亲水基团对有机和炭气凝胶孔结构的影响

Effect of hydrophilic groups in the polymer matrix on the porosity of organic and carbon aerogels produced from melamine,phenolic resole and formaldehyde

热固型酚醛树脂、三聚氰胺、间甲酚和甲醛水溶液在碳酸钠催化下,通过溶液-溶胶-凝胶过程合成有机水凝胶,有机水凝胶经溶剂置换、超临界干燥和裂解形成了有机气凝胶和炭气凝胶。在固定酚醛树脂浓度、间甲酚/酚醛树脂、甲醛/三聚氰胺、碳酸钠/酚醛树脂比值,改变三聚氰胺/酚醛树脂比值的条件下,研究了亲水基团对有机气凝胶和炭气凝胶孔结构的影响。结果表明:亲水性的三聚氰胺可增加分子间作用力,有利于凝胶的稳定;但增加三聚氰胺会加大有机气凝胶裂解过程中的质量损失,不利于凝胶的稳定。二种因素协同作用决定着炭气凝胶的孔结构、孔容和比表面。

Organic and carbon aerogels were synthesized by the solution-sol-gel polymerization of melamine （M）, phenolic resole （PR）, m-cresol and formaldehyde in a basic aqueous solution followed by supercritical petroleum drying and pyrolysis. The effect of hydrophilic groups in the polymer matrix on the porosity of organic and carbon aerogels was investigated by varying the M/PR ratio under otherwise identical conditions. It was found that increasing hydrophilic melamine content increases intermolecular interactions of polymers that form gels, which favors an improvement in the stability of gels in supercritical drying and pyrolysis. The increase of melamine content also increases the mass loss of organic aerogels during pyrolysis, which is unfavorable for their stability. The pore size distributions, surface areas, meso-porosity and macro-porosity of carbon aerogels were a compromise between the two opposing factors.