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Continuous heat generation in perovskite solar cells (PSCs), caused by solar radiation, poses a significant challenge to their lifespan. Existing active cooling methods require extra energy input and might not be effective at high temperatures. Most reported passive radiative cooling materials either lack solar transparency or require complex fabrication processes. Here, mesoporous silica nanoparticles are designed, synthesized, and assembled into multilayered stacks with a graded refractive index (GRI) by spray coating them on top of PSCs made from methylammonium lead iodide (MAPbI3) over a large scale (15.6 × 15.6 cm2). This coating offers both high transparency in the visible wavelength and high emissivity in the mid‐infrared region, leading to an average temperature reduction of 6.65 ±  1.48 °C in GRI‐coated MAPbI3 PSCs under outdoor conditions compared to non‐coated references. After 50 d, the GRI‐coated PSCs maintain 80.9 ± 8.7% of their initial photoconversion efficiency, in contrast to 6.1 ± 5.9% for the noncoated ones. The calculated cooling power of the GRI‐coated PSCs is 28.9% higher than that of the reference cells. [ABSTRACT FROM AUTHOR]

Although it is seen in the literature that composite pipes are produced by filament winding, there are limited number of studies on the use of fabric wrapping and autoclave. In this study, in order to fill this gap and contribute to the literature and industry, composite pipes were produced using fabric wrapping and autoclave methods together and their mechanical and thermal properties were investigated. The effect of carbon nanotube (CNT) reinforcement on these properties was also investigated. According to low velocity impact (LVI) test, 10%–25% impact strength increase was observed with CNT reinforcement. Thermogravimetric analysis (TGA) shows that mass loss decreased by ⁓10% and the degree of thermal degradation increased by ⁓10%. In dynamic mechanical analysis (DMA), it is observed that epoxy glass transition temperature (Tg) increased by 11% with CNT reinforcement. At the end of the study, the mechanical and thermal properties of the pipes produced by autoclave and fabric wrapping methods were improved compared to the literature and contributed to science and therefore to the increased use of prepreg carbon pipes in the industry. Highlights: Composite carbon pipes were produced by applying prepreg fabric wrapping and autoclave curing methods together.The mechanical and thermal properties of multi‐walled carbon nanotube (MWCNT) reinforced and unreinforced carbon composite pipes were investigated.According to TGA, it was observed that the mass loss decreased.Thermal decomposition temperature increased for MWCNT reinforced and unreinforced samples.According to DMA, Tg of epoxy decreased for MWCNT unreinforced sample and increased for MWCNT reinforced sample. [ABSTRACT FROM AUTHOR]

Mineral–rubber composites based on phosphorylated butadiene rubber (PhBR), including pure expanded perlite (EP) and modified phosphorylated expanded perlite (PhEP) as fillers, are developed. The process involves forming PhBR and its composites—EP/PhBR and PhEP/PhBR—through the oxidative chlorophosphorylation (OxCh) reaction. An in‐depth comparative analysis is conducted on the thermal destruction of the PhBR matrix and the EP/PhBR, and PhEP/PhBR composites. The thermogravimetric (TG)/differential thermogravimetry (DTG) analyses reveal three stages of thermal degradation for the PhBR matrix and both composites, highlighting the notable effects of EP and PhEP in the second and third stages of the degradation process. In comparison, the PhEP/PhBR composite exhibits reduced weight loss, the highest integral procedural decomposition temperature (IPDT) value, and a lower Tmax on the DTG curve, compared with the EP/PhBR composite and the PhBR matrix. The mechanism of the thermal destruction reaction and the kinetic parameters Ea and A are calculated using the model‐fitting Coats–Redfern method. [ABSTRACT FROM AUTHOR]

The thermal decomposition modeling of starch granules (rice, maize, and potato) is investigated in this work. Thermogravimetric analysis (TGA) under nitrogen conditions and different heating rates is carried out. First, a model‐free analysis is carried out to determine the variability of the activation energy with the relative conversion. The results reveal that the sequence of activation energy is rice > maize > potato. In turn, the activation energy is positively correlated (ρ = 0.98) with the relative crystallinity determined by X‐ray diffraction (XRD) analysis. Then, a fractional‐order version of the Sestak–Berggren equation is used to model the starch thermal decomposition. A least‐squares approach is used to estimate the underlying parameters by fitting non‐isothermal TGA curves. The results show that the parameters depend on the heating rate, but more strongly on the XRD relative crystallinity. Overall, the results reported in this study indicate that fractional‐order kinetics models provide an accurate description of the starch thermal degradation, without the use of the traditional TGA heuristic methods used for parameter estimation. [ABSTRACT FROM AUTHOR]

Renewable resources based polymers have been the focus of materials science scientists since they help to protect the environment in addition to reducing the petroleum resources use. Among renewable polymers poly (lactic acid) (PLA) has emerged due to its biodegradable character and proper performance similar to engineering resins, which afford wide field of applications. In this work the thermal degradation of esterified PLA with itaconic acid (PLA ITA) and the biocomposite PLA ITA FLAX was investigated using thermogavimetry (TG) which data were corroborated through Fourier transform infrared spectroscopy (FTIR). Isothermal TGs scans and FTIRs spectra were acquired from 150 to 600°C, collected data evidenced that FLAX improved PLA ITA thermal stability, delaying the decomposition of PLA ITA by up to 100 min at 250°C, ensuring safer processability at higher temperatures. From the deconvolution of the DTG peaks, the peak at lower temperature is suggested to be linked to itaconic anhydride decomposition which undergoes macromolecule dissociation, converting into itaconic anhydride and releasing water and afterwards being converted into citraconic anhydride, while the peak at higher temperature is associated to the thermal degradation of telechelic PLA. Degradation mechanism is proposed, evidenced by changes in the wavelength of CO group under the effect of temperature, as evidenced in TG‐IR spectra. [ABSTRACT FROM AUTHOR]

The management of end‐of‐life tyres faces challenges due to insufficient recycling infrastructure and technologies, as well as limited markets for the materials recovered from them. To mitigate this, waste rubber can be upcycled and used as filler material for polymer matrix composites. Before rubber‐reinforced composites can be certified for fire‐prone applications, their thermal and flammability properties must be understood. This research investigates the effect of rubber fillers on the thermal stability, flammability and flame spread characteristics of epoxy matrix syntactic foam. Thermogravimetric analysis, Fourier Transform Infrared spectrometry (FTIR), scanning electron microscopy and attenuated total reflection FTIR spectrometry were employed to elucidate changes in thermal degradation behaviours. The influence of rubber fillers on the flammability of syntactic foam was assessed using the cone calorimeter. The fire reaction properties of rubber‐reinforced foam were affected by the intensity of the incident heat flux. Regardless of the incident heat flux, an increase in rubber content led to higher total heat release. At the lower heat flux of 35 kW/m2, the fire growth rate increased with rubber content, but at the higher heat flux of 50 kW/m2, the fire growth rate decreased as the rubber content increased. Importantly, all rubber‐reinforced syntactic foams achieved a UL94 HB ranking and exhibited reduced flame spread rates compared to the unmodified foam. This study demonstrated the potential for upcycling waste rubber into sustainable engineering products and expanded the knowledge base on fire reaction properties and flame spread characteristics of such hybrid composite materials. [ABSTRACT FROM AUTHOR]

