Wood coatings of AA-NC semi-interpenetrating polymer networks (semi-IPNs), made from acid curing ammo-alkyd resins (AA) and nitrocellulose (NC), were prepared by sequential polymerization method. To investigate the effects of oil length on the properties of AA-NC semi-IPNs, three grades of alkyd resins (Alkyd) containing 38, 48, and 58% oil were synthesized with phthalic anhydride, glycerol, and soybean oil, employing alcoholysis method. The butylated urea formaldehyde resin (UF) and melamine formaldehyde resin (MF) were also prepared in this study. The AA-NC semi-IPNs were maintained at a weight ratio of AA: NC of 25: 75, where the AA was the composition of MF: UF: Alkyd of 7.5: 22.5: 70 (by weight), and 10% of p-toluene sulfonic acid solution (concentration, 25% in isopropyl alcohol) based on the weight of amino resins was added as acid catalyst. The properties of coatings such as viscosity, drying time, and get time, and the properties of films including adhesion, hardness, abrasion resistance, impact resistance, tensile strength, released formaldehyde, lightfastness, solvent resistance, and durability were examined. (C) 2004 Wiley Periodicals, Inc.