Silicone rubber adhesive shear strength

Table 4.12 Adhesive shear strengths (silicone rubber)...

Cohesive failure was found to be the predominant mode of failure for each rubber compound containing Saret 633 (Figure 8.7). Therefore, it would be expected that as the Saret 633 concentration is increased, the rubber compound would become stronger due to additional crosslinking, which would result in an increase in adhesive strength at the interface between rubber and substrate. This proved to be the case and is shown in Figure 8.8 for EPDM bonded to untreated steel. As the Saret 633 concentration was increased from 0 to 20 phr, the shear adhesion increased from approximately 0.55 MPa for the control to over 11.0 MPa. Cohesive failure was the predominant mode of failure at each concentration. Similar performance was observed for other rubbers, such as nitrile, natural, polybutadiene, silicone and hydrogenated nitrile. 

Satisfactory tensile shear stresses may be achieved in the bonding of glass-filled Noryl or PPO parts with a variety of epoxy, rubber-based, or silicone adhesives. Excellent bond strengths of greater than 5,500 psi have been obtained with Allaco M-2 adhesive (Allaco Products). None of the adhesives listed in Table 5-2 show any evidence of attack on glass-filled PPO or Noryl. 

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