Thermogravimetric Tests Research Articles

Variations of apparent activation energy based on thermodynamics analysis of zeolitic imidazolate frameworks including pyrolysis and combustion

Thermodynamics of zeolitic imidazolate frameworks (ZIFs) in pyrolysis and combustion processes at different heating rates were analyzed and kinetic parameters were calculated using thermogravimetric tests. Related results show that TG curves of both pyrolysis and combustion processes shift to the high-temperature zone with the increase of heating rates. Differences of DTG curves reaction intensity of the pyrolysis process are not evident with the increase of heating rates, while the reaction intensity of DTG curves of the combustion process is reduced gradually. The pyrolysis process can be divided into the dehydration (30–230 °C) and the pyrolysis reaction (430–950 °C). The combustion process can also be divided into the dehydration (30–250 °C) and the combustion reaction (331–449 °C). Three stages of the pyrolysis process are carried out by dynamical analysis due to changes of slopes, while the combustion process has only one stage. Dynamical parameters, such as the most probable mechanism, the pre-exponential factor and the apparent activation energy, are acquired by the way of comparison using two methods of Coats-Redfern (CR) model based on integral form and Achar-Brindley-Sharp-Wendworth (ABSW) model based on the differential form. Some interesting phenomena are also presented that effects of heating rates on the thermal decomposition and the kinetic analysis.

A much cheaper method to separate ethanol after solid-state fermentation process in renewable energy production

Abstract Planar Thermal Source (PTS) was used to separate ethanol from Solid-State Fermented crushed straw Material (SSFM) instead of the traditional separation method of water steam in Advanced Solid-State Fermentation technology (ASSF). Complete thermo gravimetric test was done on prepared material to study the mass change rules under heating of PTS. Factors considered were temperature of PTS (T, 20–100 °C), wet content of material (θ, 0.1–0.9), ethanol concentration in wet of material (ω, 0.03–0.11). The weight order of factors on material mass change speed V was T > θ > ω, and ω can be ignored for that was an order of magnitude less important than θ and T. V linearly increases with higher T, increases by power function with higher θ. V model with T and θ was regressed. As ethanol separating from SSFM can be considered as ethanol evaporating from ethanol solution, ethanol solution evaporation model was derived. Above all, model of ethanol separation from SSFM by PTS was derived. The cost model was added. Software was programmed to calculate the separation process and its cost. The method will promote the ASSF technology to produce fuel ethanol. The study can also be reference on drying process of other crushed plant material.

Influence of ammonium polyphosphate on flame-retardant behavior and smoke suppression property of EVA/magnesium hydroxide composites

ABSTRACTTo overcome the flammability and smoke generation of EVA, samples with different mass fraction of magnesium hydroxide (MH) and ammonium polyphosphate (APP), have been prepared by internal mixer and cured by compression molded. The fire characteristics including smoke and heat production of EVA composites were studied by cone calorimeter test (CCT), limiting oxygen index test, UL-94 test, scanning electron microscopy, and thermogravimetric (TG) analysis, respectively. For the sample EVA5 loading 10.0 mass% APP and 40.0 mass% MH, the LOI value can be increased to the value of 31.1 and reach V-0 level. The CCT test showed that APP and MH could significantly improve the fire safety of EVA. Remarkably, the peak of heat release rate, the peak of smoke production rate, and total smoke release for EVA5 were decreased by 75.4%, 88.1% and 70.8% compared with pure EVA, respectively. TG test showed that APP promoted the char formation in the degradation process of EVA; as a result, the residual carbon was increased. The results indicated that APP combined with MH could facilitate the formation of the rigid intumescent char and obviously enhance the flame retardancy, smoke suppression and thermal stability of the EVA matrix.

