Improvement of Properties of Particleboard by Impregnation with Phenolic Resin.

用低分子量酚醛树脂对刨花板(PB)进行处理，并对其性能进行了评价。在喷涂常规酚醛树脂胶粘剂之前，将颗粒浸入树脂水溶液或喷洒树脂溶液，或一步喷洒低分子量树脂和胶粘剂的混合物。虽然酚醛树脂处理板的力学性能和尺寸稳定性受树脂加入量(IRL)的影响很大，但处理方法并没有产生显著的差异。煮沸2小时后，经10%IRL处理的板材在干燥条件下保持了80%的强度。内结合强度(IB)随着IRL值的增加而增加，在相同的板密度水平上，IRL含量为20%的板的内结合强度是未处理板的两倍。经处理的PBS显示，即使在树脂含量较低的情况下，其溶胀率也显著降低。加速实验室生物降解试验的结果表明，加入树脂固体可以很好地提高板材的耐腐蚀性和抗白蚁能力。对于褐腐菌，在15%的IRL时，重量损失显著减少，而对于白腐菌，即使在低树脂载量的情况下，攻击也几乎完全被抑制。对处理和未处理的PBS进行不同的加速老化处理，并在每个循环的每个步骤后测量厚度膨胀(TS)和IB。低相对分子质量酚醛树脂的加入对ASTM D-1037 6次曝光后的TS有很大影响，仅含5%IRL的PB的TS值约为对照板材的一半。经20%IRL处理的PBS在循环暴露试验后很少出现回弹，低分子量树脂和高分子量树脂的组合在改善PBS的强度性能和尺寸稳定性方面效果更好。

Particleboards(PB)were treated with a low molecular-weight phenolic resin and their properties were evaluated. Particles were dipped into aqueous solutions of resin or sprayed with resin solutions before spraying the conventional phenolic resin adhesive, or sprayed with a mixture of low molecular-weight resin and the adhesive resin in a single step. Though mechanical properties and dimensional stability of the phenolic resin treated boards were affected considerably by the incorporated resin loadings(IRL), the methods of treatment did not produce significantly different results. After boiling for 2-hours, the boards treated at 10 % IRL retained 80 % of their strength values in the dry condition. The internal bond strength(IB)increased with increasing IRL values, and the boards with 20 % IRL showed twice the value of untreated controls at the same level of board density. Treated PBs showed a dramatic reduction in the rate of swelling even at low resin loading. Results obtained from accelerated laboratory tests of biodegradation suggested that incorporated resin-solids worked well to enhance decay and termite resistance of boards. For a brown-rot fungus, the weight loss was substantially reduced at 15 % IRL, whereas attack was suppressed almost entirely even at low resin loadings for the white-rot fungus.The specimens of treated and untreated PBs were subjected to various accelerated aging treatments, and thickness swelling(TS)and IB were measured after each step of each cycle. The TS after the 6-cycle ASTM D-1037 exposure was affected greatly by the addition of low molecular-weight phenolic resin ; the TS value of the PB with only 5 % IRL was about a half of that of the control boards. The spring back was rarely observed for the treated PBs with 20 % IRL after the cyclic exposure test.The combination of low- and high-molecular weight resin was found to be much more effective in improving the strength properties and the dimensional stability of PBs.