Mechanical characterization of sol–gel epoxy-silylated hyperbranched poly(ethyleneimine) coatings by means of Depth Sensing Indentation methods

• Sol–gel hybrid epoxy-silica coatings were characterized by DSI techniques.
• Coatings become harder and more rigid if the inorganic phase content increases.
• Indentation creep and recovery of coatings were analyzed in terms of composition.
• DSI and previous scratch test results have been correlated.
• Mechanical performance of coatings improves if the silica-phase content raises.

A series of hybrid epoxy-silica coatings were prepared from a synthesized hyperbranched poly(ethyleneimine) with ethoxysilyl groups at the chain ends and diglycidylether of bisphenol A in different proportions. The curing procedure was based in a first sol–gel reaction performed at 80 °C in a humid chamber followed by the anionic homopolymerization of epoxides initiated by 1-methylimidazole in an oven at 180 °C. The prepared coatings were characterized mechanically by means of Depth Sensing Indentation technique. The influence of physical ageing on indentation hardness has been evaluated. The kinetic of the delayed depth recovery has been analyzed using the phenomenological so-called Kohlrausch–Williams–Watts relaxation function. It has been found that silylated hyperbranched poly(ethyleneimine) improves simultaneously the mechanical coating performance and the elastic recovery.