SILRES® BS 7070 is used as a binder for engineered stone, typically based on quartz or replacements like e.g. glass or feldspar. The binder is cured in a radical reaction which is initiated by using a peroxidic radical initiator. The amount of binder depends on the formulation and is typically in a range of 7-13 % by weight.
The functional Silicone resin is admixed with a radical initiator and, if desired, a metal-based accelerator, before adding it to the solid mixture. It is recommended to use about 1 % of radical initiator based on the weight of the binder. All standard radical initiators can be used. Best results can be obtained when using TBPIN (tert-butylperoxy-3,5,5-trimethylhexanoate) as initiator. The use of an additional silane-based adhesion promotor is not required.
Typically, no major adjustment of process parameters compared to the standard process using unsaturated polyester resins (UPR) is necessary. Best results can be obtained when the compacted mixture is cured at temperatures roughly 20 °C higher than for mixtures based on UPR.
To ensure ideal UV-stability, it is recommended to use inorganic pigments only. Consequently, engineered stone based on SILRES® BS 7070 exhibits excellent UV-stability and is, thus, suitable for the installation in outdoor areas. Upon exposure to UV-light, no yellowing occurs. Colored engineered stone can, however, show a slight lightening upon extended UV-light exposure. Typically, ΔE-values of < 1 after 2,000 hours of QUV-B-testing are obtained for white and bright as well as for colored slabs.
Upon request, WACKER offers additives to extend the pot life of mixtures of binder and solids.
WACKER additives can also be used to pretreat quartz granules: These increase the interaction of the binder with the solids, especially with the pigments, thus increasing UV-stability and further reducing the possibility of potential whitening.
