Preparation and properties of heterocyclic aramid aerogel fibers
The heterocyclic aramid polymer containing imidazole group(PABI)was synthesized with 5(6)-amino-2-(4-ami-nobenzene)benzimidazole(PABZ)and terephthaloyl chloride(TPC)as raw materials and was then produced into PABI/metal cobalt ion(Co2+)aerogel fiber by redox-responsive wet spinning and freeze-drying using PABI/Co2+solution as spinning solution and the mixture of solution N,N-dimethylacetamide(DMAc)/hydrogen peroxide(H2O2)with a mass ratio of 95∶5 as coagula-tion bath.The chemical structure,micro morphology,specific surface area and pore structure,mechanical properties and thermal stability of aerogel fibers prepared with different solid content(by mass fraction)of PABI/CO2+spinning solution were studied.The results showed that the weak coordination interaction between PABI and Co2+contributed good fluidity and spinnability to the spinning solution,which can quickly and uniformly oxidize into a fiber with relatively dense three-dimensional cross-linked net-work structure;when the molar ratio of imidazole group to Co2+was 7∶1 in the spinning solution,the loss modulus and storage modulus of the PABI/Co2+spinning solution were both relatively high,which can provide a fairly rational density of cross-linking points to maintain the uniform mesoporous structure and high strength of the aerogel fiber;the aerogel fiber prepared had a specif-ic surface area of 127.51 m2/g,porosity of 81.41％and breaking strength of(11.19±0.47)MPa,indicating a high porosity and specific surface area and fairly good mechanical properties,when the solid content of PABI/CO2+spinning solution was 6％;and the maximum thermal decomposition temperature of aerogel fiber was 554.58 ℃,which was close to that of PABI,and the residual carbon content was higher than that of PABI after thermal decomposition,indicating a good thermal stability.
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