High Residual Content Research Articles

Mechanical Behaviour and Microstructural Analysis of Earthen Materials Reinforced with Intensive Agricultural By-Products and Binders.

Modern construction is largely dependent on steel and concrete, with natural materials such as earth being significantly underutilised. Despite its sustainability and accessibility, earth is not being used to its full potential in developed countries. This study explores innovative building materials using Alhambra Formation soil (Granada, Spain) reinforced with difficult-to-recycle agricultural waste: polypropylene fibres contaminated with organic matter and leachates. Fibres were added at a ratio between 0.20 and 0.80% of the soil mass, leachates at a ratio between 4.25 and 8.50%, and lime was incorporated at 2.00% and 4.00% for specimens with higher residue content. Physico-mechanical properties, including uniaxial compressive strength and longitudinal strain, were analysed together with the microstructure. The results showed that polypropylene fibres, in comparison to the use of leachates, improved compressive strength and ductility, reaching a compressive strength of 1.76 MPa with a fibre content of 0.40%. On the other hand, this value is 7.4% lower than the reference sample without additives. The fibre-reinforced samples showed a higher porosity compared to the samples with leachates or without additives. This approach highlights the potential of agricultural waste for the development of sustainable construction materials, offering enhancements in the strength and ductility of reinforced soils.

Phosphorylated octa-aminopropyl POSS grafting on proanthocyanidin interface decorated 2D MXene for enhanced flame-retardancy of cotton fabric nanocomposites

Two-dimensional (2D) nanosheet materials (MXenes) have unparalleled advantages in the field of flame-retardant multifunctional composites, but their dispersibility, flame retardancy and compatibility with the matrix are poor and need to be enhanced. In this research, we employed interfacial decoration and grafting modification to firstly introduce proanthocyanidins (PCs) onto MXenes surface (forming PC-MXenes) to increase the number of available active sites. On this basis, phosphorylated A-POSS was grafted onto PC-MXene (resulting in PAP@P-MXene) via a one-pot method, organic–inorganic hybrid flame-retardant PAP@P-MXene nano-coatings were subsequently constructed on the surface of cotton fabrics via an immersion method, and their structure-property relationships were verified. Thermogravimetric analysis (TGA) results revealed that PAP@P-MXene displayed a high char residue content of 32.0 % at 800 °C, illustrating its pretty good fire-safety properties. Typically, the residual char amount of coated cotton fabric with 12 wt% PAP@P-MXene (C-PAP@P-MXene-3) under a N2 atmosphere was as high as 37.1 %. Additionally, the limiting oxygen index (LOI) increased to 31 %, while the peak heat release decreased by 79.83 %. C-PAP@P-MXene-3 also displayed a UL-94 V-0 rating and self-extinguishing ability, all of which demonstrated excellent fire safety performance. The unique 2D nanosheet structure of MXenes, along with their innovative structural design and synergistic flame-retardant strategy, endows the nanomaterials with good dispersibility and flame-retardant effects, which has led to the development of new flame-retardant strategies and expanded the potential applications of MXene materials.

Response mechanism of Saccharomyces cerevisiae under benzoic acid stress in ethanol fermentation

