Thermogravimetric-infrared Spectroscopy Research Articles

Preparation and application of halogen-free and efficient Si/P/N-containing flame retardants on cotton fabrics

Cotton fabric is extensively utilized due to its numerous applications, but the flammability associated with cotton fabric poses potential security risks to individuals. A halogen-free efficient flame retardant named poly [(tetramethylcyclosiloxyl spirocyclic pentaerythritol)-piperazin phosphate] (PCPNTSi) was developed to consolidate the fire retardance of cotton fabrics. After PCPNTSi treatment, the limiting oxygen index (LOI) of cotton fabric with 30 % weight gain (CP3) was raised to 32.8 %. In the vertical flammability test (VFT), CP3 has self-extinguished performance with a char length of 8.7 cm. The heat release rate (HRR) of cotton fabric with 20 % weight gain (CP2) is 78.8 % lower than that of pure cotton fabric (CP0). In addition, the total smoke release (TSP) of CP2 is 41.7 % lower than that of CP0, indicating PCPNTSi gives cotton fabric a good capability to inhibit smoke release. Finally, the possible flame retardant mechanism was discussed by the data of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FT-IR) and thermogravimetric infrared spectroscopy (TG-IR). The results show that PCPNTSi is an intumescent flame retardant acting in both gas phase and solid phase.

Flame-Retardant and Transparent Unsaturated Polyester Based on P/N Liquid Flame Retardants and Modified Halloysite Nanotubes.

Unsaturated polyester resin (UPR) with excellent flame retardant is mainly obtained by adding large amounts of flame retardants, usually at the expense of mechanical properties. In this work, a reactive flame retardant containing phosphorus and nitrogen (DOPO-N) was successfully synthesized and incorporated in UPR as a crosslinker. The mechanical and flame-retardant properties of UPR composites were enhanced. UPR/30DOPO-N passed a UL-94 V-1 rating with a limiting oxygen index (LOI) of 30.8%. The tensile strength of UPR/30DOPO-N increased by 24.4%. On this basis, a small amount of modified HNTs (VHNTs) was added to further improve the flame-retardant properties of the composite. With the introduction of 3 wt% VHNTs, the composite passed the UL-94 V-0 rating. The peak of heat release rate (PHRR) and total heat release (THR) of it decreased by 60.7% and 48.3%, respectively. Moreover, the detailed flame-retarding mechanism of DOPO-N and VHNTs was investigated by thermogravimetric infrared spectroscopy (TG-IR), Raman spectra, and X-ray photoelectron spectroscopy (XPS). It was found that DOPO-N played a role in quenching the flame in the gas phase and cooperated with VHNTs to enhance the barrier effect in the condensed phase.

Reaction mechanism of stearic acid pyrolysis via reactive molecular dynamics simulation and TG-IR technology

Stearic acid provides a basis for developing renewable energy, such as solar energy and biomass energy. A thermogravimetric-infrared spectroscopy (TG-IR) experimental test is conducted to obtain the thermal decomposition progress and the main gaseous products of stearic acid. The result shows that small gaseous products (H2O, CO2, CO, alkanes, olefins, etc.) are released. Furthermore, the method of reactive molecular dynamics simulation (ReaxFF-MD) is utilized to look into the pyrolysis reaction mechanism of stearic acid. The main pyrolysis products of stearic acid received by ReaxFF-MD are C2H4, H2, C2H2, CH4, H2O, CO2, and CO, consisting of the result of the TG-IR test. The effect of the simulated system density and temperature on the distribution of main products is also explored. Also, the thermal kinetic analysis is conducted by the initial consumption of stearic acid under different temperatures. The primary reaction mechanism of stearic acid pyrolysis is that the stearic acid molecules dissociate through C–C bonds break to generate C2H4, CH4, C2H2, C3H6, and other small molecules and radicals, and a typical reaction mechanism scheme of stearic acid pyrolysis is presented. The results provide a reference for explaining the macroscopic explosion characteristics of dust at the microscopic mechanism level.

