Practical Application on Surface-Densified Wooden Materials

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In order to the practical application of the surface-densifying techniques by the process for reinforcing wood with polymer while simultaneously hot pressing it in a roller press, the production condition and physical properties of surface-densified particleboard and floor materials were investigated.1. When the particleboard was pressed at conditions of roll temperature of 200゜C and compression ratio of 10% to original thickness, the density of surface layer increased with the decrease in feed velocity of processing. The setting of densified layer recovered at high relative humidity of 93%. The thickness swelling of pressed particleboard with the increase of 1% moisture content was greater than control. As the smoothness was improved by pressing, that is adequate for products in which the surface of the particleboard is finished by applying wood veneers or plastic sheets. On the other hand, the internal bond, surface strength and bending properties decreased generally by hot pressing. The treatments at too high a temperature and for too long a press time damaged the bond strength between particles.2. The optimum producing condition of the floor materials which was surface-densified and reinforced with polymer by hot pressing in a roller press equipped with three pairs of roller was as follows:Polymer; High-density polyethylene (Melt index, 0.9), Treating velocity; 42cm/min, Compression ratio; 10%, Roller temperature; 200゜C (First), 90゜C (Second), Room temperature (Third).The bending behaviors of simultaneously densified and reinforced Hinoki or Sugi increased by 10 to 60% compared with untreated wood, and also the abrasion resistance and hardness were improved 5 times and 1.1 to 1.4 times, respectively.