Preparation and characterization of adhesive from spent hen proteins

Spent hens, a by-product of the poultry industry, are of little economic value while their disposal is an environmental concern. In this study, spent hen proteins were modified by sodium dodecyl sulfate (SDS) or urea to develop adhesive, and the adhesive properties on wood veneers were investigated. Adhesives prepared with 3 M urea or 3% SDS show dry strengths of 7.99±0.17 MPa and 9.35±0.17 MPa, wet strengths of 3.35±0.10 MPa and 2.90±0.59 MPa, and soaked strengths of 5.21±0.04 MPa and 8.89±0.14 MPa. The morphologies of the adhesives on the wood veneers after curing were investigated by scanning electron microscope. Effects of modifications on protein structural and thermal properties were studied with Fourier transform infrared spectroscopy and differential scanning calorimetry, respectively. Adhesive mechanisms include protein unfolding to reveal secondary structures that can interact with wood substance, interaction between protein and the modification agents that enhance the strength in the protein bulk, and indispensable mechanical interlocking. The wood adhesives prepared in this study from spent hen proteins can be used in dry and wet applications.