Abstract: In this work， an intensive investigation was carried out to determine an optimal mean particle size of less than 100 μm for the powder electrostatic spraying process of polyoxymethylene （POM） powders through comparing the performance of powder coatings made from POM powders with different average particle sizes. Polypropylene and polyurethane were then incorporated to pure POM powders to improve the impact resistance of POM powder coatings. The performance of the resultant composite coating samples were evaluated by characterizing their thickness， hardness， thickness， impact strength， chemical resistance， morphology， and wear resistance. The results indicated that all of the coating samples exhibited good appearance， acid and alkali resistance， and salt resistance together with a uniform thickness and a smooth surface. There was no shrinkage orange peel and cracking phenomena. Their adhesion grades reached above grade 1 and their friction coefficients were as low as 0.261. All of these can meet the requirement of application standards for good mechanical properties and excellent friction resistance. Moreover， the composite coatings obtained impact strength of 4.42 and 5.12 N·m when 3 wt% PP and 15 wt% TPU were incorporated， respectively. With such a modification， the impact resistance of the composite coatings was greatly improved to meet the requirement for practical applications in the specific areas.

Key words: polyoxymethylene, polypropylene, thermoplastic polyurethane, electrostatic spraying, impact resistance