EFFECT OF VARIOUS PREEXPOSURE AGENTS ON METHANE SORPTION AND DILATION IN TETRAMETHYL POLYCARBONATE

The effects caused by preexposure of tetramethyl polycarbonate (TMPC) to CO2, C2H4, and C3H8 on subsequent apparent equilibrium CH4 sorption and dilation are explored. Three exposure histories are studied: (i) no preexposure (unconditioned), (ii) preexposure to CO2, C2H4, and C3H8, respectively, followed by depressurization to vacuum (conventionally conditioned), and (iii) preexposure to high swelling levels, with the same three agents, followed by exposure to CH4 without depressurization (exchange conditioned). The unconditioned samples exhibit the lowest CH4 sorption and dilation levels while the exchange-conditioned samples exhibit the highest CH4 sorption and dilation levels. The increases above the unconditioned levels for the exchange-conditioned samples depend only on the swelling level achieved during the conditioning step and are independent of the conditioning agent. On the other hand, the increases seen for the conventionally conditioned samples show a slight dependence on the conditioning agent possibly due to the occurrence of an effective "templating" of the free volume distribution during the conditioning procedure.