Thermogravimetric Tests Research Articles

Thermal Degradation and Microhardness Analysis of Polyene with Modified Oil Resin

Thermal degradation of polyene synthesized from recycle polyvinyl chloride (PVC) and hardness of polyene coated with modified oil has been studied by thermogravimetric analysis (TGA) and microhardness test. The synthesized polyene from reaction of recycle PVC were varied from 30 minutes, 1 hour, 2 hours and 4 hours and their thermal stability has been analyzed. From differential thermal gravimetric, DTG curve, polyene from two hours reaction showed the highest degradation temperature up to 445°C due to degradation of polyene sequences. Microhardness test performed by Shimadzu DUH 211/DUH-211S dynamic ultra microhardness tester according to ASTM E384 showed that polyene derived from 2 hours PVC with modifed oil resin resulted in the highest microhardness ~ 107.99 MPa.

Synthesis and characterization of electropolymerized molecularly imprinted microporous polyaniline films for solar cell applications

AbstractThe solicitude to molecularly imprinted conjugated polymers is flourishing due to their auspicious properties for a myriad of technological and industrial applications. The preparation conditions strongly affect the structure, optical, thermal, and electrical properties of these polymers. Subsequently, a consistent contemplation is desired to entrench consanguinity between processing stipulations and these variables. Here, molecularly imprinted polyaniline films, based ascorbic acid as a template, have been synthesized via electropolymerization technique. This template has been extracted from the films to create microporous polyaniline films. The morphology and structure of these films were investigated using X‐ray diffraction and Fourier transform infrared spectroscopy. Thermogravimetric test showed an enhancement in the thermal stability of molecular imprinted polyaniline compared with non‐imprinted techniques. The optical measurements showed that the rate of light absorption is increased twice with low transmission and reflection. The electrical conductivity increased by four orders with activation energy of 0.30 eV. The optoelectronic measurements of molecularly imprinted microporous polyaniline films showed that the filling factor and external quantum efficiency are enhanced compared with non‐imprinted polyaniline films. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers

Oxidation and thermal degradation resistance of silicon carbide coated low density carbon–carbon composite

The material investigated in this study is a prototype material, where a low density and highly porous carbon–carbon composite, termed carbon bonded carbon fibre (CBCF), has been given a protective coating of silicon carbide using chemical vapour deposition. The aim of the current study was to gauge the effectiveness of the silicon carbide coating in protecting the CBCF materials from degradation within an oxidising atmosphere. Avenues of investigation included assessing the behaviour of the materials when heated to elevated temperatures within an oxidising environment (using thermogravimetric analysis and bulk oxidation tests) and also evaluating the residual strength of the composites after subjection to thermal shock/cycling. It has been found that the performance of the CBCF material in oxidising conditions has improved with the incorporation of the silicon carbide coating and also that the coated material is resilient against thermal shock/cycling.

Optimization of mineral carbonation process for CO2 sequestration by lime-rich coal ashes

Mineral carbonation is one of the alternatives considered for CO2 sequestration. This consists of inducing the artificial weathering of alkaline minerals to produce stable carbonate solids. This work presents the wet carbonation of lime-rich ashes from the fluidized bed combustion of two different fuels: a Spanish sulfur-rich lignite, with calcium carbonate and quartz as main mineral constituents, and the waste produced during the extraction of the coal. The novelty of the work is its experimental approach, which explores all the variables (pH, temperature, time, liquid to solid ratio, NaCl ratio) from a statistical survey centered on finding optimized conditions that maximize the degree of carbonation. CO2 uptake is determined by direct thermogravimetric tests. The results indicate that high carbonation efficiency (78% efficiency) is achieved for both solids at basic pH and moderate treatment times. Those conditions cause anhydrite to dissolve, increasing the availability of Ca2+ for reprecipitation as carbonate and hydroxide. At neutral pH, 72% conversion efficiency is equivalent to a capture of 8% of the CO2 theoretically emitted in the combustion of coal wastes. The proposed conditions for fly ash carbonation enables rapid CO2 capture that is applicable for upscaling and industrial use.