CO2 capture by absorption and stripping with aqueous amine is a well‐understood and widely used technology. However, drawbacks still exist in the practical applications, such as high energy consumption and easy degradation of the absorbents during the desorption process. In this paper, a novel NE‐1 absorbent was developed, and its suitable operating conditions were determined: concentration (45 wt.%), absorption temperature (40 °C), and desorption temperature (100 °C). The NE‐1 absorbent exhibits a high CO2 absorption capacity of 3.73 mol/kg, 1.33 times that of 30% monoethanolamine (MEA). After optimizing with carbamide as a corrosion inhibitor, 45% NE‐1a1 may attain an effective CO2 capacity of 2.5 mol/kg and over 70% desorption rate in five cycles, demonstrating excellent cycling stability performance. The research results have significant implications for developing an efficient and stable commercial carbon capture solvent and promoting the development of carbon reduction technologies. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Two kinds of porous polymer were prepared based on high functionality components. Thermogravimetric analysis (TGA) is used to compare the thermal degradation behavior and kinetics of these two materials. The thermogravimetric tests of rigid polyurethane foam (H‐RPUF) and polyurea aerogel (H‐PUA) were carried out in nitrogen atmosphere at different heating rates. The thermal degradation characteristics of the porous polymer were obtained. The apparent activation energy (Ea) of thermal degradation of the porous polymer was investigated by model‐free methods. The results showed that the thermal degradation temperature and ash content of H‐RPUF were higher than those of H‐PUA, and the volatile content was lower. With the rise of heating rate, thermal hysteresis effect of the two porous polymer was relatively high, while the release amount of volatiles was unchanged. For the Kissinger method, Ea of H‐PUA and H‐RPUF was 212.8 kJ mol−1 and 157.4 kJ mol−1, respectively. According to Starink method, the average activation energy of H‐PUA and H‐RPUF was 220.2 kJ mol−1 and 107.2 kJ mol−1, respectively. Obtained by Flynn‐Wall‐Ozawa model, the average activation energy of H‐PUA and H‐RPUF was 219.0 kJ mol−1 and 111.5 kJ mol−1, respectively. The data obtained from the three models all show that Ea of thermal degradation of H‐PUA is higher than that of H‐RPUF, and it is less likely to decompose. [ABSTRACT FROM AUTHOR]

Cannabidiol (CBD) vape pen usage has been on the rise given the changing political and scientific climate as well as the promotion of these delivery systems as a more accessible and lower-risk option for consumers. Despite being marketed as a safer way to use cannabis, CBD vape liquids are sold without restrictions or meticulous quality control procedures such as toxicological and clinical assessment, standards for product preservation, or investigative degradation analyses. Nine CBD-labeled vape liquid samples purchased and manufactured in the United States were evaluated and assessed for cannabinoid content. Quantification and validation of cannabinoids and matrix components was accomplished using gas and liquid chromatography with mass spectrometry analysis (GC-MS and LC-MS/MS) following liquid-liquid extraction with methanol. Samples degraded by temperature (analyzed by GC-MS) showed a greater disparity from the labeled CBD content compared with samples analyzed as purchased (by LC-MS/MS). Thermal degradation of the vape liquids showed increased levels of tetrahydrocannabinol (THC). Also, extended time and temperature degradation were evaluated in vape liquids by storing them for 5 months and then varying temperature conditions before analysis, which indicated CBD transformed into other cannabinoids leading to different cannabinoid content within the vape samples. Evaluation conducted on these vape liquids indicated the route of exposure, storage conditions, and length of storage could expose consumers to unintended cannabinoids and showed a concerning level of disagreement between the products' labeled cannabinoid content and the results generated by these analyses. [ABSTRACT FROM AUTHOR]

Within this research semi‐crystalline polylactide and composites with 50 wt.% native potato starch were compounded and injection molded. The material was mechanically characterized by tensile, three‐point bending, and Charpy impact tests. These tests were carried out in the freshly molded state and after 332 and 792 h of storage at accelerated temperature or humidity. The respective activation energy was calculated by applying the Flynn‐Wall‐Ozawa method. The focus of the study was to investigate the correlation between the activation energy and the related mechanical and thermal properties. The results showed that the addition of native potato starch as a filler prevents the decrease in activation energy over the course of the experiments. Thus, the PLA/starch composite is more resistant to the two aging conditions than the pure PLA. When considering the mechanical properties, the pure PLA showed a large deviation of results compared to the initial value in a range of +63.88% to −33.96% with regard to the respective aging conditions, whereas the PLA/starch composite properties nearly always remained at the initial values. Through the investigation of the mechanical and thermal properties, it was shown that the steady activation energies are consistent with the mechanical properties, as these have shown only a small deviation of the mechanical properties during the duration of experiments for the PLA/starch composite. [ABSTRACT FROM AUTHOR]

Kapok fiber (KF) with a naturally hollow structure has found an increasing application in filling and composite materials, most of which have a demand of flame retardancy. To realize this high-value utilization, KF was phosphorylated by a reactive phosphorus- and nitrogen-containing flame retardant for enhanced fire safety. The flame retardant was first synthesized by the reaction of urea and diethylene triamine pentakis (methyl phosphonic acid) (a commercially available scale inhibitor) with low cost, and then, applied in the phosphorylation of KF in the presence of dicyandiamide. In thermogravimetric analysis, phosphorylated KF showed 38.1% residue weight in nitrogen and 10.2% residue weight in air at 700°C, whereas the residue weight of KF was 8.4% in nitrogen and 1.5% in air. In microcalorimetric analysis, the heat release capacity and total heat release of phosphorylated KF displayed a reduction of 81% and 55%, respectively. In vertical combustion test, phosphorylated KF was difficult to ignite and had no afterburning or smoldering. The tests indicated that phosphorylated KF had excellent charring properties, low heat release, and good flame retardancy. This work suggests a promising strategy of enhancing the flame retardancy of KF and increasing its applicability in filling and composite materials. [ABSTRACT FROM AUTHOR]

In this work, indoor physical simulation experiments were used to examine the effects of shear, thermal, chemical, and microbial degradation on the properties of the hydrophobic associative polymer AP‐P4. It was discovered that the viscosity of the polymer solution generally decreased as the shear time was extended. The larger the shear strength, the lower the solution viscosity. Fitting of the nonlinear equation of solution viscosity with shear time, η = 12,988 t−1.08. When thermal degradation started, the solution viscosity first started to rise, however, this phase was just a short one. The viscosity of the solution gradually started to decrease as the thermal degradation period grew. In addition, the trends of properties like hydrokinetic radius, hydrophobic connectivity, and hydrolysis essentially followed the same patterns as those of solution viscosity. At the beginning of the degradation process, the viscosity retention of the polymer solution without oxygen is significantly higher than that of the aerobic environment. However, the difference between the two becomes smaller as the degradation time increases. In addition, the AP‐P4 had good temperature resistance and aging resistance capabilities when iron ions were present. Finally, it was discovered that AP‐P4 had a strong antibacterial effect, which decreased the viscosity brought on by microbial action. [ABSTRACT FROM AUTHOR]

