Thermogravimetric characteristics and kinetic study of biomass co-pyrolysis with plastics

The pyrolysis of pure biomass, high density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET), plastic mixtures [HDPE+PP+PET (1: 1: 1)], and biomass/plastic mixture (9: 1, 3: 1, 1: 1, 1: 3 and 1: 9) were investigated by using a thermogravimetric analyzer under a heating rate at 10 °C/min from room temperature to 800 °C. Paper was selected as the biomass sample. Results obtained from this comprehensive investigation indicated that biomass was decomposed mainly in the temperature range of 290–420 °C, whereas thermal degradation temperature of plastic mixture is 390–550 °C. The percentage weight loss difference (W) between experimental and theoretical ones was calculated, which reached a significantly high value of (−)15 to (−)50% at around 450 °C in various blend materials. These thermogravimetric results indicate the presence of significant interaction and synergistic effect between biomass and plastic mixtures during their co-pyrolysis at the high temperature region. With increase in the amount of plastic mixture in blend material, the char production has diminished at final pyrolysis temperature range. Additionally, a kinetic analysis was performed to fit with TGA data, the entire pyrolysis processes being considered as one or two consecutive first order reactions.     

Activation energy and curing behavior of resol‐ and novolac‐type phenolic resins by differential scanning calorimetry and thermogravimetric analysis

The thermal behavior, thermal degradation kinetics, and pyrolysis of resol and novolac phenolic resins with different curing conditions, as a function of the formaldehyde/phenol (F/P) molar ratio (1.3, 1.9, and 2.5 for the resol resins and 0.5, 0.7, and 0.9 for the novolac resins) were investigated. The activation energy of the thermal reaction was studied with differential scanning calorimetry at five different heating rates (2, 5, 10, 20, and 40°C/min) between 50 and 300°C. The activation energy of the thermal decomposition was investigated with thermogravimetric analysis at five different heating rates (2, 5, 10, 20, and 40°C/min) from 30 to 800°C. The low molar ratio resins exhibited a higher activation energy than the high molar ratio resins in the curing process. This meant that less heat was needed to cure the high molar ratio resins. Therefore, the higher the molar ratio was, the lower the activation energy was of the reaction. As the thermal decomposition of the resol resins proceeded, the activation energy sharply decreased at first and then remained almost constant. The activation energy of the thermal decomposition for novolac resins with F/P = 0.5 or F/P = 0.7 was almost identical in all regions, whereas that for novolac resins with F/P = 0.9 gradually decreased as the reaction proceeded. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2589–2596, 2003     

Thermal degradation kinetics of rigid polyurethane foams blown with water

The thermal decomposition behavior of rigid polyurethane foams blown with water was studied by dynamic thermogravimetric analysis (TGA) in both nitrogen and air atmosphere at several heating rates ranging from room temperature to 800°C. The kinetic parameters, such as activation energy (E), degradation order (n), and pre‐exponential factor (A) were calculated by three single heating rate techniques of Friedman, Chang, and Coats–Redfern, respectively. Compared with the decomposition process in nitrogen, the decomposition of foams in air exhibits two distinct weight loss stages. The decomposition in nitrogen has the same mechanism as the first stage weight loss in air, but the second decomposition stage in air appears to be dominated by the thermo‐oxidative degradation. The heating rates have insignificant effect on the kinetic parameters except that the kinetic parameters at 5°C/min have higher values in nitrogen and lower values in air, indicating different degradation kinetics in nitrogen and air. The kinetic parameters of foam samples blown with different water level in formulation decline firstly and then increase when water level increases from 3.0 to 7.0 pph. According to the prediction for lifetime and half‐life time of foams, water‐blown rigid foams have excellent thermostability, when used as insulation materials below 100°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4149–4156, 2006     

Thermal Stability and Early Degradation Mechanisms of High‐Density Polyethylene,Polyamide 6 (Nylon 6), and Polyethylene Terephthalate

