The thermal-mechanical properties of vulcanized styrene-butadiene rubber (SBR) are fundamentally determined by its cross-linked network structure. However, a systematic understanding of how cross-linking degree influences molecular dynamics and thermal transport remains limited. In this work, we investigate the dual micro-mechanisms through which cross-linking degree (Dc) governs both viscoelastic and thermal properties: namely, the restriction of chain segment mobility and modulation of low-frequency phonon density. The molecular dynamics (MD) simulations coupled with experimental validation are employed to investigate the effect of Dc on shear viscosity(η), bulk viscosity(ηb), specific heat capacity (Cp, Cv), and thermal conductivity(κ). Results demonstrate that increasing Dc enhances intermolecular constraints, leading to a rise in η by 65.5–23.3 γ̇ ) promotes molecular chain orientation, thereby decreasing η by 83.4–93.2

This review focuses on thermochemical heat storage (TCHS) materials and their composites, aiming to enhance efficiency for low‐temperature applications. To obtain comprehensive information on the selection of suitable high‐performing TCHS materials, variousreports from past research were critically reviewed and systematically categorized. First, the application requirements, such as hydration energy storage density dataand working temperature requirements, were compiled and categorized for silica‐based composites, metal‐organic frameworks (MOFs), zeolite‐based composites, carbon‐based composites, metal foams, polymer‐based composites, hybrid composites, and advanced, modern, synthesized composite materials. These requirements were then critically reviewed. In addition to that, it was reminded that porous silica materials, MOFs, and zeolite materials can enhance the hydration sorption performance, providing a porous structure, while high conductive carbon materials are used to enhance heat transferring property during hydration/dehydration, and also polymer composites are usually used to stabilize as a binding material for enhanced cyclic stability by preventing agglomeration and delinquency at the state of overhydration. Then, after the working pair materials (adsorbates), such as water vapor, ammonia, alcohols, and other synthetic organic materials, were reviewed, the literature data were tabulated. Lastly, past works, present status limitations, and future standpoints are presented to identify the required working‐pair materials for the development and selection of suitable materials and a sorbent working pair for high‐energy‐density and precise operating conditions of the TCHS process.

Thermochemical heat storage (TCHS) is a technology that stores thermal energy through reversible chemical reactions, providing high energy density and long-term storage with minimal losses. This review highlights recent advancements in the use of salt hydrates and porous matrix composites as sorbents in TCHS systems, with a focus on their synergistic effects. It begins with an overview of heat storage systems and adsorption concepts. This discussion then addresses key challenges related to salt-hydrated and composite adsorbent materials. In practical applications, salt hydrates for thermochemical heat storage face issues such as deliquescence, agglomeration, poor kinetics, and low thermal conductivity. Consequently, this review systematically categorizes hygroscopic salts embedded in porous host matrices, including zeolite-based materials, silica gel, carbon-based composites, minerals, metalu2013organic frameworks (MOFs), and mixed-salt composites. These findings highlight that high-conductivity carbon-based materials are utilized to enhance heat transfer, and that MOFs and zeolite 13X can improve sorption performance. Composite materials are analyzed to prevent agglomeration, enhance cyclic efficiency, and increase energy density. Additionally, binary salts confined within porous matrices exhibit notable synergistic effects on overall performance. Finally, the review discusses current limitations and suggests future research directions for developing suitable materialu2013adsorbate pairs.

