Rigid adhesives such as epoxies and cyanoacrylates break easily when a crack starts. Toughened grades add a dispersed rubbery phase, such as liquid rubber or core-shell particles, that stops cracks from running through the bondline. Peel and impact strength rise sharply with only a small loss of stiffness. Automotive crash-durable adhesives and black rubber-toughened CA are typical examples.
Use the toughened epoxy on the hinge plate, the plain one cracked off in the drop test.
Also heard as
- rubber-toughened
- impact-modified
Related terms
Epoxy
A thermoset adhesive cured by reacting epoxy resin with a hardener, the benchmark for strong, rigid structural bonds.
Cyanoacrylate
A one-part instant adhesive that cures in seconds when trace moisture on a surface triggers it.
Peel stress
Tension pulling one adherend away from the other at the edge of a bond, concentrated along a thin line.
Cleavage
Loading that pries a rigid joint open from one end, concentrating stress along the leading edge of the bond.