Sugarcane molasses is an ideal economical raw material for ethanol production because of its wide availability, low cost and nutrient content. However, benzoic acid compounds with toxic effects on yeast cells are commonly found in sugarcane molasses. At present, the molecular mechanism of the toxic effects of benzoic acid on Saccharomyces cerevisiae has not been elucidated. Here, the toxic effect of exogenous benzoic acid on S. cerevisiae GJ2008 cells was studied, and the genes differentially expressed in S. cerevisiae GJ2008 after 1.2 g/L benzoic acid stress were identified via Illumina RNA-Seq technology. The results indicated that benzoic acid significantly inhibited yeast cell growth, prolonged their rapid growth period, and ultimately reduced their biomass. During ethanol fermentation using 250 g/L sucrose under 1.2 g/L benzoic acid stress, several adverse effects were observed, such as high residual sugar content, low ethanol concentration and low fermentation efficiency. In addition, the cell morphology was damaged, the cell membrane permeability increased, intracellular nucleic acid and protein leakage increased, and the malondialdehyde content significantly increased. Moreover, the cells protected themselves by significantly increasing the intracellular glycerol content. Fourier transform infrared spectroscopy proved that benzoic acid could reduce the degree of unsaturation and increase cell membrane permeability by changing the yeast cell wall and cell membrane composition, leading to cell damage and even death. Transcriptomic analysis revealed that under benzoic acid stress, the expression of genes associated with sucrose and starch metabolism, thiamine metabolism, the glycolysis pathway, fructose and mannose metabolism, galactose metabolism and ABC transporters was significantly downregulated. The expression of genes related to ribosomes, lipid metabolism, ribosome biosynthesis, nucleic acid metabolism, arginine and proline metabolism, RNA polymerase, metabolism related to cofactor synthesis, and biosynthesis of valine, leucine, and isoleucine was significantly upregulated. These results indicated that benzoic acid inhibited glycolysis and reduced sugar absorption and utilization and ATP energy supply in yeast cells. In response to stress, genes related to the ribosome bioanabolic pathway were upregulated to promote protein synthesis. On the other hand, the expression of ELO1, SUR4, FEN1 and ERG1 was upregulated, which led to extension of long-chain fatty acids and accumulation of ergosterol to maintain cell membrane structure. In conclusion, this paper provides important insights into the mechanism underlying the toxicity of benzoic acid to yeast cells and for realizing high-concentration ethanol production by sugarcane molasses fermentation.

Effects of hydrocolloids on the structure and physicochemical properties of triticale starch during fermentation

The regulation of the structure and properties of new starch varieties has been a necessary step in the development of promising products. This study investigated the effects of 1 % xanthan gum (XG) and hydroxypropyl methylcellulose (HPMC) on the physicochemical properties and structure of triticale starch during fermentation. Frequency scanning and rapid viscosity analyzer results showed that the addition of XG or HPMC during fermentation resulted in the reduced loss factor (tanθ) and the increased peak viscosity, indicating that the network gel strength is enhanced. X-ray diffraction and attenuated total reflectance Fourier transform infrared spectroscopy experimental results revealed that adding XG or HPMC in the triticale starch during fermentation increased relative crystallinity (2.7 % and 5.27 %, respectively) and short-range order. Combined with microstructure and thermal analysis, the encapsulation effect of XG or HPMC on triticale starch increased the thermal stability of triticale starch during fermentation, which was specifically reflected by higher residue content (26.69 % and 19.13 %, respectively). This study can provide a theoretical basis for the effect of hydrocolloids on the texture and digestibility of triticale starch fermented products.

Marine-Derived Fucose-Containing Carbohydrates: Review of Sources, Structure, and Beneficial Effects on Gastrointestinal Health.

Fucose, fucose-containing oligosaccharides, and fucose-containing polysaccharides have been widely applied in the fields of food and medicine, including applications in Helicobacter pylori eradication and renal function protection. Fucose-containing carbohydrates (FCCs) derived from marine organisms such as seaweed, invertebrates, microalgae, fungi, and bacteria have garnered growing attention due to their diverse bioactivities and potential therapeutic applications. Marine-derived FCCs characterized by high fucose residue content and extensive sulfate substitution, including fucoidan, fucosylated chondroitin sulfate, and fucose-rich microbial exopolysaccharides, have demonstrated significant potential in promoting gastrointestinal health. This review describes the unique structural features of FCCs and summarizes their health benefits, including regulation of gut microbiota, modulation of microbial metabolism, anti-adhesion activities against H. pylori and gut pathogens, protection against inflammatory injuries, and anti-tumor activities. Additionally, this review discusses the structural characteristics that influence the functional properties and the limitations related to the activity research and preparation processes of FCCs, providing a balanced perspective on the application potential and challenges of FCCs with specific structures for the regulation of gastrointestinal health and diseases.