Rigid polyisocyanurate–waterglass foam composite: Preparation, mechanism, and thermal and flame‐retardant properties

ABSTRACTA rigid polyisocyanurate–waterglass foam (PIWGRF) composite was prepared with polyaryl poly(methylene isocyanate) and waterglass (WG) as the main materials; water as a blowing agent, and no polyols. We speculated the formation mechanism of the PIWGRFs on the basis of the analysis of experiment data, scanning electron microscopy characterization, and transmission electron microscopy. The results show that three‐dimensional nanoflakes derived from the cured WG was observed; this was connected with polyisocyanurate by secondary bonding (SiOHN). Thermogravimetric testing indicated that the thermal stability and residual mass (34%) of the PIWGRFs were significantly higher than those of rigid traditional polyurethane foams (T‐PUFs). When the core density of the PIWGRFs was 32.6 kg/m3, the strength was up to 162.9 KPa by excessive filling. The flame retardancy of the PIWGRFs, including the time to ignition, heat‐release rate, total smoke of release, and limiting oxygen index, was obviously better than that of the T‐PUFs. The structure of the residual char was more dense and orderly; this was also an effective barrier layer. The reason was attributed to the fact that the WG did not contain combustible elements. So, the PIWGRFs had excellent thermal stability, flame retardancy, and environmental friendliness. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46182.

THERMOGRAVIMETRIC APPROACH FOR ASSESSING THE OXIDATION LEVEL OF A BIODIESEL SAMPLE

Biodiesel, unlike diesel, is highly susceptible to autoxidation. This autoxidation is a major concern for a biodiesel producer. Various methods have been developed to estimate the degree of oxidative stability of biodiesel. These methods are useful to compare and estimate the oxidative stability between different biodiesel samples. However, an absolute value of the oxidative state will be more useful. In this study, we describe a method of estimating a figure that can be used as an indicator of the oxidation level. This indicator was determined from the thermal decomposition curve of biodiesel, as obtained from the thermogravimetric test. Biodiesel from waste cooking oil was oxidized at 80, 100 and 120 oC using different exposure areas (19.6, 63.6, and 153.9 cm2). The percentage of oxidation, measured from low (80 oC, 19.6 cm2) to highly aggressive conditions (120 oC, 153.9 cm2), was in the range of 0.4 ± 0.1 and 23.5 ± 3.3. Kinematic viscosity was also measured for the oxidized samples, and a strong correlation (R2=0.96) was observed between the percentage of oxidation products and kinematic viscosity. In addition, the oxidative effect of temperature and area of exposure on the biodiesel samples was confirmed by ultraviolet spectroscopy.

Evaluation of the physical and mechanical properties of caña brava (Arundo donax) reinforced panels

Introduction: The use of composites made of vegetable origin materials has gained importance in some areas of engineering, mainly in civil construction. Objective: The objective of this paper is to analyze the physical and mechanical behavior of panels made with cana brava fibers and vegetal resin. Methodology: For the elaboration of the panels, the fibers were extracted using a mechanical crusher. The fibers were treated with a sodium hydroxide solution. The effect of the chemical treatment was evaluated by scanning electron microscopy. The roughness of the fibers was determined using the atomic force microscopy technique. For the manufacture of the composite, a compression method was used. The physical characterization of the panels was focused on the evaluation of the effective absorption, density, and percentage of swelling. To evaluate the mechanical behavior, static bending and mechanical fracture tests were performed. To evaluate the degradation of the material with the temperature, a thermogravimetric test was executed. Results: From the results, it is possible to verify that panels made with cana brava fibers and vegetal resin can present an increase in their dimensional stability when compared to panels made with Guadua Angustifolia Kunth fibers and show higher values of strength and stiffness than panels elaborated with coconut and bamboo fibers. Conclusions: Considering that cana brava is an invasive plant, its application as reinforcement of composite panels is a viable option to promote the development and application of new materials in civil construction.

