Typical Formulation Ingredients
Phase
Ingredient
Parts by weight
A
Polyester diol (Cardolite® NX-9203LP, Cardolite)
A
Polyether triol (Voranol™ 260, Dow Chemical)
A
Calcium carbonate powder
A
Adhesion promoter (epoxy silane)
B
Modified diphenylmethane diisocyanate (Isonate™ 143LP, Dow Chemical)
Typical Properties
Mixed viscosity, cps, at 25°C
Water absorption at 25°C, % 7 Days
Water absorption at 25°C, % 14 Days
Aluminum Adhesion strength, MPa
Polycarbonate Adhesion strength, MPa
PVC Adhesion strength, MPa
Nylon Adhesion strength, MPa
Resulting Properties
The formulations above are for general purpose two component polyurethane adhesives based on polybutadiene polyol. Using polybutadiene polyol will provide much better hydrolytic stability than other conventional polyols (e.g., polyester or polyether).
Often additives are not required to provide flexibility or toughness as in the case of epoxy formulations. Polyurethanes have the capability of providing these properties through manipulation of the resulting molecule by proper choice of isocyanate and polyol. However, additives are used mainly to stabilize the adhesive relative to moisture, oxidation, UV, etc.