Extrusion of Solid Wood Impregnated with Phenol Formaldehyde (PF) Resin: Effect of Resin Content and Moisture Content on Extrudability and Mechanical Properties of Extrudate
A new deformation technique of wood flow forming is promising for industrial uses of solid wood. Flow deformability, size stability, and good mechanical properties were obtained by using wood impregnated with low molecular weight phenol formaldehyde (PF) resin. In this study, to clarify the effect of the PF resin and moisture contents in wood on the flow deformability (extrudability) and the mechanical properties of the product (extrudate), a lateral extrusion was conducted by using wood impregnated with various contents of PF resin and three levels of moisture content. The results indicated that the extrudability of wood impregnated with PF resin improved with an increase in both PF resin and moisture content. The mechanical properties of the extrudate worsened with increases in the moisture content of the wood impregnated with PF resin. Because most of the water in the wood remained in the mold during the extrusion process, chemical changes of the wood substance and PF resin occurred due to steam forming under the high temperature and pressure of the extrusion. The steam worsened the mechanical properties of the extrudate.
High-pressure densification and hydrophobic coating for enhancing the mechanical properties and dimensional stability of soft poplar wood boards
Effects of high-pressure (HP) treatment on densification of poplar sapwood boards and subsequent coatings were evaluated. Tung oil (TO) and epoxy resin (ER)-coated treatments were used to improve the dimensional stability of HP-densified wood. The density of the wood after HP densification increased from 450 ± 50 kg/m 3 for the control to 960 ± 20 kg/m 3 at 125 MPa. This process also resulted in the average thickness of HP-densified boards to reduce significantly from 29.7 ± 0.11 mm for the control to 18.8 ± 0.53 mm after HP densification at 25 MPa and 14.3 ± 0.10 mm after 125 MPa treatment for 30 s. The mechanical strength measured as the hardness of densified wood significantly increased from 35% at 25 MPa to 96% at 125 MPa treatment, compared to untreated wood. As expected both TO and ER-coated treatments significantly reduced set-recovery of densified wood when stored at four relative humidity environments. ER showed better anti-swelling performance than TO, and would be a better choice.
Effect of Thermoplastic Binder on Flow Deformation Behavior of Wood
Abstract A processing technique was recently developed to realize plastic deformation in wood impregnated with a thermoset binder. This paper proposes a new flow forming technique where a thermoplastic binder is used instead of a thermoset binder with the expectation that the formability and recyclability of the products will be improved. To clarify the effect of the thermoplastic binder on the flow deformation behavior of wood, capillary fluidity tests were performed using impregnated wood with various contents of thermoplastic binder (polymer). The extrusion load of the impregnated wood through the capillary decreased with an increase of the polymer content in the wood. Results of the second fluidity test using the first extruded material reveals that the recycled impregnated wood can flow again. The extrusion load of the second extrusion was equal to or lower than the first. These results indicate that the recyclability of the wood impregnated with a thermoplastic binder is highly promising. The internal configuration of the impregnated wood during extrusion was also dependent on the polymer content.