Thermal Decomposition Of Polymers Research Articles

Investigations of the carbonization process of hybrid polymer microspheres using the TGA-EGA method: assessment of the impact of sulphanilic acid on the process

The TGA-EGA technique was used to study the influence of sulphanilic acid (SA) on the carbonisation process of the hybrid terpolymeric precursors composed of methacrylamide, divinylbenzene, and trimethoxyvinylsilane. The pristine polymers were impregnated with saturated solution of SA, dried, and carbonized at 600 °C under N2 atmosphere. The characteristic properties of both the pristine hybrid polymers and the resulting carbons were based on FTIR, Raman, and PXRD analyses, which revealed the materials were composed of amorphous polymeric or carbon phase interpenetrated by silica/silicate disordered network. The porosimetric analysis showed the resulted carbons possessed homogeneous supermicropores with the average pore width of 0.7 nm and reduced number of mesopores compared to pristine precursors. From the TGA results, it was followed that impregnated polymers decomposed in two stages, instead of one like pristine precursors did. Moreover, IDT of impregnated polymers was reduced by about 100 °C, and their Tmax was increased by 2–5.5 °C. Their decomposition proceeded slower by 22–37% that caused increase in efficiency of the process by 10–48%. The EGA showed the decomposition of the impregnated precursors started from the degradation of the amide groups, then SA destruction took place, followed by further decomposition of the polymer. The studies led to the conclusion that SA had the protective effect on the surface of the carbonized polymers. During impregnation and thermal treatment, SA produced a deposit in pores of the precursors. This resulted in narrowing of the pore width, delaying and slowing down the polymer thermal decomposition process, as well as increasing its efficiency.

Decomposition Kinetics and Lifetime Estimation of Thermoplastic Composite Materials Reinforced with rCFRP.

Because of the high demand for carbon fiber reinforced polymer (CFRP) materials across all industries, the reuse and/or recycling of these materials (rCFRP) is necessary in order to meet the principles of the circular economy, including recycling and reuse. The objective of this study is to estimate the lifespan of thermoplastic matrix composite materials reinforced with waste materials (CFRP), which undergo only a mechanical cutting process. This estimation is carried out through the thermal decomposition of polymers, including polymer matrix composite materials, which is a complex process due to the numerous reactions involved. Some authors calculate these kinetic parameters using thermogravimetric analysis (TGA) as it is a quick method, and it allows the identification of gases released during decomposition, provided that the equipment is prepared for it. This study includes a comparison between polyamides 11 and 12, as well as between polyamide composite materials with carbon fiber (CF) and polyamides reinforced with CF/epoxy composite material. The latter is treated with plasma to improve adhesion with polyamides. The behavior of weight as a function of temperature was studied at speeds of 3, 6, 10, 13, 17, and 20 °C/min, finding stability of the polyamides up to a temperature of 400 °C, which was consistent with the analysis by mass spectroscopy, where gas evolution is evident after 400 °C. The estimation of the lifespan was carried out using two different methods including the Toop equation and the free kinetics model (MFK). The energy of the decomposition process was determined using the MFK model, which establishes the energy as a function of the degree of conversion. It is estimated that at 5% decomposition, mechanical properties are lost.

Adaptive Force Field Parameter Optimization for Expanding Reaction Simulations within Wide-Ranged Temperature.

Large-scale and long-term simulation of chemical reactions are key research topics in computational chemistry. However, there are still difficulties in simulating high-temperature reactions, such as polymer thermal decomposition. Herein, we introduce an adaptive potential parameter optimization framework designed to automatically fine-tune parameters, and the application of it to optimize ReaxFF parameters enhances the accuracy of chemical reaction simulations conducted at experimental temperatures. To achieve this, we leverage the power of Random Forests and interpretable machine learning techniques that enable the identification and selection of parameters that exert a substantial influence on the target attribute. By training deep neural network (NN) models, we established optimized parameter associations with reference properties. We train deep neural network (NN) models to establish the relationship between the optimized parameters and reference properties. We employ a Genetic Algorithm (GA) to utilize the surrogate NN model and the quantum mechanical targets to speed up the search for the optimal parameters. Our simulation results of resin pyrolysis show that the adaptive optimized ReaxFF can predict the peak temperature more accurately and obtain reasonable product composition under conditions that more closely resemble experimental scenarios. This work facilitates advances in force field parameter optimization for more accurate and universal reaction simulations.