Effect of lanthanum on thermal and mechanical properties of modified polyvinyl chloride film

Polyvinyl chloride (PVC) hybrid film containing cerium, tin and folic acid modified nano titanium dioxide is a new functional material with good compatibility, light resistance and heat resistance. In this work, the PVC hybrid film was prepared by replacing cerium with lanthanum. The hybrid film was characterized by thermogravimetric infrared spectroscopy, dynamic mechanical analysis, atomic force microscopy, x-ray photoelectron spectroscopy, scanning electron microscopy, tensile strength and thermal aging. The results show that the initial thermal stability of the hybrid film containing lanthanum is slightly higher than that of the control sample (conversion α < 1.9%). For the same gaseous component plasticizer, the peak intensity of the ester based infrared characteristic group is higher than that of the hybrid film containing lanthanum, indicating that the intermolecular force between lanthanum and plasticizer is greater than that of cerium. In the range of 350 °C–575 °C and the wave number range of 2850–3100 cm−1, the peak height of the lanthanum containing film is significantly higher than that of the control sample, which may be due to the difference of the outer layer electrons. The peak intensity of O and C atoms on the surface of the hybrid film containing lanthanum is significantly lower than that of the control sample, indicating that the surface relative concentration of lanthanum atoms is lower than that of cerium atoms. The surface roughness RMS of the hybrid film containing lanthanum is significantly lower than that of the organic tin film, which is the result of the attraction between folic acid modified TiO2, lanthanum and tin and the carbon chlorine bond in PVC. It has the function of a potential ultrafiltration membrane. In addition, the hybrid film containing 1phr lanthanum shows good energy storage modulus and low temperature resistance. The prepared hybrid film shows the characteristics of a potential multi-functional material.

Influence evaluation of ionic liquids on the alteration of nitrification waste for thermal stability

Nitrification waste (NW) is the processed product of nitro compounds, flammable and explosive, and is prone to accidents due to thermal runaway. Ionic liquids (ILs) are widely used as flame retardants and have a good inhibitory effect. The effect of 1-butyl-3-methylimidazole hexafluorophosphate and 1-butyl-3-methylimidazole tetrafluoroborate as humectants on the thermal stability of NW was investigated in this paper. The microstructure and properties of the ionic liquid hybrid NW were first investigated using scanning electron microscopy. Secondly, thermogravimetric experiments were carried out on the ionic liquid mixed NW by thermogravimetric-infrared spectroscopy to analyze the decomposition law. Finally, six advanced linear regression thermokinetic models were used to calculate its apparent activation energy, pre-exponential factor, and other thermokinetic parameters, and the reaction model was simulated through multiple linear regression. The experimental research results in this paper can provide a reference for the storage and disposal of nitro compounds and their wastes.

Thermal degradation and flame retardancy prediction of Fe, Al, and Cu-based metal-organic framework and polyethylene terephthalate nanocomposites using DFT calculation

In this research, Fe3+, Al3+, and Cu2+ containing MOFs were synthesized and added into polyethylene terephthalate (PET), respectively, namely Fe-MOF-PET, Al-MOF-PET, and Cu-MOF-PET. Fe-MOF-PET was studied as the model sample to discuss the effect of metal cations of MOF on the thermal degradation mechanism. It indicated that Fe3+ would coordinate with the CO of PET and attract the C–O bond of the ester group to occur the homolytic reaction according to quantum chemical simulation combining the experimental data, including the pyrolysis chromatography-mass spectrometry (Py-GC-MS) and thermogravimetric infrared spectroscopy (TG-IR). Furthermore, the thermal degradation reaction of Fe3+ as the standard pathway was applied to predict flame retardant properties of different MOF-PET composites. The flame retardant order, Fe-MOF-PET > Al-MOF-PET > Cu-MOF-PET, was also successfully proved by the cone calorimeter (CONE), limiting oxygen index (LOI), and vertical flame test (VFT), respectively. The worse result of Cu2+ was attributed to the “one point” fracture reaction pathway of Cu-MOF-PET, which was different from the “two points” fracture of Fe-MOF-PET and Al-MOF-PET. This research provided an effective tool for predicting the flame retardant properties of MOFs in different polymer matrix using density functional theory (DFT).