Influence of processing route and yttria additions on the oxidation behavior of tungsten

The oxidation resistance in dry air of pure tungsten and tungsten reinforced with a dispersion of 0.6wt.% Y2O3 nanoparticles has been evaluated between 873 and 1073K, temperature range that divertor in fusion power plants should endure during long-term times in the case of loss of coolant accident and/or air ingress in the vessel. Both materials were prepared by a powder metallurgy route involving hot isostatic pressing of ball milled tungsten powders and tungsten with dispersed Y2O3 nanoparticles. The results have been compared with those of pure tungsten processed by conventional techniques. Thermogravimetric tests at 873K revealed that the processing route as well as yttria addition considerably affected the oxidation resistance of pure tungsten. Mass gain of W–0.6Y2O3 at 873K was five and two times lower than that of pure tungsten prepared by conventional processing techniques and by powder metallurgy, respectively. This different behavior was related to changes in the structure and composition of the oxide scale. Above 873K, the kinetics were significantly accelerated for all materials due to the development of a non-protective oxide scale from the earliest oxidation stages, although the kinetics of Y2O3-containing material were still the slowest, specially at 973K. It was analyzed how yttria additions modify the oxidation mechanism of tungsten.

Effect of Weathering of Coal and Organic Dusts on Their Spontaneous Ignition

Weathering of coal and other cellulosic dusts occur due to the process of wetting and subsequent drying, or by subjecting them to a temperature higher than the ambient temperature for prolonged time periods. The first type of weathering occurs in a wetted storage. The second type of weathering occurs when a dust processing unit stores and maintains the dust deposit at an elevated temperature. As a result of weathering, the physical and thermal properties of the dust may change. Therefore, the weathered dust sample is expected to ignite at a different hot plate temperature as compared to that of a fresh sample, when tested in a standard test method (ASTM E 2021). In this study, three dust samples namely, wheat flour, Pittsburgh seam coal and powder river basin coal, are tested. These dust samples are subjected to one or both types of weathering. Thermogravimetric analysis and standard ignition tests are carried out with both fresh and weathered dust samples. Estimation of the activation energies and reactivity, and measurement of the minimum surface temperature for the onset of ignition have been carried out for all the cases. The implications of the observed results on industrial safety related to combustible dust layers are discussed.

Ignitability and thermal stability of asphalt binders and mastics for flexible pavements in highway tunnels

Due to their chemical composition, asphalt binders and mixtures are quite flammable and tend to produce smoke and poisonous gases while burning. Therefore, fire reaction of asphalt pavements is a topic of increasingly interest to improve fire safety in highway tunnels. Different asphalt binders and mastics containing aluminium hydroxide and magnesium hydroxide as inorganic flame retardants (FRs) were analysed through Thermo-Gravimetric Analysis (TGA) and Limiting Oxygen Index (LOI) test. Due to the lack of technical specifications for LOI measurements of asphaltic materials, a specific sample geometry and preparation as well as a testing procedure were developed and applied. The comparison between the two techniques indicated that both thermal stability and flammability are strictly related to asphalt composition. Moreover, the Thermo-Gravimetric test can be preventively used to select the most appropriate FR filler, whose decomposition temperature (together with particle size) is a factor of primary importance. Among the different flame retardants tested, the aluminium hydroxide showed the most important increase in LOI with respect to the unmodified binders. On the contrary, the SBS-modified binder, probably due to the unsaturated nature of the polymeric modifier, showed an increased flammability when compared with the base asphalt binders.

