Improved Bonding with Long Open Time Polyamides, 1994 Hot Melt Symposium Proceedings

R. L. Gordon, N. W. Harman, C. R. Frihart

Thermoplastic polyamides based on dimer acids are widely accepted by industry as adhesives for a variety of substrates including paper, wood, metal, and some difficult-to-bond plastics such as plasticized PVC. Although these products have an excellent balance of application and performance properties compared to other hot melt adhesives, they have short open-times which limit their utility in some applications. Attempts to overcome the open-time deficiency by producing softer, lower viscosity polyamides usually lead to lower strength and poor creep resistance. Recent development of a new class of polyamides has produced products with dramatically longer open-times without sacrificing the cohesive strength of the polyamides. The slower setting of these products is demonstrated by several adhesion vs. time tests and by dynamic mechanical analysis. These products offer advantages in applications requiring either large surface area coverage or long, complex bead configurations. The new long open-time polyamides can be applied by spray, roll-coat, or hand-held hot melt equipment.