Ceramic aerogels constructed from dense, non-porous ceramic nanofibers with robust and elastic properties up to 1300 °C

Elastic and compressible 3D nanomaterials comprising polymers, carbon, and metals have been prepared quantitatively in different formats. However, creating flexible and elastic ceramic aerogels with high thermal stability remains a significant challenge. In this study, sols composed of highly condensed inorganic molecular chains can be used to prepare ceramic nanofiber aerogels without adding polymers. This strategy prevents many pore defects caused by the thermal decomposition of polymers during ceramization and avoids the stress concentration generated by pore defects, which could lead to irreversible structural damage to the ceramic nanofiber aerogels under external forces. The synthesized ceramic nanofiber aerogel possesses temperature-invariant superelasticity (up to 1300 °C) and fatigue resistance to thousands of compressions with a thermal conductivity of only 0.028 W m−1 k−1. The successful synthesis of such aerogels is expected to provide a foundation for designing flexible and elastic ceramic aerogels with structural adaptability and scalability.

Thermal decomposition of flexible polyurethane foam under nitrogen and air atmospheres: Thermogravimetric analysis by ETp method

The thermal decomposition of flexible polyurethane foam (FPUF) is investigated by thermogravimetric (TG) analysis with dynamic runs at four heating rates (5, 10, 15, and 20 °C min−1) under nitrogen and air atmospheres. A reaction scheme consisting of six competitive and consecutive reactions is proposed for thermal decomposition of FPUF. The results show that the reaction scheme fits all the experimental data in this work. The kinetic parameters are extracted by model-fitting methods, based on the shuffled complex evolution (SCE) algorithm, and Gpyro software. The model-fitting methods are the EA method and the ETp method (Zhu and Liu, Thermochimica Acta, 690, 2020). This work is the first effort to analyze polymer thermal decomposition using the ETp method. The outstanding performance of the ETp-SCE method is confirmed via comparison with the EA-SCE method. The results show that the ETp method is applicable for polymer, oxidizing atmosphere, competitive reaction, consecutive reaction, SCE algorithm, and Gpyro software.

Effects of polyphenols on the thermal decomposition, antioxidative, and antimicrobial properties of poly(vinyl alcohol) and poly(vinyl pyrrolidone)

Thermal stabilizers are frequently employed to increase the thermal stability of polymers. Among the thermal stabilizers, the polyphenols and related molecules have been widely used as thermal stabilizers of polymers. However, the effect of the number of their phenolic hydroxyl groups on the thermal decomposition of polymers was relatively less studied. In this study, three phenolic compounds with different numbers of phenolic hydroxyl groups (phenol, pyrocatechol, and pyrogallol) were incorporated in water-soluble poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) to fabricate the polymer/phenolic additive composite films. The effects of the phenolic additive on the thermal decomposition of PVA and PVP were investigated through thermogravimetric analysis. The results suggested that the phenolic additive is effective as a thermal stabilizer, owing to its radical-trapping action, when its boiling point is higher than the thermal decomposition temperature of the polymer (PVA and PVP) and the polymer decomposition follows a radical pathway. In addition, to compare the effect of the number of phenolic hydroxyl groups in the phenolic additive on the properties of the composite films, their antioxidative and antibacterial activities were evaluated using the α,α-diphenyl-β-picrylhydrazyl assay and disk diffusion test, respectively.

A molecular-level fire growth parameter

The relationship between the atomic composition of polymers and the fuel generating reactions in fires has been studied at various levels using molecular dynamics simulations of polymer thermal decomposition, molar group contributions to combustion properties, and finite element models of burning that require properties obtained from thermal analyses. In this study, a conceptual model is used to link the molecular-level processes of flaming combustion measured in thermal analysis to the fire response of a polymer at the continuum level. A scaling parameter emerges from this analysis called the fire growth capacity/FGC that includes ignitability and burning rate. The FGC was measured in a microscale combustion calorimeter for 32 polymers having a wide range of atomic composition, thermal stability and char forming tendency. It was found that FGC successfully ranks the expected fire performance of these polymers when subjected to a small flame and radiant heat.

Di-tert-butylphosphate Derived Thermolabile Calcium Organophosphates: Precursors for Ca(H2PO4)2, Ca(HPO4), α-/β-Ca(PO3)2, and Nanocrystalline Ca10(PO4)6(OH)2.

