Application

Gelcoats are a critical part of most GRP laminates as they enhance both the performance and the appearance of the finished composite. Good quality is essential, which is why Neogel products are formulated for their toughness, durability, mechanical properties and resistance to corrosion, water ingress and weathering. But product quality and consistency alone cannot guarantee trouble-free production. Good workshop practices are essential and great care must be taken to ensure that mould surfaces are clean and properly prepared before gelcoating. Equally important is the way in which the gelcoat is applied. We have compiled a list of what you should do and a few things that you should avoid.

Please ensure that you:

• Establish the correct gelcoat type before starting work
• Ensure complete and thorough mould preparation
• Stir each pail thoroughly but slowly (to prevent air entrapment) before use
• Ensure that gelcoat and moulds are in the temperature range of 16-30°C before starting. Ideally the mould temperature should be 2-3°C higher than that of the NEOGEL. Cure will then start on contact giving a more glossy Neogel surface
• Keep relative humidity below 80%. High water vapour concentrations in the work area lead to under curing even at elevated temperatures. It is also essential to keep water from condensing on the mould surface
• Ensure that the mould surface is properly treated with release agent. Do not use silicone based release agents. Water based products must be perfectly dry before Neogel is applied
• Neogel is supplied ready for use. Do not add solvents such as acetone. If the application method requires a lower viscosity, up to 2% of styrene may be added
• Catalyse Neogel with MEKP at a level of 1-2%. If catalyst levels are too high or too low, undercure can result making Neogel less resistant to weathering and water ingress
• If pigment is added, ensure colour fastness and compatibility before use. Add pigment at the recommended level, accurately weighed and mixed in using low shear equipment
• When spraying, build thickness to the required level in 3 or 4 passes to enable fine air bubbles to be released
• If spraying Neogel ensure the correct nozzle settings and spray pressures and distance are used
• Apply an even layer of Neogel with a thickness from 400 to 600 microns (equal to 550-700 grams per sq.metre). With lower thicknesses Neogel may be under cured, with higher ticknesses, sags, cracks and porosity can occur. Use a gauge to check correct thickness
• Ensure that the mould is well ventilated. Styrene monomer vapours will inhibit the polymerisation and tend to stay in the lower part of the mould because of their higher specific gravity
• Apply back-up layers as soon as the gelcoat is sufficiently cured (firm film yet tacky to the touch)

Avoid the following:

• Do not entrain excessive air during mixing of catalyst and pigment
• Do not use thgh shear mixing equipment. This may cause thixotropy breakdown, pigment separation/flocculation, drainage and air entrapment
• Do not dilute Neogel with solvents other than styrene monomer. When adding styrene do not exceed the maximum level of 2%
• Do not pour Neogel directly onto the mould before brushing out (this causes shadowing). Do not use excessive brushing
• Do not use too rapid a gel time. This does not allow trapped air to escape
• Do not over or under catalyse or pigment
• Do not use silicone based release waxes as these can cause fish eyes

Visit our literature section and download the complete trouble shooting guide