A Comprehensive Review on the Thermal Stability Assessment of Polymers and Composites for Aeronautics and Space Applications

Production of Graphite Nanoplatelets via Functionalized Polyketone-Assisted Diels-Alder Chemistry: Evidence of Reduced Layer Thickness and Enhanced Exfoliation Efficiency

This study introduces an efficient and scalable method for the top-down exfoliation of graphite into graphite nanoplatelets (GNPs) using polyketones (PKs) functionalized with Diels-Alder (DA) active groups. Leveraging the reversible covalent interactions facilitated by furan and thiophene moieties in PK, combined with melt-mixing and shear force, this process achieves significant exfoliation while preserving the structural integrity of the resulting material. Thermal and rheological analyses demonstrate enhanced interfacial adhesion and stability within polymer composites attributed to the DA-driven interactions between functionalized PK and graphite. Comparative evaluations demonstrate that furan-functionalized PK exhibits superior exfoliation efficiency, highlighting its potential for producing high-quality exfoliated graphite suitable for advanced nanocomposite applications that require enhanced thermal, mechanical, and electrical properties. This method seamlessly integrates sustainability with industrial scalability, offering significant advancements in developing GNP-based materials.

Advances in Toughening Modification Methods for Epoxy Resins: A Comprehensive Review

This work provides a comprehensive review of the recent advancements in the toughening modification methods for epoxy resins. The study explores a variety of approaches, including the incorporation of liquid rubbers, core-shell rubber particles, thermoplastic resins, hyperbranched polymers, and the nanoparticle toughening method, each of which contributes to improving the mechanical properties and fracture toughness of epoxy resins. Special attention is given to the mechanisms underlying these toughening methods, such as reaction-induced phase separation, crack pinning, and energy dissipation through particle deformation. The paper also examines the synergistic effects achieved by combining different toughening agents, such as phenoxy thermoplastic rubber and core-shell rubber particles, which significantly enhance the critical fracture energy and impact strength of epoxy composites. Additionally, the challenges associated with each method, such as the potential reduction in mechanical properties and the influence of phase separation on material performance, are discussed. Through a detailed analysis of experimental studies, this paper highlights the effectiveness of various toughening strategies and suggests future research directions aimed at further optimizing epoxy resin toughening techniques for diverse industrial applications. Emerging computational modeling and machine learning applications in epoxy resin development are also systematically reviewed to highlight their potential in advancing predictive design frameworks.

Development of PMMA composites with tungsten trioxide for improved gamma radiation shielding in microsatellites

Satellites are exposed to various types of radiation and extreme temperatures in space, which can lead to damage and malfunctioning of critical components. Therefore, the use of an efficient shielding system is essential for ensuring the longevity and performance of satellites. In the ever-evolving landscape of space exploration, the demand for resilient and efficient materials to safeguard the delicate internal components of microsatellites has never been more critical. This work investigated the gamma-ray shielding performance, and the physical and mechanical properties of poly (methyl methacrylate) (PMMA) composites embedded with 0-50 wt% tungsten trioxide (WO3). The results showed that the addition of WO3 had significantly improved the gamma shielding ability of PMMA composites. Linear attenuation coefficient and half-value layer were examined using three gamma sources (Cs-137, Ba-133, and Co-60).

Mechanical, Thermal, and Flammability Properties of Eco-Friendly Nanocomposites from Recycled PET/PA-11 Blends Reinforced with Graphene Nanoplatelets