Thermal degradation, mechanical behavior and Co60 gamma-irradiation induced effects of poly(methylphenylsiloxane)/phenylene-silica hybrid material

Poly(methylphenylsiloxane) (PMPS)/phenylene-silica hybrid material was prepared by a two-step sol-gel process. In the structure of the hybrid system, the phenylene-silica framework was imported into the crosslinked PMPS matrix to obtain interpenetrating networks. The results of thermogravimetric analysis (TGA) and mechanical tests show that the products exhibit excellent thermal stability at ~400ºC in an inert atmosphere and a tensile strength up to 25.9 ± 1.7 MPa. The investigation of thermal degradation mechanism by TGA coupled with Fourier transform infrared (FTIR) spectroscopy (TGA-FTIR) reflects the linear segments unzipping (430–580ºC), the elimination of benzene (450–680ºC) and the rupture of Si-CH3 and Si-OH (620–850ºC), within which the first degradation step can be retarded by the steric effect of the phenylene-silica framework. In order to study Co60 gamma-irradiation induced effects, the hybrid products after irradiation were also studied by the same characterization, showing slightly increased crosslinking degree of PMPS and unchangeable initial degradation temperature at an irradiation dose of 1.6 × 105 Gy. The mechanical behavior for hybrid products, including tensile strength and coating film properties, was well maintained under the effect of irradiation. An increase of phenylene groups inserted in the phenylene-silica framework was confirmed to induce more significant steric interactions to polymer backbones. This effect permits the hybrid products to enhance thermal and irradiation resistance, as well as mechanical strength.

A New Kind of Silica Microspheres Used as Filler for PDMS Composite

A new kind of silica microspheres were first synthesized with dodecyltrimethoxysilane (WD10) and tetraethoxysilane (TEOS) by sol-gel method. And hybrid membrane was prepared by incorporating the as prepared filler into polydimethylsiloxane (PDMS). Thermal degradation and mechanical properties of these composites membranes were studied by means of thermogravimetric analysis and tensile testing. The experimental results showed that both mechanical properties and thermal stabilities of these composites were significantly improved by using the as-synthesized filler.

Application of Silicone TQ Resin Reinforced RTV Silicone Rubber in Architecture

A kind of silicone TQ resin was first synthesized with Dodecyltrimethoxysilane (WD10) and tetraethoxysilane (TEOS) by sol-gel method. And the RTV (Room Temperature Vulcanized) silicone rubbers using as-synthesized TQ silicone resins as filler were prepared. Thermal degradation and mechanical properties of these RTV silicone rubbers were studied by means of thermogravimetric analysis and tensile testing. The experimental results showed that both mechanical properties and thermal stabilities of RTV silicone rubbers were significantly improved by using the as-synthesized TQ silicone resins as filler. The RTV silicone rubber can be used to make the molds of architectural components ornamentation. The aim is not only to repair architectural components with decoration, but also for further study and research of ancient architectural conservation.

Coating carbon fibres with hybrid polymers for use at high temperatures

A thermal resistance coating of different high temperature resistance polymers, e.g. polysilazane and polysiloxane was applied to a carbon roving by a continuous dip coating method. Improved mechanical and thermal resistance properties of the coated carbon roving were evaluated by thermogravimetric analysis and tensile property testing under thermal stress. Investigation of the mechanical properties of coated carbon roving revealed a significant increase in their breaking strength, which amounted to more than 50% as compared to uncoated roving. The thermal stability as well as the oxidation protection of the coated sample in ambient air at temperatures up to 800℃ was much higher than that of the control sample. Topographical phenomena occurring due to the coating on the microscale were examined by scanning electron microscopy and energy dispersive X-ray analysis. The surface energy and the adhesion property of the coated substrate were determined by measuring the contact angle.

Thermal decomposition and fire behavior of glass fiber–reinforced polyester resin composites containing phosphate-based fire-retardant additives

The thermal degradation and the fire behavior of a polyester resin containing phosphate-based fire-retardant additives and its corresponding glass fiber composites were investigated. An unsaturated commercial polyester resin was modified by the addition of three phosphate-based fire retardants: ammonium polyphosphate, silane-coated ammonium polyphosphate, and melamine pyrophosphate, at 35% w/w. The effects of the fire retardants on resin thermal decomposition and small-scale fire behavior were studied using dynamic thermogravimetric tests at different heating rates and microcalorimetric measurements according to ASTM D7309-07. Different modes of degradation with different activation energy levels for the neat resin and the phosphate-loaded resins were identified by analyzing the thermogravimetric data through the Kissinger method. Since the ammonium polyphosphate-containing resin showed greater thermal and fire performance than the other systems, it was used to manufacture unidirectional glass fiber composites by a vacuum infusion process. The oxidative pyrolysis and fire behavior of the composites produced were studied using thermogravimetric and cone calorimeter tests that demonstrated improvement of their thermal stability and fire performance.

