Is silicone recyclable

Not in the way a plastic bottle is recycled. Silicone rubber is a thermoset. During curing, cross links form between the polysiloxane chains and create a chemical network that no longer melts. Heating it therefore does not produce a liquid material, it produces degradation. Grinding and reforming, as happens with PET and HDPE, is chemically impossible.

In practice this means cured silicone rubber belongs in general or residual waste, not in the separate collection for plastic packaging. Silicone is not packaging and, as a thermoset, it disrupts the sorting and processing of the plastics stream. The material goes to an energy from waste plant, where the organic fraction is incinerated with energy recovery. What remains is mainly silicon dioxide, which ends up in the bottom ash.

Chemical recycling does exist. Catalysts break the silicone network down into shorter chains and cyclic siloxanes, which can then serve as raw material for new silicone of virgin quality. The scale is still small and the plants run almost exclusively on clean, separately collected industrial streams such as production scrap and rejected parts. Contaminated moulds from a workshop are not suitable for this.

The most useful form of reuse therefore happens in your own workshop. Cured moulds and casting leftovers can be shredded and cast into new block moulds as filler material, which saves a considerable share of your new material.

Collection rules for households differ per country and often per municipality. Check with your local waste authority, and consult section 13 of the safety data sheet of the specific product.

Read more: reusing cured silicone in a new mould