Similar to toughened epoxy adhesives, the addition of toughening agents to acrylic adhesive formulations leads to increased peel and impact strength and greater durability and reliability due to more efficient transfer of stress to the rubbery phase. Also like the toughened epoxies, structural acrylic adhesives were found to be outstanding at bonding unprepared or oily metals. Structural acrylic adhesives can also be cured very fast (several minutes at room temperature), and they have excellent adhesion to many plastics and composites.
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RESULTING PROPERTIES
A formula for a toughened acrylic structural adhesive is given in the table above. This adhesive has exhibited lap shear strength on aluminum in excess of 2500 psi and T-peel values in excess of 35 piw.
This adhesive formulation can cure at either room temperature in relatively short time. Tensile shear strength, temperature resistance, and moisture resistance of these adhesives are relatively high. Peel strength of the acrylic thermosetting adhesive is improved by the addition of the toughening agent, in this case chlorosulphonated polyethylene.
