Developing hybrid wood-based panels for resources recycling

本课题的研究目的是开发一种资源可循环利用、环境友好的新型人造板。实验室尺寸和全尺寸面板进行了生产实验，并讨论了新开发的技术。日本的木材资源有两大问题。一种是日本广泛种植的针叶树，另一种是拆迁产生的废木材--第三项是从国外进口的种植园树种，即可以通过剥皮来制作胶合板的巨桉。利用这些木材资源，研制了以杨木刨花为面层、以再生木刨花为芯层的三层结构的“混杂”人造板。结果表明，与结构用板相比，这种板具有足够的强度。当面层中的股线具有取向性时，取向方向的力学性能显著提高。除了这些有/没有对齐的刨花板，五层结构板制造，以确定层厚度的影响。该板由彼此交叉取向的两个股线层、作为芯层的回收颗粒层和作为背面的两个股线层组成。结果表明，外层的取向和厚度对复合材料的力学性能影响较大，复合材料的弹性常数可以用单层板的弹性常数来预测。使用较细的股线被证明是有效的厚度方向上的尺寸稳定性。还制造了具有杉-和桉树-单板的组合的混合胶合板。桉木单板作为胶合板的面层，具有很高的弹性和强度。贴面采用杨木单板的胶合板因其良好的纹理外观而受到青睐，但其力学性能却有所下降。

The aim of this research project was to develop new type wood based panels which could be regarded as resource recycling and environmentally friendly. Laboratory size and full size panels were produced experimentally, and the technologies to be newly developed were discussed. There are two big issues concerning wood resources in Japan. One is conifers planted widely in Japan, and the other is waste wood generated from demolition_ The third item was a plantation species imported form foreign countries, that is, Eucalyptus grandis which can be used to plywood by peeling. Using these wood resources, The 'hybrid' wood based panel was discussed.Three layer strandboard with sugi-strand for face layers and with recycled wood particle for core layer was fabricated. It was revealed that this type of panel had enough strength compared with panels for structural purpose. When the strands in the face layers had orientation, mechanical properties in the aligned direction were enhanced remarkably. In addition to these strand board with/without alignment, five-layer structured boards were fabricated to determine the effects of layer thickness. The board consisted of two strand layers cross oriented each other, a recycled particle layer as a core layer, and two strand layers as the back. It was found that orientation and thickness of the outer was more effective to the mechanical properties, and that the elastic constants could be predicted by those of uni-layer board. Using thinner strand was proved to be effective for dimensional stability in thickness direction. Also a hybrid-plywood having of combinations of sugi- and Eucalyptus-veneer, were fabricated. Eucalyptus veneer used in the face ply gave very high elastic and strength properties to the plywood. The plywood using sugi-veneer in the face had the preference because of favorable face appearance of the texture, while the mechanical properties became lower.