Abstract:

In order to solve the low crosslinking activity resulted from protein denaturation of high-temperature soybean meal(HTSM), the thermal-alkali activation of HTSM was proposed, and the effects of sodium hydroxide(NaOH) dosage on the structure and properties of HTSM and HTSM-based adhesive were evaluated based on the FT-IR, XRD, XPS, TGA analysis and other traditional methods. The results revealed that thermal-alkali activation could not only unfold HTSM's globular structure to release the buried active group but also hydrolyze partial peptide into amino and carboxyl groups. Then, the crosslinking reactions between reactivated HTSM and crosslinking agent was increased, and the obtained soybean protein adhesive had equivalent thermal and water resistances with the adhesive prepared by low-temperature soybean meal due to the formation of sufficient crosslinked networks. The results of thermal-alkali activation showed that the most preferable NaOH dosage was 2%(mass fraction), and the acetaldehyde value of HTSM was 4.28 mg/g(reactivated HTSM). Correspondingly, the adhesive viscosity was 59.8 Pa·s, the soaked wet bonding strength was 1.48 MPa(63 ℃ for 3 h), the boiling-dry cycled wet bonding strength was 0.96 MPa, the boiling-water-insoluble content was 79.73%, the mass-residue ratio was 40.87%, and the temperature for maximal degradation rate was 306.1 ℃.

Key words: high-temperature soybean meal, wood adhesive, thermal-alkali activation, structure and property