This study investigates the development of sustainable nanocomposites using recycled polyethylene terephthalate (RPET) and polyamide 11 (PA-11) blends reinforced with graphene nanoplatelets (GNPs). RPET/PA-11 blends were compatibilized with 2 phr Joncryl® and processed using melt blending followed by injection moulding. The effects of varying GNP contents (1-4 phr) on mechanical, thermal, and flame-retardant properties were analysed. The nanocomposite with 1 phr GNPs exhibited an optimal balance of mechanical, flame-retardant, and thermal properties, along with improved dispersion compared to higher GNP loadings. Higher GNP concentrations led to increased stiffness but also promoted agglomeration, which negatively impacted tensile and impact strength. Thermal analysis revealed that GNPs influenced the cold crystallization behaviour of RPET, while the TGA results indicated a moderate enhancement in thermal stability. The maximum degradation temperature (Tmax) increased from 410.38 °C to 430.06 °C with 1 phr GNPs but declined at higher loadings. Similarly, flammability tests showed an improvement in the limiting oxygen index (LOI) from 19 to 24. Morphological analysis confirmed that GNPs facilitated PA-11 dispersion within the RPET matrix, particularly at lower GNP concentrations (1 phr). These findings highlight the potential of RPET/PA-11/GNP nanocomposites for multifunctional applications, providing an optimal balance between mechanical performance, thermal stability, and flame resistance. This research highlights the synergistic effect of GNPs in achieving sustainable, high-performance materials, addressing the challenges of plastic waste management and the need for eco-friendly engineering solutions for industries such as automotive, packaging, and construction.

Rational Design of Nanostructured Porous and Advanced Getter Materials for Vacuum Insulation Panels

Vacuum insulation panels (VIPs) have emerged as a cutting-edge strategy for achieving superior thermal insulation across a wide range of applications, including refrigerators, cold-chain transportation and building envelopes. The key factor for the exceptional performance of VIPs is maintaining an ultralow pressure environment within the panels, which is crucial for minimizing heat transfer. However, the presence of non-condensable gases can compromise the vacuum state, leading to a reduced insulation effectiveness during a panel's service life. This review offers a comprehensive analysis of getter materials used in VIPs, focusing on their fundamental properties, types, integration techniques and performance characteristics, further emphasizing the challenges and potential directions for the development of getter materials. Overall, this review intends to provide novel insights into the development of getter materials for use in VIPs, offering essential viewpoints to aid future studies on this topic.

Sustainable and biocompatible hybrid materials-based sulfated polysaccharides for biomedical applications: a review

Sustainable biomaterials that are both efficient and environmentally friendly are the subject of research and development efforts among scientists and academics from a variety of contemporary scientific disciplines. Due to their significant involvement in several physiological and pathological processes, sulfated polysaccharides (SPs) have garnered growing interest across various application domains, including biomedicine. Nevertheless, mechanical and thermal stability are issues for unmodified polysaccharide materials. Interactions between polymers, such as the mixing of biopolymers with synthetic or biopolymers through chemical interaction or grafting into the main chain structure of raw materials to enhance their therapeutic effects, are essential to meet the high standards of biomedical features. Another way to improve the mechanical and thermal properties is to graft appropriate fillers onto the polysaccharide backbone. The characteristics of polysaccharide bio-nanocomposites in comparison to more traditional polymers have attracted a lot of interest. With an emphasis on anti-inflammatory, anticancer, antiviral, immunoregulatory, and anticoagulant properties, this review delves into the most recent biological uses of sulfated polysaccharides. As well as thoroughly outlining the factors that impact the biological properties, such as the extraction process, molecular weight (Mw), the degree of sulfation, distribution/position, modification procedures, and the filler size, etc., this review aims to: (1) provide a systematic and critical overview of the cutting-edge research on SPs and hybrid sulfated polysaccharide bio-nanocomposites; (2) identify the key factors, mechanisms, methods, and challenges impacting SPs bio-nanocomposites; (3) elucidate the current and potential biomedical applications, advantages, manufacturing challenges, and opportunities associated with SPs bio-nanocomposites; (4) offer insights into future research directions by suggesting improvements for bio-nanocomposites, including novel materials, and advanced processing techniques.