The use of hydrolyzed rice straw (HRS) and hydrolyzed rice husk (HRH) as feedstock for pyrolysis was evaluated through kinetic and thermodynamic studies. HRS and HRH were obtained from subcritical water hydrolysis (SWH) at different temperatures (180, 220, and 260°C). The Coats‐Redfern method was used to analyze the thermal behavior through thermogravimetry (TG) and derivative thermogravimetry (DTG) curves. TG profiles showed higher decomposition in the range of 250–400°C, especially for rice straw (RS) and HRS (80 wt %). The pyrolysis curves were well predicted by a first‐order reaction model. The kinetic analysis showed a variation in activation energy (EA) between 24.3 to 41.3 kJ mol−1 and 40.4 to 54.7 kJ mol−1 for RS/HRS and rice husk (RH)/HRH, respectively. The enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS) varied from 25.9 to 39.6 kJ mol−1, 35.4 to 69.6 kJ mol−1, and −64.1 to −6.7 J mol−1 K−1, respectively, for RS/HRS, and 35 to 49.8 kJ mol−1, 43.2 to 79.3 kJ mol−1, and −53.5 to −10.2 J mol−1 K−1, respectively, for RH/HRH. These results showed that the pyrolysis reactivity using HRS is higher than HRH, which indicates the pyrolysis of HRS is more advantageous than HRH. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced composites (CFRC) are remarkably replacing conventional materials in application requiring high mechanical performance thanks to their light weight and outstanding mechanical properties. Due to the massive increase in their production and application, one of the main drawbacks resides in their disposal, both at the end of their life and as scraps and offcuts. Furthermore, the production of carbon fiber (CFs) requires high energy demand (183–286 MJ kg−1), hence the recovery of composites to reuse CF seems to be a promising option in terms of sustainability and circular economy. With the aim of identifying a methodology to recover and recycle these materials, through this work a case study is shown for optimization of the pyrogasification process. [ABSTRACT FROM AUTHOR]

Thermally induced degradation of organic photovoltaic devices hinders the commercialization of this emerging PV technology. Thus, a precise understanding of the origin of thermal device instability, as well as identifying strategies to circumvent degradation is of utmost importance. Here, it investigates thermally‐induced degradation of state‐of‐the‐art PBDB‐T‐2F (PM6):BTP (Y6) bulk heterojunction solar cells at different temperatures and reveal changes of their optical properties, photophysics, and morphology. The open‐circuit voltage and fill factor of thermally degraded devices are limited by dissociation and charge collection efficiency differences, while the short‐circuit current density is only slightly affected. Energy‐resolved electrochemical impedance spectroscopy measurements reveal that thermally degraded samples exhibit a higher energy barrier for the charge‐transfer state to charge‐separated state conversion. Furthermore, the field dependence of charge generation, recombination, and extraction are studied by time‐delayed collection field and transient photocurrent and photovoltage experiments, indicating significant bimolecular recombination limits device performance. Finally, coupled optical‐electrical device simulations are conducted to fit the devices' current‐voltage characteristics, enabling us to find useful correlations between optical and electrical properties of the active layers and device performance parameters. [ABSTRACT FROM AUTHOR]

Bio‐based alternatives for epoxy resin curing agents are a necessity for fiber reinforced polymer composites to become more sustainable. Here, the precise knowledge about the optimal curing cycle and its influence on the thermoset's mechanical properties are imperative. Therefore, the influence of the maximum curing temperature on the network structure, crystal morphology and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) cured with l‐arginine was investigated with the goal to derive structure–property relationships and a favorable curing cycle. The maximum curing temperature used can be categorized into two regimes: first, the temperature range in which the thermoset reaches complete curing and second, the temperature regime in which the thermoset is fully cured and the thermal degradation starts to diminish its mechanical properties. An optimized curing regimen for achieving high flexural strength accompanied by adequate fracture toughness entails subjecting the material to a curing cycle comprising a duration of 1 h at a temperature of 150°C, followed by an additional 2 h at a temperature of 170°C. This study represents a pioneering effort in optimizing the curing process of amino acid‐cured epoxy resin, specifically focusing on achieving the most favorable mechanical properties as a result. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LLOs) are promising candidate cathode materials for safe and inexpensive high‐energy‐density Li‐ion batteries. However, oxygen dimers are formed from the cathode material through oxygen redox activity, which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns. Herein, a flake‐like LLO is prepared and aberration‐corrected scanning transmission electron microscopy (STEM), in situ high‐temperature X‐ray diffraction (HT‐XRD), and soft X‐ray absorption spectrum (sXAS) are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes. Void‐induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage. Particle degradation originates from side facets, such as the (010) facet, while the close (003) facet is stable. These results are further understood through ab initio molecular dynamics calculations, which show that oxygen atoms are lost from the {010} facets. Therefore, the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating, which result in crevice‐voids in the ab plane facets. The study reveals important aspects of the mechanism responsible for oxygen ‐anionic activity‐based degradation of LLO cathode materials used in lithium‐ion batteries. In particular, this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO. [ABSTRACT FROM AUTHOR]

Combustion is often difficult to spatially direct or tune associated kinetics—hence a run‐away reaction. Coupling pyrolytic chemical transformation to mass transport and reaction rates (Damköhler number), however, we spatially directed ignition with concomitant switch from combustion to pyrolysis (low oxidant). A 'surface‐then‐core' order in ignition, with concomitant change in burning rate,is therefore established. Herein, alkysilanes grafted onto cellulose fibers are pyrolyzed into non‐flammable SiO2 terminating surface ignition propagation, hence stalling flame propagating. Sustaining high temperatures, however, triggers ignition in the bulk of the fibers but under restricted gas flow (oxidant and/or waste) hence significantly low rate of ignition propagation and pyrolysis compared to open flame (Liñán's equation). This leads to inside‐out thermal degradation and, with felicitous choice of conditions, formation of graphitic tubes. Given the temperature dependence, imbibing fibers with an exothermically oxidizing synthon (MnCl2) or a heat sink (KCl) abets or inhibits pyrolysis leading to tuneable wall thickness. We apply this approach to create magnetic, paramagnetic, or oxide containing carbon fibers. Given the surface sensitivity, we illustrate fabrication of nm‐ and μm‐diameter tubes from appropriately sized fibers. [ABSTRACT FROM AUTHOR]

