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Module 8: Painting GRP

Module 8: Painting GRP. Why is GRP so difficult to paint?. Issue 1: Mould release agents In order to release GRP panels easily from their mould, a coating is usually applied to prior to lay-up.

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Module 8: Painting GRP

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  1. Module 8: Painting GRP

  2. Why is GRP so difficult to paint? • Issue 1: Mould release agents • In order to release GRP panels easily from their mould, a coating is usually applied to prior to lay-up. • This mould release agent is completely incompatible with our paint systems, and MUST be fully removed prior to application of paint. • Removal of mould release is best achieved using warm soapy water.

  3. Why is GRP so difficult to paint? • Issue 2: Air pockets • PRP panels are inherently porous, and contain air air bubbles and pockets. • Air pockets can be BIG! • And they can be microscopic. • Either way they can cause issues in painting.

  4. Why is GRP so difficult to paint? • Issue 2: Air pockets • Large air pockets just under the surface expand during baking, and cause surface blisters. This can mean rework. • The best way to overcome blistering like this is to bake the panel prior to painting. • Use a temperature that is higher than that you will use to cure the paint, and bake for longer. • For example, if you process at 60oC for 30 minutes, pre-bake the panel at 90oC for 45 minutes.

  5. Why is GRP so difficult to paint? • Issue 2: Air pockets • Microscopic air pockets on the surface tend to cause a rough texture. They absorb paint, and act as a porous substrate causing poor appearance and low gloss. • This is extremely noticeable if the GRP panel is next to a flat metal panel that has a good appearance and holds gloss well. • This problem is best fixed by using a higher solids primer surfacer, and sanding. Extreme cases are fixed with putty, or by using a maxi-filler version of the primer surfacer.

  6. Why is GRP so difficult to paint? • Issue 3: Surface distortion • GRP surfaces can be rippled and distorted. This can occur before painting, or during one of the baking cycles. • The problem cannot be “cured” in the paint process, but can be fixed by using putty and high build primer systems.

  7. Questions

  8. End of Module 8

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