An X-Ray Study of Polyethylene at Pressures up to 14,000 kg/sq cm at 298 K.
RUTGERS - THE STATE UNIV NEW BRUNSWICK N J DEPT OF MECHANICS AND MATERIALS SCIENCE
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The diamond piston-anvil method was used to make x-ray wide angle diffraction studies of polyethylene at 298 K and at pressures up to 14,000 kgsq cm. The data obtained was compared with the results of a study by Ito and Marui, and their observations which were carried out at pressures up to 3000 kgsq cm were essentially confirmed. However, our data revealed that the linear-compressibility in the 110 and 200 directions did not vary with pressure in a linear fashion over the entire range. By ignoring strains in the chain direction, the volumetric strains as a function of pressure were calculated, and the data agreed well with the equation of state derived by Pastine for the crystalline phase of polyethylene. A value for the Gruneisen constant gamma sub o at atmospheric pressure and 298 K was calculated and a value gamma sub o 3.64 was obtained. This agrees well with values obtained by Ito and Marui. No phase transition was observed at 298 C for the pressure range reported.