Introduction to Polyamide Adhesives

Epoxy-polyamide adhesives, formulated with epoxy resins, contain long fatty acid carbon chains, resulting in a tough yet non-brittle cured product. They have less stringent mixing requirements, a long pot life, and are easy to apply. They exhibit strong adhesion, showing good bonding performance to metals and most non-metals. The cured product has low shrinkage (low or even non-toxic), making it an environmentally friendly adhesive. Heating can accelerate curing and improve bond strength; curing at 120°C for 30 minutes is equivalent to 7 days at room temperature. However, its heat resistance is relatively low, with a maximum operating temperature of 60°C.

Low-molecular-weight polyamide curing agents are constantly being innovated, with varieties including low-viscosity, transparent, fast-curing, high-adhesion, and water-based types. Some can achieve peel strengths exceeding 10 kN/m for epoxy adhesives, which is more than five times that of typical aliphatic amine curing agents.

Although epoxy-low molecular weight polyamide adhesives have good toughness, the bond strength of systems without toughening agents is not high. For example: 100 parts (by weight) of E-51 epoxy resin, 50 parts of 651 polyamide, 50 parts of light calcium carbonate, 2 parts of DMP-30, and 1 part of KH-550. Curing at 80°C for 3 hours. The room temperature shear strength of the bonded steel is 18.2 MPa.