Page 453 - Handbook of Adhesives and Sealants

Adhesives Families 391

TABLE 10.17 Tensile Shear Strength of Various Substrates Bonded with
Thermosetting Acrylic Adhesives 31
2
Avg lap shear, lb/in. at 77 F
Adhesive Adhesive Adhesive
Substrate* A B C
Alclad aluminum, etched .................. 4,430 4,235 5,420
Bare aluminum, etched ................... 4,305 3,985 5,015
Bare aluminum, blasted................... 3,375 3,695 4,375
Brass, blasted ............................ 4,015 3,150 4,075
302 stainless steel, blasted ................ 4,645 4,700 5,170
302 stainless steel, etched................. 2,840 4,275 2,650
Cold-rolled steel, blasted .................. 2,050 3,385 2,135
Copper, blasted........................... 2,915 2,740 3,255
Polyvinyl chloride, solvent wiped........... 1,375† 1,250† 1,250†
Polymethyl methacrylate, solvent wiped .... 1,550† 1,160† 865†
Polycarbonate, solvent wiped .............. 2,570† 960 2,570†
ABS, solvent wiped ....................... 1,610† 1,635† 1,280†
Alclad aluminum-PVC .................... 1,180†
5
Plywood, ⁄8-in. exterior glued (lb/in.) ...... 802† 978†
1
AFG-01 gap fill ( ⁄16-in.) (lb/in.) ............ 1,083†
*Metals solvent cleaned and degreased before etching or blasting.
†Substrate failure.

been used to improve flexibility and impact resistance in thermoset-
ting acrylic adhesives. Even with the addition of elastomeric modifiers,
these thermosetting acrylics are relatively rigid adhesives with low-
to-moderate peel strength and poor strength properties at low tem-
peratures. Unmodified acrylic adhesives are particularly noted for
their weather and moisture resistance as well as their fast cure at
room temperature. Selected thermosetting acrylic adhesives are listed
in Table 10.15.
One manufacturer has developed an acrylic adhesive system where
the hardener is applied to the substrate as a primer. 32 The substrate
can then be stored for up to 6 months. When the parts are to be
bonded, only the acrylic resin needs be applied between the already
primed substrates. Cure can occur in minutes at room temperature
depending on the type of acrylic resin used. In effect, this system offers
a fast-reacting, one-part adhesive with indefinite shelf life. Another
method of achieving cure with the acrylic systems is to apply the hard-
ener to one surface and the resin to the other surface. When the two
surfaces are bonded together, a fast cure occurs, developing handling
strength in 60 secs. 33 Of course, acrylic adhesives can also be metered,
mixed, and applied in the more conventional way. The fast cure and
variety of application alternatives make this adhesive valuable in
many production processes.
Because of their rapid cure and high strengths (3,000–5,000 psi),
acrylic adhesives are used in high speed automated assembly opera-