GRP is composed of strands of glass. Each individual glass fibre is very fine with a small diameter, and they are woven to form a flexible fabric. The fabric is normally placed in a mould, for instance a mould for a canoe and polyester resin is added, followed by a catalyst (to speed up the reaction). The process is repeated so that there are many layers of fibre glass and resin and allowed to dry/cure. The resulting material is strong and light. Glass Reinforced Plastic can be sanded for a smooth finish and painted.
Pipes made of centrifugally cast glassfiber reinforced plastics (GRP) consist of a combination of thermosetting plastics such as for example unsaturated polyester or vinyl ester resins, chopped glass fibers and reinforcing agents.