< VULCANISED RUBBER

SYNTHETIC RTV ELASTOMERS

RTV or ‘Room Temperature Vulcanisation’, rubbers are notable by virtue of the fact that they are mixed, set and then cure at ambient room temperature, without any artificial application of heat or pressure. RTV rubbers are usually supplied as a two pack product consisting of a ‘base’ polymer and a catalyst. Once mixed to specific proportions with the base polymer, the catalyst initiates an irreversible chemical reaction that causes the rubber to set then cure.

A catalysed RTV rubber is usually applied to a master pattern either by pouring into a surrounding mould case, or painting on directly (with a support case applied after curing). Although some RTV rubbers allow additional layers to be added to a previously set layer (as might happen if the quantity of rubber needed for a job has been under estimated), it is generally considered good practice to mix enough rubber to complete a mould section in a single application. Sandwiched layers of some RTV rubber products can delaminate under certain conditions, and this could obviously affect the serviceability of the finished reproduction mould.

Among the most versatile of all foundry moulding products, RTV rubbers are capable of accepting a wide range of filler materials for creating cast reproductions. In addition to wax and plaster of Paris, possible fillers can include high exothermic resins and a selection of low melting point metals and alloys.

As a rule, the RTV group of rubber compounds are are among the most robust and durable moulding media, this makes them an excellent choice for making moulds for long term use and storage. Three of the most common RTV type rubbers are described in the following pages.

POLYSULPHIDE RUBBERS >