Addressing the stability issues of gas film floating ring seals under high-temperature, high-pressure, and vibrational conditions, where conventional floating rings fall short, three novel microtexture configurations are proposed: convergent, stepped, and rectangular shallow grooves. Dynamic characteristic governing equations for microtextured floating ring seals were established based on the perturbation method. A comprehensive parametric study was performed for different microtextured seals, and the influence mechanisms of various microtextures on gas film pressure distribution, stiffness, and damping characteristics were systematically investigated, revealing the underlying principles affecting seal dynamics. The research indicates that microtextures on the inner circumference of the floating ring significantly optimize pressure distribution and its gradients by enhancing the gas dynamic pressure effect. Specifically, compared with the conventional structure, the convergent microstructure reduces the leakage rate by 8.98% and increases stiffness by 5.00 times by suppressing fluid flow through a gradually narrowing gap; the stepped microstructure utilizes flow separation to generate vortices, achieving a 7.23% reduction in leakage rate and a 3.67-fold increase in stiffness; the rectangular shallow groove creates localized high-pressure zones, resulting in a 15.12% decrease in leakage rate and a 6.18-fold improvement in stiffness. All three microtextures regulate vortex motion, optimize local pressure distribution, and enhance energy dissipation, thus improving gas film flow characteristics. The proposed microstructural floating-ring gas film model is well validated by experimental data, showing a maximum discrepancy of 17.03% in the leakage rate. Furthermore, the developed solution effectively suppresses gas film instability, leading to remarkable improvements in the steady-state performance and dynamic stability of the sealing system. This work thus provides a novel theoretical framework and paves a robust technical pathway for the design of high-performance seals in extreme operating conditions.

Double yielding is a typical tensile response of semi-crystalline polymers (SCPs), reflecting the coupled evolution of amorphous and crystalline phases. In this work, the double yielding behavior of metallocene-catalyzed linear low-density polyethylene (mLLDPE) is examined through polarized optical microscopy (POM), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and tensile tests. Owing to its multiple short-chain branches, mLLDPE exhibits a broad lamellar thickness distribution that governs the emergence of double yielding. Combined DSC-XRD analysis further confirms lamellar fragmentation, melting, and recrystallization during deformation. DSC peak deconvolution quantitatively distinguishes high- and low-stability crystalline domains, clarifying their sequential transformation during the two yielding events. A three-network model (TNM) is adopted to describe amorphous yielding, lamellar failure, and rubber-like chain deformation. Finite-element simulations reproduce the double yielding behavior of mLLDPE specimens (NRMSE < 3%). Both yield stresses decrease linearly with temperature (R-2 > 0.99) and follow the Ree-Eyring relation with strain rate (R-2 > 0.94). These results deepen the understanding of structure-deformation relationships in SCPs and offer a quantitative foundation for tailoring polymer microstructures to achieve targeted mechanical performance in engineering applications.

Thermochemical heat storage (TCHS) has emerged as one of the most promising long-term heat-energy storage technologies due to its high theoretical energy density and negligible heat loss during storage, making it compatible with renewable energy sources. Among sorption-based TCHS materials, salt hydrates with water vapor as the adsorbate pair are widely used due to their high hydration energy, availability, and low cost, and they require no intermediate or complicated synthesis methods. However, in practice, they remain inappropriate due to slow hydration kinetics, agglomeration, poor thermal conductivity, and structural instability during cyclic operation. Recently, many advanced TCHS matrices have been developed to address these limitations. The super-ultra-high and tunable porosity of Metal–Organic Frameworks (MOFs) and the thermally conductive 2D delaminates of MXenes provide a substantial opportunity to overcome the limitations of hydrate salts in terms of potential energy density. MOFs exhibit strong adsorption affinity through highly tunable pore architectures, whereas MXenes provide rapid heat-transport pathways and hydrophilicity through functional units like –OH, –O, etc. This mini-review provided a comprehensive overview of the synergistic effects of the MOF/MXene hybrid matrix, highlighting the combined effects of both constituents on enhanced heat storage capacity, reaction kinetics, and heat transport, as well as major practical limitations toward industrial-level application.

