Course Of Thermal Degradation Research Articles

The Evaluation of the Fire Safety of the Digestate as An Alternative Bedding Material

Digestate is the material remaining after the anaerobic digestion of a biodegradable feedstock. The use of digestate as a bedding material is analyzed marginally. The aim of the paper is to monitor the change of the solid phase of digestate due to the action of radiant heat and, based on the results, determine the options of using the solid phase of the digestate for bedding material. Experimental determination of the digestate ignition temperature was carried out according to EN 50281-2-1 (1998) by a hotplate device. Different amounts of samples (3, 5, and 10 g) on the course of thermal degradation were monitored. The results showed higher temperatures of thermal degradation in samples of additionally dried digestate, where these processes were observed earlier in terms of time. Samples of 3 and 10 g of digestate are not suitable as bedding material due to the fire safety of the material.

The Impact of Isocyanate Index and Filler Functionalities on the Performance of Flexible Foamed Polyurethane/Ground Tire Rubber Composites.

The structure and performance of polyurethane (PU) foams are strongly driven by the stoichiometry of the polyaddition reaction, quantitatively described by the isocyanate index. It determines the balance between isocyanate and hydroxyl groups in the reacting system and is affected by the introduction of additional functionalities originated, e.g., from applied fillers. Nevertheless, this issue is hardly taken into account in research works. Herein, the structure and performance of PU/ground tire rubber (GTR) composites differing in their isocyanate index (from 0.8 to 1.2) and prepared with and without considering the GTR functionalities in formulation development were investigated. Incorporating GTR into the PU matrix led to a reduction in average cell diameter (from 2 to 30% depending on the isocyanate index) compared to unfilled foams. However, formulation adjustments did not show a significant impact on cellular structure. The only decrease in open cell content was noted, from 10% for the 0.9 index to 40% for 1.2. Such changes were related to the increasing strength of the PU cellular structure able to maintain inside the increasing amount of carbon dioxide. On the other hand, considering hydroxyl values of GTR noticeably affected the thermomechanical performance of composites. The shift of glass transition temperature (Tg), even by 10 °C for 1.2 isocyanate index, enhanced the performance of materials, which was expressed in an 8-62% drop in the composite performance factor, pointing to the enhanced reinforcing effect resulting from filler incorporation. The stiffening of foams, related to the variations in PU segmental structure, also caused minor changes in the course of thermal degradation of PU/GTR composites due to the inferior thermal stability of hard segments. The obtained results provide important insights into the development of formulations of PU composites filled with materials containing reactive functional groups able to disrupt the stoichiometric balance of the polyaddition reaction.

The effect of treatment with HEMA and gamma irradiation on the starch:PVA films studied by differential scanning calorimetry and thermogravimetry

Basic studies were conducted dealing with the influence of treatment with hydroxyethyl methacrylate (HEMA) supported by gamma irradiation on physicochemical properties of the starch:PVA films (45:55, glycerol content of 30 wt%). The films were placed in a 10% monomer solution, irradiated with 60Co gamma rays applying a dose of 25 kGy, then heated at 45 °C for 2.5 h and subjected to a prolonged contact with the solution. Simultaneously, the reference sample subjected to the same treatment without action of HEMA, and additionally the samples irradiated in monomer solution without heating step, were prepared. FTIR spectroscopy has shown an effective grafting of HEMA. The differences were found between the course of thermal degradation occurring in HEMA treated sample and the reference sample both in nitrogen and in air. Data analysis indicated formation of the fractions characterized by an increased as well as by a decreased thermal stability. Simultaneously, DSC enabled to discover the differences between melting, crystallization, glass transition and structural relaxation phenomena taking place in the monomer treated and the non-treated samples. The changes were referred to a decrease in the crystallinity accompanied by an increase in the ordering in the amorphous phase. TGA and DSC data were related to chemical changes shown by FTIR spectroscopy and by gel content data and discussed in terms of degradation as well as grafting of HEMA onto the polymer matrix. The increased temperature of the treatment raised degree of the occurring changes.

