Mass Spectrometric Thermal Analysis Research Articles

Flame-Retardant Glass Fiber-Reinforced Epoxy Resins with Phosphorus-Containing Bio-Based Benzoxazines and Graphene.

This paper presents a study of the flammability and thermal decomposition products of glass fiber-reinforced epoxy resin (GFRER) with the addition of cardanol-based phosphorus-containing benzoxazine monomer (CBz) and graphene and their combinations in different proportions (up to 20 wt.%). The addition of CBz alone or in combination with graphene resulted in an increase in the limiting oxygen index (LOI) and self-extinguishing in the UL-94 HB test. The flame-retardant samples had better tensile mechanical properties than the sample without additives. The differential mass-spectrometric thermal analysis (DMSTA) of the thermal decomposition products of GFRER without additives and with the addition of CBz and graphene was carried out. CBz addition promoted the thermal decomposition of high-molecular-weight products of epoxy resin decomposition in the condensed phase and at the same time decreased the time of release of low-molecular-weight thermal decomposition products into the gas phase. Graphene addition resulted in an increase in the relative intensities of high-molecular-mass peaks compared to GFRER without additives.

Aluminum Diethylphosphinate as a Flame Retardant for Polyethylene: Investigation of the Pyrolysis and Combustion Behavior of PE/AlPi-Mixtures

The popularity of organic polymers despite their high flammability forces the introduction of flame retardants (FR) such as metal phosphinates into the combustible material. The thermal behavior of aluminum diethylphosphinate (AlPi) as FR in the widely used polymer ultra-high molecular weight polyethylene (UHMWPE) is investigated here. The study focuses on the effect of the FR on the gas phase activity when a polymer is pyrolyzed or burned. For this purpose, the fast pyrolysis of AlPi was investigated by differential mass-spectrometric thermal analysis (DMSTA). Also, the thermal and chemical structures of diffusion flames of UHMWPE + AlPi specimens were investigated using micro thermocouples and molecular beam mass spectrometry, respectively. Small amounts of AlPi (2.5 wt.%) decrease the gas temperature significantly by a maximum of 155 K related to FR-free polymer flames, indicating a retardancy effect of the additive on the flame. From the results of subsequent limiting oxygen index (LOI) tests, it is obvious that a PE burn-up cannot be achieved in a self-sustained flame when an additive content above 10 wt.% is used as FR. In the mass-spectrometric studies, the phosphorus-containing species produced in the pyrolysis experiments (DMSTA) of the neat AlPi as well as the species which are formed in flames during combustion experiments can be detected. In the flames, the concentration of the phosphorus containing compounds peaks at low heights above the polymer surface which indicate a gas phase activity of AlPi or its pyrolysis products. Besides a charring layer on top of the burning surface could be noticed. The use of AlPi as a FR for UHMWPE shows flame retardant effects in both the condensed and the gas phase.

Characterization of HCN-Derived Thermal Polymer: Implications for Chemical Evolution

Hydrogen cyanide (HCN)-derived polymers have been recognized as sources of relevant organic molecules in prebiotic chemistry and material sciences. However, there are considerable gaps in the knowledge regarding the polymeric nature, the physicochemical properties, and the chemical pathways along polymer synthesis. HCN might have played an important role in prebiotic hydrothermal environments; however, only few experiments use cyanide species considering hydrothermal conditions. In this work, we synthesized an HCN-derived thermal polymer simulating an alkaline hydrothermal environment (i.e., HCN (l) 0.15 M, 50 h, 100 °C, pH approximately 10) and characterized its chemical structure, thermal behavior, and the hydrolysis effect. Elemental analysis and infrared spectroscopy suggest an important oxidation degree. The thermal behavior indicates that the polymer is more stable compared to other HCN-derived polymers. The mass spectrometric thermal analysis showed the gradual release of several volatile compounds along different thermal steps. The results suggest a complicate macrostructure formed by amide and hydroxyl groups, which are joined to the main reticular chain with conjugated bonds (C=O, N=O, –O–C=N). The hydrolysis treatment showed the pH conditions for the releasing of organics. The study of the synthesis of HCN-derived thermal polymers under feasible primitive hydrothermal conditions is relevant for considering hydrothermal vents as niches of chemical evolution on early Earth.