The thermal stability and degradation mechanisms of three semicrystalline polymers (polyethylene terephthalate [PET], high‐density polyethylene [HDPE], and polyamide 6 [nylon 6]) were studied. Thermogravimetric traces were acquired first at heating rates of 1°C/min and 10°C/min, and it was determined that the heating rate significantly affected the thermal decay curves of the three polymers. The results allowed the selection of specific temperatures at which to carry out heating and cooling cycles from room temperature to the molten state. The thermal behaviors of HDPE, nylon 6, and PET each had particular characteristics. HDPE showed the highest thermal resistance, whereas nylon 6 displayed the lowest. PET had the lowest activation energy for degradation, 93.5 kJ/mol, and retained 14 wt% after thermal recycling with no influence of molecular weight. Thermal cycling also revealed gradual morphological changes in HDPE, nylon 6, and PET, and their crystals changed from regular to branched spherulites with variations in the nucleation patterns. Fourier‐transform infrared spectroscopy measurements allowed us to explain the early stages of degradation for each polymer. POLYM. ENG. SCI., 59:2016–2023, 2019. © 2019 Society of Plastics Engineers     

Thermogravimetric analysis of longan seed biomass with a two-parallel reactions model

The kinetic analysis of pyrolysis process of longan seed was performed in a thermogravimetric analyzer. All experimental runs were carried out by using an initial sample mass of 15 mg and final temperature of 650 °C under the inert atmosphere of nitrogen. Particle sizes in the range from 0.05–2.1 mm and the heating rates from 5–100 °C/min were employed to investigate their effects on the thermogram and the kinetic parameters. The TG curves generally showed sigmoid shape and displayed one major peak in DTG curve. The main devolatilization of longan seed occurred over the temperature range of 210–330 °C. It was found that heat transfer resistance in a particle could be reduced either by decreasing the size of particle or increasing the heating rate. The thermal decomposition of longan seed could be well described by the two-parallel reactions kinetic model. This analysis of reaction kinetic gave the values of activation energy for the decomposition of the two fractions in the model corresponding closely to those of hemicellulose and lignin.     

Thermal degradation of polymethacrylic ester containing bisphenol-S

Thermal degradation of polymethacrylic ester containing bisphenol-S, poly(BPS-M), was investigated under nitrogen and air atmosphere at various heating rates. Ozawa's method was used to calculate the kinetic parameters, activation energy, preexponential factor and reaction order. Thermodegradation of the polymer occurs in one or two stages in nitrogen and air, respectively. The temperature at the start of intense degradation (T_start) and the temperature corresponding to a 50% mass loss (T_50%) were found to be 300 and 402°C, respectively, at a heating rate of 10°C min^?1 in nitrogen. Larger sample masses have a larger temperature interval (ΔT) and a greater mass loss (ΔW). The kinetic order of degradation is unity both in nitrogen and air. The direct pyrolysis mass spectrum of the polymer shows one degradation peak. The most important degradation process under inert atmosphere is the loss of carbon dioxide, phenol and sulphur dioxide. A possible mechanism for thermal decomposition of poly(BPS-M) is proposed based on the product analyses.     

Pyrolysis kinetics of olive residue/plastic mixtures by non-isothermal thermogravimetry

The TGA studies of a pyrolytic decomposition of mixtures of olive residue/plastic were carried out. The investigation was made at the temperature ranging from 300 to 1273 K) in the nitrogen atmosphere at four heating rates β = 2, 10, 20 and 50 K min^− 1. High density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were selected as plastic samples. Based on the results obtained, three thermal stages were identified during the thermal degradation. The first two were dominated by the olive residue pyrolysis, while the third was linked to the plastics pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on pyrolysis olive residue/plastic mixtures. The maximum degradation temperatures of each component in the mixture were higher than those of the individual components. These experimental results indicate a significant synergistic effect during olive residue and plastic co-pyrolysis at the high temperature region. In addition, a kinetic analysis was performed to fit thermogravimetric data. A reasonable fit to the experimental data was obtained for all materials and their mixtures.     

Wood particle/high‐density polyethylene composites: Thermal sensitivity and nucleating ability of wood particles

The thermal sensitivity, nucleating ability, and nonisothermal crystallization of high‐density polyethylene (HDPE) with different wood fillers during wood/HDPE melt processing were investigated with thermogravimetric analysis and differential scanning calorimetry. The results showed that the wood degraded at a lower temperature than HDPE. The thermal decomposition behavior was similar across wood species. The most remarkable dissimilarities were observed between wood and bark in the decomposition rate around a processing temperature of 300°C and in the peak temperature location for cellulose degradation. The higher degradation rate for bark was explained by the devolatilization of extractives and the degradation of lignin, which were present in higher amounts in pine bark. The nucleating ability for various wood fillers was evaluated with the crystalline weight fraction, crystal conversion, crystallization half‐time, and crystallization temperature of the HDPE matrix. The nucleation activity improved with the addition of wood particles to the HDPE matrix. However, no effect of wood species on the crystal conversion was found. For composites based on semicrystalline matrix polymers, the crystal conversion may be an important factor in determining the stiffness and fracture behavior. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Thermal degradation behaviour of aromatic poly(ester–imide) investigated by pyrolysis–GC/MS