SiO2-Al2O3-P2O5무기복합체를 이용한 LiCl-KCl 방사성 폐기물의 안정화/고형화: Part 1. LiCl-KCl의 탈염화 반응거동 및 고형화특성

사용후 핵연료내 우라늄 및 초우란원소를 회수하는 파이로프로세싱 공정에서 배출되는 금속염화물계 방사성 폐기물은 높은 휘발특성과 붕규산계 유리와의 낮은 상용성으로 인해 고화처리가 쉽지 않은 폐기물이다. 이를 위해, 본 연구에서는 고화처리의 한 방법으로 탈염화 반응을 통한 고화체제조 개념을 채택하였다. 솔젤법을 이용하여 탈염화물질, <TEX>$SiO_2-Al_2O_3-P_2O_5$</TEX> (SAP)을 합성하였으며 이를 이용하여 탈염화 반응거동 반응생성물의 고형화 특성을 조사하였다. LiCl계 폐기물과 달리, LiCl-KCl폐기물의 반응은 두 개의 온도범위에서 반응이 진행되며, <TEX>$400^{\circ}C$</TEX>의 경우에는 LiCl이, 약 <TEX>$700^{\circ}C$</TEX>에서는 KCl이 주로 반응하는 것으로 확인되었다. 여러 가지 반응실험을 통하여 LiCl-KCl의 탈염화 반응에 가장 적합한 물질은 SAP 1071 (Si/Al/P=1/0.75/1 in molar)인 것으로 확인되었다. 4가지 종류의 고형화 실험을 통하여 고화체의 bulk shape과 densification은 SAP/Salt의 비에 영향 받는 것을 확인하였다. 제조된 고형화 시료는 Product Consistency Test-A법을 이용하여 기본적인 내구성을 평가하였다. 본 연구는 <TEX>$SiO_2$</TEX>, <TEX>$Al_2O_3$</TEX>, <TEX>$P_2O_5$</TEX>로 이루어진 탈염화 물질을 이용하여 반응특성과 고형화 특성에 대한 기본적인 정보를 제공하였으며, 이와 같은 실험을 통하여, 본 연구에서 제안된 탈염화 고화처리방법이 휘발특성이 높고 기존 유리매질과 상용성이 낮은 금속염화물계 폐기물에 적용이 가능함을 확인하였다. The metal chloride wastes from a pyrochemical process to recover uranium and transuranic elements has been considered as a problematic waste difficult to apply to a conventional solidification method due to the high volatility and low compatibility with silicate glass. In this study, a dechlorination approach to treat LiCl-KCl waste for final disposal was adapted. In this study, a <TEX>$SiO_2-Al_2O_3-P_2O_5$</TEX> (SAP) inorganic composite as a dechlorination agent was prepared by a conventional sol-gel process. By using a series of SAPs, the dechlorination behavior and consolidation of reaction products were investigated. Different from LiCl waste, the dechlorination reaction occurred mainly at two temperature ranges. The thermogravimetric test indicated that the first reaction range was about <TEX>$400^{\circ}C$</TEX> for LiCl and the second was about <TEX>$700^{\circ}C$</TEX> for KCl. The SAP 1071 (Si/Al/P=1/0.75/1 in molar) was found to be the most favorable SAP as a dechlorination agent under given conditions. The consolidation test revealed that the bulk shape and the densification of consolidated forms depended on the SAP/Salt ratios. The leaching test by PCT-A method was performed to evaluate the durability of consolidated forms. This study provided the basic information on the dechlorination approach. Based on the experimental results, the dechlorination method using a <TEX>$SiO_2-Al_2O_3-P_2O_5$</TEX> (SAP) could be considered as one of alternatives for the immobilization of waste salt.

