Durability of fiber-reinforced polyoxymethylene composites under the high hydrostatic pressure in the deep sea

The effect of hydrostatic pressure of up to 40 MPa on the seawater permeation, crystalline structure, and mechanical strength of carbon fiber and glass fiber-reinforced polyoxymethylene (POM) composites was investigated. The experimental results reveal that hydrostatic pressure slightly promotes seawater permeation throughout the POM composites and degrades the bonding strength of the matrix-fiber interface. In the POM matrix, the seawater hydrostatic pressure does not influence the chemical stability but induces a physical chain scission process, which is characterized by linearly decreased molecular weight. The chain scissions initially entangled in the amorphous region are supposed to have sufficient mobility to join the crystalline phase. The increased crystallinity, albeit slight, together with the compress effect of hydrostatic pressure may possibly account for the stable mechanical strengths of the POM composites. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48686.