The thermal degradation behaviours of a novel aromatic poly(ester–imide) (PEI) derived from pyromellitic dianhydride and 2,7-bis(4-aminobenzoyloxy)naphthalene have been investigated by thermogravimetric analysis (TGA) and by pyrolysis–gas chromatography/mass spectrometry (pyrolysis–GC/MS). The weight of PEI fell slightly in the temperature range of 350–450 °C in the TGA analysis, but the major weight loss occurred at 520 °C. Evolve gas analysis (EGA) of the PEI showed maximum release of pyrolyzates at 550 °C. The chemical structure of the volatile products resulted from the PEI pyrolysis at different temperatures was identified by pyrolysis–GC/MS. The cleavage of the ester linkage within the polymer chain initiated at 350 °C, and bond scission in the partially hydrolyzed pyromellitimide unit occurred in the temperature range of 450–500 °C. The bonds within the pyromellitimide unit started to cleave at 550 °C. The extensive decomposition of the pyromellitimide segment within the polymer backbone occurred at 600 °C. The possible thermal degradation pathways of this PEI are proposed on the basis of the pyrolysis products.     

Effect of heating rate on pyrolysis of low-grade pyrolytic oil

The low-grade pyrolytic oil produced from pyrolysis of municipal plastic waste in a commercial rotary kiln reaction system cannot be an acceptable fuel oil due to its low quality. Thus, the degradation of pyrolytic oil was conducted in a bench scale batch reactor, which was done by two experiment conditions of high heating rate (about 7 °C/min) and low heating rate (1.5–3.6 °C/min) up to 420 °C of reaction temperature. The characteristics of raw pyrolytic oil were examined and also the characteristics of products obtained by different heating rates were compared. Raw pyrolytic oil had higher H/C ratio and higher heating value than commercial oils, and also its peak range in GC analysis showed wide distribution including all the range of gasoline, kerosene and diesel. In the upgrading of pyrolytic oil, cumulative amount profile of product oil, as a function of reaction time, was similar in shape to the degradation temperature profile. All product oils obtained by different degradation temperature had higher H/C ratio and slightly higher heating value than those of raw pyrolytic oil. Also, the characteristics of product oils were influenced by heating rate and reaction temperature.     

KINETIC STUDY ON PYROLYSIS OF NSSC BLACK LIQUOR IN A NITROGEN ATMOSPHERE

Thermogravimetric analysis experiments were carried out to investigate the pyrolysis properties of neutral sulfite semi-chemical pulp (NSSC) black liquor ranging from room temperature to 800°C with heating rates of 20°, 30°, 50°C/min. Experimental results show that the black liquor quickly loses weight in the temperature range of 170°–370°C, 370°–570°C, and 570°–800°C. The organic volatiles are mostly released in the former two ranges, while the alkali metal salts decompose, volatilize, and react in the third range. The mechanism function of NSSC black liquor pyrolysis is determined by means of the thermal analytic dynamics method and the most probable mechanism functions. The kinetic parameters for the chemical reactions were calculated by the Coats and Redfern method and the Ozawa method. Meanwhile, the pyrolysis dynamics equation of the NSSC black liquor is presented in this work. The results show that the activation energies of the NSSC black liquor decomposition calculated by the Ozawa method in the three temperature ranges are in general lower than that those calculated by the Coats and Redfern method.     

Evaporation of pyrolysis oil: Product distribution and residue char analysis

The evaporation of pyrolysis oil was studied at varying heating rates (～1–10⁶°C/min) with surrounding temperatures up to 850°C. A total product distribution (gas, vapor, and char) was measured using two atomizers with different droplet sizes. It was shown that with very high heating rates (～10⁶°C/min) the amount of char was significantly lowered (～8%, carbon basis) compared to the maximum amount, which was produced at low heating rates using a TGA (～30%, carbon basis; heating rate 1°C/min). The char formation takes place in the 100–350°C liquid temperature range due to polymerization reactions of compounds in the pyrolysis oil. All pyrolysis oil fractions (whole oil, pyrolytic lignin, glucose and aqueous rich/lean phase) showed charring behavior. The pyrolysis oil chars age when subjected to elevated temperatures (≥700°C), show similar reactivity toward combustion and steam gasification compared with chars produced during fast pyrolysis of solid biomass. However, the structure is totally different where the pyrolysis oil char is very light and fluffy. To use the produced char in conversion processes (energy or syngas production), it will have to be anchored to a carrier. © 2010 American Institute of Chemical Engineers AIChE J, 2010     

