Effect of the Nature of Oxide Nanofillers on Changes in the Mechanical Properties of Epoxy Coatings under Thermal Cycling

The paper demonstrates the applicability of micro indentation as a sensitive method for detecting the effect of the nature of oxides as fillers on the properties of epoxy coatings in comparison with conventional physicochemical methods of infrared spectroscopy (IR) and thermogravimetry (TGA). This applicability was discovered when studying the surface mechanical properties (hardness, elastic modulus, and creep) of epoxy coatings filled with nanoscale oxides TiO۲, SiO۲, and ZnO. The behavior of the mechanical characteristics of the materials under thermal cycling at temperatures ranging from −۴۰ to +۶۰ °С was evaluated by instrumented indentation with the use of a Fischerscope HM system after ۵ and ۱۰ cycles. It is shown that the ۱۰% addition of TiO۲ oxide increases the values of hardness and the elastic modulus by ۵ and ۱۵%, respectively, while the addition of SiO۲ and ZnO decreases them by ۷ and ۵%. The micromechanical properties of the studied materials depend on the time of the increase in mechanical loading. All the compositions exhibit viscous properties consisting of hardness decrease with the decreasing rate of loading. Thermal cycling decreases the hardness and elastic modulus of the unfilled epoxy coating and those containing SiO۲ and ZnO by ۱۲ and ۱۸%, respectively, and it ensures the self-restoration of the hardness of the TiO۲-filled coating. All the additives decrease the creep index. Thermal cycling increases the creep index for all the materials under study.

Keywords:

Coatings , Epoxy resin , Mechanical properties , Thermal properties