The present work deals with the thermal behavior investigation of new biocomposite materials intended to be used for process engineering applications. Particular attention is given to the thermal degradation of such materials. Thermal characterization at different scales is performed using thermogravimetric analysis (TGA) and cone calorimeter experiments. The main purpose is to compare the thermal behavior of new bamboo‐based and banana‐based Green Biocomposites (GBCs). An intumescent fire retardant (IFR) coating, which is a mixture of APP and boric acid was applied on the GBC sample surface to study the flame retardancy. The GBC samples was first manufactured using a vacuum resin transfer molding. TGA results showed that bamboo‐based (BM‐GBC) and banana‐based (Bn‐GBC) materials exhibits similar thermal degradation pattern. While cone calorimeter experiments revealed that BM‐GBC outperforms than Bn‐GBC. The IFR coating improved the flame retardancy of both GBCs by reducing the heat release rate as well as a noticeable reduction in terms of smoke emission. Finally, to improve the thermal stability of Bn‐GBC material, SiC powder is added as a filler. The IFR coating and SiC powder addition promotes considerably the thermal behavior of Bn‐GBC materials. [ABSTRACT FROM AUTHOR]

Understanding the oxidative and thermal degradation of CO2 sorbents is essential for assessing long‐term sorbent stability in direct air capture (DAC). The potential degradation pathway of imidazolium cyanopyrrolide, an ionic liquid (IL) functionalized for superior CO2 capacity and selectivity, is evaluated under accelerated degradation conditions to elucidate the secondary reactions that can occur during repetitive absorption‐desorption thermal‐swing cycles. The combined analysis from various spectroscopic, chromatographic, and thermal gravimetric measurements indicated that radical and SN2 mechanisms in degradation are encouraged by the nucleophilicity of the anion. Thickening of the liquid and gas evolution are accompanied by 50 % reduction in CO2 capacity after a 7‐day exposure to O2 under 80 °C. To prevent long exposure to conventional thermal heating, microwave (MW) regeneration of the CO2‐reactive IL is used, where dielectric heating at 80 and 100 °C rapidly desorbs CO2 and regenerates the IL without any measurable degradation. [ABSTRACT FROM AUTHOR]

This work aimed to develop a novel colorimetric indicator film from cassava starch, isomalt and glycerol with 20% wt.% of grape skin extract (GSE) by casting to be used as an indicator of fish freshness. The plasticizers were used in the concentration of 33% at five levels: 100/0, 70/30, 60/40, 50/50 and 0/100 (%w/w isomalt/glycerol). Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and RGB colour analysis showed the homogenous distribution of GSE in the starch matrix. The presence of GSE reduces the thermal stability, k1 value, solubility, swelling values and the %E and increases the tensile strength (TS), revealing its plasticizing potential action in the presence of isomalt. The influence of pH on the colours of the film containing GSE and its indicator activity were evaluated. The results showed that the film produced operates in a wide pH range, being an excellent candidate as an indicator for monitoring fish freshness. [ABSTRACT FROM AUTHOR]

We report the use of titanium tetraalkoxide in combination with trialkyl borate as an efficient catalyst system For the synthesis of high molecular weight PBS. It is observed that, the addition of trialkyl borates during polycondensation reaction results in the formation of high molecular weight PBS. This might be due to the activation of free terminal carboxylic acids in PBS oligomer by trialkyl borates via the formation of highly reactive acyloxyboron intermediate. A plausible mechanism for the activation of free terminal carboxylic acids by trialkoxy borates has also been proposed. [ABSTRACT FROM AUTHOR]

A new mild and efficient tin and titanium based catalyst combination have been explored for the synthesis of high molecular weight poly(butylene succinate). The new catalyst system is found to be more efficient and hydrolytically—as well as thermally—stable even at 250°C. Additionally, this new catalyst system is capable of producing very high molecular weight poly(butylene succinate) polymer in good yield even at lower temperatures. [ABSTRACT FROM AUTHOR]

In this study, kenaf natural fibers were coated with acetone‐thinned epoxy resin before compounding with high‐temperature polyethylene terephthalate (PET). Thus, composites of sodium hydroxide treated and epoxy‐resin coated kenaf fibers (KF) reinforced PET (CTKF‐PET) were manufactured using extrusion and compression molding techniques at an optimized 10 wt% constant fiber loading and processing temperatures of 240, 250, and 260°C, and were characterized for mechanical, thermal, and morphological performances. The obtained results showed an optimum processing temperature of 240°C with maximum mechanical and thermal properties with good interfaces between the coated fillers and the matrix, compared to those obtained at 250 and 260°C. Thermogravimetric analysis recorded maximum onset degradation and decomposition temperatures of 338.9 and 381°C with 9.5% and 13% improvements respectively after resin coating which positively impacted the constituent coated composites compared to the uncoated KF. Differential scanning calorimetry glass transition (Tg) and melting temperatures (Tm) for the CKF‐PET composites was maximum at 119.0 and 262.8°C with 2.18% and 2.8% improvements respectively compared to uncoated composites. The overall properties of all coated kenaf‐reinforced PET (CKF‐PET) and coated‐treated (CTKF‐PET) composites were higher with improved morphological properties irrespective of the processing temperature compared to the raw kenaf (KF‐PET) composites. Hence, natural fibers can be treated with resin coating to improve the thermal stabilities of natural fiber engineering plastic composites, and the interfacial adhesion between the coated‐KF and the engineering plastic matrix. The resultant composites are suitable for high‐temperature engineering applications such as the automotive and construction industries. [ABSTRACT FROM AUTHOR]

The increasing use of composite components in various engineering disciplines necessitates detailed comprehension of their operation. When subjected to adverse environmental circumstances, such as variable humid surroundings and UV radiations, the structural and mechanical characteristics of the composites can deteriorate. Additionally, using these composite materials for structural applications such as rooftop buildings or household properties may reduce lifespan. In this study, the static and dynamic mechanical properties and the stability of novel lignocellulosic Moringa stenopetala (MS) husk fiber‐based epoxy composites exposed to various environmental factors were assessed. These harsh conditions were picked to imitate those encountered outside and influence the longevity of these composites. The obtained fiber from the husk was examined for its physiological, structural, and thermal characteristics. Using the Broido, Kissinger, Flynn‐Wall‐Ozawa (FWO), Coats‐Redfern and Kissinger‐Akahira‐Sunose (KAS) isoconventional models, the thermal degradation kinetics of the fibers were investigated. KAS method results in the best‐fitted curve and shows maximum activation energy of 175.13 KJ/mol. After husk fiber assessment, composite materials were fabricated using a Hand layup method, and their static and dynamic mechanical properties, water uptake rate, and contact angle analysis with surface energy behavior under various environmental aging circumstances were studied. In comparison to the composites "as developed," the findings indicate that the mechanical characteristics of husk fiber‐based epoxy composites are significantly reduced by humidity and UV aging. Overall, the development of thermoset composites for structural applications can utilize husk fiber. Furthermore, after curing the water and UV‐aged composites, qualities can be recovered. [ABSTRACT FROM AUTHOR]

