ALTERATION OF THE SURFACE-ENERGY OF WOOD USING LIGNIN-(1-PHENYLETHENE) GRAFT-COPOLYMERS

Graft copolymers of lignin, made by free radical graft copolymerizatio n of 1-phenylethene on lignin, increased the contact angle of water on birch wood (Betula papyrifera) and decreased the critical surface ten sion of the wood when coated onto the wood surface from an N,N-dimethy lformamide solution. The coating of copolymer changed the wood from hy drophilic (approximately 50-degrees) to hydrophobic (110-degrees). The most pronounced change in contact angle was produced by benzene-solub le extracts of the reaction product. These extracts contained lignin w ith long poly(1-phenylethylene) sidechains and pure poly(1-phenylethyl ene). They produced surfaces with the numerically highest contact angl es with water and changed the wetting behavior of the surface more tha n physical mixtures of lignin and poly(1-phenyl-ethylene) or either of the pure polymers. Despite coating weights of less than 100 mg/cm, th e critical surface tension of the birch wood coated with the various l ignin-(1-phenylethylene) graft copolymers ranged from 26.9 to 44.9 dyn es/cm while the uncoated birch had a critical surface tension of 49.6 dynes/cm.