Improved Heat Resistance Research Articles

Unveiling the Potential of Halloysite Nanotubes: Insights into Their Synthesis, Properties, and Applications in Nanocomposites

AbstractHalloysite nanotubes (HNTs) have attracted considerable attention due to their unique properties and wide range of applications. This review explores HNT‐based nanocomposites, focusing on their preparation methods and improvements in mechanical, thermal, and barrier properties. Various synthesis techniques, including solution mixing, melt compounding, in situ polymerization, and surface modification, are discussed, along with their benefits and limitations. The role of HNT characteristics such as aspect ratio, dispersion, and surface chemistry in enhancing nanocomposite properties is examined. HNTs significantly boost mechanical properties, including tensile strength, Young’s modulus, and toughness, due to their reinforcement effects. Improved dispersion and interfacial adhesion between HNTs and the polymer matrix enhance these properties. HNTs also act as thermal barriers, improving heat resistance and dimensional stability, while enhancing barrier properties against gases and moisture. These synergistic effects allow for the customization of nanocomposites for specific applications in packaging, automotive, electronics, and biomedical fields. Future research should focus on optimizing synthesis methods and processing techniques to further improve HNT‐based nanocomposites’ performance. This review provides a comprehensive overview of HNT‐based nanocomposites, offering valuable insights for advancing nanomaterials science and engineering.

Enhancing Fire Resistance of Geopolymers Modified with Thermal Insulation Additives

This study aims to improve the fire resistance of geopolymers by adding thermal insulation materials. These additives help the material perform better at high temperatures. Previous research focused on using fly ash, metakaolin, and zeolite in geopolymer composites. This study looks at how porous additives affect compressive strength and whether non-destructive testing can measure damage after heat exposure. Four temperature tests were set: 400 °C for 60 min, 400 °C for 120 min, 800 °C for 60 min, and a maximum of 658 °C for 120 min. The results showed that the compressive strength and ultrasonic pulse velocity (UPV) dropped as the temperature increased, with a sharp decrease at 800 °C. Unmodified samples broke apart at high temperatures, while modified samples lost 40% to 70% of their strength. The study confirmed that a dense, amorphous matrix improves heat resistance, even with porous additives like fly ash. A link between UPV and compressive strength was found, suggesting non-destructive testing could be useful for checking structural integrity after a fire.

Random mutagenesis and disulfide bond formation improved thermostability in microbial transglutaminase

Microbial transglutaminase (MTG) from Streptomyces mobaraensis is widely used in the food and pharmaceutical industries for cross-linking and post-translational modification of proteins. It is believed that its industrial applications could be further broadened by improving its thermostability. In our previous study, we showed that the introduction of structure-based disulfide bonds improved the thermostability of MTG, and we succeeded in obtaining a thermostable mutant, D3C/G283C, with a T50 (incubation temperature at which 50% of the initial activity remains) 9 °C higher than that of wild-type MTG. In this study, we performed random mutations using D3C/G283C as a template and found several amino acid substitutions that contributed to the improvement of thermostability, and investigated a thermostable mutant (D3C/S101P/G157S/G250R/G283C) with three amino acid mutations in addition to the disulfide bond. The T50 of this mutant was 10 °C higher than that of the wild type, the optimal temperature for enzymatic reaction was increased to 65 °C compared to 50 °C for the wild type, and the catalytic efficiency (kcat/Km) at 37.0 °C was increased from 3.3 × 102 M−1 s−1 for the wild type to 5.9 × 102 M−1 s−1. X-ray crystallography of the D3C/G283C MTG showed no major structural differences against wild-type MTG. Structural differences were found that may contribute to thermostabilization and improve catalytic efficiency.Key points• Improved heat resistance is essential to broaden the application of MTG.• The MTG mutant D3C/S101P/G157S/G250R/G283C showed improved thermostability.• X-ray crystallography of the disulfide bridge mutant D3C/G283C MTG was elucidated.

