Piotr Izak

Thermal properties of silica-coated cellulose fibers for increased fire-resistance

In this paper, two precipitation methods of silica, i.e., sol–gel method and silica polymer precipitation, were compared in terms of their impact on the thermal properties of impregnated cellulose fibers. Additionally, the pre-treatment process consisting in dipping the cellulose fibers in NaOH solution to increase the fibers porosity was examined. Three molar phosphoric acid and Flodur 3 (ester hardener based on ethylene glycol diacetate) were used as the sol–gel precipitation agents and 20 wt% aqueous solution of sodium acrylate was used as the polymer precipitation agent. The silica provider was sodium water glass type D. The obtained results have shown that the silicate layer fully covered the cellulose fibers, as confirmed by the scanning electron microscope microphotographs and mid-infrared spectra. Even after thermal treatment at 700 °C, the silicate species still remained in the ash as confirmed by the infrared bands characteristic for sodium silicates, i.e., at 960 and 880 cm−1. Thermogravimetric analysis revealed no significant difference in the weight loss of the cellulose samples treated with different precipitation mixtures, as well as between the raw and pre-treated samples. All weight losses oscillated between 40–50 wt% at 700 °C. Differential thermal analysis curves showed that the pre-treatment process shifts the temperature range in which the different phenomena occur towards higher values. We believe that these results could contribute to the development of cellulose materials with enhanced thermal properties and the process could be an attractive substitute for coatings based on orthosilicates and their derivatives.Graphical Abstract

Influence of the type of aqueous sodium silicate on the stabilization and rheology of kaolin clay suspensions

To avoid agglomeration and sedimentation of grains, ceramic slurries should be modified by stabilizers in order to increase the electrostatic interactions between the dispersed particles. In this study we present the spectral analysis of aqueous sodium silicates obtained by different synthesis methods and their influence on the rheological properties of kaolin based slurries. Infrared and Raman spectra can be used to describe the structure of silicate structural units present in aqueous sodium silicates. It was confirmed that the best stabilization results possess aqueous sodium silicates of the silicate moduli of about 2 and the optimal concentration of the used fluidizer is 0.3wt% to the kaolin clay dry mass. One of the most important conclusions is that the synthesis method of the fluidizer has no significant effect on its stabilization properties but used medium does create adequate stabilization mechanism depending on the silicate structures present in the sodium silicate solution.