Thermal Oxidative Stability Research Articles

Insight into performance and lifetime of ecofriendly pollution barriers in landfill for emergency: A thermogravimetric analysis for novel polymer materials

The novel polymer barrier wall is an in-situ remediation technology designed to effectively control the migration of pollution and prevent the diffusion of pollutants by blocking, sealing, or altering the direction of groundwater flow. With its advantages of rapid chemical reaction (achieving 95 % strength within 15 min) and portable equipment suitable for narrow and rugged emergency sites, this innovative polymer barrier demonstrates promising prospects for practical application. Hence, ensuring the long-term durability of new materials under corrosive and high-temperature leachate conditions is crucial. In this study, a comprehensive investigation was conducted on the corrosion and thermal aging performance of novel polymer materials. Firstly, the mechanical tensile properties of the polymer materials were examined after immersion in leachates, aiming to elucidate the degradation mechanism underlying these properties. Subsequently, thermogravimetric (TG) analysis was performed on the polymer materials immersed in various leachates. And the thermal stability and oxidation stability of novel materials were investigated using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR). Based on the results obtained from thermal analysis, the service life of polymer materials under different pollutants was ultimately predicted utilizing the Arrhenius model. The findings indicate that the novel polymer materials exhibit commendable durability and pose little risk of causing secondary pollution.

Cryoprotective effect of magnetic field-assisted freezing in combination with curdlan on myofibrillar protein of Litopenaeus vannamei: Oxidative aggregation, protein structure and thermal stability

To counteract the negative effects of conventional freezing methods on frozen surimi products, the present study investigated the effects of magnetic field (MF) freezing in combination with different amounts of curdlan (CUR) on oxidative denaturation, structural alterations, and thermal stability of myofibrillar protein (MP) in shrimp surimi. The results indicated that the intervention of magnetic fields alone improved the quality of frozen muscle proteins. Under the dual intervention of magnetic field-assisted freezing and CUR, small ice crystals formed with MF6 treatment resulted in significantly lower solubility, turbidity, and mean particle size than the control group (p < 0.05). Moreover, the oxidation of MP was also significantly slowed down by inhibiting the formation of hydrophobic groups and carbonyl groups, maintaining a high content of sulfhydryl groups. MF6 also exhibited a high Ca2+-ATPase activity. The α-helix content, the increase in fluorescence intensity under this condition also tend to make the secondary and tertiary structures of myofibrillar protein more stable. Meanwhile, electrophoretic profiles and CLSM showed that this condition maintains the integrity of the MP. In addition, the MF6 samples also had high protein thermal stability. However, excess CUR reduces the excellence of MP cryoprotection. As a result, MF6 has better protection and improvement effects on protein function, structure and thermal stability, and CUR was also found to have the potential for cryoprotectant development.

Facile construction of polyacrylate membranes with pendent zwitterionic side-chains for high proton conduction

Designing high-performance proton exchange membranes for fuel cells has received tremendous interests and acquired plentiful fruits. However, the complicated preparation process and consequently high cost limit their practical application. This study endeavored to facilely construct a novel type of proton exchange membrane based on polyacrylates which decorated with pendant zwitterionic groups. Chemical structure and micro-morphology of these newly prepared membranes, namely SBPA-x (x = 0, 20, 30,40), were characterized by 1HNMR, FT-IR, XPS, SEM and AFM. Swelling ratio, water uptake and ion exchange capacity were found to be positively correlated with the contents of zwitterionic groups. The hydrophilic zwitterionic groups in the membrane formed a continuous water pathway, which contributed to the proton conductivity. Particularly, SBPA-40 membrane showed the highest proton conductivity of 78.6 mS/cm and the smallest activation energy Ea as 16 kJ/mol at 80 °C and 90 % relative humidity. On the other hand, the other application properties, such as thermal stability, mechanical property and oxidation stability, were also evaluated. Results demonstrated that all the membranes possessed good thermal stability within 300 °C and presented satisfactory mechanical performance by bending and twisting. Besides, the observed power density and open circuit voltage of SBPA-40 membrane were 58.3 mW/cm2 and 0.77 V at 30 °C. In conclusion, the zwitterionic polyacrylate membranes could have prospective application in proton exchange membrane fuel cells.