A comparison study on non-isothermal decomposition kinetics of chitosan with different analysis methods

A thermal degradation study of chitosan in air atmosphere has been carried out in detail through Fourier transform infrared (FTIR) analysis, thermogravimetric (TG) analysis and differential thermal analysis (DTA) measurements. FTIR spectra reveal the variations of chemical structures of chitosan in the course of thermal degradation. The mass loss data were collected under the heating rates of 5–30 K min−1. Kinetic analysis of chitosan thermal degradation has been performed through isoconversional FWO, CR, MKN and Tang methods, and the calculated results are basically comparable for these four different methods. With the Arrhenius parameters obtained, the four methods have been attempted to reconstruct the temperature-dependent mass conversion curves and have resulted in generally acceptable results. The TG and DTA results suggest that two-stage thermal degradation processes may be better assumed. For more accurately describing the thermal degradation process of chitosan, the most probable reaction functions have thus been determined for these two stages, leading to greatly improved calculation performance over the entire conversion range. On the basis of the Arrhenius parameter values obtained, the changes in entropy, enthalpy and Gibbs free energy, and lifetime predictions have been estimated concerning the thermal degradation processes of chitosan.

Char Layer of Various Tree Parts from Selected Coniferous Wood

In the paper there is compared wood char layer of various tree parts (branches, trunk, roots) from pine, fir, spruce, larch. The samples were thermally loaded by the radiating source. The course of thermal degradation was evaluated by the char laye. The obtained results showed the influence of tree parts and wood species on calculated fire technical parameters. The values of char layer of wood from branches were the lowest. The char layer of trunk wood was the highest in case of spruce.

Low-temperature thermal removal of template from high silica ZSM-5. Catalytic effect of zeolitic framework

Topochemical and catalytic effects of ZSM-5 zeolite framework in the course of thermal degradation of tetrapropyl ammonium (TPA +) template upon calcination under oxidative (air) and inert (nitrogen, N 2) atmosphere was analyzed using elemental analysis, X-ray Photoelectron Spectroscopy (XPS) and absorption UV–Vis–NIR spectroscopy. It has been demonstrated that template residues were selectively removed from the interior of the crystals. The concentration of (N (C)-containing template species was ⩽1 atom per unit cell (u.c.)) by prolonged (24 h) calcination in air already at temperature T max = 310 °C (N-containing template species) and T max = 330 °C (C-containing template species). Calcination in N 2 requires temperatures higher by about 20 °C. The surface region of ZSM-5 crystals contained, however, a substantial amount of template residua (20–30% of N-containing and ∼60% of C-containing species) even at T max = 430 °C. This effect is associated with conversion of propylene, originating from TPA + degradation, into low volatile products by their dehydrogenation on acidic centers and defect sites of ZSM-5. The dehydrogenation reaction was enhanced under oxidative conditions. The volatility of carbonaceous and N-containing residues was further reduced by their strong interaction with defect sites of ZSM-5.

Application of the random break theory to thermal degradation of polymers

Thermal degradation of high-molecular-weight polyethylene is considered from the standpoint of the random break theory. The quantitative estimations made indicate that the vaporization conditions realized in the experiment exert a decisive effect on the total conversion rate. The heat of vaporization of macromolecular fragments formed by cleavage of C-C bonds amounts to approximately a half of the total thermal effect recorded by thermal analysis. The results obtained make it possible to rationalize some phenomena that were observed experimentally but have not been satisfactorily interpreted previously, and also to predict the influence of experimental conditions on the course of thermal degradation of polymers.

On the role and transformations of components of intumescent fire-retardant paint-and-varnish formulations in the course of thermolysis

Main components of fire-retardant intumescent paint-and-varnish formulations, such as pentaerythritol, melamine, and ammonium phosphate, were considered in detail. A comprehensive thermal study of these components was carried out, including thermogravimetric and differential thermal analyses. A mechanism of transformations of these substances in the course of thermal degradation is described.

Synthesis and modification of polysilylcarbodiimides

Conditions for the synthesis of linear polysilylcarbodiimides based on bis(trimethylsilyl)carbodiimide have been investigated. The method of preparing new silylcarbodiimidesilazane polymers via the polycondensation of bis(trimethylsilyl)carbodiimide with methylphenyldichlorosilane and cyclosilazanes has been developed. The highest molecular mass of the polymers achieves 10 000, as evidenced by GPC measurements. The structure of polysilylcarbodiimidesilazanes has been examined by IR spectroscopy and 1H NMR studies. Silazane units are incorporated into polymer chains as linear and stressed cyclodisilazane fragments. TGA experiments have revealed that silazane fragments reduce weight losses of the new polymers in the course of thermal degradation.