Nano‐sized carbon black (CB) was introduced to ethylene vinyl acetate/magnesium hydroxide (EVA/MH) composite by melt compounding and the EVA/MH/CB ternary composites were investigated in terms of their thermal, flame retardant, mechanical, and electrical properties. The results indicate that the introduction of MH and CB has no impact on thermal degradation mechanism of EVA, but inhibits its degradation substantially. The presence of CB can hinder thermo‐oxidative degradation and increase thermal stability of the EVA/MH composite significantly. The addition of CB increases the flame‐retardant efficiency of MH effectively. The EVA/MH/CB composite with 3.6% CB can achieve V‐0 rating and its peak heat release rate is 23% smaller than that of the EVA/MH composite, which only achieves V‐2 rating in UL‐94 test. The improvement in flame retardancy happens in condensed phase. On the whole, the introduction of proper CB can enhance the thermal and flame‐retardant properties of EVA/MH composite considerably without damaging its mechanical and electrical performances. This work provides a simple and cost‐effective method to further increase the properties of EVA/MH composite for wire and cable industry. [ABSTRACT FROM AUTHOR]

Plastic gears are widely used for various applications; however high environmental problems, low working life, and weak wear performance caused by high contact friction and running temperatures limited their use, particularly in medium‐to‐high power transmission. This study is an initial approach to develop and investigate hybrid woven‐natural fiber reinforced polymer composites for medium‐to‐high power transmission gears. Also, no research has been proposed to investigate the thermal stability and degradation, and wear performance of hybrid flax(F)/bamboo(B) woven composites. The current work seeks to regulate the wear, friction, and thermal stability of flax/bamboo hybrid epoxy composites by carefully selecting the stacking sequence. The composites were stacked in following sequence: F/B/B/F, B/F/F/B, F/F/B/B, and F/B/F/B. The tribological and thermal performance of the composites were investigated using a pin on a rotating disc test (ASTM G99) and thermogravimetric analysis (ASTM E 1131‐03) under ambient conditions. Results revealed that the stacking sequence significantly influenced the thermal stability and degradation, and wear properties. The thermal stability of B/F/F/B was found to be higher, demonstrating the increase in the amount of char residue in placing bamboo lamina as the skin. Tribological results indicate that the hybridization of flax/bamboo fibers into an epoxy matrix enhanced the wear performance. Also, B/F/F/B exhibited the maximum reduction in coefficient of friction and specific wear compared with pure epoxy (26%–50% and 65%–94%) and F/F/B/B (16%–49% and 21%–40%). The morphology of worn surfaces was studied in detail to correlate the specific wear rate with wear mechanisms. Based on the improved thermal and wear resistance, bio‐composite with B/F/F/B stacking can be used for gear applications. [ABSTRACT FROM AUTHOR]

BACKGROUND: Roasting plays an important role in the formation of flavor of roasted green tea; however, the changes in chemicals during this process have not been systematically studied until now. To reveal the dynamic changes in chemicals in green tea during roasting, non‐targeted metabolomics, coupled with chemometrics, was employed. RESULTS: A total of 101 non‐volatile metabolites were identified in tea samples, and 29 metabolites were identified as characteristic metabolites of roasting. A significant increase in catechins and their derivatives, organic acids, and flavonoid glycosides was observed, while the content of some amino acids and their derivatives decreased over 50% during roasting. The content of theanine glucoside increased dramatically (by 21.23‐fold at the roasting stage), and Maillard‐derived compounds also increased to varying degrees. CONCLUSION: Glycosylation, oxidative polymerization, and pyrolysis were important reactions responsible for the formation and transformation of flavor compounds in roasted green tea during roasting. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Thermal desorption/degradation with an atmospheric solids analysis probe (ASAP) and ion mobility (IM) separation are coupled with mass spectrometry (MS) analysis and tandem mass spectrometry (MS/MS) fragmentation to characterize thermoplastic elastomers. The compounds investigated, which are used in the manufacture of a wide variety of packaging materials, are mainly composed of thermoplastic copolymers, but also contain additional chemicals ("additives"), like antioxidants and UV stabilizers, for enhancement of their properties or protection from degradation. The traditional method for analyzing such complex mixtures is vacuum pyrolysis followed by electron or chemical ionization mass spectrometry, often after gas chromatography separation. Here, an alternative, faster approach, involving mild degradation at atmospheric pressure (ASAP) and subsequent characterization of the desorbates and pyrolyzates by IM‐MS, and if needed, MS/MS is presented. Such multidimensional dispersion considerably simplifies the resulting spectra, permitting the conclusive separation, characterization, and classification of the multicomponent materials examined. [ABSTRACT FROM AUTHOR]

Hydrogenated natural rubber (HNR) was prepared by diimide reduction of natural rubber (NR) latex and characterized by FT‐IR, 1H NMR and TG‐DTG. The thermal degradation kinetic models of HNR were studied under a nitrogen atmosphere by TG‐DTG. Achar and Coats–Redfern methods were used to study the non‐isothermal kinetics models change during the thermal degradation process of NR after hydrogenation. The results indicated that HNR with 34.69% and 63.74% hydrogenation degree were prepared. A one‐stage pyrolysis pathway could be observed from all the TGA curves which were shifted to higher degradation temperatures with the rise of saturation degree. The similar activation energies obtained by both Coats–Redfern and Achar methods confirmed that the kinetics calculation was accurate. The results showed the best‐fit models of the samples with the highest regression coefficient values (R2 > 0.90) were chemical reaction models. The reaction order was three (N3) in NR case and the corresponding mechanism functions were g(α) = [(1‐α)−2–1]/2, f(α) = (1‐α)3. The reaction order was two (N2) when it came to HNR with hydrogenation degree of 34.69%. The most probable mechanism functions were g(α) = (1‐α)−1–1, f(α) = (1‐α)2. As the degree of hydrogenation increased to 63.74%, the reaction order best‐fit changed to one (N1) which was proved to be the same as the ethylene‐propylene diene rubber samples. And the mechanism functions were g(α) = −ln(1‐α), f(α) = 1‐α. The thermal degradation models of polymers was closely related to the structure. And the structure effects affected the degradation behavior as well as the thermal properties of polymers. [ABSTRACT FROM AUTHOR]

Limited fossil fuel reserves combined with greenhouse gas intensification due to CO2 emissions has encouraged research in renewable fuels. In this work, a flash pyrolysis study of elephant grass cultivars—Pennisetum purpureum Schum cultivar Mott (MEG), P. purpureum Schum cultivar Roxo (REG), and P. purpureum Schum cultivar Capiaçu (CEG)—was carried out. The biomasses were evaluated in terms of energy characterization by proximate and ultimate analysis, thermogravimetric analyses (TG/DTG), X‐ray diffraction (XRD), Fourier transform infrared (FTIR), and analytical pyrolysis (Py‐GC/MS) at 600°C. The characterization results showed that these biomasses have potential for energy applications and to produce valuable chemicals. The pyrolysis products produced were mainly oxygenated, including short‐chain organic acids (C1‐C4), furans, esters, aldehydes, ketone, and phenols. Although the obtained results were similar for the three biomasses with small variations in the yields of the pyrolysis products, the study reveals an important difference in terms of energy density. CEG was proven as the most promising elephant grass cultivar to be applied for fast pyrolysis to obtain bio‐oil due to its higher dry matter production (2115 t km−2), power generated (9529 MWh km−2), HHV (16.22 MJ kg−1), lower ash content (6.75%), higher volatile content (74.84%), and higher carbon content (42.57%). [ABSTRACT FROM AUTHOR]

