ISOPOL MHG Gelcoat (White) is a high quality, Lloyd’s Approved, isophthalic polyester gelcoat. This brush gelcoat exhibits improved film levelling to ensure even application, as well as consistent curing characteristics. It has excellent physical properties, water resistance and UV light stability.
Polyester Gelcoat is used to create the resin-rich layer in contact mould making. It is painted onto the surface of moulds/plugs that have been coated with a thin layer of release agent and sets with a tacky surface on the exposed side. Resin and fibreglass reinforcement are typically applied to the tacky surface, while the mould facing surface forms the hard, smooth, shiny surface of the finished article.
Working with MHG Gelcoat MHG gelcoat should be conditioned to a temperature of 18-23 ⁰C before use. Workshop & mould temperature should also be above 18⁰C but lower than 30ºC, as they will cure too quickly. Gently agitate the gelcoat before use and allow to stand for a short period of time to regain thixotropy. MHG gelcoat is intended for brush application and has been specifically formulated to exhibit the correct resistance to drag on the brush, release air and level correctly.
Non-Sagging Brush grades should be applied at a covering rate of 500 to 550 g per sq.m. When properly applied, brush grades typically do not sag. The gelcoat will not entrap air (porosity) when applied as per instructions.
Mixing Catalyst All gelcoats require the addition of catalyst (hardener) to initiate the curing process. The quantity of catalyst is worked out as a percentage of the weight of the gelcoat (e.g. 2% of 1kg gelcoat = 20gm catalyst). Dispensers or weighing scales are advised for accuracy. Temperature plays a large role in the curing process – the higher the temperature, the faster the cure. As a general guide, 2% catalyst addition at 20ºC gives approximately a 15-20 minute pot life. Thorough mixing of catalyst into gelcoat is very important. Stir thoroughly using a mixing stick to scrape any uncatalysed gelcoat from the inner walls and base of the container. The hardening process begins immediately, so only add catalyst to a working quantity. Once catalysed, the gelcoat gradually cures, taking on a jelly-like consistency in about 10-20 minutes before becoming hard in about 30-40 minutes at room temperature (about 20ºC). The curing process generates heat within the gelcoat. Too much catalyst or large volumes of gelcoat increases this heat. Over catalysing the gelcoat (>4%) can cause the material to overheat and sometimes cause a fire.
Applying the Laminate • Mix a maximum of 2kgs at a time, enough for about 3 to 4 sq.m of coverage. • Ensure that the surface is clean, dry and has been coated with an appropriate release agent. • Brush catalyzed gelcoat onto the surface ensuring good coverage. Gelcoats will remain tacky when cured. This is to ensure good adhesion to the following layer of glass and resin