Silicone is a polysiloxane, a synthetic polymer with a silicon-oxygen backbone made from silica and fossil-derived methyl chloride. It is flexible, heat resistant and long lasting.
It replaces single-use zip bags, cling film, plastic lids, straws and bakeware liners. It does not break into microplastics as readily as ordinary plastics.
End of life is the weakness: silicone does not biodegrade, and recycling is a specialist downcycling process that is effectively unavailable to consumers, so most ends in landfill or incineration.
Verdict for the swap finder: a durability swap that is good if it replaces hundreds of single-use items, but not a plastic-free swap. Never market silicone as biodegradable or recyclable. Cost is higher than the disposable plastics it replaces.