9419508 Mandelkern The main objective of this research program is to improve our understanding of the thermodynamics, structure and properties of nonoriented, bulk-crystallized flexible-chain polymers. The research will be concerned with the interrelation between molecular, phase, and superstructures and crystallization kinetics and macroscopic properties. Carefully characterized molecular-weight and composition fractions of linear polyethylenes, as well as well-defined blends of these components will be studied. Small and wide- angle x-ray scattering will be used to investigate the phase structure. These studies will be correlated with thermal measurements and analysis of Raman spectra. The influence of the initial topology and melt structure on the resultant crystalline state will be investigated. Studies of tensile properties will be emphasized. Advantage will be taken of a recently constructed apparatus that only requires very small amounts of sample. Emphasis will be given to the influence of stain rate and temperature, as well as molecular and structural factors, on key tensile properties and the transition between ductile deformation and brittle failure. %%% These studies should give us a better understanding of the molecular and structural factors that govern macroscopic properties of crystalline polymers and improve the end-use of this class of polymers. ***
