Typical Formulation Ingredients
Phase
Ingredient
Parts by weight
A
Epoxy novolac resin (Epoxy equivalent weight 176-181, 20000-50000 cps at 52°C)
A
Epoxy resin (Epoxy equivalent weight of 177-188, 7000-10000 cps at 25°C)
A
Diglycidyl ether of 1,4-butanediol or diglycidyl ether of cyclohexanedimethanol or other diepoxide diluent
B
Mercaptan (Capcure WR-6, Cognis)
Typical Properties
Mix ratio by weight, Part A : Part B
Gel time (0.3 inch thick) at 25 ° C mins
Gel time (0.3 inch thick) at 4 ° C mins
Gel time (0.05 inch thick) at 25 ° C mins
Gel time (0.05 inch thick) at 4 ° C mins
Maximum exotherm (0.3 inch thick), °C
Heat distortion temperature, °C
Resulting Properties
These adhesives are rapid curing epoxy adhesives processing variable viscosity depending on the filler concentration. The bond will set to a handling strength in approximately 5 mins at room temperature and will develop greater than 1,000 psi tensile shear strength in approximately several hours. Practical cure rates can be achieved at temperatures as low as 4°C. The major disadvantages of mercaptan curing agents are their odor, skinning, and low heat deflection temperature.