Dimensional stability improvement of corn stalk biocomposites using two-part lignin-derived binder optimized with response surface methodology

To strengthen the dimensional stability of enzymatically treated corn stalk (ECS) biocomposites, hybrid modified lignosulfonate (HML) was used as a binder to fabricate reinforced ECS/HML composites with evaluation by response surface methodology. The effects of the preparation treatment on the enzymatic conditions, as well as the modified lignosulfonate dosage on the physicomechanical properties of the ECS/HML composites, were all evaluated. The optimum preparation parameters were determined via the Box-Behnken experimental design. High mass concentrations of laccase-vanillin and an appropriate modified lignosulfonate dosage for a relatively short enzymatic pretreatment time led to reduced residual stresses and improved dimensional properties. The optimum conditions that minimized thickness swelling (TS) and water adsorption (WA) without significantly compromising the biocomposite mechanical properties were determined to be 25 g/L laccase-vanillin, 118.8 min enzymatic pre-treatment time, and 15 wt% modified lignosulfonate. The ECS/HML composites that were treated under the optimal conditions resulted in an approximate 42% reduction in the dimensional properties without any significant decline in mechanical properties when compared to ECS panels. Unlike the loose structure of ECS biocomposites, the ECS/HML composites had a laminar shape with firm morphology.