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Abstract

In this paper the effect of particle shape on the bond improvement of epoxy-particle coating composite is evaluated. In our previous studies, it has been shown that adding foreign particles in the epoxy may enhance the bond characteristics of coating. It has been found that the enhancement of bond for coating by adding foreign particles in epoxy may come from two reasons: one comes from the mechanical improvement by foreign particles and the other comes from the chemical reaction of foreign particles which yields a better binding material. In our previous study, the size of foreign particle influenced the degree of mechanical improvement has been concluded. However, how does the shape of foreign particles influence the bond improvement of coating remains a challenging topic. We used three kinds of foreign particles with similar mechanical behavior and similar size. They are a ASTM C778 standard sand (size of 778 µm), a river sand (size of 600 µm) and a silica sand (size of 600 µm). The shape of ASTM C778 standard sand close to a sphere, the shape for the river sand is most irregular and the shape of silica sand is between the former two. Experimental results show that under the same weight ratio of foreign particle/epoxy river sand shows a best improvement of bond strength and C788 standard sand shows a worst improvement among them. Other bond characteristics, the shear stiffness per unit embedded length and the critical debonding shear load per unit embedded length, have the similar trend as the bond strength. From these results, it is concluded that the wedge effect of irregular shape particle contributes a lot to the bond improvement. Electrochemical experiments were conducted to show the corrosion prevention capacity of coatings, results revealed that adding foreign particles inside the epoxy did not influence the corrosion capacity of coating.

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