Photoinduced Birefringence and Liquid Crystal Orientation on Polymers with Different Azobenzene Content in the Main Chain

In this paper, we give an overview of novel main-chain azobenzene-based fluorinated poly(arylene ether)s with different content of azo groups, aiming at providing a better understanding of the link between a number of N═N bonds and the macroscopic response of the material. We discuss chemical synthesis and molecular structure and report on a comprehensive analysis of the polymer properties, thermal behavior, and mechanical strength. We show that a higher content of azobenzene moieties reduces the mechanical strength of the polymer materials. On the other hand, polymers with a higher content of azobenzene demonstrate higher values of induced birefringence due to a larger number of azobenzene in the trans form. The photoisomerization constants of all polymers fall within a very close range. The minor variations are attributed to the number of azobenzene groups in the polymer composition and the conformational arrangements of the polymer chain packing. The developed light-sensitive polymers were employed for dynamic control and manipulation of the liquid crystal orientation by polarization of the incident light. After the double irradiation of the substrates using appropriate photomasks, we made patterned cells that consist of domains with different high-resolution liquid crystal director orientations.

Mechanisms of Atomic Oxygen Erosion in Fluorinated Polyimides Investigated by Molecular Dynamics Simulations

Traditional polyimides have highly conjugated structures, causing significant coloration under visible light. Fluorinated colorless polyimides, known for their light weight and excellent optical properties, are considered ideal for future aerospace optical lenses. However, their lifespan in low Earth orbit is severely limited by high-density atomic oxygen (AO) erosion, and the degradation behavior of fluorinated polyimides under AO exposure is not well understood. This study uses reactive molecular dynamics simulations to model two fluorinated polyimides, PMDA-TFMB and 6FDA-TFMB, with different fluorine contents, to explore their degradation mechanisms under varying AO concentrations. The results indicate that 6FDA-TFMB has slightly better resistance to erosion than PMDA-TFMB, mainly due to the enhanced chemical stability from its -CF3 groups. As AO concentration increases, widespread degradation of the polyimides occurs, with AO-induced cleavage and temperature-driven pyrolysis happening simultaneously, producing CO and OH as the main degradation products. This study uncovers the molecular-level degradation mechanisms of fluorinated polyimides, offering new insights for the design of AO erosion protection systems.

A Comprehensive Exploration of Contemporary Photonic Devices in Space Exploration: A Review

Photonics plays a pivotal role in propelling space exploration forward, providing innovative solutions to address the challenges presented by the unforgiving and expansive realm of outer space. Photonic-based devices, encompassing technologies such as lasers, optical fibers, and photodetectors, are instrumental in various aspects of space missions. A notable application is in communication systems, where optical communication facilitates high-speed data transfer, ensuring efficient transmission of information across vast interplanetary distances. This comprehensive review unveils a selection of the most extensively employed photonic devices within the realm of space exploration.

Thermal Weathering of 3D-Printed Lunar Regolith Simulant Composites

The production of lunar regolith composites is a promising venture, especially when enabled by extrusion-based additive manufacturing techniques such as direct ink write. However, both three-dimensional (3D) printing production and usage of polymer composites containing regolish on the lunar surface are challenges due to harsh environmental conditions such as severe thermal cycling. While thermal degradation in polymer composites under thermal cycling has been studied, there is limited understanding of how polymer properties impact the mechanical performance of lunar regolith composites when both printing and usage are carried out under extreme thermal conditions. Here, we aim to bridge that gap through the creation of composites containing a lunar Highlands regolith simulant suspended in an ultraviolet (UV) curable binder, which were printed at -30 °C and thermally cycled between weekly lunar day (127 °C) and weekly night (-190 °C) temperatures. We validate that thermal stresses cause both physical and chemical degradation since the regolith simulant composites become stiffer, more porous, and show yellowing after exposure to thermal cycling. Moreover, we indicate that chemical degradation mechanisms seem to compete with residual polymerization in certain formulations. We attribute this phenomenon to partial crystallization of monomer species during printing at -30 °C, resulting in low vinyl bond conversion during initial curing. The results presented here shed light on the intricate interplay between thermal stresses, uncured polymer properties, and degradation mechanisms, which can help guide future use cases of regolith composites for lunar infrastructure needs.

