Constitutive compressive behavior of polyurea with exposure to aggressive marine environments

Abstract

The constitutive behavior of polyurea after prolonged exposure to aggressive marine environments, including saline water, UV radiation and combinations of both, was investigated in this study. A diffusion study was performed at several temperatures to determine the effect of temperature on saline water ingression into the polyurea using Crank's method. This diffusion data coupled with Arrhenius' methodology allowed for the calculation of an acceleration factor relating laboratory exposure time at elevated temperature to real-life service time. Cast cylindrical specimens were exposed to UV radiation, saline water, and various combinations of UV radiation and saline water. These combinations were: a) exposure to saline water followed by UV radiation, b) UV radiation followed by saline water, and c) saline water and then UV radiation followed by saline water. Uniaxial compressive experiments were conducted on both the virgin and exposed specimens at strain rates of 1.7×10−3s−1 and 2.6×103s−1. Under quasi-static loading conditions, the elastic modulus of the polyurea dropped by 73% after 84 days of exposure to saline water at 85 °C. Specimens exposed to UV radiation showed a maximum increase in the elastic modulus of 64% after 20 days of exposure. When tested under dynamic loading conditions, specimens exposed to saline water for 84 days showed a 48% decrease in strain energy while those exposed to UV radiation showed a 45% increase.