Page 436 - Handbook of Adhesives and Sealants

Adhesives Families 377

properties, nitrile-phenolic adhesives are used commonly for bonding
linings to brake shoes. They are also used in the aircraft industry for
bonding of aluminum facings to honeycomb cores. Other applications
include electronics, footwear, and furniture assembly.
Nitrile-phenolic adhesives are generally available as solvent solu-
tions as well as supported and unsupported firm. They require heat
curing at 300–500 F under pressure of up to 200 psi. The nitrile-
phenolic systems with the highest curing temperature have the
greatest resistance to elevated temperatures during service.

10.3.6.2 Vinyl-phenolic. Vinyl-phenolic adhesives are based on a com-
bination of phenolic resin with polyvinyl formal or polyvinyl butyral
resins. Because of their excellent shear and peel strength, vinyl-
phenolic adhesives are one of the most successful structural adhesives
for metal. Room-temperature shear strength as high as 5,000 psi is
available. Maximum operating temperature, however, is only 200 F
because the thermoplastic constituent softens at elevated tempera-
tures. Chemical resistance and impact strength are excellent.
Vinyl-phenolic adhesives are supplied in solvent solutions and as
supported and unsupported film. The adhesive cures rapidly at ele-
vated temperatures under pressure. They are generally used to bond
metals, rubbers, and plastics to themselves or each other. A major
application of vinyl-phenolic adhesive is the bonding of copper sheet
to plastic laminate in printed-circuit-board manufacture.

10.3.6.3 Neoprene-phenolic. Neoprene-phenolic alloys are used to
bond a variety of substrates. Normal service temperature is from 70
to 200 F. Because of high resistance to creep and most service en-
vironments, neoprene-phenolic joints can withstand prolonged stress.
Fatigue and impact strengths are also excellent. Shear strength, how-
ever, is lower than that of other modified phenolic adhesives.
Temperatures over 300 F and pressure greater than 50 psi are
needed for cure. Neoprene-phenolic adhesives are available as solvent
solutions and film. During cure these adhesives are quite sensitive to
surface contamination from atmospheric moisture and other process-
ing variables.

10.3.7 Polyaromatic high
temperature resins
Polyimide, bismaleimide, polybenzimidazole, and other high temper-
ature resins belong to the aromatic heterocycle polymer family that is
noted for its outstanding thermal resistance. These resins are known
as aromatic polymers because of their closed ring structure which