Investigation on the Performances of Esterified Waste Cooking Oil Rejuvenator and Recycled Asphalt.

Waste cooking oil (WCO) recycled asphalt is facing issues regarding insufficient thermal oxidation stability and aging resistance. In this research, glycerol esterification was adopted to pretreat WCO, and the consequences of this treatment on the aging resistance and thermal stability of WCO were analyzed. The impacts of varying levels of esterification of WCO on the high-temperature, low-temperature performances, fatigue properties, and aging resistance of recycled asphalt were investigated. Furthermore, the mechanisms of regeneration and the anti-aging of deeply esterified WCO recycled asphalt were revealed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) tests. The results indicated that variations in the physical properties of WCO during the aging process were reduced, and its aging resistance was improved following glycerol esterification therapy. The initial thermal decomposition temperature was increased by approximately 115 °C, which resulted in the enhancement of thermal stability significantly. Recycled asphalt obtained from deeply esterified WCO exhibited superior high-temperature, low-temperature performances, and fatigue properties. Moreover, the thermal oxidation stability and aging resistance of recycled asphalt with deep-esterified WCO could be promoted by reducing the oxidation and volatilization of light components during the aging process, with the complex modulus ageing resistance index decreasing by 13.27% and the phase angle ageing resistance index increasing by 14.71%.

Preparation of chitosan-based macromolecular antioxidant with high-efficiency free radical scavenging ability to improve the antioxidative properties of styrene-butadiene rubber/silica composites

To address the disadvantages of traditional rubber antioxidants with low molecular weight such as easy migration, poor extraction resistance, low thermal stability and antioxidant efficiency, in this work, we first prepared an antioxidant containing primary and secondary antioxidant groups (MC-MPA) through thiol-ene click reaction between N-(4-aminophenyl)maleimide (MC) and 3-mercaptopropionic acid (MPA). Then, we synthesized a chitosan-based macromolecular antioxidant with long-chain alkene, aromatic secondary amine, and thioether groups (COS-UC-MC-MPA) by sequentially grafting functional compounds 10-undecanonyl chloride (UC) and antioxidant MC-MPA onto natural macromolecular polymer chitosan (COS). The free radical scavenging ability of COS-UC-MC-MPA was assessed by using 2,2-Diphenyl-1-picrylhydrazyl (DPPH), and the results demonstrated that COS-OC-MC-MPA has high scavenging rate of 76.5 % for DPPH free radicals after 1 min of contact with DPPH dimethyl sulfoxide solution, showing excellent free radical scavenging ability. In addition, the results of accelerated thermo-oxidative aging test, thermogravimetric (TG) test, kinetic analysis of thermal-oxidative degradation, extraction resistance test, and volatilization resistance test indicated that COS-UC-MC-MPA with superior migration resistance and volatilization resistance could effectively enhance the antioxidative properties, thermal stability and thermal-oxidative stability of rubber composites. Moreover, the results of rubber processibility analysis (RPA) test and scanning electron microscopy (SEM) implied that the addition of COS-UC-MC-MPA is also conductive to improving the dispersibility of silica in rubber matrix. This study supplies a new perspective for the preparation of environmentally friendly and highly efficient macromolecular antioxidants for rubber composites.

Nano-Pd loaded composite membrane for reduced hydrogen crossover in proton exchange membrane water electrolysis via recasting method