Thermal decomposition behavior of water hyacinth (eichhornia crassipes) under an inert atmosphere

Thermogravimetric analysis experiment to understand thermal decomposition behavior of water hyacinth during the pyrolysis has been performed. Water hyacinth was taken randomly from 2 places, i.e., Selorejo and Sengguruh Dam, district of Malang, Indonesia. Those raw materials were thoroughly cleaned by using the water, then cut and dried in an oven with a temperature range of 80-90 °C for 6 hours. Subsequently, the dried samples were crushed and then filtered to a mesh size of 60. Thermal behavior of the sample was observed through the instrumentality of thermal analyzer at a constant heating rate of 10 °C/min with a nitrogen flow rate of 100 ml/min and a temperature range of 25-1000 °C. The kinetics of active pyrolysis zone were evaluated by Coats-Redfern integral method. The thermogravimetric test results show that the water hyacinth biomass decomposed into four stages during the pyrolysis process. The kinetic parameters in term of activation energy (E), logarithmic frequency factor (log A) and reaction order (n) were 60.74 kJ/mol, 4.77/min and 1.9, respectively.

Quadripolymers as Viscosity Reducers for Heavy Oil

A series of oil-soluble quadripolymers (denoted as AOSVs) have been synthesized to reduce the viscosity of heavy oil. The quadripolymers were characterized by 1H NMR spectroscopy, GPC, and TGA to determine the structures and properties. By comparing the apparent viscosities of two different kinds of heavy oil before and after the addition of the quadripolymers, we found that the efficiency of the AOSVs for viscosity reduction was markedly elevated for almost the same molecular weight and mole ratio. Thermogravimetric tests and pumping transportation simulations showed that the AOSVs have good thermal stability up to 320 °C and strong shearing resistance. Furthermore, a heavy-component model and a copolymer model were built, and simulations of the interaction process were conducted. The results indicated that the copolymers changed the density of the crude oil by breaking down asphaltene and resin agglomerates to achieve a viscosity reduction.

Master decomposition curve of carbonaceous materials used in casting powders

Casting powders are used in the continuous casting process of steels. These powders contain several oxides, fluoride compounds and carbonaceous materials. The decomposition kinetics of these carbonaceous materials regulates the melting rate of casting powders. In a previous work, a decomposition kinetics of two carbonaceous materials (coke and graphite) added to a casting powder was studied. Based on those data, in the present work, master decomposition curves (MDC) of these powders were constructed. For this, the values of both the activation energy (E) and the degree of decomposition (α), obtained in the thermogravimetric tests, were used for each heating rate (β). Then, the work of decomposition (θ D) was calculated and the MDC was obtained. From the MDC, it was possible to predict the time (t) needed to produce a given degree of decomposition (α) at different temperatures (T). Taking this into account, it was possible to validate the master decomposition curves through different thermal treatments, where the degree of decomposition was calculated by interpolating the MDCs. These values were compared with those determined experimentally by measuring the mass loss in each heat treatment. In all cases, the results showed a good correlation between the predicted and measured values. It is concluded that the use of the MDC represents a useful tool to evaluate and compare the behavior of carbonaceous materials added to casting powder.

Nanocomposites with shape memory behavior based on a segmented polyurethane and magnetic nanostructures

Shape-memory composites based on a commercial segmented polyurethane and magnetite (Fe3O4) nanoparticles (NPs) were prepared by a simple suspension casting method. The properties of the resulting nanocomposites, containing 1 to 10 nominal wt.% magnetic particles, were evaluated by thermogravimetric tests, contact angle measurements, differential scanning calorimetry, infrared and X-ray spectroscopy, static and thermal cyclic tensile tests, dynamic mechanical analysis and experiments of alternating-magnetic-field heating. It was found that most of the suspended NPs could be successfully incorporated into the polyurethane matrix, and thus composite samples with up to 7 wt.% actual concentration were obtained. On the other hand, the incorporation of magnetite nanoparticles to the shape memory polyurethane did not significantly affect most of the matrix properties, including its shape memory behavior, while added magnetic response to the nanocomposites. Thus, nanocomposites were able to increase their temperature when exposed to an alternating magnetic field, which allowed them to recover their original shape quickly by an indirect triggering method.