Strategic design unsaturated polyester resins composites with excellent flame retardancy and high tensile strength

Unsaturated polyester resin (UPR) composites with excellent flame retardancy and high mechanical property is a great challenge to its widely application. In present work, a highly efficient flame retardant (MA-DOPO) containing nitrogen, sulfur and phosphorus elements was designed via a nucleophilic substitution reaction of amino and aldehyde groups. For the UPR/MA-DOPO15 composites, its tensile strength was 28.3 MPa, which was 19.9 % higher than that of neat UPR attributing to the formation of hydrogen bonds with UPR. It should be noted that tensile strength of UPR/MA-DOPO20 composites reached the highest 39.6 MPa, showing a growth trend with the enhancement of incorporation amount of MA-DOPO. Meanwhile, the UPR/MA-DOPO15composites passed the UL-94 V-0 rating with a LOI of 27.0%, and the peak heat release rate (PHRR) and total heat release rate (THR) were reduced by 35.1% and 41.6% in cone calorimeter (CC) test comparing to that of neat UPR respectively. Moreover, the detailed flame-retarding mechanism of MA-DOPO was investigated by the thermogravimetric infrared spectroscopy (TG-IR), Raman spectrum, X-ray photoelectron spectroscopy (XPS) and pyrolysis-gas chromatography/mass spectrometry (PY-GC/MS), in which the releasement of inert gas in gas-phase and the catalytic carbonation in condensed phase jointly taking effect.

Effects of Accelerated Ageing by Humidity and Heat Cycles on the Quality of Bamboo.

The effect of humidity and heat environmental conditions on the durability of conventional bamboo materials is a pressing issue in the reserving phase of biomass materials. In this study, the relationship between the main physicochemical, pyrolytic, and mechanical properties of bamboo before and after ageing has been investigated. Exposure of engineered bamboo raw materials with moisture content up to 10% to alternating humidity and heat cycles (20 °C 98% RH-30 °C 64% RH-40 °C 30% RH) of ageing (HHT) causes degradation of the chemical polymer matrix. Byk Gardner 6840 color difference meter, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), compression intensity, thermogravimetric-infrared spectroscopy (TG-IR), and density changes are used to assess the quality of the material before and after ageing. No significant changes in the moisture content within the range of 6.12 ± 0.327 after two weeks of the engineered bamboo during wet thermal cyclic ageing were determined. However, there were significant differences in mass loss (7.75–9.93 g), cellulose crystallinity, chemical changes, compression strength, and pyrolytic properties. Differences in specimen colors were observed during 10 weeks of the accelerated humidity heat cycling ageing, and TCD variations ranged from 3.75 to 20.08 and from 0.25 and 3.24, respectively. Reduced cellulose crystallinity (36.459–22.638%), axial compressive strength (63.07–88.09 MPa), and modulus of rupture (2409–4286 MPa) were found during aging, whereas deformation and ductility properties were improved. Both natural and humidity heat ageing improve thermal stability and peak pyrolysis rates (0.739–0.931; 0.731–0.797). Humidity heat cyclic ageing will assist in the design and risk assessment of warehousing environments for industrial applications.

Synthesis of a novel flame retardant with phosphaphenanthrene and phosphazene double functional groups and flame retardancy of poly (lactic acid) composites

A novel flame retardant hexa (4- (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10 -sulfide)-hydroxymethylphenoxy) cyclotriphosphazene (HAP-DOPS) with double functional groups was synthesized, and poly (lactic acid) (PLA) composites were prepared by melt extrusion. The flame retardancy and thermal degradation behavior of flame retardant PLA composites were studied by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CCT), and thermogravimetric-infrared spectroscopy analysis (TG-IR). The experimental results showed that HAP-DOPS had a good flame-retardant effect on PLA. At flame retardant content of 5 wt%, the PLA/HAP-DOPS composite achieved a V-0 rating (UL-94, 3.2 mm) and a LOI value of 26.6%. The heat release rate (HRR) and total heat release (THR) of PLA composites were decreased by adding HAP-DOPS. The flame retardancy index (FRI) of PLA/HAP-DOPS-7.5 wt% was 1.0257, which showed good flame retardancy. The results of TG-IR showed that HAP-DOPS mainly had a gas-phase flame-retardant effect in PLA.