The operation safety of proton exchange membrane water electrolysis (PEMWE) is significantly affected by hydrogen crossover. To address this issue, this study proposes a nano-Pd particle loaded composite membrane (Nafion-Pd) using the recasting method. Nafion-Pd and commercial membrane (Nafion-115) are comparatively studied in terms of the structure characteristics, proton conductivity, stability, electrolysis performance and hydrogen crossover. The results show that the Pd particles are relatively evenly distributed in Nafion-Pd, and the doped Pd particles have minor effect on the crystallinity and wettability of the membrane. Compared with Nafion-115, the composite membrane shows a slightly decreased ion exchange capacity but a significantly increased water absorption and hydration degree, which results in a 24.8 % increase in the proton conductivity. Although the mechanical stability of Nafion-Pd decreases to a certain extent, both the oxidative stability and thermal stability are improved. The electrolysis performance of PEMWE using Nafion-Pd is slightly improved, and the hydrogen crossover decreases significantly. Hydrogen concentration in oxygen is 0.66 % at 0.1 A/cm2, which is 60.2 % and 19.5 % lower compared with the Nafion 115 and Pt-doped composite membrane, respectively. The electrolytic voltage and hydrogen concentration in oxygen are relatively stable in long-time operation, ensuring an economic and safe operation of PEMWE.

Exploring the effects of whey protein components on the interaction and stability of cyanidin-3-O-glucoside.

Anthocyanins are susceptible to degradation due to external factors. Despite the potential for improved anthocyanin stability with whey protein isolate (WPI), the specific effects of individual components within WPI on the stability of anthocyanins have yet to be studied extensively. This study investigated the interaction of WPI, β-lactoglobulin (β-Lg), bovine serum albumin (BSA), and lactoferrin (LF) with cyanidin-3-O-glucoside (C3G), and also considered their effects on stability. Fluorescence analysis revealed static quenching effects between C3G and WPI, β-Lg, BSA, and LF. The binding constants were 1.923 × 103 L · mol⁻¹ for WPI, 24.55 × 103 L · mol⁻¹ for β-Lg, 57.25 × 103 L · mol⁻¹ for BSA, and 1.280 × 103 L · mol⁻¹ for LF. Hydrogen bonds, van der Waals forces, and electrostatic attraction were the predominant forces in the interactions between C3G and WPI and between C3G and BSA. Hydrophobic interaction was the main binding force in the interaction between C3G and β-Lg and between C3G and LF. The binding of C3G with WPI, β-Lg, BSA, and LF was driven by different thermodynamic parameters. Enthalpy changes (∆H) were -38.76 kJ · mol⁻¹ for WPI, -17.59 kJ · mol⁻¹ for β-Lg, -16.09 kJ · mol⁻¹ for BSA, and 39.50 kJ · mol⁻¹ for LF. Entropy changes (∆S) were -67.21 J · mol⁻¹·K⁻¹ for WPI, 3.72 J · mol⁻¹·K⁻¹ for β-Lg, 37.09 J · mol⁻¹·K⁻¹ for BSA, and 192.04 J · mol⁻¹·K⁻¹ for LF. The addition of C3G influenced the secondary structure of the proteins. The decrease in the α-helix content suggested a disruption and loosening of the hydrogen bond network structure. The presence of proteins enhanced the light stability and thermal stability (stability in the presence of light and heat) of C3G. In vitro simulated digestion experiments demonstrated that the addition of proteins led to a delayed degradation of C3G and to improved antioxidant capacity. The presence of WPI and its components enhanced the thermal stability, light stability, and oxidation stability of C3G. Preheated proteins exhibited a more pronounced effect than unheated proteins. These findings highlight the potential of preheating protein at appropriate temperatures to preserve C3G stability and bioactivity during food processing. © 2024 Society of Chemical Industry.

Fabrication of fire-retarded epoxy asphalt composites with compatibilization and toughening for road tunnel pavements

Although epoxy asphalt (EA) mixtures have been widely used for the pavement in tunnels, it was limited by its flammability, poor compatibility and low mechanical property. To solve the above problems, a compatibilized and toughening flame retardant (ESO-AA-DOPO) was prepared via the epoxidized soybean oil (ESO), arachidonic acid (AA) and 9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO). The presence of ESO-AA-DOPO significantly improved the flame retardancy, in which passing the UL-94 V-2 rating. The peak heat release rate (PHRR) reducing by 46.2 % for EA/40A-ESO-AA-DOPO composites comparing to that of pure EA. The analysis of char residue confirmed that the catalytic formation of dense and continuous char layer residue with good thermal oxidation stability originating from the ESO-AA-DOPO. The initial stage viscosity of ESO-AA-DOPO modified EA was lower than that of pure EA. Under the action of aliphatic epoxy resin and double bond, the molecular chain of epoxy resin presented a network structure, the base asphalt was divided into micelles, and the overall distribution of EA system was a 3D networks “sea-island”, which ensuring the increase in the glass transition temperature (Tg) of the EA system. The tensile strength and elongation at break of EA/40A-ESO-AA-DOPO composites were 123 % and 207 % higher than those of pure EA attributing to the improved compatibility and the formation of 3D networks “sea-island” structure.

