Magdalena Zarzecka-Napierała

Effect of carbon fibers on thermal properties and mechanical strength of ceramizable composites based on silicone rubber

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.

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.

YAG Powder Synthesis and Characteristics

Two techniques were applied to prepare single phase YAG powder: i) citrate process based on complexing properties of citric acid with isopropyl alcohol additive as esterification agent and ii) co-precipitation from relative nitrates solution with ammonia. At low temperature heat treatment both techniques lead to the X-ray amorphous bodies. Their calcination at elevated temperatures results in single-phase YAG powder. Differences in the behaviour of the amorphous precursors during heat treatment will be shown.

Optimisation of the Ceramic Phase for Ceramizable Silicone Rubber Based Composites

The paper presents results of investigation on composition of mineral components used for ceramizable silicone rubber-basing composites. Using different crystalline phase additives it is possible to assure the proper course of the composite degradation and its transformation during ceramization process. Three crystalline components were tested as an additive to silicone rubber – bentonite, kaolinite and wollastonite. They were added simultaneously with a glassy phase. These compounds during firing evolved (decomposed) and introduced into ceramized material polycrystalline structure, responsible for its properties. The process of composites degradation during heating up to 1050°C were examined by DSC/TG technique. Characteristic of ceramized composite body created during heating was investigated by mercury porosimetry. The porosity evolution was described in the range of 600 − 1050°C.

Processing and Properties of Fire Resistant EPDM Rubber-Based Ceramifiable Composites

Abstract Low softening point temperature glassy frit, reinforcing silica, wollastonite and dicumyl peroxide were incorporated into ethylene-propylene-diene (EPDM) rubber matrix in different amounts in order to obtain ceramifiable composites. Kinetics of vulcanization of the mixes was measured. Mechanical properties, micromorphology, thermal properties and combustibility of the vulcanizates were studied as well as compression strength of the ceramic residue obtained after heat treatment. Studies show that optimal amount of glassy frit from the point of view of ceramification effectiveness in dispersed mineral phase is 40 % wt.

Optimisation of the Ceramic Phase for Ceramizable Silicone Rubber Based Composites – Microstructural Aspect

The paper presents results of investigation on composition of mineral components used for ceramizable silicone rubber-basing composites. Using different crystalline phase additives it is possible to assure the proper course of the composite degradation and its transformation during ceramization process. Three crystalline components were tested as an additive to silicone rubber – bentonite, kaolinite and wollastonite. They were added simultaneously with a glassy phase. These compounds during firing evolved (decomposed) and introduced into ceramized material polycrystalline structure, responsible for its properties. Characteristic of ceramized composite body created during heating was investigated by mercury porosimetry. The porosity evolution was described in the range of 600 – 1050°C.