Chemically Modified Canola Protein-Nanomaterial Hybrid Adhesive Shows Improved Adhesion and Water Resistance

Irrespective to the continuous research effort, the progress of protein based adhesives is still hindered due to poor adhesion and water resistance properties. Here we report an improved method to develop chemically modified canola protein-nanomaterial (CMCP-NM) hybrid adhesives with significantly improved adhesion and water resistance by exfoliating graphite oxide (GO) or nanocrystalline cellulose (NCC) at low addition levels (1% w/w NM/protein) in ammonium persulfate (APS) modified canola protein. Modification of canola protein with ammonium persulfate at optimum conditions (1% w/w APS/protein) significantly improved (p < 0.05) both dry and wet adhesion strengths from 6.38 +/- 0.31 and 1.98 +/- 0.08 MPa to 10.47 +/- 0.47 and 4.12 +/- 0.23 MPa, respectively. APS induced protein cross-linking via Tyr-Tyr and Tyr-His interactions were observed, which contributed to a covalently stabilized protein network. In the second part of the study, NCC or GO were exfoliated in CMCP at 1% w/w (NCC or GO/protein) addition level. Prepared CMCP-NM adhesive showed a further increase (p < 0.05) in both adhesion and water resistance (12.50 +/- 0.26, 4.79 +/- 0.23 MPa for NCC and 11.82 +/- 0.42, 4.99 +/- 0.28 MPa-dry and wet strength, respectively). Synergistic effects of protein cross-linking and nanomaterial exfoliation, improved cohesive interactions, thermal stability and increased hydrophobic functional groups contributed to the improvement in CMCP-NM adhesive. The outcome of this research enables the utilizing of renewable macromolecules such as protein toward replacing traditional adhesives with adverse health and environmental effects.