Study of pyrolysis kinetics of Alberta oil sand by thermogravimetric analysis

The kinetics of the thermal decomposition of Alberta oil sand has been investigated by thermogravimetric analysis (TGA) for the study of oil sand pyrolysis characteristics. The TGA experiments were carried out at four different heating rates of 10, 20, 30, 40 °C/min up to 900 °C to verify weight variation and reaction temperature. The activation energy of the thermal decomposition of Alberta oil sand obtained from the kinetic analysis was similar to that of the previous researches. Also, bitumen was extracted by solvent (toluene, THF (tetrahydrofuran)) and analyzed. Extracted bitumen was analyzed by using proximate analysis, ultimate analysis, heavy metal analysis, heating value, asphaltenes, API, SIMDIS, density, TLC, and molecular weight. The analyses of the extracted bitumen were similar to those of heavy residue.     

Pyrolysis kinetics of Athabasca bitumen using a TGA under the influence of reservoir sand

Pyrolysis kinetics of thermal decomposition of bitumen was investigated by thermogravimetric analysis (TGA). TGA experiments were conducted at multiple heating rates of 5, 10, 20°C min^–1 up to 800°C to obtain the pyrolysis characteristics of bitumen. Weight loss curve from TGA shows that two different stages occurred during bitumen pyrolysis. Differential method has been used for determining the kinetic parameters and the best fit for the order of reaction was found based on the R² values. Kinetics results confirm the presence of two different stages in bitumen pyrolysis with varying kinetic parameters. The average activation energy for the first and second stage was 29 and 60 kJ mol^?1 and the average order of the reaction was 1.5 and 0.25, respectively. Experiments have been conducted with different reservoir sand. The effect of different source of sand reveals no effect on the pyrolysis behaviour of bitumen. A considerable difference was found with the pyrolysis of bitumen–sand mixtures and bitumen alone based on coke yield and activation energy. © 2011 Canadian Society for Chemical Engineering     

Value recovery from polymer wastes by pyrolysis

Pyrolysis of polymer wastes appears to be a suitable means of dealing with an increasingly important environmental problem. To provide background on the pyrolytic behavior of wastes, model mixtures of polyethylene and polystyrene have been pyrolyzed in various gas phases including nitrogen and carbon monoxide, at atmospheric and at reduced pressures and at temperatures from about 300–900°C. When the pyrolyzing temperature is attained by gradual heating, and when pyrolysis occurs at pressures in excess of about 200 torr, the process occurs as if each component were present alone—that is, no evidence for component interaction was noted. In these cases, the known mechanisms for pyrolysis of the pure polymers can be applied to the behavior of mixtures. Complicating effects due to interactions between the starting polymers, or among the pyrolysis products, were observed in low pressure pyrolysis (?20 torr); further, it was shown that the balance of pyrolysis products depends on rates of attaining the pyrolyzing temperature, more rapid rates favoring the production of carbon-rich solid residues of possible use as carbon blacks. More detailed understanding of pyrolytic processes in polymer mixtures is needed to permit selection of conditions producing the optimum balance of useful products.     

Thermogravimetric and mass-spectrometric study of the thermal decomposition of PBCT resins

The thermal decomposition of three commercial samples of carboxy-terminated polybutadiene (PBCT) resins was studied by thermogravimetric analysis (TGA) at heating rates varying from 2° to 100°C/min. Kinetic parameters of the decomposition process at different heating rates were evaluated by means of the Fuoss method.¹ The decomposition process and the activation energy values are found to be dependent on heating rate. Mass-spectrometric analysis of the decomposition products shows that the pyrolysis products of PBCT resins are mainly low molecular weight hydrocarbons: ethylene, acetylene, butadiene, propadiene, vinylcyclohexene, etc. The rates of evolution of these hydrocarbon products vary with the carboxy content of the PBCT resin. Based on this, a carbonium ion mechanism has been suggested for the thermal decomposition. The data generated from this work are of importance for a consideration of the mechanism of combustion of composite solid propellants based on PBCT binders.     