Ultrafine Magnetite Nanopowder: Synthesis, Characterization, and Preliminary Use as Filler of Polymethylmethacrylate Nanocomposites

Magnetite (Fe3O4) nanoparticles prepared by microwave-assisted hydrothermal synthesis have been characterized in terms of morphological and structural features. Electron micrographs collected in both scanning (SEM) and transmission (TEM) modes and evaluations of X-ray powder diffraction (XRD) patterns have indicated the achievement of a monodispersed crystallite structure with particles having an average size around 15–20 nm. Structural investigations by Micro-Raman spectroscopy highlighted the obtainment of magnetite nanocrystals with a partial surface oxidation to maghemite (γ-Fe3O4). Preliminary attention has been also paid to the use of these magnetite nanoparticles as filler for a commercial polymethylmethacrylate resin. Hybrid formulations containing up to 3 wt% of nanoparticles were prepared by melt blending and characterized by calorimetric and thermogravimetric tests. For sake of comparison, same formulations containing commercial Fe3O4nanoparticles are also reported. Calorimetric characterization indicates an increase of both glass transition temperature and thermal stability of the nanocomposite systems when loaded with the synthesized magnetite nanoparticles rather then loaded with the same amount of commercial Fe3O4. This first observation represents just one aspect of the promising potentiality offered by the novel magnetic nanoparticles when mixed with PMMA.

Methane Combustion Using CeO2-CuO Fibers Catalysts

ABSTRACTThe use of three-way catalysts is an accepted method to minimize NOx and CO emissions generated by internal combustion engines. These catalysts are generally formed by the support, stabilizers, promoters metal and transition metals, the most used metals of the platinum group. The use of cerium as a promoter is usually related to its ability to store oxygen and structural aspects such as the property of increasing the dispersion of metals and slow change of phase of the stabilizing support. On the other hand, the metal copper was explored as a possible replacement for palladium and platinum in the reduction of NO by CO. In this work, fibers of cerium oxide doped with copper were obtained from an acetate solution of cerium and coppers nitrates and polyvinyl butyral (PVB). This solution went through the process of electrospinning to produce nanostructured fibers. After heat treatment, cerium oxide fibers were obtained. These fibers were characterized structurally by scanning electron microscopy (SEM), had their specific surface area determined by BET method, were subjected to thermogravimetric test to determine their thermal decomposition and were analyzed by X-ray diffraction. The catalytic activity was assessed by the amount of O2 consumed and CO and CO2 formed for the combustion of methane and air. SEM images show fibers oriented randomly in the substrate. TEM images show that the diameter of the fibers is approximately 100 nm and the size of its crystallites are around 20 nm. In the presence of the catalyst, the combustion reaction started around 500°C, with the consumption of methane and oxygen and the formation of CO and/or CO2. There was no emission of NO and NOx gases during the tests with catalysts.

Investigation of thermal behavior of Heliotropium indicum L. lyophilized extract by TG and DSC

Thermogravimetric (TG) techniques and differential scanning calorimetry (DSC) used for the study of pre-formulation or drug–adjuvant compatibility have been gaining importance in Brazil. These techniques are being used for the verification of possible interactions between drugs and adjuvants. Aiming at studying the behavior of a plant extract and its mixture with adjuvants, using these thermoanalytical techniques the plant species Heliotropium indicum L. was used. This plant which is originally from India and has been well acclimatized in Brazil has healing and anti-inflammatory properties. The methodology for obtaining the extract followed the Brazilian Pharmacopoeia methodology. And the incorporation of the extract with adjuvants was through binary mixtures (1:1 w/w). The TG and DSC curves were obtained under nitrogen atmosphere (25 mL min−1) at a heating rate of 5 °C min−1; TG tests were analyzed within a temperature range from 25 to 600 °C and DSC from 25 to 300 °C. The TG curves show good thermal stability of the extract and its mixtures with adjuvants up to 150 °C, except the propylene glycol (PLG). The DSC curves revealed an incompatibility of the extract with methylparaben and PLG mixture.

