5. Shipbuilding

Here, the most important characteristic is resistance to long-term immersion in seawater. The following points should be carefully considered:

• Effects of water absorption on strength and appearance

  Isophthalic acid-based polyester resins perform better, with a lower water absorption rate, as shown by the curves in Figure 3. , and better temperature resistance than orthophthalic acid-based resins.

  Use in hot water can lead to thermal distortion, higher water absorption and lower hardness. Table 4 shows gives the mechanical properties of some FRPs after long-term immersion in water at 30 ˚C.

• Polymerization rate

  Polymerization should be as complete as possible. The rate of...