In this study, a steam ejector is introduced before the reactor along the desorption flow path, and also a mechanical compression unit is used along the sorption vapor flow path in the reactor line path to pressurize the vapor in a conventional thermochemical heat storage (TCHS) system. The main goal was to increase the useful output heat and overall performance of the system relative to the conventional operating condition using anhydrous salts Al2(SO4)3, NH4Al(SO4)2, and KAl(SO4)2. The analysis was carried out using a mathematical model with respect to compression ratio, compression output temperature, and charging temperature. The analysis result shows that the useful output heat of hydration and coefficient of performance (COP) significantly increase when the compression ratio increases for all the materials used in this analysis. The useful output heat, or heat released during hydration, increased from 719.67 kJ to 822.33 kJ, 621.94 kJ-724.57 kJ, and 590.66 kJ-684.65 kJ for the hydrating of the materials Al2(SO4)3, NH4Al(SO4)2, and KAl(SO4)2, respectively. Similarly, the COP for hydration materials, Al2(SO4)3, NH4Al(SO4)2, and KAl(SO4)2 at the specified working conditions increased 14.26%, 16.501%, and 15.91%, respectively. However, the useful heat output linearly decreases with increasing charging temperature. The results show a significant improvement in hydration heat and total COP. Therefore, introducing an optimal compression pressurizing unit in a TCHS system can improve the performance of the system as well as conciliation with the heat demand of end users. The annual base-levelized energy storage cost analysis showed that the system with compression units is more feasible than the system working without a vapor compression unit and mechanical compression equipment. The system working using Al2(SO4)3, NH4Al(SO4)2, and KAl(SO4)2 without compression units showed 14.28%, 22.48%, and 15.94% levelized storage cost (LCOS), respectively.

Heat energy is released during the reversible chemical reaction of the thermochemical heat energy storage (TCHS) system. Thermochemical heat energy uses an anhydrous salt and water vapor, releasing heat as water vapor molecules are absorbed by the anhydrous salt particles, forming a hydrated salt. The amount of heat energy released is proportional to the amount of sorbate that could be absorbed. Therefore, materials suitable for thermochemical heat storage systems are porous and highly thermally conductive to rapidly transfer the heat generated. Today, researchers and scientists are eagerly working to develop novel materials for the system to overcome the limitations of commonly used materials that hinder achieving higher performance. Thus, this review provides a comprehensive review of the methods and materials for high-performance thermochemical heat storage systems. It includes methods ranging from simple mechanical and physical mixing and blending to melt mixing, impregnation, foaming, electrospinning of composite polymers and nanofiber materials, and stabilized cyclic degradation, along with the corresponding results. The fillet materials described are also carbon-based, metallic, and MXene composites, which enhance thermal conductivity, while composite nanofibers, metal-organic frameworks (MOFs), alumina, silica, and zeolite enhance sorption capacity, owing to their high porous surface area-to-volume ratios. It is concluded that materials with optimized porous structures, cyclic stability, and improved heat transfer can be effective for the TCHS system when suitable methods are employed and chemically compatible materials are used.

This study focused on developing a composite structure that utilizes thin film metamaterials to realize lowfrequency (0.1-1 kHz) underwater sound-absorbing. The sound-absorbing performance of the composite structure was assessed by investigating the effects of thin film materials, thickness, and mass block distribution using a combined approach of numerical simulation and experimentation. Results demonstrated that thin film metamaterials with lower modulus, such as silicon rubber (SR) thin film, have lower natural frequencies. In addition, a thicker SR film had a higher elastic strain energy density. Symmetrical mass block distribution was able to widen the absorbing bandwidth of the first three natural frequencies: improvements of 6 Hz, 2.8 Hz and 2.6 Hz were observed, respectively. Acoustic sample was fabricated and tested to verify the accuracy of numerical simulation. This study provided new insights into designing underwater sound-absorbing structures containing thin film metamaterials and supported the development of better stealth capabilities for underwater vehicles, especially in the context of low-frequency active sonar.

