Liquid Silicone Rubbers (LSR)

Liquid silicone rubber (LSR) is used in a wide variety of applications and they constitute the largest group of the silicone family. Their versatility is mainly due to the unique combination of their universal material properties: chemical resistance, hydrophobicity, excellent electrical properties and the ability to withstand extreme temperatures. They are often applied in medical products due to their excellent biocompatibility and the ability to be safely sterilized by various methods.

In order to calculate the filling process, it is usually sufficient enough if only the non-reactive viscosity model is known. The reason for this lies in the fact that the crosslinking (and consequently the viscosity increase) is negligible in many cases until the end of the filling process. As a result, the filling process of liquid silicone rubber can be handled in the same way as for thermoplastics. If the platinum catalyst is omitted in the LSR, measurement of the temperature- and shear rate-dependent viscosity can be performed easily.

If, on the other hand, both curing and shrinkage are relevant – eg. if one considers the entire curing process - the reactive viscosity, curing kinetics and specific volume vs. curing (pvTc) must also be known. One advantage of LSR's is that the components can be stored and transported without time restrictions. They do not become reactive until mixed, which is also favorable for material characterization. Liquid silicone rubbers require special handling during processing before they vulcanize, such as distributive mixing while the material is kept at low temperatures. This defines basic priciples in handling the material both during processing and characterization.

Are you interested in characterizing LSR’s? We are happy to offer you a comprehensive package for the characterization of LSR’s, including measurement of curing kinetics or pvTc. Or do you have questions regarding process simulation of LSR’s? Then please feel free to contact us: sales@simpatec.com.