Sustainable bio-based dialdehyde cellulose for transforming crystalline urea–formaldehyde resins into amorphous ones to improve their performance

Sustainable bio-based dialdehyde cellulose (DAC) was employed to transform crystalline urea–formaldehyde (UF) resins into amorphous ones for simultaneouly improving their adhesion strength and formaldehyde emission. Serial samples of the UF resins modified with DAC during the resin synthesis were extracted to understand the chemical reactions between the DAC and UF species. Fourier transform infrared, ¹H-nuclear magnetic resonance (NMR), and ¹³C NMR spectroscopies confirmed the occurrence of reactions between the DAC and UF species. As the synthesis proceeded, the crystallinity of the modified UF resins decreased from 51.7% to 17.4%, transforming the crystalline domains into amorphous ones. Thermograms showed that the DAC in the modified UF resins was decomposed at temperatures over 200 °C as degraded form, resulting in a lower cross-linking density than that of the neat UF resins. The adhesion strength of the modified UF resins was statistically similar to that of the neat UF resins, and the formaldehyde emission of the modified UF resins dramatically decreased to ∼ 64.6%. These results evidence the significant application potential of bio-based DAC in improving the sustainability and performance of UF resins.