Unsaturated Polyester Resins
- Unsaturated polyesters are condensation polymers formed by the reaction of polyols (also known as polyhydric alcohols), organic compounds with multiple alcohol or hydroxy functional groups, with unsaturated and in some cases saturated dibasic acids.
- Unsaturated polyester resins are mainly used in the production of fiber-reinforced plastics and filled plastic products, including sanitary-ware, tanks, pipes, gratings, and high-performance components for the marine and transportation industry such as closure and body panels, fenders, boat hulls/decks, and other large.
- Polyester resin offers many advantages, such as low cost, adequate resistance to water and many chemicals, resistance to weathering and aging, reasonable temperature resistance (up to 80°C), good wetting to glass fibers, low shrinkage (4%–8%) during curing, and linear thermal expansion (100–200·10⁻⁶ K⁻¹).
Vinyl Ester Resins
- Vinyl ester resins are typically formulated from styrene and a condensation product of methacrylic acid with an epoxy.
- This condensation product acts as a crosslinking agent and to improve adhesion to glass fibre.
- The curing process is radical initiated.
- These formulations are low viscosity at room temperature and can be used to infuse a reinforcing fabric preform to make large solid parts such as windmill blades.
- More typically the formulation is mixed with chopped glass fiber and sprayed onto an open molds.
- This fabrication technique is an inexpensive way to make composite parts, and it is used for such applications as boat hulls, spas, and storage vessels of various sorts.
