Abstract
Charpy specimens of a filledβpolymeric system from two partially cured and two completely cured lots obtained from one supplier were stored at selected temperature and relative humidity (RH) conditions to determine the relationship between mobile water content and the fracture toughness of the material. The fracture data showed that specimens from three of the structures exhibited similar ductileβtoβbrittle transition temperatures (DBTT) as a result of exposure to these environments even though samples from one of the three units were subjected to only part of the pure cycle. Samples from the other partially cured structure consistently displayed a more ductile fracture behavior throughout the conditioning range studied. Exposure to 100Β°F/75 percent RH environments, the highest temperature and RH of this study, appeared to enhance the fracture toughness of the material from all four units, and no evidence of deleterious chemical aging was found. Mobile water contents were measured on Charpy fracture residues, and these results correlate well with DBTTs of the filled polymer, as does RH. Charpy specimens from the partially cured structure with the best fracture performance have essentially the same water concentrations as the others, suggesting that the lower DBTTs associated with this unit may be due to a lesser degree of crosslinking.