The effects of heat stabilizer systems on the thermal stability and processability of self‐made vinylidene chloride‐methyl acrylate copolymer (PVDC‐MA) film were investigated via accelerated aging test, Congo red test, FTIR, DMA, and TG‐FTIR. These results displayed that CaSt2/ESO performed excellently in synergistic inhibition of PVDC‐MA thermal degradation. Especially, when the mass ratio of CaSt2/ESO was 1.5:1.5, the static thermal stability time of PVDC‐MA was increased from 14.5 to 46.5 min. The kinetic calculation results also verified this point. Compared with pure PVDC‐MA, the average apparent activation energy (Ēa) of thermal degradation reaction of PVDC‐MA stabilized by CaSt2/ESO enhanced from 144.1 to 169.7 kJ mol−1 (α0 ≤ 0.1), indicating that the thermal stability of PVDC‐MA in the initial thermal degradation stage was dramatically improved by CaSt2/ESO. Moreover, the mechanism of the effect of CaSt2/ESO on PVDC‐MA in the initial thermal degradation stage was further explored by the generalized master plot methods. The kinetic analysis result suggested that under the synergistic effect of CaSt2/ESO, the mechanism model followed by the degradation of PVDC‐MA changed essentially (the three‐dimensional diffusion thermal degradation mechanism transformed into two‐dimensional diffusion). [ABSTRACT FROM AUTHOR]

This study deals with the improvement of light barrier properties and stress cracking strength of polyethylene terephthalate (PET) packaging materials by incorporating calcium metaborate (CaB2O4). CaB2O4 powders were synthesized by the sol–gel method. After the extrusion process produced PET/ CaB2O4 granules, the preform and bottle production was carried out by injection molding and blow molding. Compared to pure PET, UV transmittance is reduced (~88%), and it is more effective at lower wavelengths (<800 nm). Similarly, the presence of CaB2O4 improved the environmental stress cracking performance of PET packaging materials. While the burst strength increased in the range of 0.05%–0.2% CaB2O4 concentration, it decreased at higher concentrations. The load‐carrying capacity is approximately 109% higher than pure PET. Acetic acid (COOH) degradation increased with the incorporation of CaB2O4 particles, while isophthalic acid and diethylene glycol degradations did not change. The experimental data indicate that the photocatalytic degradation of the PET bottle is prevented significantly, and its mechanical performance is also improved with the incorporation of CaB2O4. Thanks to this novel product, the quality of food and beverages in PET packaging materials can be protected from the harmful effects of light, and the deformation of PET packaging materials can be prevented for various reasons. [ABSTRACT FROM AUTHOR]

This article presents the synthesis of new derivatives of octa(3‐thiopropyl)silsesquioxane (SSQ‐8SH) via thiol‐ene reaction with simple olefins bearing alkyl groups as well as methoxysilyl, substituted aryl or fluoroalkyl groups. All products were characterized by 1H NMR, 13C NMR, 29Si NMR, FTIR, GPC, MALDI‐TOF‐MS, as well as thermal analysis (TGA) to confirm their structures, purity and thermal stability, and finally give some insight into their thermal degradation pathway. In some of the structures obtained, the T5% values take place at high temperatures and are close to 230 °C. The thiol‐ene reaction allowed to obtain 7 new compounds with high yield (>92 %), no by‐products and in a relatively short time (24 h). All products are characterized by high conversion >99 %. New derivatives can find potential use as modifiers of plastics to improve their certain properties for example hydrophobicity or thermo‐oxidative stability. [ABSTRACT FROM AUTHOR]

A thermogravimetric study of poly(ethyl cyanoacrylate) nanofibers was carried out at five heating rates with a linear increase in the temperature in a nitrogen atmosphere. The data provided by the thermogravimetric study were used to evaluate the kinetics of the degradation process using three isoconversional methods. Considering that the kinetic parameters of the process depend on the reaction mechanism, various approaches were applied in order to determine the most probable mechanism function. In this respect, the mechanism of thermal degradation of poly(ethyl cyanoacrylate) is a phase boundary reaction with cylindrical symmetry (F0.5 function) as demonstrated by the z(α) master plots method, iso‐temperature method and isoconversional method. On their basis, the values of the kinetic triplet (Ea, A and the shape of the most appropriate f(α) function) of the process were obtained, and subsequently the thermodynamic functions of the activated complex formation were calculated. The thermal stability of the polymer was predicted according to the integral procedure decomposition temperature. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The advent of space exploration and high‐speed civil transport has prompted the development of polymeric materials that can endure extreme environments. Cyanate ester (CE) is a commonly used thermoset matrix for high‐temperature applications in aerospace and defense applications. CE has high glass transition temperature (>200 °C), low moisture absorption, low coefficient of thermal expansion and is extremely thermally stable. Various additives have been reported in the literature to improve thermal stability of the matrix further to prolong the life of parts manufactured from CE. In this review, we survey various inorganic additives based on silica, clay, boron and phosphorus reported in the literature to improve the thermal properties of CE. We also discuss the thermal stability improvement mechanisms for these CE–inorganic hybrids. © 2022 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

To study the thermal stability of ethylene/vinyl acetate/vinyl alcohol (EVA‐OH) composite with filler particles, systematic thermogravimetric analysis (TGA) investigation was conducted in both nonisothermal and isothermal modes. The effect of polymer concentration on the aging behavior of EVA‐OH was investigated in the nitroplasticizer (NP) environment. Fourier transform infrared spectroscopy was used to probe chemical structural changes in the EVA‐OH polymer before and after thermal aging. The results suggest that filler addition accelerates the rate of NP exudation out of the EVA‐OH composites and deteriorates the thermal stability of NP at moderate temperatures (up to 70°C). The degradation of NP, in turn, accelerates the degradation of EVA‐OH polymer in its composite form through oxidation and hydrolysis indicating the importance of antioxidants in such phase blends. [ABSTRACT FROM AUTHOR]

The thermoplastic cassava starch (TPS)/sisal fiber (SF) composites were prepared by melt blending. The effects of SF content and its surface treated by sodium hydroxide (NaOH) and silane coupling agent (KH550) on the thermal degradation behavior and structures of TPS were investigated by thermogravimetric‐mass spectrometry (TG‐MS), Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and nuclear magnetic resonance (NMR). The thermal decomposition temperatures of TPS/SF composites increase with the SF content. The thermal decomposition products of TPS/SF composites are mainly methane, H2O, acetylene, formaldehyde, methanol and CO2. The thermal stability of composites containing SF treated by NaOH is better than that of KH550. TPS/SF composites show A + V types crystal, and the sample containing SF treated by NaOH has the highest V type crystal. The experimental results reveal that the content and the surface of SF play an important role in the thermal stability and structures changes of TPS/SF composites. [ABSTRACT FROM AUTHOR]

