As the fibre reinforced plastics industry has grown and become more sophisticated, so has the demand for protective coatings and barrier layers. The first materials marketed as protective coatings for composites were pre-formulated, compounded products called gelcoats, which are used as ‘in-mould’ coatings. Today, this has become a highly specialised business involving colour technology, air release requirements, thick film build-up and rapid cure times to produce in-mould finished surfaces with excellent gloss, colour and surface integrity retention after years of environmental exposure. The new gelcoats provide both excellent protection for structural laminates as well as the levels of gloss and colour retention demanded by the motor industry.
In the marine industry problems resulting from osmosis, in the form of surface blistering, prompted the development of fibre reinforced barrier or skin coats to be used immediately behind gelcoats in the form of match performance systems designed to minimise water pick-up and the possibilities of blister formation.
Generally, in pipe, tank and chemical plant component manufacture it is essential to protect the structural laminate from the environment to be contained. Often this can be achieved with a fibre reinforced barrier coat 2 to 3mm thick manufactured using surface tissue, light weight fibre mats and cloths using a suitable chemically resistant resin. In such cases gelcoats are not used because a pure resin without additives provides a greater level of chemical resistance. Hence, the resin-rich surface tissue provides the initial chemical resistant surface and will contain around 95% resin by weight, which is further supported by a resin-rich, structural laminate barrier layer before the final GRP structure is manufactured.
In this Section the need and performance of specialised protection systems for composite materials will be discussed with reference to the various market requirements.
Published courtesy of Dr L S Norwood, Scott Bader Company Ltd