Moisture Uptake and Release by Plastic Molding Compoundsits Relationship to System Life and Failure Mode

Plastic molding compounds show two major moisture uptake rates, one fast and one slow. The fast rate represents the moisture uptake mechanism that is responsible for moisture dependent failures in epoxy novolac plastics. It is felt that the fast rate represents transport through the organic epoxy matrix by hydrogen bonding. Silicone epoxy shows a much slower rate of moisture uptake after an initial induction period. The moisture dependent failure is therefore controlled by the slower rate in silicone epoxy. The slower rate is thought to be uptake by the silica filler matrix.