Genomic Organization and Expression Profiling of GOLDEN2-like Transcription Factor Genes in Eggplant and Their Role in Heat Stresses

GOLDEN2-like (GLK) transcription factor genes are involved in chloroplast biogenesis during all stages of plant growth and development, as well as in the response to biotic and abiotic stresses. However, little is known about this transcription factor family in eggplant. In this study, we identified 54 GLK genes in the eggplant genome (S. melongena L.) and classified them into seven groups (G1–G7). Structural analysis illustrated that the SmGLK proteins of specific groups are relatively conserved. Cis-acting elements indicated that these genes are likely to be involved in multiple responses stimulated by light, phytohormones, and abiotic stress. Collinear analysis indicated that expansion of the SmGLK gene family primarily occurred through segmental duplication. Tissue-specific expression analysis revealed that SmGLKs were preferentially expressed in leaves, fruits, and seeds. Further screening of SmGLK genes revealed their differential expression under various treatments. Notably, SmGLK18 was significantly responsive to multiple phytohormones and stress treatments, whereas SmGLK3 and SmGLK12 were highly induced by ABA, IAA, SA, and drought treatments. Our study provides new information on the eggplant GLK family systematically and comprehensively. For the first time, we propose that SmGLK18 may play a key role in improving heat resistance. This study provides valuable candidate gene resources for further functional research and will benefit eggplant molecular breeding.

Comparison of selenium-mediated regulation of heat shock protein and inflammation in-vitro and in-ovo for heat resistance enhancement in broiler

Selenium is a heat-stress-reducing substance that improves heat resistance and is being studied for its effective application in the broiler industry. However, research on feed additives is labor-intensive and time-consuming because of the need for feeding experiments. We aimed to compare the effects of selenium under heat stress in vitro and in ovo, specifically examining the gene expression of heat shock proteins (HSP) and inflammatory markers. Two groups were included in the in-vitro study: in-vitro control (TC; selenium 0 μg/ml) and in-vitro selenium (TS; selenium 5 μg/ml). The satellite cells were cultured at 42°C for 48 h after selenium treatment. The in-ovo study comprised 4 groups: in-ovo control and in-ovo selenium 1-3 (OC, OS1, OS2, and OS3; selenium 2.5, 5, and 10 μg/egg, respectively). Selenium was injected on the 18th day after hatching, and heat treatment was performed at 32-34°C from the 14th to the 21st day after hatching, and the leg muscles of the chicks were collected on the 21st day. The gene expression of heat shock proteins (HSP), caspase3, nuclear factor kappa light-chain enhancer of activated B cells (NF-kB), and IL-8 was analyzed in in-vitro and in-ovo experiments, respectively. In-vitro results showed significant increases in HSP90, HSP60, and HSP40 in TS compared to TC, with a significant decrease in HSP70. In the in-ovo study, HSP70, caspase3, NF-kB and IL-8 were significantly increased in OS1. HSP90, HSP60, HSP40, HSP27 and NF-kB were significantly decreased in in-ovo OS2 compared to in-vitro TS, implying a trend in ratio compared to control. Selenium appeared to enhance heat resistance in-vitro and in-ovo by modulating HSPs and inflammation. However, differences in mRNA expression were observed depending on the concentration of selenium. These findings suggest that selenium modulates heat resistance through different mechanisms in-vitro and in-ovo, likely due to the complexity of whole-organism interactions in-ovo compared to the single-cell-type environment in-vitro. Therefore, to directly apply in-vitro results to in-ovo, a concentration comparison study for each additive is necessary.

The megaplasmid pCER270 of Bacillus cereus emetic strain affects the timing of the sporulation process, spore resistance properties, and germination.

The acquisition of new mobile genetic elements, such as plasmids, is essential for the pathogenesis and adaptation of bacteria belonging to the Bacillus cereus group. This can confer new phenotypic traits and beneficial functions that enable bacteria to adapt to changing environments and colonize new ecological niches. Emetic B. cereus strains cause food poisoning linked to the production of cereulide, the emetic toxin whose synthesis is due to the presence of plasmid pCER270. In the environment, cereulide provides a competitive advantage in producing bacteria against various competitors or predators. This study demonstrates that pCER270 also regulates the sporulation process, resulting in spores with improved heat resistance and germination capacity. The transfer of plasmid pCER270 among different strains of the B. cereus group may enhance their adaptation to new environments. This raises the question of the emergence of new pathogenic strains, which could pose a serious threat to human health.

