THE REACTION OF BORIC-ACID WITH WOOD IN A POLYSTYRENE MATRIX

The reaction of boric acid with wood fibers in a polymer melt was exam ined using C-13-nuclear magnetic resonance (NMR), B-11-NMR, differenti al scanning calorimetry, dynamic mechanical analysis, and component ex traction and by the determination of material properties. Samples were blended at 350 and 380 degrees F in a roll mill. The use of a plastic izer in the melt to facilitate the reaction of the acid with the wood fiber was studied. NMR data showed that no significant reaction occurr ed between the boric acid and the polystyrene. Experimental evidence s upports the reaction of boric acid with wood components. The ultimate strength of the composites was either reduced or not significantly alt ered by the reaction, depending upon conditions. However, the stiffnes s increased significantly with boric acid additions for the 350 degree s F reactions, but behaved differently for the same additions at 380 d egrees F. The glass transition temperature of the polystyrene was lowe red by the addition of plasticizer, as expected, while boric acid addi tion had little effect. Extracted samples showed that some boric acid remained with the wood fraction. These preliminary data suggest that b oric acid does react with wood fiber under the conditions of this stud y. These investigations illustrate the feasibility of performing chemi cal reactions on the wood phase of wood/polymer composites during the extrusion process. Further research is recommended. (C) 1996 John Wile y & Sons, Inc.