Kinetics of thermal decomposition of PMMA at different heating rates and in a wide temperature range

Using the methods of differential mass-spectrometric thermal analysis (DMSTA), thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and fast pyrolysis (FP), thermal decomposition of high-molecular-weight polymethylmetacrylate (PMMA) has been investigated in the temperature range of 315÷500 °C. Based on these data, the kinetic parameters (the activation energy, the pre-exponential factor) were obtained of a one-step pyrolysis reaction in supposition of a first-order reaction using simple mathematical fitting and an iso-conversion method. Validity of the obtained kinetic parameters was verified by comparing the experimental data on dependence of the decomposition rate on temperature in the broad range of the heating rates with the results of simulating the above dependence, using these kinetic parameters. These parameters, obtained in the broad temperature range, may be further used in numerical simulation of PMMA combustion under fire conditions and for assessing the polymer’s flammability.

Influence of Triphenyl Phosphate on Degradation Kinetics of Ultrahigh-molecular-weight Polyethylene in Inert and Oxidative Media

The kinetics and the mechanism of thermal decomposition of ultrahigh-molecular-weight polyethylene without additive and with TPP additives in oxidative and inert media has been studied using the method of differential mass-spectrometric thermal analysis at a high heating rate and the method of thermogravimetric analysis at a low heating rate, aimed at understanding the mechanism of reducing combustibility of UHMWPE with TPP additives. The results of the study may testify to the fact that not the thermal polymer degradation reactions but the gas-phase reactions in the UHMWPE flame with TPP participation are responsible for flame retardancy of UHMWPE.

Combustion Chemistry and Decomposition Kinetics of Forest Fuels

A brief review is given of the studies in combustion chemistry and decomposition kinetics of forest fuels (FF). The methods used in the study to investigate the FF pyrolysis kinetics and the combustion of the Siberian forests are described. The experiments on FF pyrolysis were conducted at high heating rates (150K/s) in a flow reactor by the method of differential mass-spectrometric thermal analysis (DMSTA) in situ using probe molecular-beam mass spectrometry, and at low heating rates (0.17K/s) by the thermogravimetric method. The kinetic parameters of Siberian FF pyrolysis have been determined for oxidative and inert media and simulation of FF pyrolysis has been conducted using the multi-component devolatilization mechanism. The flame structure of a pine branch has been studied by probe molecular-beam mass spectrometry. Species have been identified in the dark and luminous flame zones; the width of the flame zone has been measured.

Reducing the flammability of ultra-high-molecular-weight polyethylene by triphenyl phosphate additives

The thermal degradation and combustion of ultra-high-molecular-weight polyethylene (UHMWPE) doped with triphenyl phosphate (TPP) at atmospheric pressure was studied by molecular beam mass spectrometry, dynamic mass spectrometric thermal analysis, microthermocouples, thermogravimetry, gas chromatography/mass spectrometry. The kinetics of thermal degradation of pure UHMWPE and that mixed with TPP at high (≈150 K/s) and low (0.17 K/s) heating rates was investigated. The effective values of the rate constant and activation energy of the thermal degradation reaction were determined. Burning velocity and temperature profiles in UHMWPE and UHMWPE + TPP flames were measured. The composition of the combustion products in a flame zone adjacent to the burning surface of the sample was determined. TPP vapor in the flame was detected. The addition of TPP to UHMWPE was found to reduce the flammability of the polymer. It is shown that TPP acts as a fire retardant in both the condensed and gas phases.

Reduction of flammability of ultrahigh-molecular-weight polyethylene by using triphenyl phosphate additives

The mechanism of reducing the flammability of ultrahigh-molecular-weight polyethylene (UHMWPE) with triphenyl phosphate (TPP) additives was investigated, using the methods of molecular-beam mass spectrometry (MBMS), differential mass spectrometric thermal analysis (DMSTA), thermocouple, thermogravimetry (TGA), and gas chromatography mass spectrometry (GC/MS). Kinetics of thermal degradation of pure UHMWPE and of that mixed with TPP was studied at high (∼150K/s) and low (0.17K/s) heating rates at atmospheric pressure. Effective values of the rate constants of the thermal degradation reaction were determined. Times of ignition delay, the limiting oxygen index, the burning rates of UHMWPE and UHMWPE+TPP and their temperature profiles in the flames were measured. The flame structure was investigated and the composition of the combustion products in the flame zone adjacent to the specimen’s combustion surface. TPP vapors in flame were found. Addition of TPP to UHMWPE was found to result in reduction of polymer flammability. TPP was shown to act as flame retardant both in the condensed and gas phases.