Effect of Phosphate-Bridged Monomer on Thermal Oxidative Behavior of Phthalonitrile Thermosets.

Phthalonitrile thermosets are known for their excellent mechanical, physico-chemical, and fire-retardant properties, making them attractive for aerospace and mechanical engineering applications. When producing and applying phthalonitrile-based structural parts, it is essential to consider aspects such as processability and the long-term stability of the material's properties at high temperatures. In our previous studies, we demonstrated that resins containing phosphate-bridged bisphthalonitrile monomers are easily processable due to their low melting temperature and wide processing window. In this study, we investigated the impact of bis(3-(3,4-dicyanophenoxy)phenyl)phenyl phosphate (PPhPN) monomer content on physico-chemical and mechanical properties, thermal stability, and thermal oxidative stability. This research highlights the importance of conducting long-term thermal oxidative aging studies in addition to thermogravimetric analysis to properly assess the stability of thermosets. The findings indicate that adding less than 15% of PPhPN results in the formation of a crystalline phase, which impairs the resin's processability. Conversely, a high PPhPN content reduces the material's thermal oxidative stability. Therefore, based on mechanical and physico-chemical tests after thermal oxidative aging, it can be concluded that a 10-15% concentration of the phosphate-containing monomer enables easy processability of the phthalonitrile resin and provides excellent long-term thermal oxidative stability at temperatures up to 300 °C, while maintaining a flexural strength exceeding 120 MPa and an elasticity modulus of 4.3 GPa.

Semi-Interpenetrating Polymer Network Anion Exchange Membranes Based on Quaternized Polybenzoxazine and Poly(Vinyl Alcohol-Co-Ethylene) for Acid Recovery by Diffusion Dialysis.

Acid recovery from acidic waste is a pressing issue in current times. Chemical methods for recovery are not economically feasible and require significant energy input to save the environment. This study reported a semi-interpenetrating polymer network (semi-IPN) anion exchange membranes (AEMs) for acid recovery by diffusion dialysis with excellent dimensional stability, high oxidation stability, good acid dialysis coefficient (UH +) and high separation factor (S). Semi-IPN AEMs are prepared by ring-open cross-linked quaternized polybenzoxazine (AQBZ) with poly(vinyl alcohol-co-ethylene), where AQBZ is obtained by Mannich reaction and Menshutkin reaction. All four proportions of semi-IPNs exhibit clear micro-phase separation, which is conducive to ion transport. The water uptake (WU) of the four semi-IPNs ranges from 14.2 % to 19.2 %, while the swelling ratio (SR) remains between 8.7 % and 11.3 %. These results indicate that the cross-linked structure in the designed semi-IPNs effectively control swelling and ensure dimensional stability. The thermal degradation temperature (Td5) of semi-IPN4:6 to semi-IPN7:3 varies from 309 °C to 289 °C, with an oxidation stability weight loss rate (WOX) ranging from 91.5 % to 93.5 %, demonstrating excellent thermal stability and oxidation stability. The semi-IPNs also show good UH + values ranging from 11.9-16.3*10-3 m/h and high S values between 38.6 and 45.9, indicating the promising potential of the semi-IPNs.