Effect of Alkali on the Mechanical Properties of Sansevieria Fiber Bio-Composites

This study investigated the efficacy of different alkali (sodium hydroxide (NaOH), calcium hydroxide (CaOH), and potassium hydroxide (KOH)) in removing hemicellulose and lignin from Sansevieria fibers (SF) while maintaining cellulose content. Employing a precise immersion method, the alkali treatment significantly enhanced the crystalline properties and tensile strength of the fibers. FTIR spectroscopy demonstrated alterations in functional groups, while thermogravimetric analysis (TGA) revealed improved heat resistance. X-ray diffraction (XRD) analysis confirmed the enhanced crystallinity and reduced amorphousity of the treated fibers. Moreover, tensile testing confirmed the superior tensile strength and overall mechanical properties of the NaOH-treated fibers, attributing this positive outcome to the preservation of cellulose structure and enhanced interfacial bonding with the matrix. This study found that alkali treatment increased the potential of sansevieria fibers as composite reinforcement.

Construction of polyimide films with highly linear structures using a structural reorganization approach

AbstractTo improve the thermodynamic and mechanical properties of asymmetric polyimide (PI), a method to enhance the linearity of PI by using a structural reorganization approach was designed. First, two novel diamines containing benzimidazole and benzoxazole groups, namely PADBZ and PDBOA, were constructed and synthesized. Thereafter, two new kinds of PI films (PADBZ‐PMDA and PDBOA‐PMDA) were prepared and polymerized with 1,2,4,5‐benzenetetracarboxylic anhydride (PMDA). Based on structural reorganization, PADBZ‐PMDA and PDBOA‐PMDA had repeating units of the same chemical composition and different linearity with PABZ‐BPDA and BOA‐BPDA, respectively. Comparing PADBZ‐PMDA and PABZ‐BPDA, due to the transfer in the position of benzene, PADBZ‐PMDA with high linearity showed the improved heat resistance (Tg up to 448°C), dimensional stability (CTE down to 2.3 ppm/K) and mechanical properties. PDBOA‐PMDA and BOA‐BPDA had the same situation. This study provided a unique solution to enhance the performances of PI by increasing the linearity using a structural reorganization approach.

Strong and tough semi-crystalline poly(aryl ether nitrile) with low coefficient of thermal expansion

The crystallization of poly (aryl ether nitrile) (PEN) has an essential impact on improving heat resistance, mechanical properties, chemical resistance, and dielectric properties. However, during the synthesis process, high crystallinity PEN is prone to precipitate out, which makes it difficult to carry out the synthesis reaction, which poses a significant challenge to synthesizing high crystallinity and high molecular weight PEN. In this work, hydroquinone (HQ) as the main phenolic monomer and 4,4′-biphenol (BP) as the second phenolic monomer were used to solve the technical difficulties in synthesis by copolymerization. The crystalline PEN with high molecular weight and significant crystallinity was obtained by regulating the molar ratio of BP to HQ. The effects of isothermal heat treatment on its crystalline, mechanical, and thermal properties were investigated. The influence laws of molecular chain structure and heat treatment process on the properties of PEN films were revealed. Among them, when the isothermal treatment temperature was 270 °C and the HQ: BP was 85:15, the mechanical strength reached 130 MPa, and the elongation at break could be up to an astonishing 50 %. Besides, the CTE value from 50 °C–150 °C is 40.84 ppm/°C, which is lower than most thermoplastics. Therefore, PEN with the HQ to BP molar ratio of 85:15 is suitable for large-scale production, providing new crystalline plastic specifications for high-performance special engineering plastics. A crystal bridge-tie chain model is summarized by the properties of HQ/BP-PEN films under different crystallization conditions, which provides an idea for preparing stiff and tough films.

Caffeic Acid Encapsulated Centrifugally Spun Antioxidant Fibers: Characterization and Incorporation in Cakes

