Investigation of Epoxy coatings’ adhesion to concrete substrates

One of the most important features of a surface coating is its adhesion to the substrate. Adhesion strength of surface coatings depends on two main factors: coatings’ intermolecular forces at the interface and rheological properties of the polymeric matrix that determines the fracture behavior of coating while applying force to it. By increasing the energy dissipation through the bulk, the adhesion strength at interface of coating and substrate increases. The basic principle of present research is to find the relation between viscoelastic and mechanical properties of Epoxy coatings and their adhesion to concrete substrates. Epoxy coatings are used in floor coatings as primer, base coat or top coat, because of good adhesion and corrosion resistance. Two kinds of Epoxy resins were used as primer and top coat: EPIRAN-01 (E1) and EPIRAN-06 (E6). EPIRAN-01 (primer) was supplied from IPCC with EEW and solid content of 495 and 75%, cured by polyamide hardener. EPIRAN-06 (top coat) was supplied from IPCC with EEW and solid content of 191 and 100%, cured by polyamide hardener. Concrete substrates were prepared using 3.5 Kg cement, 4 Kg sand (6-10 mm diameter), 350 g microsilica and 3.93 L water. The composition of resin and hardeners in primer and top coat is shown table 1. All samples were tested using pull-off test to evaluate the adhesion strength double layer coatings. To evaluate the mechanical properties of polymeric coatings, free films were prepared and mechanical datas were obtained using tensile test at the speed of 5 mm/min according to ASTM d889. To evaluate viscoelastic properties of free films, samples were examined by DMTA test at a frequency of 1 Hz and a temperature range 25℃ to 100℃. As shown in table 1, EP2 sample has the best adhesion strength and damping factor (tan ?) which may be due to optimum polymerization and crosslink density. Although EP3 has the largest toughness, EP2 has the optimum mechanical properties, due to optimum elastic modulus and toughness. Therefore EP2 sample has the highest adhesion strength and this behavior can be attributed to damping and mechanical properties of the bulk of polymer.