The surface of soft wood is densified
Since the properties of wood, such as hardness, wear resistance, flexural strength, dimensional stability, etc., are mainly determined by the surface, the density of the wood surface is increased, that is, the density is increased only at a certain depth on the surface of the wood, and the internal density of the wood is not Increase or decrease, which can improve the physical and mechanical properties of wood, save costs, and reduce the loss of wood volume. It is an ideal method for improving the softness of wood of artificial forests.
1. The ideal state and way of compacting the surface of wood
According to the concept and requirements of surface compaction, several idealized states can be expressed. The dense path of the wood surface includes compaction, penetration or impregnation compaction. The premise of the wood compaction technology to achieve the ideal surface densification effect is that the surface wood has high temperature and humidity and softening, while the middle part of the wood has low temperature, is not softened, and controls a lower compression ratio or compression ratio. Infiltration or impregnation is dense, and organic substances such as organic resins and elemental metal elements are infiltrated into a certain thickness of the surface layer of the wood to achieve the purpose of compacting the surface of the wood.
2. Test materials and methods and results
The triploid hair was selected, and the test piece was impregnated with a low-cost, well-permeable water-soluble low molecular weight PF resin, and then subjected to different degrees of mechanical compression to determine the density distribution and dimensional stability of the test piece in the thickness direction. , hardness and wear resistance and other indicators.
It has been experimentally found that in the wet state, the elemental expansion coefficient of the test piece decreases in the chord direction or in the radial direction as the PF resin group content increases. In the dry state, the expansion rate of the test piece has a negative value, because during the immersion process, some of the resin or wood itself is leached, and shrinkage occurs during the drying process, which has a greater influence on the dimensional stability than the immersion process. The effect of the expansion. With the increase of the solid content of the PF resin, although the chord and radial expansion ratio of the test piece are negative, the absolute value thereof is lowered, which is favorable for maintaining the dimensional stability. After the test piece was boiled for 2 hours, the string and radial expansion ratio in the wet and dry state changed with the increase of the solid content of the PF resin. In the wet state, the chord and radial expansion ratio of the test piece decrease with the increase of the solid content of the PF resin; while in the dry state, the chord and radial expansion ratio of the test piece are negative, and the absolute value increases with the solid content of the PF resin. It is reduced, and the absolute value decreases faster when the solid content of the PF resin is low.
3. Conclusion
The combination of resin impregnation and mechanical compression on wood, as the solid content and compression ratio of the resin increase, the surface density of the wood increases more than the density of the inner layer, and an ideal surface densification effect can be obtained. When the wood specimen was impregnated with a solid content of 15% PF resin and compressed, the average density of the test piece increased by 12.6% and the average density of the test piece when the compression ratio was 11%, compared with the untreated wood. Increase the surface density by 35.7% by 57.5%. The dimensional stability of PF resin impregnated table laminate wood is improved. When cold water immersion and boiling water boiling, the string and radial expansion ratio of wood in wet and dry state are reduced to different extents, and the wear resistance of wood surface is also improved. .
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