Epoxy resin

Epoxy is the strong two-part glue many people know from hardware stores. Once cured, it's a hard, tough plastic that sticks to almost anything, resists heat and chemicals and barely shrinks. It can't be melted again, which makes it a thermoset.

The resin is made from bisphenol A and epichlorohydrin, reacted together with sodium hydroxide, which strips off the chlorine as salt. Each bisphenol A molecule ends up capped at both ends with an epoxide, a tight three-membered ring of two carbons and an oxygen. That's the resin, a honey-like liquid, or a solid if the chains are longer. It stays stable until it meets a hardener, such as an amine, or a catalyst set off by heat or light. Then the epoxide rings spring open and lock everything into a rigid network.

Epoxy is all over a TV. It binds the glass cloth in FR-4 laminate circuit boards and the layers of package substrates. It's the binder in black mold compound around chips, a key ingredient of solder mask, the clear lens of an infrared LED and the dark, infrared-passing case of an infrared receiver. In the LCD panel, an epoxy-based sealant, often blended with acrylate, holds the liquid crystal in.