GB859106A - Reinforced plastic molding process - Google Patents

Abstract

859,106. Moulding fibre-reinforced resin. REEVES, J. F. May 25, 1959, No. 17692/59. Class 87(2). [Also in Group XXXII] A mould cavity reducible in volume is used, a flexible porous material, e.g. fibre glass cloth, first being positioned in a predetermined arrangement in the cavity and a free-flowing liquid plastic under atmospheric pressure then being added while maintaining the cavity at a constant volume large enough to avoid substantial pressure on the material and for a period of time sufficient to cause the plastic to penetrate the material and displace the entrapped air the volume being subsequently reduced so as to apply pressure to the material and the cavity maintained at the reduced volume until the plastic hardens. The mould illustrated, which is for the manufacture of large trailer tanks of the milk transport type, comprises a lower mould 4 and a movable upper mould 3, a gutter 14 surrounding the entire upper edge of the lower mould. The inner surface of the lower mould is first sprayed or otherwise coated with a plastic layer, e.g. a polyester resin to which a thixotropic agent has been added, forming a pressure-sensitive adhesive surface over which a reinforcement 17 of fibre glass cloth is placed. The cavity is then lined with a thermal insulating material 18, e.g. balsa wood, the lower mould 4 being used as a jig over which the balsa wood is curved and fitted together. Deformable material such as fibre glass mat is interposed between the balsa wood 18 and the cloth 17 to avoid the formation of voids. At this stage a stainless steel lining 19, which is first sprayed or otherwise coated with spray resin, is placed on the partly completed balsa wood construction. Deformable material such as fibre glass mat should be inserted between the balsa wood 18 and the lining 19 as it is difficult to curve or form the balsa wood so as to exactly conform with the lining. The tank skirts are additionally reinforced with fibre glass cloth 17c hung between the walls 4a, 9a from wooden blocks 23. Fibre glass mat is arranged between the two cloth layers so as to provide a cushioning effect. The upper mould 3 coated on its surface 9 with fibre glass cloth 17c is then lowered but not fully closed. Plastic of water-thin consistency, e.g. of polyester resin to which a catalyst and promoter have been added to cause it ultimately to harden, is then pumped into the moulding enclosure, control of the filling being effected by dropping a dip stick into one or more riser pipes 29. The plastic is maintained at atmospheric pressure until the entrapped air has escaped when the bolts 8 are placed in position and the nuts 13 screwed down, the excess and still free-flowing, water-thin liquid plastic being driven upwardly into the gutter 14. Specification 815,036 is referred to.