A rapid and efficient system to adapt commercially available polymers for melt electrowriting (MEW) for the fabrication of micro‐fibrous scaffolds is introduced. Poly(ε‐caprolactone) (PCL) is currently the gold standard for MEW due to its low melt viscosity and its use in tissue regeneration. While several other polymers have been used for MEW, they involve small‐scale custom synthesis meaning beyond PCL there is a scarcity of commercial polymers suitable for MEW. Furthermore, PCL has a long degradation time and lacks the elasticity needed for many applications. Poly(L‐lactide‐co‐ε‐caprolactone) (PLCL) is an elastic polymer with relatively fast degradation profile and is commercially available in high purity. Its high melt viscosity, however, makes it incompatible with MEW at normal operating temperatures. Rather than modifying the MEW machine, this study uses a simple pre‐treatment of PLCL to tailor the melt viscosity. This treatment involves heating PLCL at 150 °C for 24–48 h to enable MEW printing into scaffolds at 110 °C with fiber diameters 14–40 µm. Scaffolds maintained their elasticity after the thermal degradation process, becoming the first PLCL low‐temperature MEW scaffolds. Moreover, this approach can be readily adapted by any MEW user without manipulating the polymer beyond the thermal treatment in an oven. [ABSTRACT FROM AUTHOR]

To improve thermal, mechanical and adhesion properties, epoxy resin was modified with methyl phenyl silicone (MPS), acrylonitrile butadiene styrene (ABS) and graphene oxide (GO). In order to increase compatibility and stability, MPS intermediate was grafted on epoxy resin through condensation reaction. Transmission electron microscopy images showed well dispersion of GO particles in the system proving successfully preparation of the MPS grafted epoxy/ABS/GO nanocomposite. Single lap shear strength for steel‐epoxy/carbon fiber composite joint in sample containing 15% MPS and 2% ABS improved up to 108% compared to neat epoxy. Such an improvement occurred when only 5% MPS, 2% ABS and 0.1% GO were used showing GO could decrease required content of modifiers in this case. Tensile strength of sample containing 5% MPS and 2% ABS was 49.89 MPa and it reached 55.23 MPa by adding 0.1% GO while it was 37.12 MPa in pure epoxy. Nanocomposite modified sample had a residual char of 20 wt%. at 600°C and increment of 30°C in initial degradation temperature and 7°C in maximum degradation temperature compared to pure epoxy. These finding beside 23% increasing in calculated activation energy using Kessinger's and FWO method's proved significantly improved thermal stability of modified epoxy resin. Scanning electron microscope images of fractured surface of specimens showed micro size domains obtained by phase separation cause toughness improvement and crack energy absorption. [ABSTRACT FROM AUTHOR]

Summary: This study evaluates two kinetic mechanisms to predict, on matter‐level and material‐level scales, the thermal degradation of thin plates of oak and eucalyptus as representing vegetative fuel involved in wildfires. The lumped mechanism considers four successive steps, whereas the simplified one includes two steps. The kinetic parameters of these mechanisms were identified with thermogravimetric analysis in air for heating rates between 2 and 30 °C min−1. On the matter‐level scale, kinetic mechanisms were tested for heating rates inside and outside the parameters optimization range. The simulations of the mass loss were close to the experimental data. The lumped mechanism gave better results than the simplified one. On the material‐level scale, the mass loss and temperature recorded during thermal degradation of thin wooden plates, with a heating cone, were compared to simulations performed with GPYRO. When only the gasification stage occurred, both mechanisms predicted results close to the experimental data. When char oxidation occurred, the beginning of the gasification stage was well predicted, whereas some differences appeared during the transition between the gasification and char oxidation stages. The performance of both mechanisms indicates that a two‐step mechanism is capable of modeling the thermal degradation of thin wooden plates on a material scale. [ABSTRACT FROM AUTHOR]

Organically modified montmorillonite (OMMT, Cloisite 20) was used as reinforcing filler to prepare nanocomposites from a blend of polypropylene (PP) and eco‐friendly degradable polybutylene succinate (PBS). A PP grafted with maleic anhydride was also added as a compatibilizer. Scanning electron microscopy observations indicated that the blend morphology was affected by the presence of OMMT, which acted as a compatibilizer between PP and PBS. Rheological measurements showed a significant increase of the complex viscosity when OMMT was added above a certain amount. X‐ray diffraction indicated an intercalated structure for all nanocomposites. The addition of OMMT improved mechanical properties of neat matrices and blends. The electrical insulation properties were preserved for low concentrations of OMMT, up to 2 wt%. Then, to guarantee good mechanical properties without deteriorating electrical ones, while maintaining a sufficient bio‐based composition, the 70/30 (PP/PBS) blend with clay concentrations of less than 2 wt% appeared to be the most satisfactory nanocomposite for applications in the field of electrical insulation. [ABSTRACT FROM AUTHOR]

Melt electrowriting (MEW) has been widely used to process polycaprolactone (PCL) into highly ordered microfiber scaffolds with controllable architecture and geometry. However, the integrity of PCL during specific processes involved in routine MEW scaffold development has not yet been thoroughly investigated. This study investigates the impact of MEW processing on PCL following exposure to high temperatures required for melt extrusion as well as atmospheric plasma, a widely used surface treatment for improving MEW scaffold hydrophilicity. The change in polymer molecular weight and melt temperature is characterized, in comparing unprocessed and processed samples, in addition to analysis of the mechanical and surface properties of the scaffolds. No significant difference in the molecular weight or mechanical properties of the PCL scaffolds is evident following 5 days of cyclic heating to 90 °C. Exposure to plasma for up to 5 min significantly increased hydrophilicity and surface adhesion force, characterized via contact angle and atomic force microscope, however, significant polymer degradation occurred evidenced by increased brittleness of the scaffolds. This study demonstrates the degradation of PCL following fabrication via MEW and surface treatment to guide the optimization of scaffold development for subsequent applications in tissue engineering and biofabrication. [ABSTRACT FROM AUTHOR]

The dimethyltin(IV) complex with 1,4‐dizacycloheptane (homopiperazine) was synthesized. The complex is of 1:1 stoichiometry. The complex was characterized by elemental analysis, spectroscopic techniques as infrared (IR) and nuclear magnetic resonance (NMR), and thermal measurements. Homopiperazine coordinates to dimethyltin(IV) by the two nitrogen atoms. The complex decomposes in two steps. The kinetic parameters of thermal decomposition process have been calculated using Coats–Redfern and Horowitz–Metzger methods. The high values of the energy of activation of the complexes reveal the high stability of the complex due to their covalent bond character. The two decomposition steps are endothermic. Density Functional Theory (DFT) calculations have been carried out to investigate the equilibrium geometry of homopiperazine and its complex. The calculated total energies, energies of highest occupied molecular orbital (HOMO), energies of lowest unoccupied molecular orbital (LUMO), and dipole moments are reported. Antibacterial, antifungal, and anticancer activities of homopiperazine and its dimethyltin(IV) complex were tested. The molecular docking studies were performed to find the possible binding modes to the most active sites of the receptor of breast cancer oxidoreductase and those of Escherichia coli. [ABSTRACT FROM AUTHOR]

