Hydrolytic Degradation

Chemical Mechanism

Exposure to water molecules causes the ester, amide, or ether groups in a polymer chain to undergo cleavage. When hydrolytic degradation occurs, the reaction rate increases with higher temperatures and the presence of acidic or basic catalysts. This process gradually reduces the molecular weight of the material, which reduces its tensile strength.

Designers must choose materials with stable chemical bonds to avoid this failure mode in wet environments.

Material Selection

Transitioning from laboratory prototypes to outdoor industrial applications requires rigorous testing of moisture resistance. Evaluating hydrolytic degradation during the prototyping stage helps engineers select the right protective coatings or additives. If a material is selected too early, before long-term humidity testing is complete, the final product may fail prematurely in the field.

This failure can lead to expensive recalls and warranty claims.

Industrial Consequence

Using susceptible plastics in critical structural applications can cause sudden component failures and operational shutdowns. Preventing hydrolytic degradation requires the use of stabilizers or alternative materials such as polyolefins in wet conditions. In a typical automotive application, using unstabilized polyesters in engine compartments has been shown to result in component failure within two years of operation.

By selecting polyamides or adding specific moisture scavengers, manufacturers can extend the operating life of these parts to ten years, thereby protecting the vehicle’s long-term reliability. This material change avoids the costs associated with unscheduled maintenance and maintains high safety ratings in humid climates.