FREE-VOLUME DISTRIBUTIONS OF AN EPOXY POLYMER PROBED BY POSITRON-ANNIHILATION - PRESSURE-DEPENDENCE

Positron annihilation spectroscopy has been applied to measure the free-volume hole distributions in an epoxy (DGEBA/DDH/DAB) polymer (T(g) - 62-degrees-C) as a function of quasi-isotropic pressure in the range of 0-14 kbar. The hole radius and volume distributions de from orthopositronium lifetime distributions are found to be dramatically shifted to small values and to be narrower as a function of pressure. The hole radius distributions are found to be between 3.5 and 0.5 angstrom and to have maxima at 2.45, 2.02, 1.40, and 0.78 angstrom under the external pressure of 0.001, 1.8, 4.9, and 14.0 kbar, respectively.