A kind of four‐functional epoxy resin containing tertiary ester groups (FETE) was designed and synthesized by two‐step reaction: first, the nucleophilic substitution reaction between linalool and isophthaloyl chloride, and then epoxidation. The chemical structure of obtained product was determined by infrared (IR) spectroscopy and nuclear magnetic resonance spectroscopy. Unlike traditional thermosetting epoxy resins, the cured FETE could degrade rapidly at low temperature (200–300°C). Dynamic mechanical analysis analysis showed that through copolymerization of FETE with (4,5‐epoxycyclohexane‐1,2‐dicarboxylic acid diglycidyl ester) epoxy resin (TDE‐85), the glass transition temperature (Tg) of copolymer system could be adjusted in the range of 136–179°C; FETE had good miscibility with TDE‐85. The thermal degradation behavior of the copolymer system was studied by theoretical calculation, thermogravimetric (TG), and TG coupled with FTIR analysis, the results showed the thermal decomposition performance of the copolymer system could be adjusted in the range of 200–400°C. The tertiary ester groups in FETE were easy to thermally degrade and caused the network skeleton of the copolymer system to collapse. The FETE would have good prospects in reworkable electronic packaging, recycling or degradable epoxy resin area. [ABSTRACT FROM AUTHOR]

Thermal degradation of PVC occurs in two stages, with each stage subdivided into two substages. The first refers to the dehydrochlorination, where hydrochloric acid is formed, and giving polyene structures. Hitherto, the degradation mechanism and action of hydrochloric acid as a catalyst during the dehydrochlorination stage are poorly known. Recently, the importance of the tacticity has gained attention for its influence on the dehydrochlorination mechanism. The present work focused on the dehydrochlorination stage, studying the molecular structure by FTIR analysis and the kinetic parameters by TGA analysis in Nitrogen atmosphere, based on three mathematical methods: Friedman, Kissinger, and Flynn‐Wall‐Ozawa. The sample was a pure homopolymer obtained by suspension polymerization. The dehydrochlorination kinetics follows a first order reaction model and occurs by nucleation and growth. The dehydrochlorination begins with the loss of very labile chlorine atoms present in defective and isotactic molecular segments. The formed HCl acts as a catalyst in the degradation. Following 40% conversion, a drop in Ea is observed. After that, chlorine atoms present in syndiotactic and atactic sequences, are released and, added to the large number of polyene chain sequences, and an increase in Ea is observed up to 60% conversion, where the dehydrochlorination stage is concluded. [ABSTRACT FROM AUTHOR]

Degradable polymers are often desirable for the fabrication of medical implants, but thermal processing of these polymers is a challenge. We describe here how these problems can be addressed by discussing the extrusion of fibers and injection molding of bone pins from a hydrolytically degradable tyrosine‐derived polycarbonate. Our initial attempts produced fibers and pins with bubbles, voids, and discoloration and resulted in the formation of large polymer plugs that seized screws and blocked extruder dies. The material and process parameters that contribute to these issues were investigated by studying the physical and chemical changes that occur during processing. Differential scanning calorimetry and thermogravimetric analysis combined with IR analysis showed that residual moisture and solvents in conjunction with heat cause degradation and crosslinking as indicated by gel permeation chromatography. Rheology and melt flow index measurements were useful in characterizing the extent of dependence of polymer viscosity on temperature and molecular weight. With these insights, we could process our polymer into fibers and rods by controlling residual moisture, time, and temperature and by adjusting processing parameters in real time. The systematic approach described here is applicable to other degradable polymers that are difficult to process. [ABSTRACT FROM AUTHOR]

An in depth understanding of the kinetics of the decomposition of plastic mixtures is necessary to enhance chemical recycling approaches, in particular by pyrolysis. The fact that plastic waste is usually composed of mixtures of plastics constitutes a hindrance for secondary recycling but may not be a particular difficulty for tertiary recycling. In this study, an analysis of the thermal degradation of mixtures of high‐density polyethylene (HDPE) and polypropylene (PP), in different proportions, was carried‐out under pyrolysis conditions using thermogravimetric analysis (TGA) under nonisothermal conditions, at different heating rates. Both isoconversional and model‐fitting approaches were used to estimate kinetic parameters from the experimental information. It was found that both the degradation of HDPE and PP, as well as their mixtures, can be described by a single‐step degradation process but that the degradation process is influenced by the proportion between the two plastics. The HDPE/PP mixtures in which PP has a higher ratio than HDPE cause the degradation onset temperature for the mixture to be lower than either pure PP or pure HDPE. Also, it was found that the apparent activation energy estimated was lower for these mixtures in comparison with the pure polymers. This implies that there are extensive interactions between the plastics during the degradation procedure and, from an operational point of view, it may be actually easier to degrade plastic mixtures than the corresponding pure streams, a conclusion that is important in the context of tertiary recycling of plastic mixtures. Furthermore, it was observed that a compensation effect exists that encompasses all the kinetic data for the mixtures, regardless of the composition, indicating that, although significant changes occur in relation to the activation energy, the underlying degradation mechanism remains the same. [ABSTRACT FROM AUTHOR]

High‐performance binary blends between poly(ether imide) (PEI) and flame‐retardant poly(butylene terephthalate) (PBT) are modified with 5, 10, and 15 wt% of poly(tetrafluoroethylene) (PTFE) using a two‐step melt‐processing method. Morphology study reveals that PTFE does not interfere with PEI and PBT interfacial interaction during blends fabrication, and the dual‐phase inversion observed for binary PEI/PBT blends in previous works remains the same. Thermal degradation and fire resistance analyses show that charring layer formation is the major flame protection process and that PTFE enhances charring production for ternary blends. According to UL94 horizontal burning test, all blends are categorized as slow‐burning materials. Bomb calorimetry and thermal gravimetric analyses reveal that there is an interaction between PTFE with PEI and PBT phases, as well as with their degradation products. This phenomenon is explained by X‐ray photoelectron spectroscopy analysis, and it is attributable to Sb‐F species which enhances the formation of an intumescent layer. [ABSTRACT FROM AUTHOR]

Synthetic polymers are ubiquitous materials widely used in construction, automotive, electronics, and countless commercial products. With the growing trend of polymer applications in everyday life, upholding the rigorous fire safety regulations has become a matter of concern. In this regard, numerous studies have been conducted for improving the fire retardancy of polymers, mainly through incorporating a diverse group of fire‐retardant compounds into polymer‐based composites. This review article aims to present a comprehensive overview of recent advances in the fire‐retardant categories for polymeric materials especially emphasizing the nanosized fire retardants. Along with an attempt to focus attention on the consumption of conventional and possibly harmful fire retardants, potential eco‐friendly alternatives are represented. A detailed discussion on the flame retardation mechanisms and conventional fire characterization techniques are also discussed. [ABSTRACT FROM AUTHOR]