Friday, October 27, 2017

Duratec 904-001 Hi-Gloss Additive

Gelcoat will not harden if exposed to air.  When it is sprayed into a mold, the mold itself keeps the air away from that side and allows it to cure.  When the fiberglass cloth and resin is layed up on top of the gelcoat, it keeps the air away from that side.   

If you are using gelcoat in a layup like the picture above, you actually do not want the surface of the gelcoat to cure hard because the subsequent cloth layers will not have a molecular bond and stick very well, and delamination could occur.

To get gelcoat to harden when it is exposed to air such as an external repair of spray job, liquid wax is added or a mold release agent is sprayed over it to keep the air away.  While curing, the wax rises to the surface and forms a barrier to the air.  The key to getting this to work out well is to not add too much wax, which causes porosity, and not have the gelcoat cure too fast, giving enough time for the wax to rise.  It's a tough balancing act and if it fails, the gelcoat will be sticky and gum up the sandpaper.

A California company, Dura Technologies has created an additive that you mix 1:1 with gelcoat.  It slightly thins the mixture but best of all, it allows the gelcoat to air cure and not be sticky.  Since we will be spraying multiple layers to build up a sandable thickness, a layer of wax does not form on the surface between coats preventing adhesion of multiple layers.  They also claim that it allows a Hi-Gloss super hard surface and it makes spraying gelcoat like spraying paint.   

We'll see. 904-001.pdf

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