Strength and physical properties of structural type particleboards.

研究了在胶粒中添加低相对分子质量(Mn=389)的酚醛树脂对板材性能的影响。用水分散酚醛树脂浸渍或喷雾的方法对日本柳杉(Cryptomeria Japan Onica)稀释液制备的丝状颗粒进行处理。此外，还在颗粒上喷洒了8%的粘结酚醛树脂(Mn=962)。另一方面，采用浸渍树脂和粘结树脂混合喷雾到颗粒的一次喷雾方法。利用机械定向仪对准颗粒，制得10 mm厚的单层板材。板材的弯曲性能随板密度的增加而增加，取向方向的抗弯强度约为无定形板材的两倍。在含有10%浸渍树脂的板上，90%的原始MOR在2小时沸腾测试后被零售。酚醛树脂浸渍刨花板的厚度膨胀率有很大改善，仅为对照刨花板的一半左右。在相对湿度为50%到90%的条件下测量的线膨胀(LE)值基本上受颗粒排列的影响。经过六次ASTM加速老化后，含10%浸渍树脂的板材的TS下降了约为对照板材的50%，且内结合强度保持率非常高。一次喷洒的方法是最有效的，而且看起来很实用。

The effects of adding a low molecular weight(Mn=389) phenolic resin to particles on board properties were investigated. Strand particles,prepared from sugi(Cryptomeria japonica)thinnings,were treated with a water-dispersed phenolic resin by the dipping or spraying method. In addition,8% bonding phenolic resin(Mn=962) was sprayed to the particles. On the other hand,the one shot spraying method,which the mixture of impregnating and bonding resin is sprayed to particles,was used. The particles were aligned by means of a mechanical orienter and 10-mm thick single layer boards were produced. The bending properties of the boards increased with the increases in board density and also MOR in the oriented direction was about twice that of random boards. At a board with 10% impregnating resin, the 90 percent of the original MOR was retaianed after a 2-hour boil test. The phenolic resin impregnated particleboards showed greatly improved thickness swelling and exhibited only about one-half the thickness swelling of a control board. Linear expansion (LE) values measured for the range of conditionings at 50 to 90%RH were affected substantially by particle alignment. After six cycles of ASTM accelerating aging,TS of the board with 10% impregnating resin decreased approximately up to 50% of the values observed in control boards and the internal bond strength retention was outstanding. The one shot spraying method is the most effective and it seems to be practical.