High-Pressure Treatment Effects on Density Profile, Surface Roughness, Hardness, and Abrasion Resistance of Paulownia Wood Boards

The goal of this study was to investigate the effects of high-pressure (HP) treatment on the mechanical performance properties of Paulownia ( spp.) wood boards. The boards were HP treated at selected pressures (20, 40, 60, 80, and 100 MPa) for 30 s. A special vacuum-packing technique that sandwiched the test boards between two steel plates was used for the HP treatment to prevent board distortion. Thickness, density, vertical density profile (VDP), cell wall percentage (VC), porosity percentage (VH), surface roughness, hardness, and abrasion resistance were evaluated to assess the performance properties of the treated and untreated boards. HP treatment resulted in 45.7% to 60.0% reduction in thickness of the boards, while it increased the density by 88% to 170%. The VDP of densified boards was distributed uniformly, and core densities were only slightly higher than surface densities. HP treatment made the Paulownia board surfaces much smoother, and three roughness parameters were reduced with increasing treatment pressure level. Hardness values of the boards were improved by 84% to 173%. The mass loss values of HP treated wood samples in abrasion tests were significantly reduced by 40.7% to 75.0%. The results of this study demonstrate that HP treatment is a useful method to improve the end-use properties of low-density wood like Paulownia.