Preparation of a novel melamine formaldehyde resin with palmitoylated melamine involved and its functional coating

Abstract

Generally, melamine-formaldehyde resin (MF) has some defects, including poor fluidity, high cross-linking density, high curing shrinkage rate, and a tendency to cause brittle fracture in cured films. These factors pose significant obstacles for the direct application of MF in coatings. In this study, a novel purified palmitoylated melamine (PM) intermediate was synthesized by acylation reaction between equal molar palmitoyl chloride (Pc) and melamine(M), and then mixed with M (with 10% mass substitution of M). The mixture was reacted with formaldehyde, butanol, and polyethylene glycol 400 (PEG400) to prepare palmitoylated melamine-formaldehyde resin (PMF). The prepared PMF displays excellent direct coating ability on various hard substrate surfaces, with a cured coating film surface that is uniform and smooth. In addition, the coating exhibits excellent surface hydrophobic function (with a water contact angle is up to 100°), high light transmittance (with a gloss of 135° and a light transmittance of 95.8%), intrinsic flame retardancy (with a limiting oxygen index is 27.6% and a surface resistance to cigarette burning of 5 grade), self-cleaning properties (hydrophobicity, lipophobicity and lubrication) and other comprehensive properties. The adhesion of the coating (cross cut test) was 0 grade, the impact resistance is 80 mm, the pencil hardness was 8H, the wear resistance of the coating was only 0.02 mg per 100 revolutions (0.02 mg/100r), and the coating surface resistance to chemical contamination (tested with acetone, 10% citric acid solution, and 25% sodium hydroxide solution) was level 5. These advantages of great significance for the expansion of the application field of melamine-formaldehyde resin.