Silicone

Silicones are polymers with a backbone of alternating silicon and oxygen atoms, a bit like a flexible version of glass, with small carbon groups hanging off each silicon. Depending on chain length and cross-linking, they can be oils, gels, rubbers or hard resins. They stay stable from far below freezing to over 200 °C and resist sunlight and weather.

The usual building block is dimethyldichlorosilane, a silicon atom carrying two methyl groups and two chlorine atoms. Mixed with water, each chlorine is swapped for an -OH group, giving off hydrogen chloride. Those -OH groups don't last on silicon: when two meet, they lose a water molecule and leave a silicon-oxygen-silicon link. Again and again, this strings molecules into chains and rings of polydimethylsiloxane. The chains are then lengthened, cross-linked and cured into the final form.

In a TV, silicone has three jobs. In a white LED, clear silicone holds the phosphor over the chip; unlike epoxy, it doesn't yellow under intense blue light. In the remote control, silicone rubber forms the soft keypad. In the diffuser plate, tiny silicone resin beads scatter light. Silicones are made from silicon, the element; the names are easy to mix up.