By: The Stoner Molding Solutions Experts

Composite fabricators who mold with polyester or vinyl ester resins/gel coats are confronted with the issue of styrene monomer build up on the mold surface.  Every time a molding cycle occurs, a small quantity of styrene monomer attaches itself to the mold surface.  Over time and frequency of molding cycles this manifests itself as dull spots on the mold surface.  Not only do the dull spots potentially require sanding or polishing of the finished part to restore uniform gloss, they also make the part more difficult to release.  For high volume producers achieving one or more molding cycles per day, styrene monomer build up is a significant headache that fairly quickly leads to taking the mold out of production and performing mold maintenance to remove the buildup.

As most high volume fabricators are using a semi-permanent release agent to achieve multiple release cycles, a stripping of the mold now requires reapplication of the sealer and release agent.  A simple solution to significantly extend the number of molding cycles achieved before mold maintenance is required due to styrene build up is to incorporate a washing of the mold with Mold Cleaner after several molding cycles.  There is a common misconception by fabricators that Mold Cleaners will remove a semi-permanent release agent from the mold surface.  This is not the case.  Abrasion removes a semi-permanent from the tool.

There is no common number of molding cycles it takes for a mold to show styrene build up as fabricators use different resins that have different gel & cure properties.  Furthermore, mold geometry, molding processes, molding cycles per day, and temperature all affect build up.  Regardless, the idea is to perform a cleaning of the mold surface with Mold Cleaner BEFORE actual build up is observed.  When applying the Mold Cleaner, liberally saturate a clean, non-abrasive medium such as a white cotton rag (no seams) followed by a final buffing with a micro fiber towel.  If this process is performed prior to actual observation of styrene build up, then little effort is required for the solvents to emulsify any styrene and remove it.  Stoner uses a special blend of solvents in KantStik Mold Cleaner that are specifically designed to remove styrene and surface contaminates such as grease, sweat, etc.  After the cleaning, perform a tape test to insure there is adequate slip for the next molding cycle.  If not, apply more semi-permanent.

If this process is performed consistently and regularly, the fabricator will achieve better looking parts, produce more parts, reduce significantly the amount of time a mold is out of service, and lower their overall costs of mold maintenance.  Please note this procedure ONLY WORKS with semi-permanent systems.  Unfortunately the solvents used in Mold Cleaner will also remove paste wax.

If you have questions proper mold cleaning, please reach out to us. The Stoner Molding Solutions experts are eager to assist you in saving time and money.

Stoner Molding Solutions is a leading supplier of industrial mold release agents in the polyurethane, plastic, rubber and composites fields, based in Quarryville, Pa. For more information, call Toll-free 1-888-303-5198 (US) or +1-717-500-3515 (International).