AbstractThe primary aim of this study was to formulate a cake with high antioxidant activity through the incorporation of centrifugally spun gelatin-based fiber which was enriched with caffeic acid. Characterization analyses were conducted to evaluate fibers with different concentrations of caffeic acid (2% and 4%), while simultaneously the effects of thermal and citric acid crosslinking on the physical and functional properties of the encapsulated fibers were investigated. The study revealed varying encapsulation efficiencies of caffeic acid in gelatin fibers (56.34–94.55%), markedly affected by substantial reduction of thermal crosslinking, contrasting with citric acid’s minimal impact. Additionally, citric acid increased total phenolic content (TPC), but thermal treatment notably decreased antioxidant activity (AOA) due to its impact on radical scavenging and phenolic group dissociation. The addition of citric acid significantly reduced water vapor permeability by 22% suggesting an induced crosslinking in both thermal-treated caffeic acid and citric acid samples. The study highlighted reduced AOA and phenolic content in thermally treated fibers (thermally treated gelatin with 2% caffeic acid vs thermally treated gelatin with 4% caffeic acid), suggesting lower water solubility and improved thermal stability with approximately 24% remaining weight after thermogravimetric analysis. Despite this, cakes with thermally treated fibers had higher AOA due to improved heat resistance of fibers. Generally, adding fibers to cakes decreased hardness and pH while increasing TPC, AOA, and volume index, showing a novel approach using centrifugally spun fibers to enrich foods with antioxidants.

Well-designed flame retardants for epoxy resin composites that simultaneously improve heat resistance, mechanical properties and fire safety

Epoxy resin (EP) flammability severely limits its application in some industrial fields, while flame retardant epoxy resin (FREP) often suffers from the problem of not being able to balance flame retardant properties with mechanical properties. To solve the problem, in this work, HDP, a reactive flame retardant was succeeded in synthesizing by the one-pot method using protocatechuic aldehyde (PH), 2,4-diamino-6-phenyl-1,3,5-triazine (DPT), and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) as reactive monomers, was used to improve the flame retardancy of EP. And evaluated the effect of HDP on the curing reaction, heat resistance and mechanical property of EP. The introduced of four phenolic hydroxyl groups and two secondary amine groups enhanced the compatibility of the flame retardant HDP in EP and improved process performance. The apparent activation energy (Ec) was reduced by 8.1 %, facilitating the curing of EP/DDM. When 5 wt% of HDP (with only 0.36 wt% phosphorus content) was added to EP, the flexural strength and modulus of FREP increased by 21.0 % and 14.9 %, respectively, and the Tg increased by 9.0 % compared to EP. Cone calorimeter test (CCT) data showed that compared to EP, samples of EP/HDP-5 showed a 14.5 % and 21.6 % reduction in total heat release (THR) and total smoke production (TSP), respectively, and a 13.7 % increase in coke yield (CY). EP/HDP-5 has a high limited oxygen index (32.5 %) and passes the UL-94 V-0 classification. The excellent char formation and flame retardancy was owed to the dual role of the condensed and gas phases of FREP in the combustion process.

Heat-resistant boron–nitrogen doped lignin-derived adsorbent-catalyst for gaseous aromatic pollutants removal

Lignin-based carbon material can be utilized as carbonaceous adsorbents for the removal of toxic gaseous organic pollutants, while the poor heat-resistance limited its widely application. Here in, B–N co-doped lignin carbon (BN–C) with high thermal stability was synthesized, and the optimized BN-C (1:2) exhibited notably improved heat resistance with the decomposition temperature up to 505 °C, and excellent adsorption capacity for o-dichlorobenzene (o-DCB) (1510.0 mg/g) and toluene (947.3 mg/g), together with good cyclic stability over 10 cycles for o-dichlorobenzene. The existence of abundant hexagonal boron nitride (h-BN) with good thermal conductivity contributed to the superior heat-resistance of BN-C (1:2), and the high specific surface area (1764.5 m2/g), enriched hydroxyl functional groups and improved graphitization degree contributed to its enhanced adsorption performance. More importantly, BN-C (1:2) supported Ru could effectively remove o-DCB and toluene at wide temperature range (50–300 °C). The present work guided the development of heat-resistant lignin-derived adsorbent-catalyst for gaseous aromatic pollutants removal, which benefits both environmental protection and resource utilization.

