Primers or adhesion promoters are low viscosity materials applied to surfaces that raise the surface energy of low surface energy substrates and provide chemically linking between adhesives and sealants and difficult to bond substrates. Primers tend to be substrate and adhesive/sealant specific, i.e., some primers are recommended for polyolefins but not metals and some are recommended for cyanoacrylates but not epoxy adhesives. Consult manufacturer data sheets for more information.