GOALI: To Understand Flow-Induced Crystallization Characteristics of Polyethylene

California Institute Of Technology, Pasadena CA

Investigators

Abstract

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.