Thermal Stability and Flammability of Styrene-Butadiene Rubber-Based (SBR) Ceramifiable Composites
Ceramifiable styrene-butadiene (SBR)-based composites containing low-softening-point-temperature glassy frit promoting ceramification, precipitated silica, one of four thermally stable refractory fillers (halloysite, calcined kaolin, mica or wollastonite) and a sulfur-based curing system were prepared. Kinetics of vulcanization and basic mechanical properties were analyzed and added as Supplementary Materials. Combustibility of the composites was measured by means of cone calorimetry. Their thermal properties were analyzed by means of thermogravimetry and specific heat capacity determination. Activation energy of thermal decomposition was calculated using the Flynn-Wall-Ozawa method. Finally, compression strength of the composites after ceramification was measured and their micromorphology was studied by scanning electron microscopy. The addition of a ceramification-facilitating system resulted in the lowering of combustibility and significant improvement of the thermal stability of the composites. Moreover, the compression strength of the mineral structure formed after ceramification is considerably high. The most promising refractory fillers for SBR-based ceramifiable composites are mica and halloysite.
Influence of cenospheric fillers on the thermal properties, ceramisation and flammability of nitrile rubber composites
In this paper, the influence of cenospheric fillers of different particle sizes on the thermal properties and flammability of butadiene-acrylonitrile rubber is presented. A part of fly ash cenospheres was coated with an iron and iron (III) oxide layer. A series of examinations were conducted, these took the forms of: thermal analysis; oxygen index analysis; cone calorimeter measurements; SEM; AFM. These examinations enabled the explanation of iron-based combustion inhibition processes in terms of catalysis of char formation and elastomer cross-linking. Cenospheres itself without additional coatings or fillers provide high surface for polymer chain adsorption, and hence degradation of composite is reduced. Additionally, the results of the investigation on the effectiveness of cenospheric filler usage for ceramisation are discussed. It is proven that the durable ceramic structure is formed owing to the addition of cenospheres in the presence of an inorganic flux. Thus, replacement of silica by lightweight cenospheres is possible. Cenospheres with an iron coating and in the presence of wollastonite and an inorganic flux allow obtaining the NBR composites which are non-flammable in the air atmosphere; furthermore, the ceramic layer formed during the composite combustion has advantageous mechanical properties.
Novel CaO−SiO 2 Sorbent and Bifunctional Ni/Co−CaO/SiO 2 Complex for Selective H 2 Synthesis from Cellulose
Catalysis- and sorption-enhanced biomass gas- ification is a promising route to high-purity hydrogen (H2); however, most CaO-based sorbents for CO2 capture have poor surface area and mechanical properties, lose carrying capacity over multiple uses, and have insufficient porosity to accommodate extra catalyst sites. We aimed to develop a high-surface-area CaO−SiO2 framework onto which catalysts could be grafted. The best CaO−SiO2 sorbent (nCa/nSi = 2:1) maintained a CaO conversion of 65% even after 50 carbonation−decarbonation cycles, better than commercial micrometer-sized CaO or tailored CaO, because of stabilization via Ca−O−Si interactions and an ordered porous structure. Bimetallic catalyst grains (Ni/Co alloy, <20 nm) could be evenly loaded onto this structure by impregnation. The resulting bifunctional complex produced H2 at nearly the same rate as a mixture of catalyst and commercial CaO while using less total sorbent/catalyst. Furthermore, this complex was much more durable due to its higher coking resistance and stable structure. After 25 carbonation−decarbonation cycles, the new catalyst−sorbent complex enhanced the H2 yield from cellulose far more than a mixture of catalyst and commercial CaO did following the same treatment.