Kinetics of thermal decomposition of some biomasses in an inert environment. An investigation of the effect of lead loaded by biosorption

The thermal behavior of some types of raw and lead-polluted biomasses typical in south Spain was studied by non-isothermal thermogravimetry. Experiments were carried out in nitrogen atmosphere at three heating rates (5, 10 and 20°C/min). The results of thermogravimetric tests carried out proved that the presence of lead did not change the main degradation pathways of selected biomass (almond shell (AS) and olive pomace (OP)). However, from a point of view of mass loss, lead-polluted samples showed higher decomposition temperatures and decomposition at higher rate. The determination of activation energies was performed by isoconversional methods of Flynn–Wall–Ozawa (FWO), Kissinger–Akahira–Sunose (KAS) and Friedman (FR). In general, lead-polluted samples showed lower activation energies than raw ones. Then, Coast-Redfern method was applied to determine kinetic function. The kinetic function that seems to determine the mechanism of thermal degradation of main components of all samples was nth order reaction. Finally, a model based on three parallel reactions (for three pseudocomponents) that fit to nth order reactions was evaluated. This model was appropriate to predict the pyrolysis behavior of the raw and lead-polluted samples in all pyrolysis conditions studied.

Performance of methylphenyl hydrogen-containing silicone oils for LED encapsulation

ABSTRACTThree-dimensional light-emitting diodes (LEDs) are the preferred light source for bulb lamps due to their 360° illumination. Addition curing silicone resins have usually been used to encapsulate LEDs. LED-filament encapsulation needs silicone resins having high thermal performance and thixotropy. Herein, a low refractive index and highly anti-thermal aging silicone oil was synthesized by hydrolysis and co-condensation method, and used to prepare an encapsulation material for high-power LED-filament. The cured silicone materials were characterized by thermogravimetric analysis (TGA) and thermal aging test under 180°C and 250°C. The results demonstrated that the thermal stability of the cured silicone resins with short-chain phenyl silicone as a crosslinker was higher than that with long-chain methyl silicone oil crosslinker. Owing to the excellent thermal stability, appropriate hardness, high transparency and photoelectric efficiency, this LED encapsulation material is a promising candidate for high-power LED package.

Thermal and Rheological Properties of the Mucilage from the Fruit of Cordia lutea

In recent years, natural gums and mucilages have been shown to be useful in the food and pharmacological industries. In this study, the mucilage of the fruit of Cordia lueta has been extracted and characterised in order to explore its potential applications. Thermogravimetric tests were used to measure the water content of this natural mucilage. Differential scanning calorimetry allowed assessing thermal transitions and thermal degradation of the samples. Steady flow rheometry was used to measure the viscosity of the samples as a function of the shear rate. Dynamic oscillatory rheometry was used to study the variation of the storage and loss modulus of the mucilage as function of the oscillatory frequency and stress. The results showed that this mucilage is a polysaccharide network that behaves as a pseudoplastic fluid. Its storage modulus is not completely independent from the oscillation frequency. In addition, the stress sweeps showed that C. lutea mucilage has a reversible stress softening behaviour. The findings reported in the present work suggest that this mucilage can be used as a rheology modifier for commercial foods and biomedical materials.

Global Reaction Model to Describe the Kinetics of Catalytic Pyrolysis of Coffee Grounds Waste

In view of the constant search for new sources of renewable energy, the particulate agro-industrial waste reuse emerges as an advantageous alternative. However, despite the advantages of using the biomass as an energy source, there is still strong resistance as the large-scale replacement of petroleum products due to the lack of scientifically proven efficient conversion technologies. In this context, the pyrolysis is presented as one of the most widely used thermal decomposition processes. The knowledge of aspects of chemical kinetics, thermodynamics these will, heat and mass transfer, are so important, since influence the quality of the product. This paper presents a kinetic study of slow pyrolysis of coffee grounds waste from dynamic thermogravimetric experiments (TG), using different powder catalysts. The primary thermal decomposition was described by the one-step reaction model, which considers a single global reaction. The kinetic parameters were estimated using nonlinear regression and the differential evolution method. The coffee ground waste was dried at 105°C for 24 hours. The sample in nature was analyzed at different heating rates, being 10, 15, 20, 30 and 50 K/min. In the catalytic pyrolysis, about 5% (w/w) of catalyst were added to the sample, at a heating rate of 30 K/min. The results show that the one-step model does not accurately represent the data of weight loss (TG) and its derivative (DTG), but can do an estimative of the activation energy reaction, and can show the differences caused by the catalysts. Although no one can say anything about the products formed with the addition of the catalyst, it would be necessary to micro-pyrolysis analysis, we can say the influence of the catalyst in the samples, based on the data obtained in thermogravimetric tests.