Multifunctional and high‐stability RGO/PANI wrapped polyurethane foam for flexible piezoresistive sensor applications

AbstractDue to its excellent durability and steady mechanical qualities, three‐dimensional porous polyurethane foam (PUF) presents a wide range of possibilities for flexible piezoresistive sensors. Its extreme flammability, poor electrical conductivity, and susceptibility to outside factors present serious difficulties, though. In this study, a waterborne polyurethane‐coated flexible PUF sensor that incorporates reduced graphene oxide (RGO) and polyaniline (PANI) through a methodical, step‐by‐step dip‐coating methodology is successfully developed. The final product has a water contact angle of 133°, which improves its ability to adapt to a variety of environmental circumstances. Flexible graphene sheets are incorporated to improve heat resistance and flame retardancy, and PANI and RGO provide strong bonding to the PUF framework, ensuring outstanding structural stability even after 1500 cycles. The flexible foam sensor shows promise for use in flexible piezoresistive sensors and electronic skin due to its remarkable strain monitoring range of up to 70%, quick response time of 0.39 s in sensitivity experiments, and adaptability to different physical activities like walking and gesturing.

Relationship between Improvement of Heat Resistance using Enthalpy Relaxation and Heat Treatment Temperature in Polystyrene Injection Moldings

Relationship between Improvement of Heat Resistance using Enthalpy Relaxation and Heat Treatment Temperature in Polystyrene Injection Moldings

Improvement of heat resistance in silicone rubber by Fe-doped TiO2 nanoparticles prepared via flame spray pyrolysis

In recent years, the development of heat-resistant silicone rubber has been a research hotspot. In this paper, a kind of Fe doped TiO2 nanoparticles (Fe-TiO2) was prepared via flame spray pyrolysis, which can significantly improve the high temperature resistance of silicone rubber. The results show that, on the one hand, the prepared Fe-TiO2 can inhibit the breakage of Si-O main chain; on the other hand, because Fe is doped into the lattice of TiO2, it causes the change of TiO2 crystal phase and produces more oxygen vacancies, which is more beneficial to capture free radicals in silicone rubber matrix, so that Fe-TiO2 can effectively inhibit the excessive cross-linking of silicone chain caused by methyl oxidation on the side of silicone rubber. TGA results showed that after adding Fe-TiO2, the 5 % thermal weight loss temperature of methyl vinyl silicone rubber increased from 392.8 °C to 435.6 °C.

Integrated analysis of transcriptome and small RNAome reveals regulatory network of rapid and long-term response to heat stress in Rhododendron moulmainense

Main conclusionThe post-transcriptional gene regulatory pathway and small RNA pathway play important roles in regulating the rapid and long-term response of Rhododendron moulmainense to high-temperature stress.The Rhododendron plays an important role in maintaining ecological balance. However, it is difficult to domesticate for use in urban ecosystems due to their strict optimum growth temperature condition, and its evolution and adaptation are little known. Here, we combined transcriptome and small RNAome to reveal the rapid response and long-term adaptability regulation strategies in Rhododendron moulmainense under high-temperature stress. The post-transcriptional gene regulatory pathway plays important roles in stress response, in which the protein folding pathway is rapidly induced at 4 h after heat stress, and alternative splicing plays an important role in regulating gene expression at 7 days after heat stress. The chloroplasts oxidative damage is the main factor inhibiting photosynthesis efficiency. Through WGCNA analysis, we identified gene association patterns and potential key regulatory genes responsible for maintaining the ROS steady-state under heat stress. Finally, we found that the sRNA synthesis pathway is induced under heat stress. Combined with small RNAome, we found that more miRNAs are significantly changed under long-term heat stress. Furthermore, MYBs might play a central role in target gene interaction network of differentially expressed miRNAs in R. moulmainense under heat stress. MYBs are closely related to ABA, consistently, ABA synthesis and signaling pathways are significantly inhibited, and the change in stomatal aperture is not obvious under heat stress. Taken together, we gained valuable insights into the transplantation and long-term conservation domestication of Rhododendron, and provide genetic resources for genetic modification and molecular breeding to improve heat resistance in Rhododendron.

