Casting
Another process for the application of UP-resins without using reinforcing
fibres is the casting process. The resin is cast manually or by means of a
dosing machine in a hollow mould where it cures and solidifies.
In many cases the resins are mixed with fillers to obtain less shrinkage
during cure or to save costs on raw materials. The fillers can also have a
functional effect, such as giving colour or hardness to the cast article. In
some cases the mould is coated with a gel coat before or the resin is coloured
with a colouring paste.
The casting process is used for the production of sanitary articles
(washbasins, kitchen sinks, etc), marking stones, waste water gutters, cattle
feeding troughs, furniture ornaments.
Another application of the casting process, where no fibre reinforcement is
used, is the production of buttons. In this case the activated resin is poured
into a rotating cylinder. The curing system is adjusted in such way that a
slow and gradual cure develops. Before the curing is complete, the still
flexible sheet of resin is taken from the cylinder and rolled out. Button
rounds can be punched from the sheet and subsequently cured in hot water.