Thermally and hydrolytically unstable di-tert-butyl phosphate (dtbp-H) has been used as synthon to prepare discrete and polymeric calcium phosphates that are convenient single-source precursors for a range of calcium phosphate ceramic biomaterials. The reactivity of dtbp-H toward two different calcium sources has been found to vary significantly, e.g., the reaction of Ca(OMe)2 with dtbp-H in a 1:6 molar ratio in petroleum ether forms a mononuclear calcium hexa-phosphate complex [Ca(dtbp)2(dtbp-H)4] (1), whereas the change of calcium source to CaH2, in a 1:2 molar ratio under otherwise similar reaction conditions, yields the calcium phosphate polymer, [Ca(μ-dtbp)2(H2O)2·H2O]n(2). Compounds 1 and 2 have been extensively characterized by various spectroscopic and analytical techniques. The solid-state structures of both 1 and 2 have been determined by single-crystal X-ray diffraction studies. In discrete molecule 1, the central calcium ion is surrounded by two anionic dtbp and four neutral dtbp-H ligands in an octahedral coordination environment. Compound 2 is a one-dimensional polymer in which adjacent calcium ions are connected through double dtbp bridges. Solid-state thermolysis of bulk 1 in air leads to the exclusive formation of calcium metaphosphate β-Ca(PO3)2 in the entire temperature range of 400-800 °C. Thermal decomposition of polymer 2, however, can be fine-tuned to produce either α-Ca(PO3)2 or β-Ca(PO3)2 depending on the thermolysis conditions employed. Although the sample sintered at 600 °C produces exclusively α-form of Ca(PO3)2, the sample annealed at 800 °C or above produces β-form. Both α- and β-forms can also be successively formed one after other by a slow heating of a freshly prepared 2 on the powder diffractometer sample holder. Additional forms of ceramic phosphates have been prepared by solvothermal conditions because of the highly labile nature of the tert-butoxy groups of dtbp in 1 and 2. Solution decomposition of either 1 or 2 in boiling toluene at 140 °C in a sealed tube produces calcium dihydrogen phosphate [Ca(H2PO4)2·H2O] as the only product in the form of single crystals. Solution thermolysis of 2 in protic solvents such as water and methanol can be biased to produce other calcium phosphate biomaterials such as hydroxyapatite [Ca10(PO4)6(OH)2]and calcium monohydrogen phosphate [Ca(HPO4)] in the presence of additional calcium precursors such as CaO and Ca(OMe)2, respectively.

Thermal behavior study and degradation mechanism by TG/MS/FTIR technique of some poly(aryl ether ether ketone)s

This study assesses the thermal and thermo-oxidative stability of some aromatic poly(aryl ether ether ketone)s as well as the degradation mechanism by the TG/MS/FTIR technique (simultaneous mass spectrometry and Fourier transform infrared spectroscopy of off-gases from thermogravimetric analyzer), in two working atmospheres, air and helium. This type of polymers is used in many applications in the electronic, automotive and aerospatial fields. The polymers were synthesized by polycondensation reaction of 4,4′-difluorobenzophenone with several bisphenols, such as 9,9-bis(4-hydroxyphenyl)fluorene, 4,4′-cyclohexylidenebisphenol, 2-(bis[4-hydroxyphenyl]methyl)benzoic acid (phenolphthalin) and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole. They were characterized by FTIR and 1H NMR spectroscopy, solubility, inherent viscosity and thermogravimetric analysis. Moreover, the main products of polymer thermal decomposition were determined in air and in inert atmosphere (helium). The degradation mechanism of the analyzed samples is influenced by their structure and working atmosphere. Molecular dynamics simulation was also used to evaluate thermal stability of the polymers.

Facile preparation of activated carbon foam via pyrolysis of waste bread under CO2 atmosphere

Activated carbon foam was prepared via direct pyrolysis of waste bread (WB) under CO2 atmosphere. The product was characterized by N2 adsorption/desorption and Fourier transform infrared spectroscopy (FTIR). The preparation process was investigated online by a thermogravimetric analyzer coupled with FTIR (TG-FTIR). The adsorption isotherms of methylene blue (MB) by the product were investigated. The experimental data demonstrated that the product had a high surface area of 1575 m2 g−1 and a total pore volume of 0.883 cm3 g−1. Thermal decomposition of polymers in WB mainly occurred between 200 and 500 °C, leading to the release of carbonyl compounds, aliphatic hydrocarbons, alcohols, and furans. The dominant CO2 activation process started at above 800 °C. The MB adsorption equilibrium data followed Langmuir model with a monolayer adsorption capacity of 403 mg g−1. This study provides a reference for the utilization of WB as a promising precursor of activated carbon foam adsorbent, which has highly porous structure and excellent floatability in water.