Incorporation of Silicone Mold Residues Influence on Acoustic Properties of Subfloor Mortars

The determination of minimum performance criteria for residential buildings has encouraged the development of new technologies by companies linked to the construction industry. In this context, the acoustic performance of floor systems is of great importance. One of the solutions to improve the performance of these systems is the incorporation of lightweight aggregates to replace natural fine aggregates in the subfloor mortars, with the aim of attenuating the noise caused by impact, thus improving acoustic performance. Therefore, the objective of this study was to analyze the properties of a subfloor mortar in a 1:4 ratio (cement:sand), with the incorporation of silicone mold residue, replacing natural fine aggregate, in proportions of 10%, 20%, and 30%. %, and a water/cement ratio (w/c) of 0.93. Tests were performed in the fresh and hardened state, such as incorporated air content, mass density, consistency index, flexural tensile strength, compressive strength, water absorption by capillarity, in addition to a specific test to determine the difference in sound pressure level between specimens. The results indicated that the mortar consistency was influenced by the incorporation of waste, increasing with its incorporation. The increase in consistency positively influenced the mechanical resistance of the mortars, which showed an increase with higher residue content, due to the reduction in the amount of voids. Consequently, densities also increased with high waste content. The acoustic test showed satisfactory results, with good attenuation of 10%, indicating an 8 dB improvement in the sound pressure level. The results presented show that the residue has great potential for acoustic attenuation.

Preparation of high-density green body based on binder jetting 3D printing using spheroidized SiC powder

Silicon carbide (SiC) ceramic stands as a critical material in the realm of high-performance engineering ceramics. However, Crafting SiC ceramics with intricate structures and superior mechanical properties presents notable challenges in shaping, sintering, and processing. Binder jetting (BJ) additive manufacturing has the outstanding advantages of high forming efficiency and no thermal deformation, especially suitable for printing complex structure SiC components.; however, BJ printed green bodies often exhibit low density, resulting in high residual silicon content and diminished strength of the final components. In this work, we introduce a novel strategy to fabricate high-strength SiC components with complex geometries by improving the density of printed SiC green bodies. This method involves modifying the morphology of SiC powder through the molten salt method to increase the density of BJ 3D printed green bodies from 1.24 ± 0.13 g/cm³ to 2.01 ± 0.03 g/cm³, followed by a reactive melt infiltration process. The resulting RB-SiC ceramics display exceptional flexural strength, averaging 280.60 ± 33.05 MPa, and an elastic modulus of 294.67 ± 4.90 GPa. These values represent some of the highest for flexural strength and elastic modulus reported among 3D-printed SiC composites. With its robust mechanical performance and streamlined fabrication process, this strategy holds substantial promise for the production of structural SiC ceramics.

Preparation and interfacial microstructure of high thermal conductivity diamond/SiC composites

Diamond/SiC composites offer valuable applications in thermal management because of their exceptional thermal properties. Currently, the predominant method employed for crafting diamond/SiC composites is the reaction sintering approach. However, it encounters the challenge of a high residual silicon content. In this study, we introduced techniques such as bimodal diamond particles and high-density carbon sources (submicron diamond powder) to enhance the diamond content and reduce the residual silicon, optimizing the phase composition. The results indicated the diamond/SiC composite demonstrated a thermal conductivity of 666 W/m·K, a thermal expansion coefficient of 2.73 × 10−6 K−1, and an elastic modulus of 753 GPa. Furthermore, the meticulous assessment of the interface microstructure of diamonds in the diamond/SiC composite was conducted using transmission electron microscopy. The formation of nanocrystal-SiC and interface defects were elucidated by the mechanism of carbon dissolution saturation.