Sustainable aviation fuel: Impact of alkene concentration on jet fuel thermal oxidative test (JFTOT)

AbstractOf the processes that are approved to produce synthetic kerosene for use in jet fuel, about half produce olefinic kerosene that is hydrotreated. The alkene concentration in synthetic kerosene is indirectly regulated through the thermal oxidative stability specification. Perceptions about the deleterious influence of alkenes on thermal oxidative stability suggest that olefinic kerosene must be deeply hydrogenated. The extent of olefin saturation required has economic implications. To evaluate what an acceptable alkene concentration in synthetic kerosene is, the impact of alkene concentration on the outcome of the jet fuel thermal oxidative stability test (JFTOT) performed at 325°C in accordance with the ASTM D3241 standard test method was experimentally evaluated. Model synthetic kerosene mixtures to which different concentrations of alkenes (1‐decene, α‐methylstyrene, indene) were added, as well as control samples were studied. In the concentration range investigated, up to 10 wt% 1‐decene, 5 wt% α‐methylstyrene, and 2 wt% indene did not lead to increased fouling in the JFTOT. Fouling passed through a minimum value with increasing alkene concentration and alkene concentration on its own was a poor predictor of thermal oxidative stability. Analysis of the kerosene collected after passing through the JFTOT found measurable changes in density and refractive index. Dissolved oxygen reacting during thermal oxidative stability testing was accounted for mostly in oxygen‐containing products in the kerosene boiling range, which indicated that the heavier products were mainly hydrocarbon in nature. In addition to initiation by autoxidation, the investigation also pointed to the existence of a second thermally initiated fouling pathway that does not require the presence of oxygen.

Revealing the Molecular Interaction between CTL Base Oil and Additives and Its Application in the Development of Gasoline Engine Oil

In order to improve fuel economy to meet the standard for passenger car oil, a new formulation with good viscosity–temperature performance for gasoline engine oil is required. In this study, coal-to-liquid (CTL) base oil, with a high viscosity index and good low-temperature performance, was selected as the base oil to develop the gasoline engine oil. A systematic study on the molecular interaction between the CTL base oil and the viscosity index improver (VII), including three kinds of hydrogenated styrene diene copolymers (HSD-type) and four kinds of ethylene propylene copolymers (OCP-type), was conducted. It was found that in general, in CTL base oil, the HSD-type VII exhibited a much higher viscosity index, a significantly lower shear stability index, a higher thickening ability, and a lower cold-cranking simulator (CCS) viscosity than that of OCP-type VII. Moreover, when comparing CTL base oil with mineral oil 150N, the combination of CTL base oil and the VII displayed a lower CCS viscosity than that of mineral oil, suggesting it had better low-temperature performance and was able to quickly form a protective oil film on the surface, which was beneficial for the cold start. The functional group distribution state of the VII in base oil was analyzed using synchrotron radiation micro-infrared microscope (SR Micro-IR) technology, which revealed that HSD-1 had a better molecular interaction with CTL6 than 150N because of the better uniformity of the C=C group distribution. Based on this, a SP 0W-20 gasoline engine oil was developed by the combination of CTL base oil and the HSD-1 viscosity index improver, together with an additive package, a polymethacrylate pour point depressant, and a non-silicone defoamer, which showed excellent low-temperature performance, thermal oxidation stability, and detergency performance compared to the reference oil.

Improvement of carbon fiber oxidation resistance by thin ceramic coating using silica particles

Carbon fiber-reinforced plastics have become indispensable materials in energy saving and new energy technologies, such as automobiles, wind power generators, and hydrogen tanks for fuel cells. However, the lack of oxidation resistance limits the high-temperature applications of carbon fibers. In this study, we developed a coating technology for carbon fibers to improve their oxidative resistance. Carbon fibers with silicon carbide coatings were obtained by the adsorption of silica colloids on carbon fibers using electro adsorption, followed by heating. The resulting coating has small thickness and strong chemical connections. The thermogravimetric analysis confirmed that the oxidation start temperature of the coated carbon fibers was higher than that of carbon fibers. Moreover, the mechanical properties of the coated carbon fibers were maintained. Therefore, the proposed coating technology can broaden the application of carbon fibers as the alternative to some SiC fiber applications. Further, it is applicable for recycling carbon fibers to increase their value in terms of thermal oxidation stability.

