Fibreglass Reinforced Polyester:
       Material and Process Specifications:

Fibre Glass
Glass Reinforced Polyester (GRP) is commonly known as fibreglass. Hand laid process is the most simple form.

In this process chopped glass fibre strand or mat is impregnated with Polyester resin. The application of several layers results in a laminate the thickness of which can be controlled (common thickness between 2mm-3mm). Hand lay process is carried out at room temperature and allows the use of relatively inexpensive mould made out of wood, plaster or GRP. This process is done on the negetive mould so that a positive can be taken out.

Process:
1. A release agent(wax or polyvinyl alcohol) is applied to the clean mould surface to prevent the laminate from sticking.
2. Two coats of UV stabilised gel coat with pigment and along with catalyst and accelerator are applied to give the part its colour and to achieve the desired surface finish. This protective layer thickness should be 0.3mm ± 10% and it is normally given a drying time of between 15 to 30 mins. depending on the room temperature, humidity and other conditions.
3. A coat of UV stabilised Isopthalic Polyester resin along with pigments is applied. One layer of surfacing mat is applied wherever the surface has curves or bends. Once it has gelled to the gel coat another layer of UV stabilised Isopthalic Polyester resin is applied.
4. Two layers of fibre glass chopped strand mat in criss cross directions are laid in position. Each mat layer is laid in different directions to maximise strength. A brush or roller is used to remove air bubbles and to make sure the mats are saturated in resin. A drying time of between 4-6 hours is given to this. Use of fillers in fabricating gel coat/laminates is strictly disallowed. Similarly, no additionalmonomer such as styrene should be added in the resin.
5. A coat of UV stabilised Isopthalic Polyester resin is applied and it is left for curing and the surplus fibre and resin at the edges are trimmed away. Curing time can be between 8 to 20 hours.
6. After release from the mould, there should not be any blistering or cracking on the surface.
7. The finished FRP laminate should have 27%-30% glass laoding by weight. This will usually correspond to 1 Kg fibre glass mat : 2Kg resin. Approved Polyurethene painting system on the final surface is also to be applied.

Materials and quantities:
1. Fibreglass chopped strand mat (min. density 450gm per sq m) and surfacing mat (30 gsm) are to be used.
2. Only UV stabilised Isophthalmic polyester resin (UV stabiliser content 0.6%by weight) should be used.
3. Gel coat is UV stabilised Isopthalic resin with catalyst methyl Ethyl ketone Peroxide(min 3% sol mixed in the ratio of 2% by weight) with accelerator Cobalt octate(min 3% sol mixed in the ratio of 2% by weight). Pigment (mixing ratio 20% by weight) also need to be added.
4. Manufacturers UV Stabilised Isopthalic Polyester Resin, catalyst Methyl Ethyl KetonePeroxide, accelerator Cobalt Octate:
M/s Bakelite Hylam Pvt. Ltd.,
M/s Network Polymers Pvt. Ltd.,
M/s Sunteck Fibre Pvt. Ltd.
5. Surfacing mat is in nominal thickness of 0.05cm supplied usually in 1m width rolls of 250m.
Manufacturers:
M/s FGP Ltd.,
M/s Owens Corning,
M/s UP Twiga
6. Fibreglass chopped strand mat of density 450 gsm. Emulsion bonded:
M/s FGP(450E),
M/s Owens Corning(M705),
M/s UP Twiga
Powder bonded:
M/s FGP(450P),
M/s Owens Corning(M723),
M/s UP Twiga.
7. Pigments for FRP:
M/s Kerox Ltd., Bangalore;


Warning:
If FRP is not properly UV stabilised, then it will develop cracks after a period of 2-3 years.



(Please Note:
The specifications and processes mentioned above are a suggestion for proper treatment of materials used in Signages. They in no way indicate absolute figures and also there may be other ways of achieving the same.)