Flame retardant activity of SiO2-coated regenerated cellulose fibres |
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Authors: | Silvo Hribernik Majda Sfiligoj Smole Marjan Bele Miran Gaberscek |
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Affiliation: | a Faculty of Mechanical Engineering, University of Maribor, Smetanova ulica 17, SI-2000 Maribor, Slovenia b National Institute of Chemistry, Hajdrihova 19, SI-1000 Ljubljana, Slovenia |
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Abstract: | An alternative route to lower the flammability of viscose fibres is presented. Instead of adding a flame retardant to the viscose dope chemically, we have grown a layer of silica (SiO2) on the surface of a regenerated cellulose fibre via a sol-gel process. One set of samples was used as-received, while the other was pre-treated in an 18% NaOH solution, giving a rough, etched surface to the fibre. The different surface morphology of both fibre types triggered a different growth of silica layers. On an untreated fibre, silica formed a 300-400 nm thick surface layer containing a high density of cracks and holes. Conversely, on a NaOH pre-treated fibre, the silica layer intruded into fibre interior, adhered more tightly to the fibre structure and formed an almost defect-free, thin (100 nm) layer on the outer fibre surface. This type of silica layer increased the temperature at which the fibre started to decompose by 20 °C. It also hindered significantly the flow of oxygen to the generated volatiles during the thermal decomposition, and increased the temperature of glowing combustion of the residual char; the temperature of the corresponding exothermic peaks increased by ca. 20 °C and 40 °C. In contrast, the thermal effects of silica coatings that grew on an untreated fibre were much smaller. |
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Keywords: | Regenerated cellulose fibres Thermal properties Silica Flame retardant |
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