Impact of Pure, Co-, and Sequential Fermentations with Hanseniaspora sp. and Saccharomyces cerevisiae on the Volatile Compounds of Ciders

Pure, co-, and sequential fermentations of Hanseniaspora uvarum, H. guilliermondii, and Saccharomyces cerevisiae strains were evaluated to improve the aromatic quality of ciders. In sequential fermentations, Hanseniaspora strains were used as starter, followed by S. cerevisiae inoculation succeeding one, two, and three days of fermentation. Kinetics, physicochemical parameters, and volatile compounds were assessed during 10 days of fermentation. The headspace technique was used to capture the volatile compounds from the ciders obtained in each experiment and analyzed by gas chromatography. Fermentations with pure strains of Hansenisaspora sp. showed a high population (>1010 CFU/mL) but had a low fermentation rate (2.3–3.8 CO2 g/L/d), low consumption of amino acids (20–40 mg/L) with a high residual content, high sugar consumption (80–90 g/L), and low alcohol content (<2.0% v/v). The H. uvarum strain produced a notably high ester content (245 mg/L). In the co-fermentations, H. guilliermondii with S. cerevisiae highlighted a significant production of higher alcohols, similar to that produced by S. cerevisiae alone (152–165 mg/L). In general, the maximum fermentation rate of the sequential inoculations was lower than co-fermentations but showed low residual nitrogen content (<69 mg/L) and good conversion of sugars into ethanol (4.3–5.7% v/v). The highest concentrations of volatile compounds were observed in treatments involving the two non-conventional strains: H. uvarum with S. cerevisiae inoculation after three days (564 mg/L) and H. guilliermondii after just one day (531 mg/L) of fermentation. These differences stemmed from the metabolic activity of the strains. H. uvarum was influenced by the presence of Saccharomyces, whereas H. guilliermondii did not exhibit this effect. Thus, a pure H. uvarum inoculum has the potential to produce a demi-sec cider with low alcohol content and high content of esters, contributing to a fruity aroma. In addition, ciders with sequential inoculation were the most promising for dry cider processing concerning fermentation parameters and bioaroma enrichment.

Residual ANTXR1+ myofibroblasts after chemotherapy inhibit anti-tumor immunity via YAP1 signaling pathway

Although cancer-associated fibroblast (CAF) heterogeneity is well-established, the impact of chemotherapy on CAF populations remains poorly understood. Here we address this question in high-grade serous ovarian cancer (HGSOC), in which we previously identified 4 CAF populations. While the global content in stroma increases in HGSOC after chemotherapy, the proportion of FAP+ CAF (also called CAF-S1) decreases. Still, maintenance of high residual CAF-S1 content after chemotherapy is associated with reduced CD8+ T lymphocyte density and poor patient prognosis, emphasizing the importance of CAF-S1 reduction upon treatment. Single cell analysis, spatial transcriptomics and immunohistochemistry reveal that the content in the ECM-producing ANTXR1+ CAF-S1 cluster (ECM-myCAF) is the most affected by chemotherapy. Moreover, functional assays demonstrate that ECM-myCAF isolated from HGSOC reduce CD8+ T-cell cytotoxicity through a Yes Associated Protein 1 (YAP1)-dependent mechanism. Thus, efficient inhibition after treatment of YAP1-signaling pathway in the ECM-myCAF cluster could enhance CD8+ T-cell cytotoxicity. Altogether, these data pave the way for therapy targeting YAP1 in ECM-myCAF in HGSOC.

Nanoporous gold with microporous structure prepared by sodium dodecyl sulfate-mediated electrochemical dealloying

Nanoporous gold (NPG) is a promising catalytic material for the oxidation of CO and methanol applications. However, NPGs are prone to extensive macroscopic cracking that often decrease mechanic properties of NPGs and depresses their catalytic action. To produce crack-free NPG with an ultra-finer porosity in room temperature, the anionic surfactant sodium dodecyl sulfate (SDS) was added in electrochemical dealloying process. SDS has the effect of reducing the surface diffusion of gold which hinder the initial coarsening of ligaments and prevents interior silver atoms from being exposed and dissolved. As a result, the pore and ligment size are finer, but higher residual silver of NPG samples. NPG with pore size down to 2 nm and the ligament 4.0 nm was successfully fabricated with 13.32 mM SDS in perchloric acid solution. The surface diffusion coefficient of Au atoms was 1.6 × 10−24 m2·s−1, nearly 3 orders of magnitude smaller than that of Au atoms in the absence of SDS (2.8 × 10−21 m2·s−1). Nanoindentation results demonstrated that high residual silver content made NPG samples harder and stiffer，the specific surface areas of NPG with 6.66 mM SDS was 190 m2 g−1 by BET. This work provided very important clues on how to control the crack free ultrafine nanoporous structure of other materials.

