High-Strength, High-Flexibility, Formaldehyde-Free Impregnated Decorative Paper Based on Polyamide Epichlorohydrin/Poly(vinyl alcohol)/Melamine via Layer-by-Layer Self-Assembly

Impregnated decorative paper is an important and high-value wood-based panel decorative material. However, traditional melamine–urea–formaldehyde impregnated decorative paper (MUFP) suffers from formaldehyde emission and brittleness. Therefore, it is crucial to develop high-performance, formaldehyde-free, flexible impregnated decorative paper as an alternative to MUFP. Here, a layer-by-layer self-assembly strategy is adopted to prepare high-performance, formaldehyde-free polyamide epichlorohydrin (PAE)/poly(vinyl alcohol) (PVA)/melamine (MA) impregnated decorative paper (PMPP). The first PAE resin layer acts as a wet strength agent, while the second PVA/MA resin layer acts as a toughening agent, forming a dual network structure through chemical and hydrogen bonding. Due to the unique layer-by-layer self-assembled dual-network structure, the elongation at break and work of fracture of PMPP is 4.4% and 265.50 mJ, respectively. These values are nine- and eight-times higher than those of MUFP, respectively, demonstrating the excellent toughness of PMPP. Additionally, PMPP is subjected to water activation and hot pressing, and its surface properties meet the GB/T15102–2017 Chinese national standard. In addition, the formaldehyde emission of PMPP is only 0.01 mg/L, which meets the environmental standards of China’s GB/T 28995–2022 (≤1.5 mg/L), Europe’s EN 717–1 (≤0.5 mg/L), and Japan’s JAS 234:2003 (<0.3 mg/L). Thus, this work offers a novel approach to achieve high-performance, formaldehyde-free, flexible impregnated decorative paper.