Multifunctional polyester-cotton fabrics with excellent flame retardancy, superhydrophobicity, antibacterial property and UV resistance

In this study, multifunctional polyester-cotton fabrics (PTCO) were constructed by gradually assembling polyethyleneimine phenyl phosphonate (POI) and different hydrophobic agents, respectively. The effect of different hydrophobic agents including tetraethyl orthosilicate, perfluorooctyltriethoxysilane (PFDTES), and hexadecyltrimethoxysilane on the thermal stability, flame retardancy, hydrophobic property, UV resistance and antibacterial property of PTCO/POI was investigated in detail. PTCO/POI-SiF had better flame retardancy due to the flame-retardant effect of PFDTES and POI, and the limiting oxygen index increased from 29.8 % to 31.2 %. The thermal oxidation stability of PTCO/POI-SiH and PTCO/POI-SiF was significantly improved in high temperatures, and the char residues at 700 °C were increased from 4.1 % to 7.6 % and 7.4 %. And PTCO/POI-SiH and PTCO/POI-SiF had excellent superhydrophobic properties with water contact angles of 151° and 162° and sliding angles of 4° and 3°. The ultraviolet protection factors of them were increased to 56.9 and 63.3, respectively, which had a good UV resistance. And both PTCO/POI-SiH and PTCO/POI-SiF had excellent antibacterial effects for E. coli and S. aureus. The breaking force, whiteness and moisture permeability of the finished fabrics had not been changed. Therefore, it is believed that PTCO/POI-SiH and PTCO/POI-SiF are promising for application in multifunctional fabrics.

Leguminous ferritin, a natural protein for iron supplementation, Pickering emulsion formation and encapsulation of bioactive molecules

AbstractFerritin is a naturally occurring iron storage protein. Leguminous ferritins exhibit unique structural features, including diverse subunit composition and an extension peptide, which contribute to superior thermal stability compared to animal ferritins. The high iron content, remarkable effectiveness, low risk of oxidative damage and thermal stability make the leguminous ferritin an attractive candidate for iron supplementation. Moreover, apoferritin is an excellent nanosized carrier for encapsulating bioactive compounds due to its inherent inner cavity, water solubility, biocompatibility, and reversible self‐assembly behavior. However, the harsh condition during encapsulation by unmodified ferritins may cause damage to sensitive bioactive compounds. Thus, different processing methods are employed to alter the leguminous ferritin structures, including chemical, enzymatic, mild heat treatments, and nonthermal processing to achieve gentler encapsulation conditions for a wide range of bioactive compounds. Another challenge is to improve the stability of leguminous ferritin to withstand gastric digestion. The degradation of ferritin by proteases may lead to premature release of bioactive compounds. Recent works demonstrated that certain phenolic compounds such as proanthocyanidin‐induced protein association, thereby enhancing digestive stability of ferritins, leading to a sustained release and a potentially greater bioavailability of bioactive compounds. Leguminous ferritin also has the potential to serve as a stabilizer for the Pickering emulsion, where the hydrophilic and hydrophobic compounds can be encapsulated in the ferritin nanocages and oil phase, respectively. The release and absorption of bioactive compounds in encapsulates and emulsions will need to be further demonstrated through in vivo studies.

2D Tantalum Disulfide Reduction Strategy Customized Ta2O5/rGO Heterointerface Aerogel Toward Boosting Electromagnetic Wave Absorption and Flame Retardancy.

The exceptional and substantial electron affinity, as well as the excellent chemical and thermal stability of transition metal oxides (TMOs), infuse infinite vitality into multifunctional applications, especially in the field of electromagnetic wave (EMW) absorption. Nonetheless, the suboptimal structural mechanical properties and absence of structural regulation continue to hinder the advancement of TMOs-based aerogels. Herein, a novel 2D tantalum disulfide (2H-TaS2) reduction strategy is demonstrated to synthesize Ta2O5/reduced graphene oxide (rGO) heterointerface aerogels with unique characters. As the prerequisite, the defects, interfaces, and configurations of aerogels are regulated by varying the concentration of 2H-TaS2 to ensure the Ta2O5/rGO heterointerface aerogels with appealing EMW absorption properties such as a minimum reflection loss (RLmin) of -61.93dB and an effective absorption bandwidth (EAB) of 8.54GHz (7.80-16.34GHz). This strategy provides valuable insights for designing advanced EMW absorbers. Meanwhile, the aerogel exhibits favorable thermal insulation performance with a value of 36mW m-1 K-1, outstanding fire resistance capability, and exceptional mechanical energy dissipation performance, making it promising for applications in the aerospace industry and consumer electronics devices.

