Ceramizable (ceramifiable) silicone rubber-based composites are modern elastomeric materials for fire protection application. The most important sector of economy using such materials is cable industry because there are special types of electric circuits that have to keep working in the case of fire. These kinds of composites can create ceramic phase protecting copper wire from melting under high temperature. When temperature increases, polymer matrix degrades (creating silica residue as one of the products) and mineral particles dispersed in silicone rubber matrix stick together creating stiff, durable, insulating and porous ceramic skin. In this paper, the influence of surface modification of montmorillonite with quaternary ammonium salts on ceramization of their silicone rubber composites is presented. Filler modification was studied, determining changes to its surface energy and thermal stability. Mechanical properties, flammability and thermal stability of composites were determined. Ceramization of the composites was discussed from the point of view of their mechanical properties and structure of ceramic phase after heat treatment, determined by compression stress tests, porosimetry and scanning electron microscopy adequately. Results show that type of modifier applied strongly affects properties of silicone rubber-based ceramizable composites before and after ceramization. Samples containing surface-modified montmorillonite produce significantly less heat during their thermal decomposition than composite filled with unmodified montmorillonite. Moreover, incorporation of montmorillonite modified with ammonium salt of linear organic chain causes the creation of nano-porous structure after ceramization. On the one hand, it facilitates heat insulation, but on the other hand, high total volume of pores adversely affects mechanical endurance of the ceramic phase.
7 February 2018 in Journal of Chemical & Engineering Data
The process of palladium(II) chloride complex ion adsorption on activated carbon was investigated. The influence of variable parameters such as the initial concentration of the Pd(II) complex (from 0.04 to 2.25 mmol·kg–1) and temperature (from 294 to 348 K) was determined. Experiments were conducted in the solution with pH equal to 0 and 1. It was found that the Freundlich adsorption isotherm describes the process better than the Langmuir model. The observed sorption capacity as high as q294K = 42.4 mg·g–1 and q323K = 67 mg·g–1 for activated carbon was found at 294 and 323 K, and it is increasing with temperature increase. The obtained results showed that the palladium(II) complex may react with functional groups present on the surface of activated carbon. The thermodynamic parameters such as the equilibrium constant and heat and entropy of adsorption were derived. The enthalpy value is equal to −6.7 kJ·mol–1, and the entropy is equal to −23 J·mol–1·K–1. It is suggested that, during chemisorption of palladium(II) chloride complex ions, the palladium dichloro-oxide or PdCl2 is formed on the surface of activated carbon.
Ceramizable (ceramifiable) silicone composites are one of the most important elastic technical materials produced industrially. These composites are commonly used to increase flame retardancy of electrical cables and to ensure integrity of electricity network during fire by their ability to create a continuous ceramic structure. In this paper, ceramizable silicone composites filled with different contents of carbon fibers were tested. The research was focused on the characterization of ceramic structure created during heat treatment of the composites and thermal properties of the composites. For this purpose, morphology (SEM) and compression strength of the ceramic structures were studied. To describe process of ceramic structures creation, TG/DSC analysis was done. These tests have demonstrated that, the increase in carbon fibers amount improves the mechanical properties of ceramic structure regardless of heat treatment conditions.