Microporous Polyimide Films Based on Blends of Polyamido Acid and Cellulose Derivatives

The effect of a blowing agent, cellulose diacetate, on the structural nonuniformity and physicomechanical properties of polyimide films was studied by thermogravimetric analysis and scanning electron microscopy. Changes in the gas permeability of the films in the course of thermal degradation of the blowing agent were estimated. The feasibility was demonstrated of using these films for fabrication of composite membranes.

Thermal studies and spectral characterization of the chelate of bis-(η5-cyclopentadienyl titanium(IV) with salicylidene-4-methylaniline

A new chelate (η5-C5H5)2Ti(SB)2, whereSB=O, N donor Schiff base salicylidene-4-methylaniline, was synthesized. The course of thermal degradation of the chelate was studied by thermogravimetric (TG) and differential thermal analysis (DTA) under dynamic conditions of temperature. The order of the thermal decomposition reaction and energy of activation was calculated from TG curve while from DTA curve the change in enthalpy was calculated. Evaluation of the kinetic parameters was performed by Coats-Redfern as well as Piloyan-Novikova methods which gaven=1, ΔH=1.114 kJ·mol−1, ΔE=27.01 kJ·mol−1, ΔS=−340.12 kJ·mol−1·K−1 andn=1, ΔH=1.114 kJ·mol−1, ΔE=20.01 kJ·mol−1, ΔS=−342.60 kJ·mol−1·K−1, respectively. The chelate was also characterized on the basis of different spectral studies viz. conductance, molecular weight, IR, UV-visible and1H NMR, which enabled to propose an octahedral structure to the chelate.

Interchain crosslinking model in the course of thermal degradation of polypyromellitimide

An analysis has been made of the chemical and structural changes occurring in the polyimide PM when heated from 500 to 600°C. A model of the crystalline regions of PM is taken as the starting structure of the polymer. To analyze the thermochemical process the authors enlist the high-resolution 13C NMR data in a solid, X-ray photo-electron and mass thermal spectroscopy. A model describing the thermolysis of PM in this temperature interval and the structure of the coke residue is proposed not inconsistent with the experimental findings and provides a basis for the interpretation of the electrical properties of thermolysed PM and thermolysis of other PIs.

Thermal degradation of model compounds with blocked hemiacetal group related to (4-O-methyl-D-glucurono)-D-xylan

Reduced (4-O-methyl-D-glucurono)-D-xylan and nine methylglycosides related to this polysacharide were studied by dynamic and isothermal thermogravimetry. It could be stated from the results that the thermal stability of saccharides is increasing with increasing number of pyranose units. The models related to (4-O-methyl-D-glucurono)-D-xylan are more thermally stable than the corresponding hexoglycanic models. Rates of gasification of models containing uronic acid methylesters are higher than those of neutral methylglycosides. The rate of polysaccharide gasification was the highest one from all models studied. The supramolecular structure of polysaccharide is dramatically influencing the course of thermal degradation.

The composition and structure of solid char residues after thermal degradation of polystyrene, PVC and polyamide. Part I

AbstractThe study of char residues after thermal degradation of synthetic polymers, especially the identification of their morphology, structure and chemical composition is presented in this paper. Special attention was focused on the polystyrene, PVC and polyamide char residues. By means of microscopy in reflected light and reflected polarized light the manifestations of optical anisotropy were observed. X‐ray analysis was used for the examination of the microstructure of PVC char residues carbonized at temperatures above 1000°C. For PVC char residues the electric resistivity was determined. The results have proved the close connection between the structure and properties of char residues and the intensity and course of thermal degradation of polymers.

Effect of sample size and environment on the thermal degradation of polymers

A model that takes into account mass transfer resistances at the polymer-melt and at the melt-carrier gas interfaces during the course of thermal degradation of relatively ‘large’ samples of polymer, is proposed. It is tested against experimental weight loss data for polypropylene, in the temperature range 390–430°C, obtained from the pyrolysis of 0·1–5 g samples. The weight loss data do not follow first-order kinetics and depend on the sample size. It is found that the model is capable of predicting the experimental observations.

Thermal properties of 5-(subst)-amino-1,2,3,4-thiatriazoles

The thermal properties of 5-(subst)-amino-1,2,3,4-thiatriazoles were studied using TG and DTA. 5-amino-1,2,3,4-thiatriazole was actively decomposed at the melting temperature. The active thermal decomposition proceeds at a very fast rate, being accompanied by exothermic reactions of recombination. In comparison with this, the different-5-(subst)-amino-1,2,3,4-thiatriazoles are decomposed at slower rates in several degradative steps. The effects of some substituents on the total course of thermal degradation are discussed.