The development of tensile shearing bond strength in 35 kinds of cold setting epoxy resins have been investigated according to ASTM D 1002-64. The experimental conditions were as follows: The adherend was an atmospheric corrosion resisting steel, the curing period was 1, 2, 4 or 8 days, and the curing was made under the atmospheric condition at 4°C in 65 per cent R. H. or the underwater condition at 4°C.
The results show that the tendency of the strength development can be classified into three types; the increase curve type, the decrease curve type and the convex curve type. The latter two types basically belong to the same category because the decrease curve type also must have a peak. Their characteristics have to be improved by the addition of flexibilizer. In all cases, the strength reached a constant level at about 8 days' curing.
The value of the strength at the constant level varied from 2 to 124kg/cm² with the average value of 58kg/cm² in the case of atmospheric curing, while it varied from 1 to 111kg/cm² with the average value of 39kg/cm² in the case of underwater curing. 28 kinds of the epoxy resin systems showed higher strength values in the case of atmospheric curing than those in the case of underwater curing, but other 7 kinds of epoxy resin systems showed the reverse results. The total average of the ratio in the strength between underwater curing and atmospheric curing for all the samples was about 65 per cent.