Development and application of novel technique for characterising the cure shrinkage of epoxy resins

The development of a novel hot-stage microscopy technique to measure the level of cure shrinkage that occurs in an epoxy thermoset microdroplet with different epoxy-to-hardener ratios is presented. The equipment setup, sample preparation, and experimental procedure are described in detail. A comparable method to characterise cure shrinkage, a modified rheometry technique, is also reviewed. Shrinkage measurements using the hot-stage microscopy method are shown to characterise the full range of shrinkage that occurs both before and after the resin gel point, hence producing values greater than those found previously in the literature. However, when used in conjunction with the gel point values for the different ratios, measured using rheometry, the technique produces results for shrinkage post-gelation that concur well with literature values. The modified rheometry technique showed potential for measuring the level of cure shrinkage with a varying cure temperature profile, with more work required to perfect the method in defining the cross-over point for sample loading for different epoxy-to-hardener ratios.