GOALI: To Understand Flow-Induced Crystallization Characteristics of Polyethylene

在这个学术与工业联系机会(GOALI)项目中，将对材料进行协调研究。半结晶聚合物提供了由结晶材料赋予的高度理想的强度组合和由微晶之间的精细分散的非晶区提供的韧性。这种纳米复合结构的形貌和取向分布决定了最终的材料性能。这类聚合物能够生产高强度纤维、薄膜和注塑零件，广泛应用于汽车和生物医药行业。聚烯烃是占主导地位的半结晶聚合物(年产量超过1250亿磅)，在经济增长和生活水平提高方面发挥着至关重要的作用。然而，作为它们加工-结构-财产关系基础的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，试图发现加工历史对聚乙烯的微观结构和材料性能产生巨大影响的分子基础。加州理工大学独特的实验能力使其能够实时观察在等温条件下精确定义的剪切过程中和之后的结构发展。雪佛龙-菲利普斯正在提供一系列聚乙烯样品，这些样品跨越了被认为是工业中最重要的分子变量。加州理工学院和雪佛龙-菲利普斯公司将对这些材料进行协调研究，以深入了解流动增强结晶过程中发生的一连串事件，这些动力学如何取决于分子属性，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，这种大学-行业合作产生的对加工-结构-性能关系的分子洞察力可以加快新聚乙烯树脂的开发，以提高生产率和/或卓越的产品性能。加州理工学院和雪佛龙-菲利普斯公司之间的合作将为研究生和本科生提供共同的导师，将他们的学术培训与工业问题联系起来。

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.