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.
“House-of-cards” structures in silicone rubber composites for superb anti-collapsing performance at medium high temperature
Ceramifiable polymer composites, especially silicone rubber composites, are widely used at elevated temperatures. These composites could convert into freestanding ceramified residues at temperatures above ∼1100 °C through eutectic reactions between the pyrolyzates of polymer matrices and ceramifying agents. However, it remains challenging for polymer composites to be used at the medium high temperatures (500–900 °C), because of the gap between the temperatures of polymer decomposition and the eutectic reaction. Here, we demonstrate that when the Laponite platelets in the preformed “house-of-cards” structure (Laponite-armored hollow composite particles, referred to as LHCPs) are used as fillers for silicone rubber, the resultant composites can well maintain their shape and mechanical strength in this critical temperature range as mentioned above. As revealed by microscopic and crystallographic studies, the superb anti-collapsing performance at medium high temperatures was indicated to stem from the “house-of-cards” structure of the LHCPs. These composites may find potential in some high temperature applications, for example, fire resistance cables, where both shape-maintenance and mechanical support at medium high temperatures are required in order to ensure electric supply in fire.
Formation of unexpected ions from a first-generation polyamidoamine dendrimer by use of methanol: an artefact due to electrospray emitter corrosion?
We report the formation of unexpected ions during the analyses of a first-generation polyamidoamine dendrimer in negative ion mode using an ion trap equipped with an electrospray ionisation source. These surprising ions corresponded to an increase of 12 m/z units over those expected. The formation of the unexpected ions was dependent on the tuning of the solution flow rate and the capillary high voltage. In addition, measurements of unusual value of the current suggested that a reaction was occurring in the corona plasma. The influence of methanol in this phenomenon was demonstrated by using CD(3)OH in the sample preparation. We propose two structures to explain the observed adduct based on the results of MS(2) experiments and by referring to previous work dealing with 12 m/z units addition. We showed that a corona discharge caused by alterations taking place to the electrospray capillary emitter was the origin of these unexpected ions. Finally, we discuss the mechanism involved in the formation of the ions and we propose means to control such artefacts.