Surface Crack Occurrence and Resistance During Moisture Content Changes in MF-Resin-Impregnated Paper-Decorated Blockboard

In multi-layered wood materials, varying rates of dimensional changes can easily lead to cracking, which can have a negative impact on their structure and functionality. This study focuses on cracking issues of decorated blockboard caused by moisture content changes. First, surface cracks on the decorated blockboard were observed and classified using optical microscopy and scanning electron microscopy (SEM). Second, from modeling perspectives, the critical tensile strength of the surface of the decorated blockboard was predicted to be 16.93 MPa, providing guidance for crack-resistant modification. Subsequently, halloysite nanotubes (HNTs) were incorporated into MF-resin-impregnated paper, achieving a Grade 5 crack resistance for decorated blockboard. The interaction between HNTs and MF resin forms a multiscale stress–dispersion system, as confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), indicating hydrogen and covalent bonding between HNTs and the MF resin. With a 5% HNTs addition, the tensile strength and strain break of the MF-resin-impregnated paper reached 36.60 MPa and 1.12%, respectively, representing increases of 97.39% and 60.00%, respectively, effectively preventing surface cracking. This has significant implications for improving the durability and performance of decorated blockboard in practical applications.