Effect of heat treatment of nanodiamonds on the scratch behavior of polyacrylic/nanodiamond nanocomposite clear coats

•Addition of DND particles increases scratch resistance of polyacrylic coatings.•Heat treatment of DNDs greatly increases their potential in increasing scratch resistance.•Unlike HT-NDNDs, addition of AR-NDNDs does not improve the scratch resistance.•Regarding pendulum hardness, NDND particles show better results than the DNDs. In the current paper, effects of heat treatment of nanodiamond particles on the scratch behavior of polyacrylic/diamond nanocomposite coatings were studied. Two types of nanodiamond, i.e. one produced by detonation synthesis (DND) and the other produced by nondetonation synthesis (NDND) were used as reinforcement phase to increase scratch resistance of polyacrylic base polymeric clear coat. Heat treatment was used as the surface modification route. Coatings containing both types of particles in two surface conditions (as-received and heat treated) were compared to each other and also to the neat polyacrylic coating. The results showed strong effect of heat treatment on scratch resistance of coatings based on the scratch width criterion. The effect of heat treatment was more pronounced on DND particles than on NDNDs. However the pendulum hardness showed a reverse trend.