This study addresses challenges in developing high-performance flexible pressure sensors by innovating material composition and microstructure design. Using PDMS as a substrate with carbon fiber and graphene fillers, the team fabricated piezoresistive materials via space-limited assembly. A femtosecond laser etched grooves and columnar microstructures onto the surface, enhancing sensor performance. The microstructures, smaller than carbon fibers, localized graphene in piezoresistive regions, boosting sensitivity, while carbon fibers formed a conductive network elsewhere. Testing revealed that reducing piezoresistive material thickness significantly improved sensitivity: a 0.1 mm layer achieved 1.36 kPa-1, 74% higher than 0.2 mm. Optimizing microstructure geometry enhanced performance: a 0.3 mm pillar-array sensor achieved 1.87 kPa-1 sensitivity (vs. 1.11 kPa-1 for grooves and 0.62 kPa-1 for non-structured), with 0.998 linearity. The spatial confinement assembly enabled localized graphene distribution in piezoresistive regions, amplifying stress concentration effects. These results highlight that thinner materials and tailored microstructures amplify sensitivity and linearity by concentrating stress and homogenizing conductive pathways. The findings demonstrate a viable strategy for creating high-precision, flexible pressure sensors, advancing applications in health monitoring and wearable technology through improved electromechanical coupling and structural design.

Double yielding, a distinctive tensile behavior of semicrystalline polymers (SCPs), was investigated in metallocene-catalyzed linear low-density polyethylene (mLLDPE) with narrow molecular weight distribution and uniform short-chain branching. During tension, the dumbbell specimens underwent four stages-quasi-linear elasticity, first yield and softening, second yield and softening, and rubber-like deformation-where the surface deformation evolved from nearly uniform strain to localized necking, accompanied by surface temperature rise and self-heating. Digital image correlation (DIC) and infrared thermography revealed pronounced strain localization during the second yield, with local strain exceeding 600% and similar to 2 degrees C heating under near-adiabatic conditions. Yield stresses exhibited temperature and strain-rate dependencies consistent with linear and Ree-Eyring models, while modulus and hardening-softening coefficients varied systematically with external conditions. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and -ray diffraction (XRD) were employed to characterize the surface morphology and crystallinity evolution at various tensile stages, thereby elucidating the deformation mechanism underlying the double-yielding behavior. A novel application of DSC peak deconvolution quantitatively distinguished high- and low-stability crystalline domains, elucidating their sequential transformation during double yielding. These results provide quantitative evidence linking crystalline heterogeneity to the mechanical response of mLLDPE and offer a basis for performance optimization in SCPs.

The double yielding phenomenon of homopolymer polypropylene (H-PP) is reported for the first time, along with a systematic investigation of PP/CaCO3 composites. The tensile deformation process is divided into four stages, with double yielding occurring in stages II and III. Differential scanning calorimetry (DSC), polarized light microscopy (PLM), scanning electron microscopy (SEM), and thermal infrared imaging indicate that CaCO3's effect is filler content dependent: an appropriate filler content (10%) induces beta-crystal formation that promotes uniform deformation, whereas high levels (20%) lead to particle agglomeration and premature second yielding. A mechanism involving two synergistic plastic processes, namely intraspherical and interspherical deformation, is proposed. In HPP, the first yield is governed by amorphous phase deformation and the second by- alpha-crystal transformation, while in PP/CaCO3 composites, interspherical deformation drives the first yield and loose beta crystals yield before necking, delaying the- alpha-crystal-dominated second yield. Quantitative analysis using the Ree-Eyring, linear, and quadratic regression models provides key insights into yield stress, local temperature rise, softening slopes, and stress drops, offering a scientific basis for optimizing these composites in high-performance engineering applications.

This paper investigates comprehensively the operational dynamics of a thermochemical heat storage (TCHS) reactor for low-temperature applications using polyaluminum sulfate and takes into consideration a developed simulation model with an experimentation validation. Significant concordances were found between the developed simulation model and the experimental results. Results reveal optimized conditions for the charging process using an electrical heater, with a heating temperature of 120 degrees C at 10 K/min over 500 minutes. This achieves full material charging, with stabilized pressure drops at an equilibrium of 80 mbar, corresponding to a temperature of approximately 108 degrees C, and yielding a thermal power of 950 W. An inlet vapor pressure of 18 mbar at 10 degrees C for 5 hours is sufficient to completely discharge the bed, with pressure drops reaching around 30 mbar and a thermal power of 300 after reaction completion. Insights into conversion extents during both processes are provided, along with a remarkable thermal efficiency of 90% and a coefficient of performance (COP) of 97%, surpassing recommended theoretical values (50%). The study suggests further enhancing system performance through the design and implementation of a dedicated heat exchanger. The achievement of 75% of the targeted thermal power specification represents a significant milestone, offering valuable contributions towards the realization of sustainable technological advancements of both the reactor technology of TCHS and state-of-the-art thermal energy storage solutions. From the research, it is possible to infer further suggestions for enhancing this performance by designing and implementing a dedicated heat exchanger for both heat supply and retrieval mechanisms.

