A typical resin has medium viscosity while the gelcoat is a material of higher viscosity. A gelcoat is normally 3 times more thixotropic than a typical resin. This ensures that a layer of recommended thickness can be applied as a single / double coat without any drainage on the given surfaces.
Gelcoat is the outermost layer of the laminate and it applies to the laminate in small quantity (a film size of 500 – 600 µ) this thickness is preferably build up in two coats this layer is used as a protective as well as aesthetic layer to the resin laminate. It also gives the very good cosmetic look to the laminate.

The number of coats depends on the performance of the mould and the mould releasing agent. Please read the instructions given by the manufacturer on the mould release agent for the better results. If you are applying wax or PVA at least three to five coats are recommended before start of the moulding and if it is pva then it should be properly dry before moulding.

Considering 1 sq. mt. of CSM it is generally recommended to have a resin: glass ratio of 2.5: 1. However it varies from individual to individual; more skilled operators work up to 1.8: 1 ratio also, since they achieve proper wetting and consolidation due to their experience.

The amount of catalyst used is highly dependent on the climatic conditions and hence, the percentage added should varies as per the applicable. Less % of catalyst is used during warm conditions and more % of catalyst is added during cold conditions.
Lowest percentage should not be lesser than 0.8 % (on the basis of resin) by the volume of resin and any lower will affect the curing cycle and the laminate will remain under cured. Another option is to get a slower reactivity catalyst though it will extend the gel time of working.
The highest percentage should be 2.5 % by volume of the resin, and any higher will affect the curing cycle. This will lead to fast curing, may cause warpage and cracks in the final product.

Normal clear resin will give you yellow colouring and due to higher exotherm in the normal resin, there might be a chance of cracking or mould may get eroded. Hence, we highly recommend using the specially formulated resin which will have optimum exotherm and will give you clear colour.

A normal pigment used from the market will definitely alter the properties of the final product. Gelcoat is the outermost and most important protective layer for the final product. Using a normal pigment will promote yellowing and the colour fading after some months of use.
Hence, always use pigment pest from the reputed manufacturer.

It is generally recommended to add up to 4% by volume of gelcoat for most of the colours, however it varies depending on the colour and pigment paste concentration.
For the resin, it is recommended to add up to 2-3% by volume of the resin.

A vinyl ester resin has excellent chemical resistance, hydrolytic stability and higher heat resistance. Hence, they are used in areas and applications exposed to the high corrosive atmosphere. However, a general polyester resin is not such a high-performance product and its application is limited to certain areas.

Your final product design depends on the performance of your mould. It is highly recommended to clean the moulds well before application of release agents as all major product failures, poor surface appearance, or lower production is a result of poor mould performance.

There are a special set of resins that exhibit specific characteristic properties for mould making and are called as tooling resins and tooling gelcoats that are used in the preparation of the mould. You are only recommended to use such resins for mould making.

A general unsaturated polyester resin is having limited compatibility with the carbon and aramid fibre in terms of waiting. Hence, it is always recommended to use only vinyl ester resins and epoxy resins formulated to be compatible with carbon fibre structure.

A good finished of the pultruded products is depends on various factors like speed of the line, temperature and the type of LPA use. Hence, your advice to use Polystyrene type of LPA in your slurry formulation.

We can consider this problem in terms of wrinkling which is due to impurities in the catalyst, solvent, and water contamination and also due to over cured surface.
This can be avoided by using good quality catalyst and good quality solvents (It should be moisture free). This can be also avoided by lowering the catalyst percentage.

Acid number is always express on solid basis where polyester resins are use in coating industries since resin will go with the high loading of pigments. in the composite industry polyester resin are not really going with the high loading of pigments hence acid number is always express on solution basis.