DYNAMIC X-RAY DIFFRACTION FROM POLYETHYLENE

• Main Authors: Kawaguchi, Tatsuro, Itoh, Taisuke, Kawai, Hiromichi, Keedy, Daniel, Stein, Richard S
• Format: Report
• Language: English
• Subjects: CRYSTAL STRUCTURE; Crystallography; HEAT OF ACTIVATION; INTENSITY; Physical Chemistry; POLYETHYLENE PLASTICS; Polymer Chemistry; RHEOLOGY; STRAIN(MECHANICS); X RAY DIFFRACTION

The technique of dynamic x-ray diffraction is described in which the periodically varying diffracted x-ray intensity is analyzed for a sample of a polymer film subjected to a periodic strain. The intensity change may be resolved into a real part, delta I', varying in-phase with the strain and an imaginary out-of-phase component, delta I''. This resolution is carried out for the amorphous scattering and the diffraction from two planes of medium density polyethylene at 30C and at frequencies between 0.02 and 1.25 HZ. Delta I' decreases with frequency and delta I'' increases with frequency in the range as a consequence of a crystal orientation process having a relaxation time of the order of 1 sec. Measurements at temperatures of 30, 45, and 60C produce a frequency shift associated with an activation energy of 25 Kcal/mole which is close to that for the alpha-2 process studied mechanically. By integrating the delta I values over azimuthal angle it is possible to determine the real and imaginary parts of the dynamic orientation function, delta f' and delta f''.