A structured approach to the determination of residual stresses in an epoxy-amine coating and the influence of thermal ageing on the thermomechanical properties, residual stresses and the corresponding failure modes of coating

Abstract

The purpose of this research was to develop a structured approach for the calculation of residual stresses in organic coatings through the experimental determination of thermomechanical properties of the epoxy-amine coating. The feasibility of this proposed method was validated by the presence of cracks on epoxy amine coating subjected to isothermal ageing at 180 °C for a period of 8 weeks, followed by thermal shock by water quenching at 0 °C, when the tensile strength of coating (8.00 MPa) was surpassed by the accumulated residual stress in the coating (9.66 MPa). The influence of thermal ageing on the thermomechanical properties, residual stresses and the corresponding failure modes were also evident. Significant variation of thermomechanical properties such as the increase in Tg from 77.60 °C to 120.50 °C, reduction of thermal expansion coefficient from 51.74×10−6°C−1 to 40.27×10−6°C−1, reduction of elastic modulus from 1600 MPa to 1400 MPa, and reduction of ultimate tensile strength from 27.00 MPa to 8.00 MPa after thermal ageing were observed. These variations have ultimately led to the increase of residual stresses in coatings that has resulted in the formation of cracks.