Bio-Composite Films Based on Carboxymethyl Chitosan Incorporated with Calcium Oxide: Synthesis and Antimicrobial Activity

The utilization of biopolymers incorporated with antimicrobial agents is extremely interesting in the development of environmentally friendly functional materials for food packaging and other applications. In this study, the effect of calcium oxide (CaO) on the morphological, mechanical, thermal, and hydrophilic properties as well as the antimicrobial activity of carboxymethyl chitosan (CMCH) bio-composite films was investigated. The CMCH was synthesized from shrimp chitosan through carboxymethylation, whereas the CaO was synthesized via a co-precipitation method with polyethylene glycol as a stabilizer. The CMCH-CaO bio-composite films were prepared by the addition of synthesized CaO into the synthesized CMCH using a facile solution casting method. As confirmed by XRD and SEM, the synthesized CaO has a cubic shape, with an average crystalline size of 25.84 nm. The synthesized CaO exhibited excellent antimicrobial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) (>99.9% R). The addition of CaO into CMCH improved the mechanical and hydrophobic properties of the CMCH-CaO films. However, it resulted in a slight decrease in thermal stability. Notably, the CMCH-CaO10% films exhibited exceptional antimicrobial activity against E. coli (98.8% R) and S. aureus (91.8% R). As a result, such bio-composite films can be applied as an active packaging material for fruit, vegetable, or meat products.

Thermal Conductive Polymer Composites: Recent Progress and Applications

As microelectronics technology advances towards miniaturization and higher integration, the imperative for developing high-performance thermal management materials has escalated. Thermal conductive polymer composites (TCPCs), which leverage the benefits of polymer matrices and the unique effects of nano-enhancers, are gaining focus as solutions to overheating due to their low density, ease of processing, and cost-effectiveness. However, these materials often face challenges such as thermal conductivities that are lower than expected, limiting their application in high-performance electronic devices. Despite these issues, TCPCs continue to demonstrate broad potential across various industrial sectors. This review comprehensively presents the progress in this field, detailing the mechanisms of thermal conductivity (TC) in these composites and discussing factors that influence thermal performance, such as the intrinsic properties of polymers, interfacial thermal resistance, and the thermal properties of fillers. Additionally, it categorizes and summarizes methods to enhance the TC of polymer composites. The review also highlights the applications of these materials in emerging areas such as flexible electronic devices, personal thermal management, and aerospace. Ultimately, by analyzing current challenges and opportunities, this review provides clear directions for future research and development.

The Impact of ZnO Nanofillers on the Mechanical and Anti-Corrosion Performances of Epoxy Composites

Epoxy resins were reinforced with different ZnO nanofillers (commercial ZnO nanoparticles (ZnO NPs), recycled ZnO and functionalized ZnO NPs) in order to obtain ZnO-epoxy composites with suitable mechanical properties, high adhesion strength, and good resistance to corrosion. The final properties of ZnO-epoxy composites depend on several factors, such as the type and contents of nanofillers, the epoxy resin type, curing agent, and preparation methods. This paper aims to review the preparation methods, mechanical and anti-corrosion performance, and applications of ZnO-epoxy composites. The epoxy-ZnO composites are demonstrated to be valuable materials for a wide range of applications, including the development of anti-corrosion and UV-protective coatings, for adhesives and the chemical industry, or for use in building materials or electronics.

