Fig. 5: Effect of Pergut on the initial strength
Peel strength [N/mm]
Example: Light-colored phase-stable Baypren contact adhesive
Initial formulation: Baypren 320 Rhenofit® D/A Bayoxide Z aktiv® Pergut S 40 Heat-reactive alkyl phenolic resin
100 pbw 7 pbw 4 pbw 0/10 pbw 40 pbw
Ethyl acetate White spirit, boiling range 65/95°C Cyclohexane Methyl ethyl ketone
35 pbw 70 pbw 140 pbw 105 pbw
The color of Baypren-based adhesives is dic- tated by the resin. With resin-free formula- tions, the open time is shorter, particularly in toluene-free adhesive solutions. In such cases, the addition of Pergut can prolong the open time while giving higher initial bond strength. Such resin-free adhesives al- so have good storage stability and have no “phasing” tendency. Baypren 328 (Fig. 6) has been developed specifically for this application. It differs from the other standard grades with respect to the faster solubility of the chips, lighter inherent color and better resistance to discoloration.