The preparation and performance of a novel lignin-based adhesive without formaldehyde

It is significant to develop low cost, environmental friendly and renewable bio-based adhesives without formaldehyde. In this paper, acetonitrile extracting lignin (AEL) was used as raw material, modified by phenol and mixed with aqueous of polyvinylpyrrolidone (K30), a biocompatible agent, to prepare a high-performance formaldehyde-free lignin-based adhesive. The results of the experiments showed the optimal condition as follows: the mole ratio of lignin to phenol 1:2, the reaction temperature 80 ℃, the reaction time 3 h, the concentration of K30 10%, mole ratio of PAEL to K30 1:0.4, the shear strength of the adhesive reach up to 1.70 MPa (Technical lignin-based adhesive only 0.11 MPa), and it was still as high as 1.02 MPa after soaking in water for 24 h. Compared with the adhesive (1.12 MPa) on the market, the as-prepared sample shows a much higher shear strength, meeting the National Primary Standard of plywood (≥1.0 MPa) and according with national standard.