Evaluation of Epoxy Resin for Cryogenic Use by Positron Annihilation Method

Change of Characteristics of Epoxy Resin with Crosslinking Density and Positron Lifetime

Abstract

The positron annihilation method has been applied to evaluate unoccupied space in epoxy aiming at the design of the molecular structure for cryogenic use. To confirm the model in which molecular free space is needed in the epoxy for cryogenic use, the molecular weight between crosslinkings in epoxy was changed. The increase of molecular weight between crosslinkings brought an increase of fracture toughness even at liquid helium temperature and the model was found to be confirmed. The increase of molecular weight between crosslinkings was also found to decrease the 3rd lifetime of positrons. It suggested that the epoxy main chains were folded and this was confirmed by the molecular mechanical calculation.