Rubber is an elastic hydrocarbon polymer, also called an elastomer and is a thermoset material. Thermoplastics are materials with the property becoming hard and rigid when cured and are moldable when heated. Rubber softens or fuses when heated and hardens and becomes rigid again when cooled without undergoing any appreciable chemical change. Natural rubber comes from a milky emulsion in the sap of several varieties of plants, called latex. Rubber can also be produced synthetically through the polymerisation of a variety of monomers to produce polymers. Synthetic rubber can be derived using many different chemical formulae or blended with other chemicals, giving it different chemical properties, and produced in varying thicknesses, both of which affect its coefficient of expansion.

Synthetic rubbers include:

EPM and EPDM (ethylene propylene rubber)
Aflas
Nitrile
Polyisoprene and butyl
Polybutadiene (Styrine Butadiene Rubber or SBR) or Nitrile called buna N rubber)
Chloroprene, also called neoprene
Silicone RTV (Room Temperature Vulanized)
FKM Viton®, Tecnoflon®
Santoprene® (PP and EPDM)
Flouorosilicone Rubber
Polyurethane Rubber
Epichlorohydrine Rubber (ECO)
Polysulfide Rubber
Cholorsulfonated Polyethylene (CSM), (Hypalon®)

Silicone rubber is vulcanized using peroxide or sulfur and, sometimes, platinum to cure it. Silicone rubbers, such as caulking compounds, are composed of one or two part liquids cured with moisture or platinum or metal. Successful long term bonding of rubber to itself -- and to other substrates -- requires careful preparation and matching of the adhesive being used with the differing coefficients of expansion (COE) and chemistries of the substrates involved. This COE differential is not usually an issue in bonding rubber to rubber but may be an issue when bonding rubber to rigid substrates, depending on the rubber. BONDiT^TM products are among the few available that can be used to bond rubber to substrates with differing COE's and chemistries for harsh environments and long term deployment without debonding.

Our first recommended product for the vulcanized rubbers is the BONDiT^TM B-45. BONDiT^TM A-43 will bond to cured RTV silicone as a primer. BONDiT^TM B-45 will then bond to the A-43.

Our recommendation would change if Aflas or silicone rubber or RTV silicone is one of the substrates, in which case we recommend priming that substrate with an adhesion promoter, such as BONDiT^TM A-43, prior to using B-45. If bonding EPDM or neoprene to silicone, we recommend priming the silicone with A-43, coating C-31 on top of that, and then vulcanizing the EPDM rubber to silicon rubber.

Your application may call for other BONDiT^TM adhesives or primers, depending on the resistance to chemicals, moisture or impact, or elongation required. To see our tables comparing properties of the various BONDiT^TM products click here.

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

Call or email us for advice on COE ratings and matching BONDiT^TM products for your specific substrates and application at (707) 284-8808 or reltek@reltekllc.com.