A Numerical Model to Predict the Relaxation Phenomena in Thermoset Polymers and Their Effects on Residual Stress during Curing, Part II: Numerical Evaluation of Residual Stress

This article proposes a numerical routine to predict the residual stresses developing in an epoxy component during its curing. The scaling of viscoelastic properties with the temperature and the degree of conversion is modeled, adopting a mathematical formulation that considers the concurrent effects of curing and structural relaxation on the epoxy's viscoelastic relaxation time. The procedure comprises two moduli: at first, the thermal-kinetical problem is solved using the thermal module of Ansys and a homemade routine written in APDL, then the results in terms of temperature and the degree of conversion profiles are used to evaluate the viscoelastic functions, and the structural problem is solved in the mechanical module of Ansys, allowing the residual stresses calculation. The results show that the residual stresses mainly arise during cooling and scale with the logarithm of the Biot number.

Simulation and Experimental Study of the Isothermal Thermogravimetric Analysis and the Apparent Alterations of the Thermal Stability of Composite Polymers

Composite polymers are an interesting class of materials with a wide range of applications. Among the properties of polymers which are currently being enhanced via the development of composite materials is their thermal stability, which is typically evaluated via thermogravimetric analysis (TGA). In this work, a paradox is recognized regarding the considered relationship between the polymer-filler interactions leading to a good dispersion of the filler and the improvement of thermal stability. Simulation of the TGA signal during isothermal measurements of composite polymers is performed along with experimental measurements. It is shown that there are at least three factors that can cause apparent alterations of the thermal stability of composite polymers, namely, the different buoyancy due to the different densities of the composites and the neat polymer, the different thermal diffusivity of the composites and the fact that the mass loss (or remaining mass) of the composites, conventionally, is expressed per overall mass of the composite and not per mass of polymer. The relative contributions of these factors are evaluated and it is found that the conventional expression of mass loss has the most profound effect. Furthermore, it is shown that it is proper to express and evaluate the TGA results of composite polymers per degradable (polymer) mass of the composite and not per overall mass of the composite.

Nanostructured Poly-l-lactide and Polyglycerol Adipate Carriers for the Encapsulation of Usnic Acid: A Promising Approach for Hepatoprotection

The present study investigates the utilization of nanoparticles based on poly-l-lactide (PLLA) and polyglycerol adipate (PGA), alone and blended, for the encapsulation of usnic acid (UA), a potent natural compound with various therapeutic properties including antimicrobial and anticancer activities. The development of these carriers offers an innovative approach to overcome the challenges associated with usnic acid's limited aqueous solubility, bioavailability, and hepatotoxicity. The nanosystems were characterized according to their physicochemical properties (among others, size, zeta potential, thermal properties), apparent aqueous solubility, and in vitro cytotoxicity. Interestingly, the nanocarrier obtained with the PLLA-PGA 50/50 weight ratio blend showed both the lowest size and the highest UA apparent solubility as well as the ability to decrease UA cytotoxicity towards human hepatocytes (HepG2 cells). This research opens new avenues for the effective utilization of these highly degradable and biocompatible PLLA-PGA blends as nanocarriers for reducing the cytotoxicity of usnic acid.

Recent Advances and Challenges in Polymer-Based Materials for Space Radiation Shielding

Space exploration requires the use of suitable materials to protect astronauts and structures from the hazardous effects of radiation, in particular, ionizing radiation, which is ubiquitous in the hostile space environment. In this scenario, polymer-based materials and composites play a crucial role in achieving effective radiation shielding while providing low-weight and tailored mechanical properties to spacecraft components. This work provides an overview of the latest developments and challenges in polymer-based materials designed for radiation-shielding applications in space. Recent advances in terms of both experimental and numerical studies are discussed. Different approaches to enhancing the radiation-shielding performance are reported, such as integrating various types of nanofillers within polymer matrices and optimizing the materials design. Furthermore, this review explores the challenges in developing multifunctional materials that are able to provide radiation protection. By summarizing the state-of-the-art research and identifying emerging trends, this review aims to contribute to the ongoing efforts to identify polymer materials and composites that are most useful to protect human health and spacecraft performance in the harsh radiation conditions that are typically found during missions in space.