Improvement of the flame retardant and thermomechanical properties of epoxy resins by a vanillin-derived cyclotriphosphazene-cored triazole compound

A vanillin-derived cyclotriphosphazene-cored triazole compound (HHCTP) was successfully synthesized as a flame retardant for epoxy thermosets with high efficiency while preserving their thermomechanical properties. 1H- and 31P nuclear magnetic resonance (NMR), as well as Fourier Transform infrared (FT-IR), were applied to confirm the molecular structure of HHCTP. The dynamic mechanical analysis (DMA) measurements demonstrated that the introduction of HHCTP improved the storage modulus of the epoxy composites but decreased the glass transition temperature. The epoxy thermoset containing 7.5 wt% HHCTP (EP/HHCTP-7.5) achieved a UL-94 V-0 classification and an LOI of 31.5%, manifesting its outstanding flame-retardant efficiency. In addition, the cone calorimeter results showed that the total heat release (THR) and the peak value of the heat release rate (PHRR) of EP/HHCTP-7.5 were decreased by 35.6% and 50.0%, respectively, in comparison with those of the unmodified epoxy. To further study the flame retardant mechanism of HHCTP, pyrolytic gas species were detected utilizing thermogravimetric-infrared spectroscopy (TG-FTIR). In addition, the microstructure of the char residues was analyzed via X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) techniques. The phosphazene groups in HHTCP clearly stimulated the production of an intumescent, compact, and strong char layer, which improved the flame retardancy of the DGEBA matrix during burning, according to the SEM data. As a result, the underlying components were protected from further degradation and combustion, resulting in effective flame retardancy of the DGEBA thermoset.

Combustion and Thermal Properties of Flame Retardant Polyurethane Foam With Ammonium Polyphosphate Synergized by Phosphomolybdic Acid

Phosphomolybdic acid (PMA) as a synergist was added into polyurethane (PU) rigid foam with ammonium polyphosphate (APP) to improve its flame retardancy and thermal stability. The combustion performance of PU was studied by limiting oxygen index (LOI), UL-94, and a cone calorimeter. The thermal degradation behavior of PU was determined by thermogravimetric analysis (TG) and thermogravimetric infrared spectroscopy (TG-IR). Experimental results showed that the introduction of PMA could further improve the flame retardant performance of PU/APP composites and significantly increase the amount of carbon residue at high temperatures. Adding 3wt% PMA to PU containing 12wt% APP could make the foam pass UL-94 V-0, increase the carbon residue at 800°C by 69.16% in the air atmosphere, and decrease the THR by 24.62% compared to those of PU/15APP. TG-IR results showed that the presence of PMA reduced the production of small-molecule gas-phase products. As for the mechanical properties of PU composites, the addition of PMA influences their density and compressive strength obviously. The results suggest that PMA and APP have good synergistic flame retardancy on PU and can reduce its fire risk.

Thermogravimetric-infrared analysis and performance optimization of co-pyrolysis of oily sludge and rice husks

In this paper, thermogravimetric-infrared spectroscopy was used to analyze co-pyrolysis of oily sludge (OS) from oil penetration and rice husks (RH) at various ratios (1:0; 3:1; 1:1; 1:3; 0:1), obtaining pyrolysis weight-loss behaviors, the laws of mutual synergy, and gas volatilization characteristics. The Coats-redfern and response surface method were employed to analyze kinetics and optimize pyrolysis, respectively. The Ti, Tmax, and Tf increase as the heating rate increases, and the weight loss increases in the second stage. With the increase of the proportion of RH, the Ti and Tmax of the mixture increase, while the Tf and residual content decrease. The co-pyrolysis of the OS and RH has synergistic effects. The addition of RH is beneficial to reduce the E of OS pyrolysis. The mixing ratio affects the strength of small-molecular-gases volatilization. When the RH ratio is 58.9% at 10K/min, the minimum predicted E and residual amount of co-pyrolysis are 58.602 kJ/mol and 42.6%, respectively.

