A mechanism study on preparation of rayon based carbon fibers with (NH4)2SO4/NH4Cl/organosilicon composite catalyst system

The mechanisms of the preparation of rayon based carbon fibers with (NH4)2SO4/NH4Cl/organosilicon composite catalyst system were studied. The thermal behaviors of rayon fibers that were treated with different catalysts were studied by thermogravimetry–mass spectrometry (TG–MS) and the surface of treated rayon fibers was studied by scanning electron microscopy (SEM) analysis. Our data showed that the composite catalyst treated rayon fibers underwent pyrolysis under lower temperatures and in a wider range of temperatures. Rayon based carbon fibers prepared with different catalyst system showed different mechanical properties. The presence of (NH4)2SO4/NH4Cl/organosilicon increased the production of H2O, CO2, CO and decreased the production of tar, aldehyde, furan and phenol derivatives. The composite catalyst also promoted the pyrolysis reaction of rayon fibers by lowering its activation energy. Organosilicon seemed to have two aspects of effects on the process of preparing rayon based carbon fibers. It could enhance the penetrability of (NH4)2SO4/NH4Cl to the interior of rayon fibers and protect the fiber surface in the pyrolysis process. Moreover, organosilicon may participate in the crosslinking reactions of rayon fibers and enhance the drawability of rayon fibers in carbonization process. Our experiments demonstrated that (NH4)2SO4/NH4Cl/organosilicon was an effective composite catalyst system in the preparation of rayon based carbon fibers.