The mechanical behavior of polymeric materials reflects the underlying physics of the mobility of the polymer chains. We have investigated the response of polycarbonate under three different conditions that will alter the polymer mobility: changes in temperature, strain and aging. We have examined the degree to which we can superpose the effects of these conditions to create master curves that can extend predictions beyond the range of feasible laboratory time scales. It was found that superposition could be successfully applied in each case, but that time-temperature superposition led to a master curve that was significantly different from that found using time-strain superposition. It was also found that curves fit to the [relatively short time] individual relaxation measurements at different temperatures could not be fit to the resulting master curve. Experiments were also performed to investigate the polymer mobility in volume recovery below the glass transition. It was found that volume equilibration required much longer than equilibration of the mechanical response in aging experiments, suggesting that simple free volume models may be inappropriate.
|Number of pages||19|
|Journal||ACS Symposium Series|
|State||Published - 1998|