There is a lot of mumbo-jumbo out there and very little concrete information on the resins and coatings used in fibreglass (boat) construction and repair. So here goes:
Fiberglass (aka GRP--glass reinforced plastic) is made somewhat analogously to reinforced concrete: The glass fibers, like the rebar, are the skeleton that reinforce the resin (concrete).
Fiberglass is made ("laid up" in the jargon) by layering resin-soaked glass-fiber (mat, mesh, chopped strad, etc.) in or on a frame (the frame giving the shape of whatever you're making--boat, surfboard...). The resin hardens (polymerizes/cross-links) over a few hours. Additional layers are added before the polymerization reaction is complete, ensuring the layers are held together by chemical (covalent) bonds.
Two types of resins make up the majority of fibreglass--polyester and epoxy.
Polyester resins are more accurately called unsaturated polyester resins--unsaturated meaning they contain carbon-carbon multiple bonds (in this case double bonds) which are necessary for the polymerization/cross-linking reaction: Polyester resins are actually solutions of unsaturated polyester linear polymers in styrene (which gives polyester resins their characteristic harsh odor). When a catalyst (usually methyl ethyl ketone hydroperoxide) is added, a free-radical-polymerization reaction takes place forming a network of polyester molecules cross-linked by styrene units:
This is a simplified drawing of the molecules and reactions of polyester resins. In fact, diols other than propylene glycol are used as are various diacids or anhydrides, as well as styrene replacements, allowing tuning of the polyester resin properties. Of course, styrene molecules also sometimes react directly with other styrene molecules and polyester molecules react with other polyester molecules.
Epoxy resins are made by reacting linear epoxyethers with amines. These are sufficiently reactive that they have to be stored separately (Unsaturated polyester resins and styrene will not react at room temperature without a catalyst and can be stored together as a solution). The amine component is often referred to as the hardener; the epoxyether is usually called simply, "resin."
References
1. "Chemistry And Chemical Technology Of Unsaturated Polyester Resins And Related Resins, a presentation by Prof. Dr. rer. nat. Reinhard Lorenz on 31.03.2011.
Fiberglass (aka GRP--glass reinforced plastic) is made somewhat analogously to reinforced concrete: The glass fibers, like the rebar, are the skeleton that reinforce the resin (concrete).
Fiberglass is made ("laid up" in the jargon) by layering resin-soaked glass-fiber (mat, mesh, chopped strad, etc.) in or on a frame (the frame giving the shape of whatever you're making--boat, surfboard...). The resin hardens (polymerizes/cross-links) over a few hours. Additional layers are added before the polymerization reaction is complete, ensuring the layers are held together by chemical (covalent) bonds.
Two types of resins make up the majority of fibreglass--polyester and epoxy.
Polyester resins are more accurately called unsaturated polyester resins--unsaturated meaning they contain carbon-carbon multiple bonds (in this case double bonds) which are necessary for the polymerization/cross-linking reaction: Polyester resins are actually solutions of unsaturated polyester linear polymers in styrene (which gives polyester resins their characteristic harsh odor). When a catalyst (usually methyl ethyl ketone hydroperoxide) is added, a free-radical-polymerization reaction takes place forming a network of polyester molecules cross-linked by styrene units:
This is a simplified drawing of the molecules and reactions of polyester resins. In fact, diols other than propylene glycol are used as are various diacids or anhydrides, as well as styrene replacements, allowing tuning of the polyester resin properties. Of course, styrene molecules also sometimes react directly with other styrene molecules and polyester molecules react with other polyester molecules.
Epoxy resins are made by reacting linear epoxyethers with amines. These are sufficiently reactive that they have to be stored separately (Unsaturated polyester resins and styrene will not react at room temperature without a catalyst and can be stored together as a solution). The amine component is often referred to as the hardener; the epoxyether is usually called simply, "resin."
References
1. "Chemistry And Chemical Technology Of Unsaturated Polyester Resins And Related Resins, a presentation by Prof. Dr. rer. nat. Reinhard Lorenz on 31.03.2011.