Superior heat‐resistant polylactide/poly(butylene succinate) blend fibers via in‐situ reactive compatibilization

AbstractBlending poly(butylene succinate) (PBS) with polylactide (PLLA) has proven effective in improving heat resistance of PLLA fibers. Unfortunately, it remains challenging to maintain good spinnability for PLLA/PBS blends with high content of PBS with which further improved heat resistance could be anticipated. In this study, reactive melt‐extrusion was devised to in‐situ generate PLLA‐PBS copolymers by introducing zinc acetate as a transesterification catalyst into PLLA/PBS blends. The compatibility between the PLLA and PBS phases was greatly improved by the formation of PLLA‐PBS copolymers, resulting in excellent melt‐spinnability even for the PLLA/PBS blends with high PBS content up to 20 wt%. In addition, an increase in crystallinity of PLLA was achieved in PLLA/PBS blend fibers, thanks to the enhanced compatibility. More importantly, the presence of PBS nuclei retarded the molecular orientation of the amorphous PLLA phase, consistent with the effective results from the relaxation heat‐setting treatment. These led to an exceptionally improved heat resistance of the PLLA/PBS blend fibers. As an encouraging result, the boiling water shrinkage was significantly reduced from ca. 20% for neat PLLA fibers to 3.7% for the PLLA/PBS blend fibers with 20 wt% PBS content. These findings may open up a facile and effective route to develop PLLA/PBS blend fibers showing sound spinnability, greatly improved heat resistance and softness.

Thermally Conductive, Healable Glass Fiber Cloth Reinforced Polymer Composite based on β-Hydroxyester Bonds Crosslinked Epoxy with Improved Heat Resistance

Thermally Conductive, Healable Glass Fiber Cloth Reinforced Polymer Composite based on β-Hydroxyester Bonds Crosslinked Epoxy with Improved Heat Resistance

Effects of the chain length of nonaromatic epoxy resins on thermomechanical and optical properties: experiments, and ab initio and molecular dynamics simulations.

Epoxy resin has been extensively used in the field of advanced electronic materials as an adhesive and encapsulant owing to its excellent material properties. However, recently, there has been a demand for further improvement in heat resistance, high transparency, environmental resistance, and enhanced handling properties for high-brightness light-emitting diodes. Conventional aromatic epoxy resins lack light resistance; therefore, a colorless and transparent epoxy resin without aromatic rings is desirable. In this study, tris(2,3-epoxypropyl) isocyanurate (TEPIC) was used as a nonaromatic epoxy resin, and three types of TEPIC with different side-chain lengths were prepared. The ultraviolet (UV)-visible absorption properties of TEPIC were evaluated using time-dependent density functional theory, and the practicality of the numerical prediction of light resistance was verified. TEPIC yields a UV absorbance spectrum with a lower intensity than those of conventional aromatic epoxy resins, suggesting that TEPIC is expected to have high light resistance. In addition, their thermomechanical properties and the influence of molecular structure were evaluated using both molecular dynamics (MD) simulations and experiments. The MD simulation and experimental results were in good agreement, indicating that the long side chains of TEPIC suppress triaxial deformation-induced failure and improve ductility instead of decreasing strength and stiffness. In addition, the longer side chains form a dense molecular structure with less free volume. These results indicate that numerical approaches can be used to predict various properties of epoxy resins and interpret them from the molecular structure. Accordingly, these approaches can be used to aid the material development process.

Tensile and heat resistance behavior of modified thermoplastic polyurethane elastomer in anisotropic neodymium‐iron‐born bonded magnet

AbstractThe emergence of anisotropic neodymium‐iron‐boron (NdFeB)‐bonded magnets with high energy density and freedom of shape design is effective in minimizing the dimensions and mass of electric motors. However, limitations in mechanical strength and heat resistance at elevated temperatures hinder their further application. To overcome these challenges, we present a novel approach to enhance the tensile strength and heat resistance of the NdFeB‐bonded magnet involving the modification of thermoplastic polyurethane (TPU) through the melt‐mixing method with a styrene–acrylonitrile‐glycidyl methacrylate terpolymer (SAG) modifier and engineered TPU was then employed in fabricating NdFeB‐bonded magnets via calendering molding. The microstructure of the magnets exhibited aligned NdFeB particles due to mechanical stress during calendering molding, which results in anisotropy. Interestingly, the magnetic properties of bonded magnets based on modified TPU remain almost the same compared to their unmodified counterparts, showcasing a maximum energy product of around 12 MGOe. The mechanical tests demonstrated a maximum 32.4% increase in the tensile strength of bonded magnets based on modified TPU. A progressive shift to a higher temperature (100 to 120°C) of magnet samples fractured occurs in the heat resistance measurement of the bonded magnets based on modified TPU, meaning improvement in heat resistance of NdFeB bonded magnets.