A study conducted by French researchers from the CNRS « Catalyse, Polymérisation, Procédés et Matériaux » laboratory of the Université Claude Bernard in Lyon, have described in Science [1] a new method of recycling silicone waste (caulk, sealants, gels, adhesives, cosmetics, etc.).
According to the authors, this chemical recycling process can bring any type of used silicone material back to an earlier state in its life cycle where each molecule has only one silicon atom. Allowing to design new silicones infinitely, this solution would have the potential to significantly reduce the sector’s environmental impacts!
The raw material used to make silicones is naturally occurring quartz [2]. Its constituents are decomposed using metallurgy at high temperature to obtain pure silicon. That then reacts with methyl chloride to form chlorosilanes, molecules essential to all silicone-based polymers. These first two transformations are very energy intensive and emit CO2, the main greenhouse gas causing climate change.
The recycling technique would make it possible to circumvent this energy-consuming step.
“Moreover, as this chemical recycling process gives direct access to (methyl)chlorosilanes, which can be separated and purified industrially, it guarantees the quality of silicone materials from recycling, and can do that infinitely without loss of properties,” said the authors in a press release.
Amid growing tensions over natural resources—particularly quartz and its derivative, silicon, which are critical to the electronics industry—this process also enables access to new sources of silicones.
The authors and their industrial partners [3] continue their research to make the process industrially applicable and target other stages of silicone manufacturing.