Characteristics, kinetics, infrared analysis and process optimization of co-pyrolysis of waste tires and oily sludge

The ecology was severely harmed by waste tires (WT) and oily sludge (OS). The OS and WT combinations' co-pyrolysis features, synergistic effects, and gas products were studied using thermogravimetric-infrared spectroscopy (TG-FTIR). To study kinetics and optimize pyrolysis, the Coats-Redfern and response surface methods were used. The results revealed that the OS and WT co-pyrolysis has synergistic effects. The major pyrolysis temperature range and the pyrolysis residual rate increased as the heating rate increased, and the E of the reaction increased. The strength of small-molecular-gases precipitation was modified by increasing the ratio of WT to OS, which increased OS pyrolysis. CH4, CO2, CO, and H2O are the most common gas products. The minimum estimated E and residual amount were 40.599 kJ/mol and 39.33%, respectively, when the WT mixture ratio was 58.7% and the heating rate was 10 °C/min. All the study contributes basic data to the development of the treatment of OS and WT in collaboration.

Pyrolysis of waste Fischer-Tropsch wax: An experimental study

To achieve carbon neutrality and optimize China's energy structure, pyrolysis (thermal cracking) was selected to recycle the Waste Fischer-Tropsch wax (WFTW) produced in large quantities from Fischer-Tropsch synthesis plants, which has rich hydrocarbon content and high calorific value. Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), thermogravimetry-mass spectrometry (TG-MS), and thermogravimetric-infrared spectroscopy (TG-IR) were used to investigate the pyrolysis characteristics and mechanism of WFTW. The TG and DSC showed that the main pyrolysis temperature range of WFTW was 230–480 °C, and the heating rate affected the temperature range greatly. Theoretically, more than 87% of the calorific value in the WFTW can be recovered as liquid fuels, and the most suitable heating rate was 15 °C/min. TG-MS and TG-IR showed pyrolysis products at different stages to further investigate the pyrolysis process and provide a basis for recycling WFTW. The activation energy calculated by Kissinger method is 215 ± 3 kJ/mol, and the mean apparent activation energy calculated by Starink method is 133 ± 14 kJ/mol, showing a good agreement with Kissinger method at a high conversion rate (70–80%).

A Novel Low-Temperature Fluorination Roasting Mechanism Investigation of Regenerated Spent Anode Graphite via TG-IR Analysis and Kinetic Modeling.

Spent anode graphite, a hazardous solid waste discarded from the recovery of spent lithium-ion batteries (LIBs), had created social and environmental issues but has been scarcely investigated. Thus, a feasible, environmentally friendly, and economical process of low-temperature fluorination roasting and water leaching technology was proposed to regenerate spent graphite anodes. The results showed that the physical and chemical properties of regenerated graphite with a purity of 99.98% reached the graphite anode standard of LIBs and exhibited a stable specific capacity (340.9 mAh/g), capacity retention (68.92% after 470th cycles), and high initial Coulombic efficiency (92.13%), much better than that of waste carbon residue and similar to that of commercial graphite. Then the reaction mechanism and kinetic modeling of fluorination roasting of spent anode material was mainly explored by differential thermogravimetry and nonisothermal analysis methods. The results showed that the complexation and phase-transformation process of non-carbon valuable components in spent anode graphite occurred through three consecutive reactions in the 80–211 °C temperature intervals. The reaction mechanism of the whole process can be kinetically characterized by three successive reactions: third-order chemical reaction, Z-L-T eq, and second-order chemical reaction. Moreover, the thermodynamic functions of the fluorination roasting were calculated by the activated complex theory (transition state), which indicated the process was nonspontaneous. The mechanistic information was in good agreement with thermogravimetric-infrared spectroscopy (TG-IR), electron probe microanalysis, scanning electron microscopy, energy-dispersive spectrometry, and simulation experiments results.

A high molecular weight formaldehyde-free polymer flame retardant made from polyvinyl alcohol for cellulose

Polyvinyl alcohol and phosphoric acid were used as primary raw materials to synthesize a polyvinyl alcohol/ammonium phosphate flame retardant (PVAAP) for cotton fabrics. The limiting oxygen index of the cotton fabric treated with 24% PVAAP was 42.1. After 50 standard laundry cycles, the limiting oxygen index remained relatively high (26.3), suggesting that the 24% PVAAP can be used as a durable flame retardant. The vertical flammability test of the cotton fabric treated with PVAAP exhibited no afterflame and afterglow. The cone calorimetry test indicated that the peak of the heat release rate and total heat release of the cotton fabric treated with 24% PVAAP were significantly lower than those of the control cotton. Thermogravimetric and thermogravimetric-infrared spectroscopy revealed that the initial decomposition temperature of the PVAAP-treated fabric was substantially lower than that of the control fabric, and more residual carbon was generated. The PVAAP altered the thermal decomposition pathway of the treated cotton. The X-ray diffraction patterns and scanning electron microscopy images suggested that the PVAAP treatment did not change the structure of the fibers.

