Page 306 - Handbook of Adhesives and Sealants

270 Chapter Seven

TABLE 7.5 Recommended Silane Coupling Agents for Various Resins. (Union
Carbide, Dow Corning Corp. and General Electric Co. Supply Silane Coupling
Agents)
Silane functionality Applications
Vinyl Free radical cure systems: crosslinked polyethylene,
peroxide cured elastomers, polyesters. Polyethylene.
Polypropylene
Epoxy Epoxy, acrylics, urethanes, polysulfide
Methacryl Unsaturated polyester, acrylic
Amino Epoxy, phenolic, melamine, urethane, butyl rubber
Mercapto Epoxy, sulfur cure rubbers, urethane, polysulfide
Ureido Phenolic, urethane

Virtually all glass fibers used in fiber glass composites are treated
with silane ‘‘finishes’’. The resulting physical properties and the resis-
tance of the composite to deterioration by water immersion are greatly
enhanced by the addition of the coupling agent. Table 7.6 shows the
effect of silane treatment to reinforcing glass fibers on the dry and wet
flexural strength of several composite materials. The moisture resis-
tance properties of filled molding compounds are also enhanced by the
treatment of the fillers with silane adhesion promoters prior to com-
pounding. Silane promoters on wollastonite fillers in thermoplastic
polyester molding compounds (50% filled) will improve the flexural
strength after 16 hrs in 122 F water by as much as 40%.
Silanes are also generally effective in improving adhesion to metals,
including aluminum, steel, cadmium, copper, and zinc. Table 7.7 shows
the relative influence of the type of substrate on the effectiveness of
the silane coupling agent in improving adhesion. It should be noted

TABLE 7.6 Effect of Various Silanes on Glass Reinforced Thermoset Resins 26
Flexural strength
Resin system Silane Dry Wet
Polyester control 60,000 35,000
A-174 87,000 79,000
Epoxy control 78,000 29,000
A-186 101,000 66,000
Malamine control 42,000 17,000
A-187 91,000 86,000

Dry High temperature a
Phenolic control 69,000 14,000
A-1100 85,000 50,000

a Aged 100 hr at 500 F and tested at 500 F.