Evaluation storage capacity of six kind late-maturing Actinidia arguta resources

Actinidia arguta has a high edible value, nutritional value, and abundant resources; however, it is not durable. The selection of late-maturing, durable storage resources is one idea for solving this problem. Through phenological observations, we identified six types of late-maturing resources as experimental materials in this experiment, named CJ No.10, CJ No.6, CJ No.7, CJ No.9, CJ No.3, and CJ No.8, and compared the sensory, physicochemical, nutritional quality, and taste changes during storage to determine durable storage resources. The specific conclusions are as follows: at the end of storage, CJ No.8 and CJ No.7 had good sensory and physicochemical qualities, with high Vc and SSC content in CJ No.3, high total phenol, and flavonoid content in CJ No.8, high TA residual content in CJ No.9, and higher reducing sugar content in CJ No.7 and CJ No.10. Correlation analysis showed that the weight loss rate was positively correlated with the decay rate and sweet taste value and negatively correlated with flavonoid content and firmness. PCA showed that the differences in the storage capacity of all resources were mainly related to firmness, sensory score, weight loss rate, sweet taste, Vc, and SSC. The PCA scores showed that CJ No.8 had better storage resistance than the other resources. CJ No.8 could be promoted as a high-quality late-mature storage-resistant variety to promote the sustainable development of A. arguta industry.

Recovery of residual carbon from coal gasification fine slag by a combined gravity separation-flotation process

Recovering inner residual carbon is important for fully utilizing coal gasification fine slag (CGFS) resources. In this study, we adopted a combined gravity-separation and flotation process to efficiently recover residual carbon by considering the characteristics of the CGFS and optimizing the operating factors of the process. CGFS is principally a mixture of residual carbon and ash, with low-density particles containing more of the former. Accordingly, residual carbon is preliminarily enriched by gravity separation, in which gas velocity (vg) and water velocity (vw) significantly impact separation efficiency, followed by feed volume (m). The residual carbon in the initial concentrate was preliminarily enriched (i.e., loss on ignition (LOI): 55.90%; combustible recovery (Ro): 72.36%) under appropriate operating conditions (i.e., vw = 0.04 m/s, vg = 3 m/s, m = 150 g). Moreover, the quality of the flotation concentrate was most influenced by collector dosage (mc), followed by aeration rate (η), frother dosage (mf), stirring speed (w), and grinding time (t) during flotation of the primary concentrate. The flotation concentrate exhibited LOI and Ro values of 90.95% and 50.34%, respectively, under the optimal flotation conditions (i.e., mc = 20 kg/t, mf = 15 kg/t, w = 2600 rad/min, η = 200 L/h, t = 360 s); it has a high residual carbon content and is an ideal raw material for preparing fuels or carbon materials.

Thermal properties of cellulose nanofibrils and nickel-titanium alloy-reinforced sustainable smart composites