Synthesis and evaluation of a novel monomeric amine as sodium montmorillonite swelling inhibitor

A novel monomeric amine sodium montmorillonite swelling inhibitor: N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide was obtained from diethanolamine, 1-bromotetradecane, and 1, 2-dibromoethane. N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide was characterized by means of Fourier transform infrared, 1H NMR spectroscopy, elemental analysis, linear swelling tests, particle size distribution tests, X-ray diffraction, and thermogravimetric. Linear swelling tests showed that the swelling height of sodium montmorillonite in 1.0 wt% N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide solution was only 2.0 mm after 16 h (fresh water was 5.0 mm). Particle size distribution tests exhibited that the median diameter and mean particle size of sodium montmorillonite in 1.0 wt% N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide solution obviously increased to 16.1 and 85.4 µm, respectively (fresh water was 8.1 and 21.8 µm). In thermogravimetric tests, in comparison with pure sodium montmorillonite, the decrease of water content in sodium montmorillonite/ N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide indicated N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide expelled the water molecules out of the interlayer, which was beneficial to wellbore stability. Fourier transform infrared spectra of certain concentration N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide/sodium montmorillonite indicated the successful physical adsorption and interaction between N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide with sodium montmorillonite. In addition, the results of X-ray diffraction tests showed the obtained 1.0 wt% N1, N2-ditetradecy- N1, N1, N2, N2-tetrakis (2-hydroxyethyl) ethane-1,2-diaminium bromide solution could remarkably reduce the interlayer distance of wet sodium montmorillonite (from 1.94 to 1.37 nm).

Insight into effects of pore diffusion on smoldering kinetics of coal using a 4-step chemical reaction model

Pore diffusion plays a crucial role in coal smoldering fires, however, its effects have been inadequately investigated. This paper aims to study influences of pore diffusion of oxygen (O2) on chemical reaction and apparent reaction rate of coal smoldering. Non-isothermal thermogravimetric (TG) tests for two bituminous coal samples at three heating rates (2, 5 and 10 K/min) were conducted, and a 4-step decomposition scheme was constructed. The decomposition schemes contained two competing paths: Coal oxidation → β-Char oxidation → Ash (Path One), and Pyrolysis → α-Char oxidation → Ash (Path Two). A number of kinetic triplets (reaction order, pre-exponential factor and activation energy) and stoichiometric coefficients of the developed decomposition schemes were optimized by a Genetic Algorithm (GA) tool. Emphasis was put on influences of pore diffusion on chemical reactions (e.g. pyrolysis, coal matrix's and chars' oxidation) and on competing paths. Research results show that Knudsen diffusion plays a dominant role in pore diffusion that retards coal oxidation and its successive char oxidation on the Path One, but basically enhances char oxidation on the Path Two. Pore diffusion may exert ignorable influence on pyrolysis as it takes place without O2. The investigation is beneficial for understanding mechanism of smoldering of coal piles and coal dust layers.