Recent developments in P(O/S)–N containing flame retardants

ABSTRACTSynthesis of organophosphorus compounds containing nitrogen as heteroatom and its application as a flame retardant (FR) have attracted much attention in the academic and industrial communities over the past decade. Such compounds are relatively easy to synthesize and offer advantages such as high thermal stability, which is useful for high temperature processing, improved char stability, density, and yield during the thermal decomposition of polymer, and release phosphorus species active in the flame inhibition process. Though a variety of phosphorus–nitrogen (P–N) compounds can be found in the literature, this review mostly summarizes the recent (since 2013) development in phosphorus (O)‐nitrogen containing flame retardants which have been published in peer‐reviewed journals. General strategies of synthesizing P(O)–N compounds as FRs from various phosphorus‐based starting materials are highlighted in this review. Some of the most common classes of researched P(O)–N containing compounds as FRs include the phosphinamides, phosphonamides, phosphoramides, phosphoramidates, phosphorodiamidates, phosphonamidates and their thio counterparts which are usually obtained via a one‐ or two‐step synthetic strategy. Incorporation of these compounds as FRs in various polymer systems such as polyurethane, epoxy resins, polyamides, cellulose, polylactide, poly(butylene terephthalate), polycarbonates, and acrylonitrile–butadiene–styrene are discussed in detail in this review. Special emphasis on the various fire and thermal performances of the new materials are also summarized. The mechanical performance of new materials and the influence of these additives on polymer processing are also briefly discussed. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 47910.

Electromagnetic Fields in Technology of Processing of Polymeric Materials

The issues related to the implementation of the process of depolymerizing of waste polymers, initiated by thermal action of an intense electromagnetic microwave field, are considered. The reactions considered are distinguished by the possibility of reducing the initial monomers or oligomers. The required reaction temperatures are achieved by indirect heating due to the presence of carbon thermal converters in the mixture or the use of liquid reagents characterized by high microwave losses. The results of the study of two different mechanisms of depolymerizing, namely the decomposition of the polymer in a glycol medium and thermal decomposition, are shown. The methods of mathematical modeling of the joint problem of electrodynamics and heat conduction are analyzed to estimate the temperature regimes of the processes of thermal decomposition of polymers. Experimental studies are illustrated by examples of the depolymerizing of polyethylene terephthalate, polystyrene and polymethyl methacrylate, the destruction products of which were esters of terephthalic acid, styrene and methyl methacrylate.

Production and Characterization of Zirconia (ZrO2) Ceramic Nanofibers by Using Electrospun Poly(Vinyl Alcohol)/Zirconium Acetate Nanofibers as a Precursor

ABSTRACTZirconia (ZrO2) inorganic ceramic nanofibers were produced using electrospinning of the poly(vinyl alcohol)/zirconium acetate as a precursor followed by calcinating and sintering to decompose the polymer and turn the metal salt (zirconium acetate) into the metal oxide. Characterization of the nanofibers, including polymer thermal decomposition, chemical and crystal structure, phase transformations, and fiber morphology were investigated by simultaneous thermal analysis (STA), thermomechanical analysis (TMA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM). The results showed that the polymer decomposition started at 250°C and zirconia nanofibers with different phases (tetragonal and monoclinic) were obtained by the calcination of the precursor nanofibers at various temperatures between 500°C and 1100°C. The initially crystallized zirconia phase, which formed at 500°C, was tetragonal and with increasing calcination temperature, zirconia nanofibers with increasing amount of monoclinic phase were formed. Consequently, at 1100°C, the tetragonal phase disappeared and was transformed to the monoclinic phase of the zirconia completely. Increasing the calcination temperature caused the fiber average diameter decrease and grain growth took place due to the removal of the polymer and organic groups; neighboring grains sintered to each other and formed fibers with a high aspect ratio. At 1100°C the grains size was about the same as the fiber diameter.

Relation of joint strength and polymer molecular structure in laser assisted metal and polymer joining

The study of laser assisted metal and polymer joining has been conducted to identify the mechanism of the hybrid joint. The bonding mechanism has been revealed to be due to the expansion pressure of pyrolysis fragments. Previous research has dealt with superficial factors without consideration of the polymer thermal decomposition phenomenon, which is the major factor of the joining strength. With experiments and simple chemical analysis for simple structured polymers this paper presents the quantitative relationship among the joint strength, the expansion pressure, the gas fragment composition, and the molecular structure. To verify the relation of the joint strength and the polymer molecular structure, the results were analysed and compared with the results of previous studies. Correlation of the quantified joint strength and the quantified expansion pressure and the monomer yield is also defined. The results confirm that the joint strength is correlated with the polymer structure.