Polymer Science: Peer Review Journal Rheological Properties of Low-Density Polyethylene/Random Copolymer- Polypropylene Fan Zepeng, Wang Kejian*, Li Sihan, Lou Zihao and Wang Zhiwei College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, China *Corresponding author:Wang Kejian, College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, China Submission: March 14, 2023;Published: April 05, 2023 DOI: 10.31031/PSPRJ.2023.04.000598 ISSN: 2770-6613 Volume4 Issue5

Underwater vessels face significant challenges as the high hydrostatic pressure of deep water affects their stealth performance. Linear models may not accurately depict the deformation of structures under hydrostatic pressure due to its non-linear properties of rubber and therefore, influence the results. This study utilized uniaxial tension and compression test data of styrene-butadiene rubber to fit four constitutive models and the optimal was selected to calculate the sound-absorbing performance under hydrostatic pressures,. Results showed that the Yeoh model fitted by uniaxial compression with r2 of 0.9928. Viscous losing, waveform conversion and locally resonance are main sound-absorbing mechanisms. The maximum sound-absorbing coefficient of structure at 0 MPa is 0.8914 at 7.6 kHz and the sound-absorbing performance mostly decreases with increasing hydrostatic pressure, Maximum reduction of 32 % was achieved at 3.2 kHz. Experiments verified the accuracy of simulation results, and the mean relative errors between the simulated results and the experimental results are 15.28 % (0 MPa), 16.91(0.5 MPa) %, 16.67 % (1 MPa) and 16.38 % (2 MPa), respectively. These findings can provide guidance for development of underwater sound-absorbing structures in hydrostatic pressure conditions.

In recent years, there has been a growing interest in changes in dynamic mechanical properties of mixed rubber during dynamic shear, yet the influence of vulcanized characteristics on the dynamic shear behavior of vulcanized rubber, particularly the effect of cross-linking density, has received little attention. This study focuses on styrene–butadiene rubber (SBR) and aims to investigate the impact of different cross-linking densities (Dc) on dynamic shear behavior using molecular dynamics (MD) simulations. The results reveal a remarkable Payne effect, where the storage modulus experiences a significant drop when the strain amplitude (γ0) exceeds 0.1, which can be attributed to the fracture of the polymer bond and the decrease in the molecular chain’s flexibility. The influence of various Dc values mainly resides at the level of molecular aggregation in the system, where higher Dc values impede molecular chain motion and lead to an increase in the storage modulus of SBR. The MD simulation results are verified through comparisons with existing literature.

采用单螺杆挤出机将CaCO3与高密度聚乙烯(HDPE)混合挤出造粒,制备了不同的HDPE/CaCO3拉伸样条,通过静态拉伸试验表征了拉伸速率(2、5、10、50、100 mm/min)和CaCO3质量分数(10％、20％、30％)对材料拉伸性能的影响.研究表明,随着CaCO3含量的增加,材料的弹性模量增加,屈服强度降低,断裂伸长率及断裂功降低.对于同一种HDPE/CaCO3材料,随着拉伸速率的增加,材料的弹性模量及屈服强度明显增加,断裂伸长率及断裂功降低.采用Eyring模型定量地描述了应变速率对拉伸强度和弹性模量的敏感程度,当应变速率大于0.001 5 s-1时,材料弹性模量和屈服强度的测试结果逐渐稳定.

本文介绍了连续碳纤维增强热塑性树脂基复合材料的回收技术,展示了连续碳纤维增强聚苯硫醚复合材料板件采用热变形进行再制造为球冠形制品的回收方法,指出褶皱和分层需要解决的关键问题.