Kinetic and Structural Properties of Semicrystalline Polyolefins derived from NMR, Thermal Analysis and High Resolution Microscopies

Florida Agricultural And Mechanical University, Tallahassee FL

Investigators

Abstract

A research program is described that uses previous experience in the area of semicrystalline polymers and the use of NMR spectroscopy to advance the characterization and structural properties of polyolefins. The research is also projects to improve our understanding of the development of crystalline structure from the non-oriented isotropic melt or during annealing a previously crystallized system. The PI plans to build upon the base of pervious NSF funded programs that allowed training in the use of solid-state NMR, to extend a novel NMR method to obtain the crystallite thickness distributions and mean average thicknesses of narrow fractions of linear polyethylenes previously characterized with other techniques. The method will also be tested in polypropylenes using AFM, SAXS and TEM data to build the required calibrations. A combination of NMR, DSC and AFM will be used to establish the role of a specific lamellar morphology and/or chain conformation in the amorphous regions, in the unique isothermal melting observed in polypropylenes. The kinetics of this process will be also studied. The proposal also includes a research program to assess the nature of the structural changes that take place with time upon annealing previously crystallized polyolefins. Changes will be evaluated in relation to the initial crystalline morphology. Emphasis is given the NMR investigation of relaxation properties of the chains in the intercrystalline regions and WAXS analysis of the halo of well characterized metallocene type polyethylenes and polypropylenes. %%% The FAMU-FSU College of Engineering is a jointly managed program of the Florida State University, a Research I institution with an enrollment of 35,000, and Florida A&M University, a Historically Black University with and enrollment of 12,000. Faculty hold joint appointments at both institutions, and students from both universities enroll in the same engineering classes. The present enrollment at the College of Engineering consists of approximately 50% minority students and over 25% women, making it unique in several respects. The proposed work includes active participation of graduate students and training in current techniques of characterization of polymers. These activities parallel the commitment of the PI to education of students in the area of Polymer Science and Engineering. The PI plans to take advantage of recently NSF funded instrumentation (NMR spectrometer and AFM) to FAMU and FSU at the College of Engineering to expand on characterization and the details of the crystalline state of novel polyolefins.