A molecular based kinetic study on the thermal decomposition of poly-α-methyl styrene

Solid polymer thermal decomposition involves complex physical and chemical processes that are closely related to the microscopic molecular information (chemical structure, physical configuration, etc.). However, some important molecular information such as molecular weight is seldom involved in previous solid thermal decomposition studies due to the complexity of solid polymer itself. This work proposes a kinetic equation to study solid polymer thermal decomposition in which the influence of molecular weight to the decomposition is included based on an independent identical particle (IIP) model. Applications of this equation to the thermal decomposition of solid poly-α-methyl styrene (PαMS) show that: 1) there is good agreement between experimental and theoretical thermal decomposition rates; 2) molecular weight can affect not only the activation energy but also the pre-exponential factor of the thermal decomposition kinetic equation; 3) the higher the molecular weight is, the faster the PαMS decomposes in the main decomposition temperature range.

Study on thermal decomposition of polymers by simultaneous measurement of TG–DTA and miniature ion trap mass spectrometry equipped with skimmer-type interface

Simultaneous thermogravimetry-differential thermal analysis and miniature ion trap mass spectrometry (TG-DTA-ITMS) instrument equipped with a skimmer- type interface has been successfully developed. The system allows precise real-time monitoring analysis of activated organic compounds such as pyrolysates because gaseous transformation of the evolved gases from the TG-DTA is suppressed by the skimmer-type interface. Also, excessive fragmentation during ionization of molecules can be avoided with the soft ionization method by photoioniza- tion. In addition, the miniaturized ITMS is equipped with unique tandem MS capability. These features permit a better understanding of the complicated thermal behavior and the precise pyrolysates of materials. The pyrolysis of various standard reagent polymers such as polymethyl methacrylate, polystyrene, and polyphenylene sulfide has been examined by the TG-DTA-ITMS in inert atmo- sphere. The synergy effect of the skimmer-type interface and the ITMS was evaluated comparatively with conven- tional quadrupole mass spectrometry results. It was con- firmed that the real-time monitoring ITMS/MS worked satisfactorily. Here, we demonstrate a valuable application of the TG-DTA-ITMS in the detailed analysis of com- mercial polymers.

Polymer–clay nanocomposites thermal stability: experimental evidence of the radical trapping effect

The radical trapping flame retardant mechanism of polymer–clay nanocomposites is frequently claimed to be responsible for improving the thermal stability of polymers. However it had never been demonstrated. Herein using in situ time-resolved X-ray Absorption Spectroscopy (XAS) we present experimental evidence that Fe3+ embedded in the clay can act as electron acceptors during polymer thermal decomposition. Therefore it contributes to improve the polymer thermal stability.

Simulation of thermal decomposition of a polymer at random scissions of C-C bonds

A mathematical formulation of the polymer thermal decomposition model at random scissions of C-C bonds in the backbone is presented. The model is based on ideas about a macrokinetic character of the observed process Polymer → Gaseous products, and the thermofluctuation nature of the bond scission. The suggested approach makes it possible to calculate the decomposition rate in a wide pressure range at any initial molecular weight distribution of the polymer. As an example, a comparison of the calculation results for temperature-time dependences of the conversion degree and decomposition rate with experimental data obtained in isothermal and non-isothermal regimes is performed for linear polyethylene.

Thermal decomposition of monosaccharides derivatives applied in ceramic gelcasting process investigated by the coupled DTA/TG/MS analysis

The paper reports the decomposition of saccharides derivatives in comparison to commercial substances during the process of binder removal from ceramic samples. The saccharides derivatives are polymers synthesized from glucose and fructose with acryloyl group in the sugar molecule. The synthesized compounds played the role of binder in the shaping of ceramic powders by gelcasting method. The method belongs to colloidal processes and allows to produce ceramic elements of complicated geometry. As ceramic powder Al2O3 was used. The thermal analysis have been done on apparatus coupled with mass spectrometer. MS analysis showed what types of gasses are released to the atmosphere during the thermal decomposition of polymers. The obtained results showed important differences in decomposition of polymers obtained from commercial acrylamide, 2-hydroxyethyl acrylate and N,N′-methylenebisacrylamide in comparison to synthesized glucose and fructose derivatives. The measurements allowed to establish the sintering program of the green ceramic samples and evaluate whether harmful NO x gases are released to the atmosphere.

Development of Methods for Improving Accuracy of Estimating Polymer Melt Flow Rate and Their Application to Polymer Thermal Decomposition Process

ポリマーが熱分解するプロセスにおいて，分子量の指標であるMelt Flow Rate（MFR）のサンプル分析頻度が高く，オペレータの負荷が多大となっている問題がある．これの解決のため，Just-In-TimeモデリングでMFR推算ソフトセンサーの構築を行った．実用化にあたり，物理モデルを考慮し，さらに異常値・欠損値を含むプロセス変数を有効利用する方法により精度向上を達成した．また，構築したシステムは，モデル劣化を回避でき，高い精度で運用可能であることを確認した．