The Investigation of Thermal Degradation and Combustion of Ultra-High Molecular Weight with the Addition of Triphenylphosphate

The influence of triphenylphosphate (TPP) on ultra-high molecular weight polyethylene (UHMWPE) gasification under thermal decomposition was studied. The temperature at which formation of gaseous products begins was measured for pure and TPP-doped UHMWPE. The kinetics of thermal decomposition of pure UHMWPE and mixed with TPP at high rates of heating (~ 100–200 K/s) was studied. The activation energy and the pre-exponential factor of the rate constant of the decomposition reaction were determined for pure and TPP-doped UHMWPE. The time ignition of the samples in air at their heating from the top surface to a temperature of 350 and 400 С was determined. The studies were conducted using dynamic mass-spectrometric thermal analysis (DMSTA) microthermocouples and visualization of process

Mechanism and kinetics of the thermal decomposition of 5-aminotetrazole

The kinetics of 5-aminotetrazole thermal decomposition in the condensed phase at high heating rates (∼100 K/s) was studied by the dynamic mass spectrometric thermal analysis using a molecular beam sampling system, and the product composition was determined. Two routes of 5-aminotetrazole decomposition were distinguished, one yielding HN3 and NH2CN (route 1), and the other N2 and CH3N3 (route 2). The activation energy and rate constant of 5-AT decomposition were determined for each route.

Thermal impurity reactions and structural changes in slightly carbonated hydroxyapatite

Lattice and surface impurity reactions and structural changes induced by them in slightly carbonated hydroxyapatite (SCHA) treated at 25-1100 degrees C were comprehensively studied. The SCHA was processed by a conventional wet synthesis at a high possible temperature(96 degrees C) using ammonium containing parent reagents. IR-spectroscopy, XRD, TG-DTA technique and mass spectrometric thermal analysis (MSTA) were employed for characterization of the samples. NH4+ with H3O+ in cationic-and CO3(2-) (A- and B-positions) with HPO4(2-) in anionic sites, and H2O, CO3(2-)(HCO3(-)) NO3(-), NxHy on the surface of particles were found and considered as impurity groups. Complicated changes in lattice constants of theSCHA stepwise annealed in air (for 2 h) were revealed; the changes were associated with reactions of the impurity groups. Filling the hexed sites with hydroxyl ions above 500 degrees C was shown to happen partly due to lattice reactions but was mainly owing to hydrolysis of the SCHA by water molecules in air. Decomposition of CO3(2-) groups proceeded through both thermal destruction and reactions with some of the impurity ions. The decarbonation in A-sites occurred at much lower temperatures (450-600 degrees C) than in B-sites (700-950 degrees C) and was first revealed to happen in two stages: due to an impurity reaction around 500 degrees C, and then through thermal destruction at 570 degrees C. A redistribution of CO3(2-) ions, decreasing in amount on the whole, was observed upon annealing above 500 degrees C. To avoid possible erroneous conclusions from TG-data, a sensitive method was shown to be required for monitoring gaseous decomposition products (such as the MSTA in this study), in case several impurity groups were present in a SCHA.

Thermal and Tribological Properties of Fullerene‐Containing Composite Systems. Part 3. Features of the Mechanism of Thermal Degradation of Poly‐(N‐Vinyl‐Pyrrolidone) and Its Compositions with Fullerene C60

By mass‐spectrometric thermal analysis (MTA) the thermochemical features of poly(N‐vinyl pyrrolidone) (PVP) and its compositions with fullerene C60 were studied. The mechanism of PVP thermal degradation was investigated; in particular the nature of the low‐temperature degradation (between 75 and 300°C) accompanied by output of pyrrolidone was explained as well as the influence of fullerene C60 on this mechanism. It was shown that during thermal degradation of copolymer PVP‐C60, there is a disappearance of the low‐temperature peaks of the output of pyrrolidone that is interpreted as an increase of the thermal stability of N‐vinyl‐pyrrolidone fragments in this product in comparison with their thermal stability in pure PVP.

Directional Synthesis of Hybrid Polymers from 2- and 4-Vinylpyridines

Formation of hybrid three-dimensional structures by treatment of copolymers of 2- and 4-vinylpyridine with butyllithium, followed by grafting of tert-butyl acrylate molecules, was studied by mass-spectrometric thermal analysis and 13C NMR spectroscopy.

