，通过研究它们对分子组成的依赖；2)表面熔体断裂，使用一种新的实验设计，作为分子配方的函数；3)入口材料不稳定性，用粒子跟踪测速法研究，并与总熔体断裂相关。长期以来，熔融塑料的机械故障一直阻碍着牛奶瓶、杂货袋、服装（纤维）、汽车保险杠、汽车轮胎和微电子电路板等普通物品的高效生产。所提出的活动的结果可能会产生实际的解决方案，以推迟或消除制造中的熔体断裂，从而使许多塑料制品能够以更快的速度和更低的能源成本制造。阿克伦全球聚合物学院（http://www.agpa.uakron.edu/nn-scied-researchfeatures.html）提供基础设施，允许区域高中教师和学生访问。之前研究的6部电影最近被上传到YouTube.com上，点击量超过500次（关键词：聚合物流变学）。

Melt fracture in soft solid-like polymeric materials (CMMI 0926522)AbstractThis project will study nonlinear mechanics of a major class of engineering materials, i.e., entangled polymeric liquids that are produced at a rate of a few hundred billion pounds per year. Specifically, the proposed research will probe molecular mechanisms responsible for different types of fracture-like failure (technically known as melt fracture) that occur during processing of these materials. Strategies based on molecular engineering will be developed to reduce or remove melt fracture to improve the mechanical performance of these materials. Various experimental methods will be applied to elucidate true physical origins of rupture-like failures related to 1) yielding and failure in simple shear by studying their dependence on molecular composition, 2) surface melt fracture using a new experimental design as a function of molecular formulation, 3) entry material instability to be investigated with particle-tracking velocimetry and correlated with gross melt fracture.The mechanical failure of molten plastics has long prevented more efficient making of such common items as milk bottles, grocery bags, clothing (fibers), car bumpers, automobile tires and microelectronic circuitry boards. Results from the proposed activities may produce practical solutions to postpone or remove melt fracture in manufacturing so that many plastics articles can be made at a faster speed and lower energy cost. Akron Global Polymer Academy (http://www.agpa.uakron.edu/nn-scied-researchfeatures.html) provides the infrastructure to allow access to regional high school teachers and students. Six movies from previous research have recently been uploaded onto YouTube.com and received over five hundred hits (key word: Polymer Rheology).