GOALI: To Understand Flow-Induced Crystallization Characteristics of Polyethylene

在这个与工业界学术联络的资助机会（GOALI）项目中，将进行材料的协调研究。半晶聚合物提供了晶体材料所赋予的强度和晶体之间精细分散的非晶区域所提供的韧性的高度理想的组合。这种纳米级复合结构的形貌和取向分布决定了材料的最终性能。这类聚合物能够生产高强度纤维、薄膜和注塑件，广泛应用于从汽车到生物医学行业。聚烯烃是主要的半结晶聚合物（每年生产超过1250亿磅），在经济增长和提高生活水平方面发挥着至关重要的作用。然而，对结构形成的基本理解在很大程度上仍然是一个谜。加州理工学院和雪佛龙-菲利普斯公司的科学家们正在合作，以发现加工历史对聚乙烯微观结构和材料特性的巨大影响的分子基础。加州理工学院独特的实验能力可以在等温条件下精确定义剪切期间和之后实时观察结构发展。雪佛龙-菲利普斯公司正在提供一系列聚乙烯样品，这些样品涵盖了工业上最重要的分子变量。这些材料的协同研究将在加州理工学院和雪佛龙-菲利普斯公司进行，以深入了解流动增强结晶过程中发生的级联事件，这些动力学如何依赖于分子属性，以及这些动力学如何与由完全相同的聚乙烯样品制成的吹膜的结构和机械性能相关。反过来，从这种大学-工业合作中产生的对加工-结构-性能关系的分子见解可以加速新型聚乙烯树脂的开发，从而提高生产率和/或提高产品性能。加州理工学院和雪佛龙-菲利普斯公司之间的合作伙伴关系将为研究生和本科生提供与工业问题相关的学术培训的共享指导。

In this Grant Opportunity for Academic Liaison with Industry (GOALI) project, coordinated studies of materials will be conducted. Semicrystalline polymers offer the highly desirable combination of strength conferred by crystalline material and toughness provided by finely dispersed noncrystalline regions among the crystallites. The morphology and orientation distribution of this nano-scale composite structure dictates the ultimate material properties. This class of polymers enables production of high strength fibers, films and injection molded parts widely used from automotive to biomedical industries. Polyolefins are the dominant semicrystalline polymers (over 125 billion pounds produced annually) and play a vital role in economic growth and increased standard of living. Yet the fundamental understanding of structure formation that underlies their processing-structure-property relations remains largely a mystery. Scientists at Caltech and Chevron-Phillips Co. are teaming up to discover the molecular basis of the dramatic effects of processing history on the microstructure and material properties of polyethylene. Unique experimental capabilities at Caltech enable real-time observations of structure development during and after precisely-defined shearing under isothermal conditions. Chevron-Phillips is providing an array of polyethylene samples that span the molecular variables considered most important in industry. Coordinated studies of these materials will be conducted at Caltech and Chevron-Phillips to provide insight into the cascade of events that occur during flow-enhanced crystallization, how these dynamics depend on molecular attributes, and how these dynamics relate to the structure and mechanical properties of blown films made from precisely the same polyethylene samples. In turn, the molecular insights into processing-structure-property relations emerging from this university-industry collaboration can speed development of new polyethylene resins for improved production rates and/or superior product performance. The partnership between Caltech and Chevron-Phillips will provide shared mentorships for graduate and undergraduate students relating their academic training to the industrial issues.