Thermal Decomposition Of Composites Research Articles

Electrical conductivity and thermal stability of polyaniline and water-soluble polymer nanocomposites

Electrically conductive composites with film-forming properties based on polyaniline (PANI), polyvinyl alcohol (PVA), and polymethacrylic acid (PMAA) were obtained. The composites were synthesized mechanochemically by mixing calculated amounts of PANI and PVA or PMAA. The electrical conductivity increases with an increase in the content of the conductive component in the composite up to a PANI–PVA ratio of 50 to 50. Further increase of PVA in the composite leads to a decrease in the specific electrical conductivity. Similar patterns are observed for PANI–PMAA composites. The study of the effect of temperature on the electrical conductivity of composites made it possible to determine the activation energy of charge transfer (Ea ). The numerical values of Ea lie in the range of 0.371 to 0.981 eV and depend on the ratio of PANI–PVA and PANI–PMAA polymers in the composites. The thermal decomposition of composites and starting components is complex. Several areas are observed on the mass change curves, which indicate a multi-stage thermal decomposition process.

Poly(amidoamine) dendrimer-grafted carbon nanotubes as a hybrid multifunctional curing agent for epoxy-modified polyurethane

Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the first generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two different epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and different chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray diffraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.

Impact of Basalt Filler and Ceramizable Additives on the Toxicity of Gaseous Products Emitted from Thermal Decomposition of Silicone Rubber Composites.

The article illustrates the impact of basalt filler in the form of flakes and fibres on the toxicity of gaseous products that formed during the thermal decomposition of silicone rubber composites. The values of specific emissions of gases were determined with the help of the IR spectroscopy and further applied to calculate the toxicometric index. The presented method of measuring the concentrations of gaseous products resulting from thermal decomposition consists in the application of a fluidised bed reactor, which makes it possible to conduct the decomposition of a sample at a precisely assumed temperature value and imitate the conditions of a real fire. At a temperature lower than 700 °C, the gases resulting from the thermal decomposition of composites are particularly toxic due to the presence of significant concentrations of formaldehyde that does not undergo oxidation to more stable inorganic products. At a temperature of 600 °C the toxicity of gases for the samples with ceramizable additives and without them was similar. In the first case, there appeared to be a positive synergistic effect of mineral and basalt additives, and the basalt additives themselves increased the toxicity of gases. At higher temperatures of decomposition, the exponentially increasing rate of the oxidation reaction in the gaseous phase results in the lack of significant differences between the toxicity of gases for the samples with and without basalt additives. The toxicometric index value at temperatures of 700 °C and 800 °C was by one or two orders of magnitude higher, respectively, than the one that was observed in the temperature range of 500–600 °C, as inorganic components appear in the place of formaldehyde.

The influence of degree of fragmentation of Pinus sibirica on flammability, thermal and thermomechanical behavior of the epoxy-composites

Abstract In this study, lignocellulosic flour obtained through grinding of Pinus siberica wood (S) was used as a filler for developing epoxy-based (EP) composites characterized by reduced flammability. The influence of filler particle size on flammability, thermal and thermomechanical behavior of the natural composites was discussed in reference to the morphological analysis of final products as well as filler geometrical changes induced by processing. The structural analysis was realized with using 3D tomography. It was found, that introduction of 20 wt% of Pinus siberica wood caused a sharp drop in the heat release rate values, and the lowest results (2.5 times lower compared to EP) was determined for composite with the highest degree of fragmentation. The residue investigation confirmed the influence of particles size on the formation of the swelling structure of char, which effectively inhibits the combustion processes. Moreover, the analysis of gaseous products emitted during the thermal decomposition of composites was performed. The addition of investigated filler caused a decrease in the amount of degradation products, while the quantity of polycyclic aromatic hydrocarbons (PAHs) increased.

Fabrication and Characterization in Composites of Nanoenergetic Materials and Porous Metal with UV Ink Method

The preparations of composites of porous metal and nanoenergetic materials were studied. Composites of porous metal (nickel, aluminum and magnesium) and nano-scale aluminum powder and CL-20 have been synthesized with UV (ultraviolet) ink method, respectively. The structure, morphology, infrared characteristic, thermal decomposition of composites were characterized by using Mercury Injection Apparatus, Scanning Electron Microscope, Fourier Transform Infrared Spectroscopy, and Differential Scanning Calorimeter. The results showed that nanoenergetic materials could deposit into pores of porous metal without collapsing after solidification. Constituents of the composites could coexist with each other without chemical changes. Thermal decomposition temperature was lower after the addition of nanoenergetic materials. System enthalpy increased significantly with the addition of CL-20 and reactive porous metal. The new composites have potential applications in the field of structural and energetic materials.

Eco-composite developed using biomorphous stiff skeleton of carbonised yucca and furfuryl alcohol as a filler

The aim of this research was to prepare a monolithic porous carbon–carbon composite on the basis of porous stiff skeleton obtained via carbonisation of blocks cut from horticultural waste, lignified inflorescence stems of yucca, Yucca flaccida. Then the blocks were infiltrated by furfuryl alcohol, polymerised, cross-linked and carbonised. Raw yucca carbonised at various temperatures and the resultant ecological composites were characterised using the following methods: helium gas densitometry, ultrasonic and electrical resistance measurements, the physical adsorption of N2 gas at −196 °C, scanning (SEM) and transmission (TEM) electron microscopies. Elemental analysis, i.e. the CHN content and organic constituents, were determined for raw yucca. The thermal decomposition of composites and their precursors were investigated at temperatures ranging from 20 to 940 °C using thermogravimetric analysis (TGA). The composites were found to be highly porous carbon materials thermo-resistant in inert atmosphere with a strong skeleton and hierarchically ordered structures. Their elastic and electrical properties were found to be anisotropic and dependent on the support properties.