UV Curing for Open Molding Composite Parts

UV curing significantly reduces cure times resulting in increased mold turns and production. In the typical open molding process, resins and fiberglass reinforcement are manually or spray-applied to a gel-coated mold followed by either enter an oven cure or an ambient cure. In either case, the curing takes a long time.

By contrast, in the UV curing process, the open mold enters a UV curing chamber where the entire part surface is exposed to UV light, which starts the curing reaction in seconds. It is possible to cure clear, non-pigmented resin and fiberglass as thick as 1/8 inch or more. It is also possible to cure clear gel coats and some pigmented gel coats, depending on their thickness and color.

Typically, fabricators using unsaturated polyester resins can simply add photoinitiators (the component that generates free radicals upon exposure to UV light beginning the reaction) to their existing resins. Photocurable resins are also available from various suppliers.

UV curing offers the open molder the following benefits:

  • Higher productivity
  • More mold turns
  • Less work in process
  • More consistent finished parts
  • Reduced floor-space requirements
F300s in UV oven

Depending on the part shape and size, the UV lamps move over the part surface via robots or simple mechanisms, the part moves under stationary UV lamps, or a combination of both.

Sometimes a hybrid cure is used, especially for parts that are a challenge for the UV light to cover the entire part surface. In such a hybrid cure, both photoinitiators and traditional composite resin catalysts are used - the UV light quickly sets the surface and kicks off the catalyst cure.

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