Modification of the surface chemistry of TMP with enzymes

Abstract

SUMMARY: The surface chemistry of thermomechanical pulp (TMP) was modified with specific enzymes and the effect of extensive enzymatic treatments was studied with surface-sensitive spectroscopic methods (ESCA and ToF-SIMS) and by contact angle measurements. Fibers and different types of fines, i.e. fibrils and flakes, were isolated from the enzymatically treated pulps and analyzed separately. Enzymatic treatment had a pronounced effect on surface extractives, especially those found on the surface of fibrils. All the enzymatic treatments decreased the surface coverage of extractives on fibrils, but ToF-SIMS results indicate that only lipase and laccase treatments selectively removed extractives from the surfaces of fibrils and that other treatments only made the film of extractives thinner. Laccase treatment also reduced the content of guaiacylic lignin units on the surface of fibers, fibrils and flakes. All the treatments studied here lowered the contact angle of water on pulp handsheets, probably due to removal of extractives from the surface. ESCA and ToF-SIMS gave complementary information about the surface chemistry of pulp fibers and fines. ToF-SIMS was found to be suitable for studying chemical modifications on the surface of mechanical pulp components. When these two analytical techniques are combined, it must be remembered that their analysis depth is different, that ESCA results are dependent on proper extraction, and that ToF-SIMS is not a quantitative analysis method for organics.