Polyester resins such as these are of the ‘unsaturated’ type. Unsaturated polyester resin is a thermoset, capable of being cured from a liquid or solid state when subject to the right conditions. It is usual to refer to unsaturated polyester resins as ‘polyester resins’, or simply as ‘polyesters’. There is a whole range of polyesters made from different acids, glycols and monomers, all having varying properties.
There are two principle types of polyester resin used as standard laminating systems in the composites industry. Orthophthalic polyester resin is the standard economic resin used by many people. Isophthalic polyester resin is now becoming the preferred material in industries such as marine where its superior water resistance is desirable.
UP Resins are widely used in a host of applications where advantage may be taken of their good range of mechanical properties, corrosion resistance and low weight. Un-reinforced versions are most commonly used for clear casting resins, coatings, buttons, body fillers, work-surfaces (such as polyester marble), polyester concrete (for applications such as road drainage) and in the manufacture of Gel Coats (applied to composite materials to improve the surface finish).
The main features of the unsaturated polyester resins include: Liquid, in their use:
Poor linear shrinkage
Excellent wettability of the fibres and charges
Cold cross-linking by addition of hardener
Minimisation of the effect of sagging in vertical stratification (thixotropic properties)
Unsaturated polyester resins are the condensation products of unsaturated acids or anhydrides and diols with/without diacids. The unsaturation present in this type of polyesters provides a site for subsequent cross-linking.
The UPRs are widely used in the building & construction industry. The growth of the construction industry is an important indicator of a country’s development, as it creates investment opportunities across various related sectors. This growth in the construction industry is projected to propel the demand for FRP products. This would lead to growth in demand for UPRs in diverse applications.
Few Indian Major Players
Ashland India Pvt. Ltd.
Ineos Styrolution India Ltd.
Kanoria Chemicals & Inds. Ltd.
Lanxess India Pvt. Ltd.
Reichhold India Pvt. Ltd.
Satyen Polymers Pvt. Ltd.