Rafał Anyszka

Thermal behavior of silicone rubber-based ceramizable composites characterized by Fourier transform infrared (FT-IR) spectroscopy and microcalorimetry.

Ceramizable (ceramifiable) silicone rubber–based composites are commonly used for cable insulation. These materials are able to create a protective ceramic layer during fire due to the ceramization process, which occurs at high temperature. When the temperature is increased, the polymer matrix is degraded and filler particles stick together by the fluxing agent, producing a solid, continuous ceramic phase that protects the copper wire from heat and mechanical stress. Despite increasing interest in these materials that has resulted in growing applications in the cable industry, their thermal behavior and ceramization process are still insufficiently described in the literature. In this paper, the thermal behavior of ceramizable silicone rubber–based composites is studied using microcalorimetry and Fourier transform infrared spectroscopy. The analysis of the experimental data made it possible to develop complete information on the mechanism of composite ceramization.

Effect of modified graphene and carbon nanotubes on the thermal properties and flammability of elastomeric materials

The paper presents the test results of the effect of modified graphene and multi-wall carbon nanotubes on the thermal and mechanical properties and flammability of acrylic rubber and styrene-butadiene rubber. The rubbers were cross-linked with the use of organic peroxide. Based on the test results obtained by optic and AFM methods, a relationship between the surface morphology of the nanocomposites obtained was presented. By means of thermal analysis methods (TG, DTG, DTA) and a micro-calorimeter, it has been found that the nanofillers used considerably increase the thermal stability and decrease flammability of the nanocomposites. The mechanical properties of the elastomeric materials obtained depend on the type and content of nanofiller.

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.

Ceramizable Composites for Fire Resistant Applications

The paper concerns composite materials made of silicone rubber matrix and ceramic fillers used as flame resistant coverings for electrical cables. Under fire, such materials must be able to form, relatively quickly, compact and stiff protecting coating, strong enough to maintain integrity of electrical circuit, even up to melting temperature of metal core. The residue of fired silicone rubber or silica filled elastomer exhibit a form of white powder. There is no evidence of solidification of silica particles, even after heating at 1100°C. However, the addition of some ceramic phases results in reaction with silica matrix (starting at about 900°C) producing a liquid phase, what facilitates particle binding. At lower firing temperatures (600°C) the problem of binding between the product of pyrolysis (silica) and filler is also present, what results in formation of fragile surface shield. The problem can be overcome by the addition of certain inorganic materials to the silicone rubber matrix. The paper discusses their influence on ability of silicone rubber composites, additionally containing glassy phase, wollastonite, mica, aluminium hydroxide, montmorillonite or calcined caoline, to ceramization.

Sulfur/Organic Copolymers as Curing Agents for Rubber

It is widely acknowledged that waste sulfur generated from the petroleum industry creates huge storage and ecological problems. Therefore, the various methods of utilization are becoming increasingly attractive research topics worldwide. The thermal ability of elemental sulfur to homolytic cleavage of S8 rings enables its free radical copolymerization with unsaturated organic species and the obtaining of chemically stable polymeric materials. Here we report a novel possibility to use sulfur/organic copolymers obtained via “inverse vulcanization” as curatives for rubber. For this purpose, several various sulfur/organic copolymers were synthesized and analyzed from the point of view of their performance as rubber crosslinking agents. Solvent extraction was used to purify sulfur/organic copolymers from unreacted (elemental) sulfur. Thermal properties of the prepared copolymers were characterized by thermogravimetric analysis and differential scanning calorimetry (TGA–DSC). Crosslink density and structure of cured elastomers was studied by equilibrium swelling, thiol-amine analysis and freezing point depression. Mechanical properties of the vulcanizates were determined under static and dynamic conditions (DMA—dynamic mechanical analysis). It is proved that the utilization of sulfur/organic copolymers as curatives enables an effective crosslinking process of rubbers. Taking into account the results of a crosslink density analysis and mechanical properties of the vulcanizates cured with purified copolymers, it is evident that relatively long copolymer macromolecules are also involved in the formation of chemical bonds between unsaturated rubber macromolecules.

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.