Imparting superhydrophobicity and flame retardancy simultaneously on cotton fabrics

An eco-friendly hydrophobic flame retardant, ammonium salt of octadecyl phosphate (AMOP) was synthesized and its structure was verified by 1HNMR, 13CNMR and 31PNMR. AMOP imparted flame retardancy and superhydrophobicity to cotton fabrics simultaneously. The water contact angles and limiting oxygen index values of treated cotton reached 161.8° and 27%, respectively. After 30 laundering cycles, the hydrophobicity sustained very well. Thermogravimetric analysis and thermogravimetric-infrared spectroscopy suggested AMOP changed the thermal decomposition path of cotton fibers and the treated sample released less flammable gas during the thermal decomposition process. Cone calorimetry results showed the total heat release and the heat release rate of treated cottons were much lower than those of control cottons. Fourier-transform infrared spectroscopy, energy dispersive X-ray analysis and X-ray photoelectron spectroscopy suggested the AMOP successfully grafted on cotton fabrics through P-O-C groups. Scanning electron micrography showed AMOP caused a rough surface.

A novel high whiteness flame retardant for cotton

A novel self-buffering flame retardant ammonium amino trimethylene phosphate (AATMP) was synthesized by a facile one-step water-solvent method to solve the problem of flammable cotton triggering easily and spreading fire. The structure of AATMP FR was verified by FT˗ IR, 1H NMR, 13C NMR, and 31P NMR spectra. AATMP was grafted onto cotton fabrics using the dip-dry-cure method, and the grafted cotton was confirmed by FT-IR spectra. The limiting oxygen index (LOI) of cotton treated with a mass concentration of 15% AATMP solution reached 43.9%. After 30 and 50 laundering cycles, LOI values were maintained at 34.8% and 29.7%, respectively, suggesting that AATMP can be used as a durable flame retardant. The vertical flammability of treated cotton indicated no afterflame or afterglow time for comparison. Cone calorimetry results revealed that the total heat release of treated cotton was 1.6 MJ/m2, lower than that of control cotton (2.8 MJ/m2). The peak heat release rate of control cotton was 195.1 kW/m2, much higher than that of treated cotton (16.1 kW/m2, further confirming the efficient fire resistance of AATMP. Thermogravimetry analysis and thermogravimetric-infrared spectroscopy indicated that AATMP FR altered the thermal decomposition pathway of treated cotton. X-ray diffraction patterns and scanning electron microscopy suggested that the structure of treated fibers was hardly affected. The tensile strength and whiteness of treated cotton fabrics were sustained well due to the self-buffering property of the neutral AATMP molecule.

Effects of thermal treatments on the characterisation and utilisation of red mud with sawdust additive.

Extremely large amounts of red mud (bauxite residue) are generated globally every year from alumina refining industries, which are being disposed of on engineered landfills. The objective of this study is to investigate the effects of thermal treatments on red mud for development of utilisation strategies. Thermal treatments of red mud samples and their characterisations were investigated under inert (N2) and oxidative (air) conditions with and without sawdust addition at 200-600°C. After calcination, the resulting samples were analysed using thermogravimetric-infrared spectroscopy (TG-IR) for functional group transformations, thermogravimetric analysis (TGA) for thermal loss profiles and X-ray diffraction (XRD) for mineral transformations. The characterisation results showed that in N2 environment, boehmite in red mud was transferred to transition alumina at around 400°C while losing water from structural components. The addition of sawdust for incubation and calcination of red mud in air increased the surface area, whereas that in nitrogen atmosphere lead to reduction of hematite to magnetite at around 500°C. The incorporated carbon materials played a major role in increasing the surface area especially for pore size less than 2.5 nm. This treated red mud with altered mineral composition and improved properties for binding contaminants can be used for environmental remediation and in the process of metal recovery such as iron.