Surface properties of woody thin boards composed of commercially available lignin and cellulose: Relationship between the orientation of lignin and water repellency

Woody thin boards were prepared from lignin, cellulose, and water by compression molding at 180°C and 25 MPa for 10 min. Boards with higher contact angles gave lower values of relative permittivity on their surface. Attenuated-total reflection Fourier transfer infrared spectroscopy suggested that more lignin existed on the surface of the boards with the high contact angle, which was also supported by scanning electron microscopy and atomic force microscopy. Our findings thus revealed that the orientation of lignin at the surface resulted in increased hydrophobicity of the surface and contributed to the enhancement of water repellency.