Calcium carbonate modified urea–formaldehyde resin adhesive for strength enhanced medium density fiberboard production

This study investigated the improved properties of calcium carbonate (CaCO(3)) modified urea–formaldehyde (UF) resin adhesive for medium density fiberboard (MDF) production. The CaCO(3) modified UF resins were prepared by adding different proportions of CaCO(3) to a low molar ratio UF resin at the initial stage of a typical synthetic process of the resin. The physicochemical properties of the resins were measured. The mechanical and environmental performances of the resin-bonded MDF panels were tested. The results show that the viscosity and free formaldehyde content of UF resins with or without CaCO(3) modification were not significantly different. The solid content of the CaCO(3) modified UF resin was significantly lower than that of the control group. In addition, the measured gel time of the CaCO(3) modified UF resin was 111–149 s, which was longer than that of the control resin (82 s). The gel time was further extended with the increase of the CaCO(3) content in the UF resin. The chemical group and crystal structure of UF resins with or without the modification of CaCO(3) were not significantly different. The internal bonding (IB) strength of the MDF panels significantly increased from 0.75 MPa to 0.97 MPa when the UF resin was modified with 2% of CaCO(3). This study provides scientific support for the preparation of inorganic mineral modified UF resins for strength enhanced wood-based panel manufacturing.