Pyrolysis and thermo‐oxidative degradation of polycyclopentadiene

Thermal degradation of polycyclopentadiene polymer (PCPD) was investigated by pyrolysis gas chromatography (PGC) in the temperature range of 500–950°C. The nature and composition of the pyrolyzates at various temperatures are presented, and the mechanism of degradation is explained. The activation energy of decomposition (E_a) was obtained from an Arrhenius‐type plot using the concentration of the product ethylene (C₂) at different pyrolysis temperatures and the value was found to be 138 kJ mol⁻¹. Thermo‐oxidative degradation of PCPD in the presence of ammonium perchlorate (AP), the most commonly used oxidizer for polymeric fuel binders, was studied at a pyrolysis temperature of 700°C. The compositions of the products with varying amounts of AP are given, and the exothermicity of oxidative decomposition reactions is evaluated. The energetics of the degradation processes are compared with those of polybutadiene type polymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 635–641, 2000     

Thermal decomposition of chlorinated poly(vinyl chloride) (CPVC)

Chlorinated poly(vinyl chloride) (CPVC) shows reductions in flammability and smoke production over PVC. The thermal decomposition of pure CPVC (without stabilizer or lubricant) was studied by dynamic thermogravimetric analysis (TGA) at heating rates from 5 to 100°C/min in atmospheres of nitrogen, air, and oxygen. In each case, a two‐step decomposition was observed similar to that for PVC where dehydrochlorination is followed by pyrolysis/oxidation of the carbonaceous residue. The rate of dehydrochlorination was dependent on atmosphere, occurring slightly slower in nitrogen than in air, and slightly more quickly in oxygen than in air. The decomposition of the residual char was clearly dependent on the conditions in which it was formed. Under dynamic conditions, chars formed at high heating rates appeared more resilient to oxidative degradation than those formed more slowly. However, when chars were formed by heating at different rates and then held at 500°C, the char formed at the slowest heating rate was the slowest to be oxidized. The uptake of oxygen by the char appears to be rate‐limiting. At low heating rates char oxidation is similar in both air and oxygen. As the heating rate is raised, the rate of mass loss of char in air becomes progressively closer to that in nitrogen until at 100°C/min they are almost identical. This work is important to the understanding of the decomposition and flammability of CPVC and flame‐retarded CPVC, where the char formation is one of the flame‐retardant mechanisms.     

Thermal degradation study of interpenetrating polymer network based on modified bismaleimide resin and cyanate ester

Interpenetrating polymer networks (IPNs) based on different ratios of a modified bismaleimide resin (BMI/DBA) and cyanate ester (b10) have been synthesized via prepolymerization followed by thermal curing. A systematic thermal degradation study of these new BMI/DBA‐CE IPN resin systems was conducted by thermogravimetric analysis at different heating rates both in N₂ (thermal stability) and in air (thermal‐oxidative stability). The cured BMI/DBA‐CE IPN resin systems show excellent thermal stability, which could be demonstrated by 5% weight loss temperature (T_5%) ranging between 409 and 423 °C, maximum decomposition rate temperature (T_max) ranging between 423 and 451 °C, and the char yields at 800 °C ranging from 37% to 41% in nitrogen at a heating rate of 10 °C min^?1. The apparent activation energy associated with the main degradation stage of the cured BMI/DBA‐CE IPN resin systems was determined using the Kissinger method. The obtained results provide useful information in drawing correlation between thermal properties and structure. © 2003 Society of Chemical Industry     

Flammability of polyacrylonitrile and its copolymers II. Thermal behaviour and mechanism of degradation

Homopolymeric polyacrylonitrile and fibre-forming copolymers containing either vinyl acetate or methyl acrylate comonomer have been studied by thermal analysis (DSC, TGA and DTG) at various heating rates (10–100 K min^?1) and under air and nitrogen. Three well-defined pyrolysis stages have been observed which occur over the temperature ranges 250–350°C, 350–550°C and above 550°C. Each stage involves a competition between volatilisation and cyclisation or char-forming reactions which depends on heating rate and the presence or absence of oxygen. The well-established dominance of cyclisation in the 250–350°C temperature range obtained during carbon fibre production from acrylic precursors occurs only at low heating rates. At high heating rates, volatilisation dominates and this explains why acrylic polymers have high flammabilities when heating rapidly. The full pyrolysis mechanism has been semi-quantitatively analysed and the role that comonomers play discussed. This has enabled a fuller understanding of the potential burning behaviour of these polymers to be developed.