Optimization of preparation conditions of soy flour adhesive for plywood by response surface methodology

Response surface methodology was applied to optimize the preparation conditions of soy flour adhesive (SFA). A boiling water test was used to assess the wet strength of plywood bound with this adhesive. The effects and interactions of treatment time (X-1), treatment temperature (X-2) and additive amount of acid-salt solution (X-3) on wet strength were investigated. The regression model for the SFA preparation was significant (p < 0.0001). X-2 and X-3 had a significant effect on wet strength, whereas the effect of X-1 was insignificant. X-2 and X-3 showed interactions with wet strength. The optimal preparation conditions were: acid-salt solution 3.0 g, treatment time 33 min and treatment temperature 29 degrees C. Under these conditions, the wet strength was 1.18 +/- 0.08 MPa, which is in agreement with the predicted value (1.11 MPa). An analysis of the Fourier transform infra-red spectroscopy spectra of the SFAs further confirmed the validity of the optimal preparation conditions. (C) 2013 Elsevier B.V. All rights reserved.