Research and Development on Wood-Carbon Composites from Charcoal of Wood Thinnings as an Electromagnetic Shield and Fire Resistive Material

为开发利用木材疏料、木材工业废弃物、林业废弃物和未利用树种的新材料，以木材和竹子为原料的木炭为原料，进行了碳-酚醛树脂球复合材料的研究与开发。在高温下炭化的木质炭具有高导电性、高导热性、高耐热性和高防火性，在红热下既不熔化也不软化。各种木炭被用于制造电磁屏蔽和耐火复合材料。探讨了炭化温度与耐火复合材料之间的关系。根据日本工业标准（JIS） K 7201，采用氧指数法、烧透法和氧乙炔炬切割法测试了碳复合材料的耐火性能。根据ASTM ES7-83的要求，采用双腔法对复合材料的电磁屏蔽性能进行了测试。随着炭化温度的升高，木材和木材组分碳复合材料的耐火性能和屏蔽性能均有所提高。在800或以上的温度下炭化的木炭的复合板的低可燃性是由于木炭的石墨化。在烧透法中，由于炭化炭的电阻率、各向同性的高导热性和缓慢的氧化，复合材料板的耐火性得到了提高。1200℃以上炭化木炭制备的复合板具有较高的电磁屏蔽效率，这也是由于木炭的石墨化和各向同性的高导电性。根据美国MIL STD 285标准和JIS A 1304标准，对碳复合粉末覆盖刨花板的电磁屏蔽性能和防火性能进行了全尺寸测试。与相同板厚和密度的控制相比，碳复合覆盖刨花板在延迟点火和未暴露表面温升情况下的防火性能均有提高。对电场的电磁屏蔽效能在40 dB（- 70dB）以上，满足办公楼隔墙、外壳和计算机辅助设备屏蔽材料的标准。经化学镀金属化的木质颗粒适合作为电磁屏蔽碳木复合材料的原芯材。少

In order to develop new materials utilizing wood thinnings, residues and wastes from wood industries, forestry wastes, and unused wood species, research and development studies on carbon composites (carbon-phenolic formaldehyde resin sphere) from charcoal of wood materials and bamboo were conducted. Wood charcoals carbonized at a high temperature were highly electric conductive, highly thermal conductive, highly resistive to heat and fire, and were neither melted nor softened under red heat. Various kinds of wood charcoal were used in the manufacture of electromagnetic shield and fire resistive composites.Relationships between carbonizing temperature and the fire resistive composites were examined and discussed. Fire resistivity of the carbon composites were tested by an oxygen index method in accordance with the Japan Industrial Standards(JIS) K 7201, by a burn-through method, and by cutting with oxygen-acetylene torch. Electromagnetic shielding property of the composites was tested b … More y a dual chamber method in accordance with ASTM ES7-83. Fire resistive and shielding effects of the carbon composites from wood and wood components were improved by the increase of the carbonizing temperature.The low combustibility of the composite boards from charcoal carbonized at 800ﾟC or above was due to the graphitization of charcoal. Fire endurance of the composite boards was improved by time delay in the burn-through method and this is due to the resistivity, isotropically high thermal conductivity and slow oxidation of charcoal graphatized by high temperature carbonization.The high electromagnetic shielding efficiency of the composite boards from wood charcoal carbonized at 1200ﾟC or above was also due to the graphitization of the charcoal and isotropically high electric conductivity of the composite boards.The electromagnetic shielding and the fire resisting performance of the carbon-composite-powder overlaid particleboards were evaluated in full-scale test in accordance with US MIL STD 285 and JIS A 1304,respectively.The fire endurance of the carbon-composite overlaid particleboard was improved both at time delay ignition and temperature rise at the unexposed surface when compared with the controls of the same board thickness and density. The electromagnetic shielding effectiveness was over 40 dB( - 70dB) against electric field, which satisfied a standard as shielding materials for partitions and enclosures of office buildings and computer aids.Wood particles metalized by an electroless plating were found suitable as a raw core material for the electromagnetic shield carbon-wood composites. Less