Mechanical characterization of sol gel epoxy silylated hyperbranched poly(ethyleneimine) coatings by means of Depth Sensing Indentation methods
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 degC in a humid chamber followed by the anionic homopolymerization of epoxides initiated by 1 methylimidazole in an oven at 180 degC. 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.