Improvement of Properties of Particleboard by Impregnation with Phenolic Resin.

采用低分子量酚醛树脂对刨花板进行了处理，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用树脂溶液喷涂，或用低分子量树脂与胶粘剂树脂的混合物一次喷涂。酚醛树脂处理后板材的力学性能和尺寸稳定性受树脂掺入量（IRL）的影响较大，但不同处理方式对板材的力学性能和尺寸稳定性影响不显著。在煮沸2小时后，用10% IRL处理的板在干燥条件下保留了80%的强度值。内部结合强度（IB）随着IRL值的增加而增加，在相同的板密度水平下，IRL值为20%的板的内部结合强度（IB）是未处理的两倍。处理过的PBs即使在低树脂负荷下也能显著降低膨胀率。加速实验室生物降解试验的结果表明，掺入树脂固体可以很好地增强木板的腐烂和抗白蚁能力。对于褐腐菌来说，15%的IRL显著降低了其失重，而对于白腐菌来说，即使在低树脂负荷下，其攻击也几乎完全被抑制。将处理后和未处理的PBs试样进行各种加速老化处理，并在每个循环的每个步骤后测量厚度肿胀（TS）和IB。低分子量酚醛树脂的加入对6次ASTM D-1037暴露后的TS影响较大；仅5% IRL的PB的TS值约为控制板的一半。在循环暴露试验后，用20% IRL处理的PBs很少观察到回弹。低分子量树脂和高分子量树脂的组合在提高PBs的强度性能和尺寸稳定性方面更为有效。

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.