Experimental review of oxygen content at mixing layer in cone calorimeter

This work aims to elucidate whether the hypothesis of zero oxygen at the mixture layer when flame takes place is assumable for every kind of material. For that purpose, we investigated the oxygen concentration there by cone calorimeter tests. A modified holder was developed in order to collect oxygen in this mixture layer. In addition, thermogravimetric tests were carried out so as to relate the possible effects of the presence of oxygen in the atmosphere where the pyrolysis process takes place, since the cone calorimeter does not allow to control the oxygen level of the atmosphere during the experiment. The reaction rates and per cent of residue in the cone calorimetric tests were measured and compared with the results from thermogravimetric tests. Six products were analysed which can be classified in three main groups: lignocellulosic, thermoplastic polymers and thermoset polymers. Cone calorimetric results showed that for some of the materials analysed (PET, Nylon and PUR foam) the oxygen level at mixture layer decreased until values close to zero. The comparison of reaction rates between cone calorimetric and thermogravimetric tests revealed the char layer created in cone calorimetric tests over the exposed face for brushed fir, Nylon and PET established an important heat barrier that modifies the thermal behaviour of these materials.

Development of new biodegradable packaging

The aim of this work was the development and the characterisation of biocomposite films obtained from a mixture of corn starch and microcrystalline cellulose and the study of the influence of a plasticisers mixture on the behaviour of these films. These have been characterised in order to use them as new formulations to produce films for food packaging. The films obtained are generally homogeneous, opaque, thin, smooth and having a good coherence with no visual defects. The results of the tests (water sorption isotherm, water vapour permeability, thermogravimetric and mechanical test) have shown improvements on the films’ properties using a plasticisers mixture (glycerol/DL-lactic acid) better than those obtained by plasticisation by glycerol or by DL-Lactic acid taken individually. This is explained by the fact that the plasticisers mixture (glycerol/DL-lactic acid) has a double plasticising effect: internal plasticisation due to the intercalation of polymer-substituted chains between the polymer chains and external plasticisation due to glycerol molecules. In addition, the hydrogen bonds formed in this new plasticisation are more stable than those formed during the use of glycerol or of the DL-lactic acid separately, thereby giving rise to a material with improved properties.

The Effect of Boron and Titanium Microalloying on the Scale Formation of AISI 304 Austenitic Stainless Steel in Simulated Walking Beam Furnace Conditions

The effect of microalloying boron and titanium on AISI 304 austenitic stainless steel scale formation is studied. Thermogravimetric tests simulating walking beam furnace conditions are performed at temperatures of 800, 1100, and 1300 °C for 3 h on samples of AISI 304 steels with different alloying amounts of B and Ti. Scaling at 800 °C is negligible on all the samples, while scaling is clear at 1100 and 1300 °C. The thermogravimetric results show that even in small amounts, boron and titanium have an effect on scale growth rate. FESEM microscopy and accompanying EDS analyses are used to study oxidation area element composition. The FESEM images are also used to compare the oxidation zones’ area fractions of metal, pores, and oxide between different alloying amounts for the samples of 1300 °C tests. Calculations for scale formation activation energy are done based on the thermogravimetric data. The steel sample with the lowest alloying of boron and titanium shows a noticeably different growth rate, which is nearly linear in both the 1100 and 1300 °C tests. Differences between alloying amounts in accumulated scale during the 180 min period in kg m−2 are greater at 1100 °C than they are at 1300 °C.

Thermal Degradation and Combustion Performance Comparison of Plywood Based on Inorganic Adhesive and Phenol-Formaldehyde Resin

The main objective of this work was to study a new inorganic adhesive used for wood-based panel. Inorganic adhesive and its poplar plywood were prepared to investigate their properties. Thermo-gravimetric analysis tests revealed that the total mass loss of inorganic adhesive was 76.24%, which was higher than that of phenol-formaldehyde resin (64.97%). The results showed better thermal stability of inorganic adhesive. For inorganic adhesive plywood, approximately 30% decrease in peak of heat release rate, 62% in total smoke production and 20% in mean CO2 yield, respectively, were seen compared to the control by cone calorimeter analysis. Scanning electron microscopy imaged wider glue line of inorganic adhesives plywood, which was related to the bonding strength of plywood. Thus the inorganic adhesive of fireproofing made in lab could be better used for plywood processing.