ABSTRACT The study focused on the synergistic effect of cellulose nanofibrils (CNFs) as a lignocellulosic bionanomaterial and nickel-titanium (NiTi) alloy as a shape memory smart metallic material reinforcer on the thermal properties of sustainable smart composites. The casting process was used to produce composites with CNF loadings of 1%, 3%, and 5% and NiTi loadings of 3% into epoxy resin. Thermal properties were evaluated using thermogravimetric (TGA), derivative thermogravimetric (DTG), differential scanning calorimetry (DSC), and dynamic mechanical thermal (DMTA) analysis. The TGA results revealed that the CNF/NiTi-reinforced groups have considerable higher degradation temperatures and thermal stability than the control group. Also, at 800°C, CNF/NiTi-reinforced groups had a higher residual content than the control group. DTG results showed that the addition of CNFs decreased the degradation speed. Although the NiTi loading was constant, it was determined that the addition of CNFs increases the storage modulus (E′), loss modulus (E″), tan delta (Tan δ), and glass transition temperature (Tg). Overall, it can be concluded that CNF/NiTi-reinforced composites indicated significantly improved thermal stability, decomposition temperature, residual content, elastic, and viscous properties. These smart composites can be used for advanced material applications requiring thermal stability.

Utilization of Coal gasification fine ash for construction material: From physical and chemical properties to the hydration activity of thermally modified CGFA

Coal gasification technology is the core of clean and efficient utilization of coal, while coal gasification fine ash (CGFA) is the solid waste inevitably produced in the coal gasification process. Due to the high residual carbon content and water retention of CGFA, the solubility of its silica-aluminium-calcium-containing minerals is poor, which affects its potential cementing properties in construction materials. In this paper, the basic physicochemical properties were investigated, and it was found that small particles of CGFA (CGFA-S) had more active mineral components, lower residual carbon content (17.17%) and weaker water retention (6.91%), which facilitated the removal of impurities and water. In addition, the best effects were achieved at a heat treatment temperature of 650 °C, which exposed the minerals and increased the solution solubility, and the leaching concentrations of Si4+, Al3+, and Ca2+ increased by 21.2%, 44.6%, and 97.8%, respectively. However, when the temperature was too high (815 °C), the minerals recrystallized, leading to structural instability and dissolution difficulties, and the concentrations of the three major ions were reduced by 84.4%, 82.0%, and 42.2%, respectively, compared with the control.Finally, the optimal heat treatment temperature was 650 °C, with the highest exothermic hydration rate (11.92 mW/g) and the highest cumulative exothermic heat (199.81 J/g). The hydration products were tightly bound, and the cement mortar specimens had the highest compressive strength, with a 28d strength of 45.4 MPa.

A metallothionein gene from hard clam Meretrix meretrix: Sequence features, expression patterns, and metal tolerance activities

Metallothioneins (MTs) are low-molecular weight cytoplasmic heavy metal binding proteins. MTs can regulate the concentration of essential or non-essential metals in organisms, and have many important biological functions, including detoxification, trace element metabolism, and anti-oxidation. In the present study, we cloned and characterized a metallothionein gene (designated as MmMT) from the hard clam Meretrix meretrix. The complete cDNA sequence of MmMT contained an open reading frame (ORF) of 629 bp, which encoded a protein of 76 amino acids with a predicted molecular mass of 7.66 kDa and a calculated theoretical isoelectric point of 7.24. MmMT is highly similar to previously identified MTs from other species, with typical metallothionein features such as a high cysteine residue content and the absence of histidine and aromatic residues. The mRNA transcripts of MmMT were prevalent in all the tested tissues, and the expression levels of MmMT were highest in the hepatopancreas and hemocytes. During the stimulation of Vibrio splendidus, the mRNA transcripts of MmMT in the hepatopancreas and hemocytes were significantly increased. The Escherichia coli overexpressing MmMT performed strong growth in the media supplemented with CdCl2 and CuSO4 compared to the control strains. These results provide useful information for further investigation of the functions of MmMT in metal detoxification and the innate immune system.

The influence of bioturbation on the petrophysical characteristics of the lower cretaceous reservoir rocks of the Northern Caspian

The Caspian Sea is one of the most perspective areas for oil and gas exploration. Significant hydrocarbon reserves are contained in the polymictic sand reservoirs of the lower cretaceous (Aptian-Albian) deposits of the North Caspian fields, which are characterized by an irregular distribution of pelitic and silty fractions. This results in high residual water content and low permeability, poor consistency of filtration-volume properties between them. This predetermines high heterogeneity of reservoirs in hydrocarbon reservoirs and unusually low specific electrical resistivities when producing water-free hydrocarbon inflows. As the authors’ studies have shown, the most important reason for the complex structure is the intense bioturbation of deposits virtually throughout the productive section, which actively affects redistribution of clay material in the reservoir rocks and ultimately leads to a decrease in the resistivity of reservoirs to the point where they can be classified as low resistivity.

