Physical ageing of epoxy in a wet environment: Coupling between plasticization and physical ageing

Abstract

This paper shows how physical ageing and plasticization processes are coupled in an amine-based epoxy. The study combines several ageing conditions including thermal ageing in the dry state (from 40 to 60 °C), ageing in a humid environment (RH 50% and RH 75%) as well as immersion in seawater at several temperatures from 15 to 40 °C. First results are presented to highlight that the two processes (physical ageing and plasticization) both occur when the epoxy is immersed in water. A step-by-step approach is then used to evaluate how the plasticization process induced by the presence of water is affected by physical ageing and vice versa. It appears that the plasticization process, which leads to a large decrease in maximum stress under tensile loading, is not affected by physical ageing of the epoxy. The physical ageing mechanism is not affected by the presence of water in the polymer, i.e. the same increase in maximum tensile stress (26 MPa) is observed in air and in water. However, the kinetic rate of physical ageing is much faster in water due to the plasticization of the polymer. These effects must be considered when accelerated aging methods are applied. Highlights ► Plasticization process induced by water absorption is not greatly affected by physical ageing. ► Physical ageing process occurs in both dry and humid environments. ► Physical ageing is much faster in the presence of water (by a factor of 10).

Effect of Immersion in Water or Alkali Solution on the Structures and Properties of Epoxy Resin

“…This study focused on the environmental aging resistance of the epoxy resin matrix, including long-term exposure to humidity, temperature, water/salt or alkali solution, etc. It was found that the property evolution of the resin matrix was mainly dependent on the water absorption, and the effect of water molecules on chemical reactions included the destruction of the original group (such as the crosslinking fracture of the molecular segment) and the generation of microcracks and micropores from the swelling of the resin matrix, which had complex effects on the macro mechanical properties of the resin [9][10][11]. Therefore, the evaluation of structures and properties evolution of epoxy resin exposed to the above service environments is significant to provide rapid laboratory testing and long-life evaluation of epoxy resin for engineering applications.…”

Influence of Seawater Ageing on Fracture of Carbon Fiber Reinforced Epoxy Composites for Ocean Engineering

“…At lower temperatures, these changes will take longer. Previous work on this same epoxy resin without fiber reinforcement [35] showed such an embrittlement with physical ageing, with faster property changes at closer to Tg temperatures. This is a reversible process; complete recovery of initial properties was noted after rejuvenation, a thermal treatment above Tg.…”

Creep and Residual Properties of Filament-Wound Composite Rings under Radial Compression in Harsh Environments

“…Based on these values, water is found more detrimental to than temperature. According to Guen-Geffroy et al [ 28 ] and Yang et al [ 14 ], when epoxy resin is aged in a wet environment, the decrease in its can be primarily associated with plasticization. In general, these values are consistent with the values from DSC, and the values are the closest ones.…”