Flame retardance in some polystyrenes and poly(methyl methacrylate)s with covalently bound phosphorus-containing groups: initial screening experiments and some laser pyrolysis mechanistic studies

Styrene (ST) and methyl methacrylate (MMA) have been copolymerized with a variety of comonomers containing covalently-bound phosphorus-containing groups, including vinyl phosphonic acid, several dialkyl vinyl phosphonates, and various vinyl and allyl phosphine oxides. The flame retardance of these polymers has been preliminarily assessed through thermogravimetric analysis and measurements of limiting oxygen index (LOI) and char yields. All the phosphorus-containing polymers produce char on burning (and also on heating in air or nitrogen) and have LOIs higher than those of the parent homopolymers, indicating significant flame retardance involving condensed-phase mechanisms. However, despite there being general correlations between LOI, char yield and phosphorus-content, some copolymers have higher than expected LOI and/or char yield, whilst others have lower, indicating that phosphorus environment is important. In order to explore mechanisms of flame retardance in more detail, laser pyrolysis/time-of-flight mass spectrometry and mass spectrometric thermal analysis have been applied to study the decomposition behaviour of three of the MMA copolymers: those containing pyrocatecholvinylphosphonate (MMA-PCVP), diethyl- p-vinylbenzylphosphonate (MMA-DE pVBP) and di(2-phenylethyl)vinylphosphonate (MMA-PEVP) as comonomers. The laser pyrolysis experiments provide an insight into probable polymer behaviour behind the flame front in a polymer fire and show that copolymerization of MMA with the comonomers does not greatly change the pyrolysis mechanism compared with that of poly(methyl methacrylate) (PMMA). However, the amounts of MMA monomer evolved during pyrolysis are much reduced for the copolymerized samples. Since MMA is the major fuel evolved during the combustion of PMMA and its copolymers, this effect must be a major contributing factor to the reduced flammability shown by the copolymers. MMA-DE pVBP underwent the most extensive decomposition following laser pyrolysis. In particular, significant amounts of highly flammable methane and ethene were detected. Such increased amounts would occur also if the copolymer were to be exposed to high temperature conditions when burnt. Hence, its seems reasonable that the MMA-DE pVBP has a lower LOI value than expected, despite it giving a relatively high yield of char. Mass spectrometric thermal analysis studies of the MMA-PEVP provide evidence that the PEVP unit decomposes around 200°C, eliminating styrene, with evolution of MMA reaching a maximum some 50°C higher. Possible mechanisms for these processes are suggested.

Investigation of the Thermal Degradation of Poly(p-Nitrostyrene) by Pyrolysis GC-MS

The thermal degradation of poly(p-nitrostyrene) has been studied by mass spectrometric thermal analysis and pyrolysis gas chromatography. It was shown that the main thermal degradation process is depolymerization. Polymer cross-linking leads to a change in the thermal degradation mechanism.

Thermal degradation of poly-p-nitrostyrene

The thermal degradation of poly-p-nitrostyrene has been studied by mass spectrometric thermal analysis and pyrolysis gas chromatography. It was shown that the main thermal degradation process is depolymerization. Polymer crosslinking leads to a change in thermal degradation mechanism.

Mass-spectrometric investigation of the thermal stability of polymethyl methacrylate in the presence of C60 fullerene

The thermal degradation of polymethyl methacrylate, synthesized by the method of free-radical polymerization, in a mixture with C60 fullerene has been investigated by mass-spectrometric thermal analysis. C60 suppresses the first two, low-temperature, stages in the thermal degradation of polymethyl methacrylate and thereby increases its thermal stability.

Effect of C60 on the thermal stability of polyethylene glycol grafted to it

The thermal degradation of regular polymer networks, cross-linked by C60 molecules along the end groups of polyethylene glycol, has been investigated by mass-spectrometric thermal analysis for the example of polyethylene glycol grafted to fullerene C60. The character of the thermal degradation of the networks is substantially different from that of free polyethylene glycol and other polymer systems investigated earlier. The grafting to C60 increases the thermal stability of polyethylene glycol.

The criterion of forming the carbon layer on the interface of the SiC fiber reinforced lithium aluminosilicate(LAS) composite

The criterion of forming the carbon layer on the interface of the SiC fiber reinforced lithium alumino-silicate (LAS) composite studied by thermodynamic and mass spectrometric thermal analysis was presented for the first time in this paper.

Investigations of the thermal degradation of polymer metal precursors for high temperature superconducting ceramics

Polymer metal precursors are characterized by thermal degradation and mass spectrometric thermal analysis while the HTS phases are characterized by X-ray diffraction and measurements of the electrical resistance. It is to be assumed that the methacrylic acid groups of the polymer does not only form salts with the metal ions but also complexes.