Silicone, or polysiloxane, is an inorganic polymer consisting of a silicon-oxygen backbone (...-Si-O-Si-O-Si-O-...) with side groups attached to the silicon atoms. Certain organic side groups can be used to link two or more of these -Si-O- backbones together. By varying the -Si-O- chain lengths, side groups, and crosslinking, silicones can be synthesized into a wide variety of materials. They can vary in consistency from liquid to gel to rubber to hard plastic. The most common type is linear polydimethylsiloxane or PDMS.

The second largest group of silicone materials is based on silicone resins, which are formed by branched and cage-like oligosiloxanes. Silicones are odorless, colorless, water resistant, chemical resistant, oxidation resistant, stable at high temperature, and have weak forces of attraction, low surface tension, low freezing points and do not conduct electricity. They have many uses, such as lubricants, adhesives, sealants, gaskets, breast implants, pressure compensating diaphragms for drip irrigation emitters, dishware, Silly Putty, and many other products.

Due to their thermal stability and relatively high melting and boiling points, silicones are often used where organic polymers are not applicable. Their unreactivity generally makes them non-toxic. Silicone is often mistakenly referred to as "silicon". Although silicones contain silicon atoms, they are not made up exclusively of silicon, and have completely different physical characteristics from elemental silicon.

The word "silicone" is derived from ketone, and is technically not the correct term for these polymers. A true silicone group has a double bond between oxygen and silicon, like a ketone group with Si in place of C (the same terminology is used for compounds such as silane, which is an analogue of methane). Polysiloxanes are called "silicone" due to an early mistaken assumption about their structure, but it has since been shown that they contain no silicone groups at all.

Silicone can come in many different chemical formulae (due to additives) giving it different chemical properties, and in varying thicknesses -- both of which affect its coefficient of expansion. Successful long term bonding of silicone to itself, and to other substrates, requires careful preparation and matching of the adhesive being used with the differing COEs of the substrates involved. BONDiT^TM products are among the few available that can be used to bond silicone to substrates with differing COE's for harsh environments and long term deployment without debonding.

Our first recommended product for bonding silicone plastic is BONDiT^TMA-37 adhesion promoter and adhesive.

Among the other substrates to which silicone plastic can be bonded using BONDiT^TM products are: UHMW, Delrin, fluoropolymers, rubber, polyethylene, polyolefin, polypropylene, polyurethane, other silicones, thermoplastics, thermoset, urethane, ceramics, glass, fiberglass, wood, metals, stone, aggregate and concrete.

To see our chart showing elongation rankings of the various BONDiT^TM products click here. Call or email us for advice on for COE ratings and matching BONDiT^TM products for your application at (707) 284-8808 or reltek@reltekllc.com.