Requirements

The environment and stresses to which ships are subjected impose a number of requirements on the bonded joints they comprise:

• resistance to seawater, with frequent or permanent contact: seawater often stagnates almost permanently on the bottom of the boat. Table 1 shows the water resistance of some reinforced plastics (US specifications). Warmer water in some countries is more aggressive. Adhesives must have water resistance levels compatible with those of glass-reinforced plastics;

• resistance to fatigue and the alternating stresses of wave impact on the hull: one impact every five or six seconds gives 600,000 impacts after 1,000 hours at sea. In this respect, flexible polyurethane...