Investigation of the pore blockage of a Brazilian dolomite during the sulfation reaction

The influence of the temperature and reaction time on the sulfation process of a dolomite is investigated in this paper. The sulfation effectiveness was evaluated and correlated with changes in the physical characteristics of a Brazilian dolomite during the reactive process. Calcination and sulfation experiments were performed under isothermal conditions for dolomite samples with average particle sizes of 545μm at temperatures of 750°C, 850°C and 950°C at different times of sulfation. Thermogravimetric tests were applied to establish the reactivity variation of the dolomite in function of the time in the sulfation reaction and evaluate the methodology of the samples preparation. Porosimetry tests were performed to study the pore blockage of dolomite during the sulfation reaction. The highest values of BET surface area were 25.55m2/g, 29.55m2/g and 12.62m2/g for calcined samples and after their sulfation processes, conversions of 51.5%, 61.9% and 42.8% were obtained at 750°C, 850°C and 950°C, respectively. Considering the process as a whole, the best fit was provided by a first-order exponential decay equation. Moreover, the results have shown that it is possible to quantify the decreasing in the dolomite reactivity for sulfur dioxide sorption and understand the changes in the behavior of the sulfation process of limestones when applied to technologies, as fluidized bed combustor, in which sulfur dioxide is present.

Thermal and burning properties of wood flour-poly(vinyl chloride) composite

The present study deals with the effects of wood flour on thermal and burning properties of wood flour-poly(vinyl chloride) composites (WF-PVC) using thermogravimetric (TG), cone calorimetry (CONE), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/ MS). TG tests show that an interaction occurred between wood flour and PVC during the thermal degradation of WF-PVC. Wood flour decreased the temperature of onset of decomposition of PVC. However, the char formation could be increased by adding wood flour to PVC. CONE test indicates that wood flour had positive effects on heat release and smoke emission of PVC. Comparing with PVC, WF-PVC reduced average heat release rate and the peak HRR by about 14 and 28%, respectively; smoke production rate was also decreased. The degradation mechanism was studied by Py-GC/MS. The results show that the volatile pyrolysis products of WF-PVC are very different from PVC. The yields of HCl and aromatic compounds decreased dramatically, and the aliphatic compounds increased by the incorporation of WF.

The Influence of Clay-Like Sepiolite on the Structure and Properties of Polyurethaneurea/Sepiolite Nanocomposites

A series of polyurethaneurea (PUU) nanocomposites based on clay-like sepiolite (Sp) with the modification of γ-aminopropyltriethoxysilane (KH550) were prepared via in situ polymerization from poly(propylene glycol), tolylene-2,4-diisocyanate (TDI) and 3,3'-dichloro-4,4'- diamino-diphenylmethane(MOCA). Morphology and structure of nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results indicated that KH550-Sp was dispersed homogeneously in the PUU matrix, which facilitated the formation of chemical bonds between KH550-Sp and the hard segment of PUU. The thermostability and mechanical properties were studied by the thermogravimetric (TG) analysis and tensile tests. The results showed that the onset decomposition temperature and tensile strength of nanocomposites was higher than those of pure PUU.

Electro-mechanical and thermal characteristics of silver-electroded ionic polymer–metal composite actuator

The proposed work is in line with the evaluation of electro-mechanical and thermal characteristics of silver-electroded ionic polymer–metal composite (IPMC). IPMCs are fabricated first using Nafion-117 as base polymer and non-precious metal silver as surface electrode by chemical decomposition method. Several testings are performed on fabricated IPMC to evaluate its thermo-mechanical and micro-structural properties. The characteristics of the electrode layer and deposited particles on IPMC surface are studied using scanning electron microscope. The bending experiment of the actuator is conducted by applying direct current potential and the tip displacement measured. Thermo-gravimetric analysis and differential scanning calorimetry test are carried out, and thermal stability of the actuator is investigated. The crystal structure of IPMC is investigated by X-ray diffraction analysis. Micro-tensile test of the specimen is carried out to ascertain the stress–strain relationship and comparison is made with the base polymer, Nafion. The experimental investigations, characterization, and performance of the IPMC demonstrate its effectiveness to be used as actuator and artificial muscle materials.