Testing pressure variations in press - by hot pressing resin=impregnated sheet together with absorbent sheet whose colour variations produced indicate high and low pressure areas

摘要

The pressure applied over areas by presses for hot pressing laminates are tested by placing a test laminate of resin-impregnated sheets between the platens and hot pressing this together with an absorbent sheet on at least one of its sides. The figure shows one press daylight with two heated platens (1,2) and polished thin metal cauls (3,4) next to the laminar stacks (5,6) on the othersides also (7,8). A test laminate (9) is placed at the centre and consists of a rigid thermally stable substrate film (10), a dark-coloured resin-impregnated sheet (11) and a light-coloured absorbent sheet (12) plus a strip-off separator film (13). The sheets (11) and (12) can be paper. Under the pressure and heat resin is pressed proportionally to the pressure control out of the impregnated sheet (11) into the absorbent layer (12). An absorbent layer (12) can also be used each side rather than merely one. The colours of the sheet (12) when the separator (13) has been removed indicate the areas of high and low pressure produced. ADVANTAGE - The method tests the press under production conditions (i.e. not e.g. cold as hitherto).