Thermal Stability of Amorphous Metal Oxides: The Interplay of Secondary Cations, Degree of Substitution, and Local Structure

Thermal Stability of Amorphous Metal Oxides: The Interplay of Secondary Cations, Degree of Substitution, and Local Structure

The control effect and mechanism of antioxidants on the flavor deterioration of Sichuan pepper essential oil during thermal processing

The impacts of varying heating temperature on the flavor of Sichuan pepper essential oil (SPEO) have been studied. The high temperature heating was found to accelerate the oxidation of SPEO and caused the deterioration of its flavor (odor and pungency taste). With the intervention of antioxidants including RE, AP, and TPP, both thermal oxidation stability and flavor stability of SPEO were enhanced. Addition of 1.5% TPP had the best control effect, which significantly improved the overall flavor of heated SPEO and made the overall flavor of SPEO heated at 100°C highly similar to that of original SPEO. According to the results of GC-MS and OAV analyses, the control effect of antioxidants on odor deterioration of SPEO was mainly through significantly inhibiting the decrease in content and OAV of both linalool and terpenes, and restricting the formation of some oxygenated compounds such as aldehydes. The results of HPLC analysis showed that the control effect of antioxidants on the thermal taste stability of SPEO was mainly dependent on blocking the chemical reactions of sanshools, especially hydroxy-α-sanshool.

PAN-precursor to carbon fibre: An investigation of manufacture and material properties for varying comonomer composition

This study presents the conversion of polyacrylonitrile (PAN) co-polymers containing methyl acrylate (MA) and varying concentrations of itaconic acid (IA) comonomers, from precursor fibre into carbon fibre using pilot scale continuous processes. The impact of itaconic acid on fibre processability, thermal behaviour, energy consumption, and final mechanical properties during thermal oxidative stabilization (TOS) and carbonization are investigated. Itaconic acid concentration varies from 0.3 to 3 wt % and with increasing concentration of itaconic acid, the precursor fibre exhibited lower exothermicity and enhanced reactivity, resulting in 7 % less energy consumption during stabilization. Higher itaconic acid content led to improved carbon fibre properties. A 20 % increase in tensile strength was recorded for carbon fibres containing the highest amount of itaconic acid along with a higher amount of graphitic structure and carbon yield. Overall, this study explores the impact of precursor design on fibre properties as a route to the manufacture of carbon fibre with reduced embodied energy. The results of this study illustrate pathways to improve the efficiency and effectiveness of carbon fibre production, and to ultimately create high-performance, lightweight, and more sustainable carbon fibre-reinforced composites.

Thermal-oxidative stability of PVC compositions modified with a bromine-containing plasticizer-flame retardant

The possibility of creating polymer compositions based on polyvinyl chloride plasticized with a bromine-containing flameretarding plasticizer has been investigated. Their thermostability at introduction of plasticizer with different bromine content was evaluated. The optimal concentrations of bromine in the flame-retarding plasticizer to increase the thermal stability of the polymer composition have been established. It is noted that increasing the concentration of bromine in the flame-retarding plasticizer increases the rate of elimination of hydrogen bromide and slows down the thermal destruction of the polymer matrix. It is shown that during thermo-oxidative degradation of plasticized PVC composite, hydrogen bromide is first eliminated from flame-retarding plasticizer, which accelerates the process of polyene formation and additional cross-linking of polymer macromolecules. An increase in the tensile strength of plasticized compositions at the introduction of optimal dosages of flame-retarding plasticizer was observed.