Long-term evolution of the compression properties of polyurethane foam under seawater corrosion

Polyurethane foam (PUF) can be used as a filling material for compressible layers in subsea tunnels. However, its long-term durability under subsea conditions has rarely been studied. In this study, confined compression tests were conducted on PUF immersed in artificial seawater for 400 days to investigate its durability in a corrosive environment. The test results demonstrated that the elastic modulus E and yield strength ac of aged PUF samples exhibit a U-shaped evolution, first decreasing with time up to 180 days and subsequently increasing to 74.4 % and 93.6 % of their initial values, respectively, when immersed in artificial seawater for 400 days. The scanning electron microscopy (SEM) images of the aged PUF samples show that the decrease in E and ac is mainly induced by the corrosion of artificial seawater, leading to the initiation and propagation of microcracks and windowburst. The increase in E and ac after 180 days may be induced by the formation of hydrogen bonds.