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Composite manufacturing processes
Published in A.R. Bunsell, S. Joannès, A. Thionnet, Fundamentals of Fibre Reinforced Composite Materials, 2021
R. Bunsell, S. Joannes, A. Thionnet
The surface finish of the composite which is made depends on the quality of the surfaces of the mould. Many structures have a gel-coat which is a surface layer of resin, usually containing other products which act both as fillers and modify the properties of the resin. Such a gel-coat takes on the finish of the mould and, if this is very smooth, can provide an excellent surface finish. Most pleasure boats and some bigger boats such as mine sweepers, are made by applying the composite to an open mould which has the shape of the hull. The attractive appearance of many of these crafts is due to the quality of the moulds and the gel-coat which ensures a smooth surface finish. The gel-coat can be coloured to give the composite material a particularly desired appearance and is also used as a protective layer against abrasion and water ingress, although this latter characteristic is not as obvious as it is often claimed as water can diffuse through such a resin layer. Environmental ageing is discussed in Chapter 11. which discusses long-term behaviour. The gel-coats vary as a function of the composite system used but are often of the same type of resin as used in the matrix. They should not be diluted with acetone as the presence of this solvent can cause problems due to outgassing, forming bubbles and porosities, so producing an unacceptable finish. In the case of polyester resins, the gel-coat can be diluted with styrene monomer. They can be applied to the inside of the mould with a brush or projected onto it. The gel-coat has to be left to gel before the composite can be added to mould and the mould closed.
Rheology and Insulation Behaviour of Composites
Published in G. Mohamed Zakriya, G. Ramakrishnan, Natural Fibre Composites, 2020
G. Mohamed Zakriya, G. Ramakrishnan
A common surface coating or finish for fibre-reinforced composites is a gel coat. This is specifically formulated with polyester resin and is generally applied to the composite material to improve chemical resistance, improve abrasion resistance, and provide a moisture barrier. Gel coats are used to enhance the look of products such as the surface of a boat hull or golf cart. A unique benefit of gel coats is that they are available in many colours, created by the incorporation of pigments as per the specification of an engineer. They protect the look of the product and provides weather resistance for outdoor products. They filter out ultraviolet (UV) radiation, improve chemical resistance, add flame resistance, improve abrasion resistance, and can be layered as a moisture barrier.32,33
Polymer Applications in the Construction Industry
Published in Nicholas P. Cheremisinoff, Elastomer Technology Handbook, 2020
The gel coats may be applied by brush, roller, or spray equipment. In the latter case, great care is necessary since one of the components (styrene) can evaporate quickly and cause undercure resulting in a most unsatisfactory product. A very humid atmosphere can cause the same trouble as, in fact, can moisture of any nature. The presence of moisture will mean a longer curing time (which can be speeded up by the application of heat). In any case, the cure should be made as rapid as possible.
Investigating the mechanical performance of advanced marine coatings used for bonding composites to aluminum in-mold
Published in The Journal of Adhesion, 2022
Codrington E. Barzey, Ronnal P. Reichard
Unsaturated polyester coatings, such as gelcoats, are extensively used as an in-mold coating in the fiber-reinforced plastics (FRPs) industry. Gelcoat is a combination of unsaturated polyester resin and additives. These additives can be pigments, titanium dioxides, ultraviolet stabilizers, inhibitors, and other fillers depending on the specific application of the gelcoat. Manufacturers in the FRP industry use gelcoats as an in-mold coating to improve FRP products’ surface properties and aesthetics. The operator sprays the gelcoat into the mold, allows it to cure, and then laminates the FRP onto the gelcoat in the mold. The laminate is allowed to cure, and the part is removed from the mold and trimmed.[8] This method produces FRP products with finished surfaces without the need for painting. Despite its initial benefits, gelcoats suffer from poor elongation and weathering properties. Research completed by researchers Min et al. and Cherian et al. showed that unsaturated polyester resins suffered from the same disadvantages. They found that the addition of polyurethanes dramatically improved the resin’s mechanical properties. [9,10]10