The effect of time and aging temperature on structural and mechanical properties of pipeline coating

Accelerated aging of an organic coating for marine applications has been studied in this work. The studied material, a polymer based on high density polyethylene (HDPE), was immersed in synthetic sea water and at several temperatures. Three values of temperature were undertaken 23 +/- 3, 70 and 90 degrees C. The impact of aging on some of the mechanical and structural properties of this material has been investigated after various aging cycles. Sorption kinetics was studied through water absorption rate response at different temperatures. Similarly, diffusion coefficients of solvent molecules in the coating samples were determined. The activation energy and the mixing enthalpy were also deduced. Also, through this investigation, it was shown that a degradation of mechanical properties was obviously observed. Elastic modulus and tensile strength were in particular decreased. It was also shown that such degradation largely depends on both the aging temperature and aging cycle (immersion duration). A time-temperature dependence of the coating degradation was shown. Finally, the evolution of the mechanical properties coincides perfectly with the structural modifications and chemical changes deduced from FTIR characterization. (C) 2008 Elsevier Ltd. All rights reserved.