In general, TS decreased as PMDI replacement with RBA increased (Fig. 1(a)). TS decreased from 9.8 MPa for the control to 5.1 MPa for the sample with 10% of PMDI (ratio 20:1) replaced with RBA. As the amount of RBA added to the straw increased, the amount of water absorbed also increased. During hot pressing, this water turned into steam that abruptly expanded when the press was opened. While low amount of steam may not affect particleboard properties, large amount of steam may cause cohesively weak particleboard or may even cause the board to burst. For this reason, it was not possible to obtain high quality particleboard samples for the 20 and 30% (ratio 20:1) PMDI replacement treatments, which corresponded to 50% of moisture content or greater in the particleboard.