Evaluation of Wood Surface Modification Using Hot Melting Plastic Droplets for Contact Angle Measurements

Abstract

There are several methods to measure the contact angle between the solid surface and liquid phase. One of the most applicable ones is known as the sessile drop method, on which a liquid droplet is deposited on a solid surface to measure the contact angle by a high-resolution camera. In this paper, molten thermoplastic droplets are placed directly on the surface of modified wood in order to assess the compatibility between hydrophobic thermoplastics and hydrophilic wood surfaces. For this purpose, two groups of spruce veneers are treated with acetic acid anhydride (AA) or maleic acid anhydrides (MA), respectively. Droplets from high density polyethylene (HDPE) are deposited on the wood surfaces at isothermal conditions. The results show that thermoplastic droplets exhibited higher contact angles at AA treated surfaces than at MA treated ones. This suggests that MA reduces the polarity of the wood surface compared to AA, which has an increased compatibility with wood surface.