采用 ZnCl2对橡胶木屑进行化学活化制备出活性炭。 ZnCl2与橡胶木屑的浸渍质量比为1.0-2.0,活化温度为500℃,时间为60 min。通过扫描电镜、X射线衍射和BET比表面分析仪探讨浸渍比例对活性炭孔结构的影响。结果表明,当浸渍比为1.5：1时,样品的比表面积和孔径分别为1301 m2/g 和0.37 cm3/g。通过化学发泡工艺将不同质量分数(1%,2%,3%,5%,8%)的活性炭填充至聚氨酯中制备出聚氨酯复合材料。在1-5 GHz频率范围内,复合材料吸收微波。随着活性炭含量增加,在1-3 GHz范围内,介电常数(ε’)和回波损耗增加。活性炭含量为8%时复合材料的介电常数达到最大值3.0。在1.8 GHz时,复合材料的回波损耗为10 dB。在-2.5 GHz,电磁屏蔽效率大于3 dB。与传统聚合物材料如填加金属的聚氨酯和聚酯相比,所制复合材料呈微波段吸收,可作为电磁屏蔽材料。
Activated carbons were prepared from rubber wood sawdust by chemical activation using ZnCl2 as an activation agent at 500 ℃ for 60 minutes with ZnCl2/dried rubber wood sawdust mass ratios from 1. 0 to 2. 0. Flat polyurethane ( PU) composites filled with the activated carbons were prepared by a chemical foaming method using different loading amounts of the activated car-bons to investigate their complex permittivity and the microwave absorption properties for use in electromagnetic interference ( EMI) shielding. It was found that the best activated carbon is obtained at a ratio of 1. 5, which has the highest Brunauer-Emmett-Teller surface area and a micropore volume of 1 301 m2/g and 0. 37 cm3/g, respectively. With increasing activated carbon content, the di-electric constant (ε’ ) and the return loss increase in the frequency range of 1-3 GHz. The composite filled with 8% activated car-bon has a maximum dielectric constant of 3. 0 and its return loss is above 10 dB at the global system mobile phone frequency of 1. 8 GHz. Its EMI shielding efficiency is in the useful range of approximately 3 dB over a wide frequency range of 1-2. 5 GHz. Compared with conventional materials such as polyethelene and polyester filled with metal additives, this composite is suitable for microwave absorption and is a potential candidate for EMI shielding applications.
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