Effect of solution road RomixSoilfix on deformation performance of granular base material: A laboratory and field investigation

Granular base material (GBM) is widely used as a base course in flexible pavement, since it has good performances to disperse stress and resist deformation. However, due to the increasing cost of pavement construction resulted by the low stiffness of GBM, the application of flexible pavement was rarely reported in Chinese expressways. This paper aimed to investigate the effect of Solution Road RomixSoilfix (SRX) on deformation performance of GBM and to evaluate the feasibility of SRX modified GBM (SRX-GBM) as a flexible base in expressway structure. A series of experimental tests were performed to analyze the influence of SRX content on curing process, stability and deformation performance of SRX-GBM. Subsequently, a flexible pavement was constructed using the SRX-GBM base course at the field sections on Tengchong to Longchuan Expressway in Southwest China. Results show that the use of SRX improves the California bearing ratio (CBR) of GBM, which raises from 145% to 417%. The dry shrinkage resistance and water stability of SRX-GBM are obviously better than cement-stabilized macadam. The results of triaxial tests demonstrate that the resilient behavior of SRX-GBM is dependent on the stress characteristics and curing times. The existing stress-related model is available for evaluating the changes of stress contribution to the Mr with the increase of SRX content. Since the base course has a high residual moisture content in a humid climate, the CBR of 250% was proposed by field CBR and deflection tests as a criterion for controlling curing time.

Flame retardancy, combustion, and ceramization behavior of ceramifiable flame‐retardant room temperature vulcanized silicone rubber foam

AbstractTwo types of ceramifiable flame‐retardant room temperature vulcanized (RTV) silicone rubber foam containing mica power (MP) were prepared by using glass powder (GP) as fluxing agents and aluminum hydroxide (ATH) as flame‐retardant agent, respectively. The flame retardant, combustion behavior, and thermal stability of ceramifiable flame‐retardant RTV silicone rubber foams were investigated. The results show that GP is not conducive to the flame retardancy and thermal stability improvement of the foams. On the contrary, MP and ATH can significantly improve the flame retardancy and thermal stability at high temperatures of the foams. The foams with addition of MP and ATH can reach to a high limiting oxygen index value of 35.8 with V‐0 rating in the vertical combustion test, and the total heat release and total smoke production of the foams are 21.0% and 61.7% lower than of the pure RTV silicone rubber foam, respectively. Furthermore, the structural and morphological changes of the foams under different pyrolysis conditions were studied, so as to reveal its ceramifiable mechanism under different fire scenarios. The results show that GP does not promote the formation of more char residue during pyrolysis, but it can greatly lower the ceramifiable temperature, resulting in a superior ceramic phase char residue. The foams including MP and ATH have a high char residue content; nevertheless, a comparatively higher temperature is necessary to create ceramic phase char residue.

Epoxidized vinyl silicone rubber-based flexible ablative material with low linear ablation rate

Thermal stability and residual content of traditional silicone rubber at very high temperature are unsatisfactory for thermal insulations. This work used anionic ring-opening polymerization to prepare epoxidized vinyl silicone rubbers with high residual content. Their structures and properties of the rubbers were evaluated. The one with 84% vinyl and 6% epoxy group showed high thermal stability in air. Epoxidized vinyl silicone rubber/carbon fiber/aramid fiber insulators showed a linear ablation rate which met the stringent ablation performance requirements for a solid motor insulation material. In addition, the thermal degradation behavior of the epoxidized vinyl silicone rubbers was investigated in detail. This work provides a strategy to develop insulation materials for solid rocket motors.