Which factor is NOT a cause of pre-release?

High humidity is not typically considered a cause of pre-release in composite materials. Pre-release occurs when the cured composite or gel coat releases from the mold prematurely, which can be influenced by various factors related to the materials and the process used.

Promoter levels can directly affect the curing process of resins. Using too much promoter can accelerate the polymerization to the point where the mixture may not adhere properly to the mold surfaces, leading to pre-release issues.

Excessive film thickness may lead to improper curing and heat buildup, which can also cause the composite to release from the mold due to uneven curing or cooling rates.

Using an improper release agent can lead to inadequate bonding and increased likelihood of pre-release. If the release agent is not suitable for the type of composite material being used or is applied improperly, it can create a surface that allows for early separation of the cured part from the mold.

In contrast, while high humidity can affect the overall environment and potentially influence curing, it is not a direct cause of pre-release, which is more closely linked to the materials and application techniques used during the composite forming process.