GB856427A - Improvements in or relating to the manufacture of reinforced synthetic resin articles - Google Patents

Abstract

A moulded reinforced synthetic resin article of complex shape is produced by a method comprising first impregnating a knitted fabric, which is extensible under load, with a heat-hardenable synthetic resin e.g. a phenolformaldehyde resin in admixture with a filler, e.g. chalk, partially curing the heat-hardenable synthetic resin impregnated in the knitted fabric, and thereafter subjecting the knitted fabric so treated to a moulding operation to produce the complex shape, in which operation the curing of the synthetic resin is completed. A complex shape is one which requires a deep draw of the reinforcement during the closing of the mould, i.e. an amount of draw which is beyond the limit of extensibility of the commonly-employed substantially inextensible reinforcement fabrics. The knitted fabric may be of any organic or inorganic material or mixture of organic and inorganic materials, that is capable of being knitted into a fabric that is extensible under load, and can be bonded by the synthetic resin, e.g. glass, rayon or cotton. The synthetic resin may be used in the form of a solution. The impregnated and partially cured cloth may be cut into sheets and a number of plies, depending on the required thickness of the final object, placed over the female half of a matched mould. The plies are held around the periphery of the mould cavity by means of a pressure plate or draw ring and the heated male half made to descend slowly, warming and extending the sheets at points of contact. The mould is finally closed under pressure, and the sheets allowed to cure. Alternatively, the sheets may be heated by infra-red lamps after they have been clamped over the female mould, so that the male half can be made to descend at a faster rate.