5. Shipbuilding

The most important characteristic here is resistance to prolonged immersion in seawater. The following factors must be carefully considered:

• Effects of water absorption on strength and appearance

  Isophthalic acid-based polyester resins offer better performance and lower water absorption, as shown by the curves in Figure 3 in , and better heat resistance than orthophthalic acid-based resins.

  Use in hot water can cause thermal distortion, increased water absorption, and reduced hardness. Table 4 in lists the mechanical properties of several FRP materials after prolonged immersion in water at 30 °C.

• Curing rate

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