In-situ double polymerization to build IPN structural melamine resin coating with excellent structural toughness and intrinsic hydrophobicity

Melamine-formaldehyde resin (MF) is a typical thermosetting amino resin. The cured MF film usually shows some defects such as autogenous-shrinkage, easy brittle fracture, and easy to swell and crack, so it is difficult to use MF as paint or coating directly. In this study, a novel melamine-formaldehyde resin oligomer (dMFO) which has two reactive groups (-CH₂OH and -CH=CH₂) was prepared by introducing hydroxypropyl acrylate (HPA) in the synthesis process of MF. The dMFO is then used as a coating resin and cured by thermal-assisted double polymerization (named as IDTC) to construct the dMFO coating with an in-situ interpenetrating polymer network (IPN). The result shows that the dMFO coating exhibits good structural toughness and intrinsic hydrophobicity just like an impact resistance of 110 mm, abrasion resistance of 1.4 mg/100R, and adhesion of 6.32 MPa. Furthermore, the cured dMFO coating showed an obvious intrinsic hydrophobicity, with a water contact angle of 92.3°and water resistance time of 8.5h. From the synthesis of dMFO, curing process and properties of the coating, it is shown that the reasonable IPN structure of dMFO coating is constructed by in-situ interpenetration of thermoplastic macromolecular segments in the thermosetting three-dimensional network structure. The developed dMFO coating technology is of great significance in promoting a practical application of MF in the field of coating and painting.