Adhesive strength bonding temperature effect

Fig. 38. Effect of resin type in Neoprene latex 750 adhesives on canvas-to-canvas peel strength. Bonds aged 7 days at room temperature [14].

As with PSA, the phenolics are added primarily for increased cohesive strength and temperature resistance ([216], pp. 284-306). More phenolic is used in adhesives with higher strength requirements, e.g. for metal-metal bonding. Resins based on /j-/-butyl phenolics are most commonly selected ([216], pp. 284-306). They are usually present in the adhesive at 35-50 parts per 100 rubber (phr), with typical optima at 40-45 phr ([216], pp. 284-306). Significant deviation from this optimum may have drastic effects. 

The phenoxy resins can also be plasticized with many of the common plasticizers and still maintain a high percentage of strength, while the bonding temperature is substantially reduced. An effective hot-melt adhesive is one in which polyvinyl ether is blended into the phenoxy resin. 

Bonding strength at low temperatures is another property that can be enhanced by the chemical incorporation of flexibilizer (Fig. 25). Comparison of the effect of temperature on the shear modulus and the torsional adhesive strength of a bonded aluminium-to-aluminium joint reveals that the incorporation of a flexibilizer reduces the shear modulus but, by imparting greater flexibility, increases the torsional adhesive strength of the bond at low temperatures. ... 

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