New processes for extrusion and injection moulding of foamed rubber products

摘要

The extrusion of automotive door sealings is a sophisticated process. For the characterisation of rubber compounds for this process, a novel test procedure is presented for establishing the correlations between compound properties and expansion behaviour during the extrusion process. In addition to the compound properties, the influence of sample geometry and and vulcanisation temperature can be assessed. This method has some advances compared to the use of an oscillating shear vulcameter with an additional normal force measurement. For the same manufacturing process, the use of physical blowing agents attracts more and more interest as an alternative to chemical blowing agents. Experiments carried out with EPDM-compounds on a laboratory extrusion line with hot air vulcanisation using physical blowing agents will be presented, which show the influence of process parameters on the foaming behaviour. Foamed rubber components produced in injection moulding are produced to-day by adding chemical blowing agents during compounding. As an alternative, physical foaming is presented here. In the injection moulding machine the compound is charged with nitro-gene or carbon dioxide during the injection phase. A special injection nozzle has been developed for this purpose. Foam density and cell structure can be influenced in the moulding process.