Due to its good chemical and physical properties, Liquid Silicone Rubber (LSR) is used in many areas, e.g. automotive, medical and household. LSR can be used between - 50°C to 200°C, it is biocompatible and weather-proof. But compared to other elastomers, LSR is more expensive. For this reason the density should be reduced in order to lower the price.
One possibility is to use expandable microspheres. These comprise a thermoplastic shell encapsulating a low boiling point liquid hydrocarbon. Under the influence of heat, the thermoplastic shell softens and the hydrocarbon expands. This effect could be used in the processing of LSR parts which are cured under heat. One challenge is to determine the balance between the expansion of the microspheres and the cross-linking of the silicone to produce an optimal foam.
The test specimen, which are a tensile bar and puck for compression set, are produced with an injection molding machine. Different proportions of microspheres were mixed in. The test specimen were characterized differently, firstly in terms of their mechanical properties and secondly in terms of the distribution of microspheres.