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Energy efficient buildings, propulsion components and thermal protection systems require materials with high thermal protective properties. Traditional polymer composites or ceramic materials have limited comprehensive applications because of their poor thermal protective properties or poor processability. Herein, a novel fire resistant and thermally insulating polymer/ceramic hybrid ceramifiable composite was developed based on low temperature sintering principle and foaming on fire strategy. Specifically, the influences of raw materials of low temperature ceramics, such as glass frit, phosphate, etc, on the properties of ceramifiable ethylene-vinyl acetate (EVA) composites were investigated. Its fire resistance and thermal insulation properties were evaluated by simulating different sintering environments. The results show that the ceramifiable composite exhibits the highest improvement in fire resistance because a crystalline phase was formed at high temperatures. Gas evolution from the thermal decomposition of ammonium polyphosphate (APP) and EVA contributes to the formation of the porous structure in ceramic residues. The optimal system can resist above 1000 °C flame for 30 min without disintegration, and the temperature of the unfired side was maintained around 200 °C. The reliability of the strategy was verified by the effective medium theory model. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, a type of red mud/slag-based cenospheres/geopolymer foam was directly fabricated using the direct foaming method at room temperature. The effects of high-temperature exposure (700–1100 °C) on the phase evolution, pore structure, and properties of the foams were investigated. The results showed that the untreated foam was amorphous structure. The porosity of the foams increased from 36.4 ± 0.6% (1 wt%) to 71.9 ± 0.1% (5 wt%) with the addition of H 2 O 2. The compressive strength of the foams was 1.20–18.15 MPa, which was attributed to the good bond between the cenospheres and red mud/slag-based geopolymer matrix, the fractured spheres, and the crack deflection. After this high-temperature exposure, the foam crystallized mainly into the leucite and mullite phases. The density and compressive strength of the foams decreased as the exposure temperature increased. The thermal conductivity of the foams reached the lowest value of 0.169 W/(m⋅K) and 0.108 W/(m⋅K) with 5 wt% H 2 O 2 before and after the exposure, respectively. These foams have demonstrated good potential for application in the building insulation field. [ABSTRACT FROM AUTHOR]

Thermal protection has always been an important issue in the energy, environment and aerospace fields. Porous ceramics produced by the particle-stabilized foaming method have become a competitive material for thermal protection because of their low density and low thermal conductivity. However, the study of porous ceramics for composite systems using particle-stabilized foaming method was relatively rare. Here, silica-alumina composite porous ceramics were prepared by particle-stabilized foaming method, which was achieved by tailoring the surface charges of silica and alumina through adjustment of the pH. Porous ceramics exhibited porosity as high as 97.49% and thermal conductivity (25 °C) as low as 0.063 W m−1 K−1. The compressive strength of porous ceramics sintered at 1500 °C with a solid content of 30 wt% could reach 0.765 MPa. Based on the light weight and excellent thermal insulation properties, the composite porous ceramic could be used as a potential thermal insulation material in the spacecraft industry. [ABSTRACT FROM AUTHOR]

[Display omitted] • Macro PPBESK beads with hierarchical pores are fabricated via NIPS approach. • PPBESK beads have a good thermal insulation property in a wide temperature window. • The compression modulus of PPBESK beads is more than 50 times higher than PS foam. • The performance can be controlled by the composition of the coagulation bath. Preparation of porous materials from high-performance polymers holds great promise for various advanced engineering applications like thermal insulation. However, it is still a great challenge to fabricate them due to the difficulties in manufacturing them. Herein, a high performance polymer material poly(aryl ether sulfone ketone)s containing phthalazinone and biphenyl moieties (PPBESK) was utilized to fabricate porous materials via a frequently used and simple method named non-solvent induced phase separation (NIPS). Macro porous PPBESK beads have been fabricated in different non-solvent coagulation baths. The kinetics of the phase inversion processes are visualized by the optical microscope. The multi-scale porous structures formed inside the beads endow them an excellent thermal insulation performance in a wide temperature window and a high mechanical performance that the compression modulus is more than 50 times higher than Polystyrene (PS) foam. Therefore, these PPBESK beads provide an optimized combination of functionalities including high mechanical strength and good thermal insulation, which could turn out to be useful in harsh environmental applications. [ABSTRACT FROM AUTHOR]

Materials with complex inner structure can be challenging to characterise in an effective way. The effective material parameters significantly depend on the structure, and thus on the interface properties. In the present paper, we focus on metal matrix syntactic foams, and we attempt to determine their effective thermal parameters. We supplement the results with their mechanical properties as well. For thermal characterisation, we use the heat pulse experiment to study their transient thermal response. We observed deviation from Fourier's law in multiple situations, and thus we propose an evaluation procedure for such experimental data using the Guyer–Krumhansl heat equation. We provide an iterative procedure to efficiently find the effective thermal diffusivity values provided by the Guyer–Krumhansl and Fourier equations based on the measured transient response. Furthermore, we studied the effective parameters, the specific heat, mass density, thermal conductivity and thermal diffusivity. We found that the standard estimations significantly overestimate the thermal conductivity. Furthermore, we propose a method for deducing a more reliable thermal diffusivity and thermal conductivity based on the transient temperature history, i.e., we propose to estimate Fourier's thermal diffusivity based on averaging the parameters of the Guyer-Krumhansl equation according to the observed diffusive time scales. We also found that for such metal matrix syntactic foams, even with knowing the constituents, the contact thermal resistance makes more challenging to provide a prior estimate for the effective thermal conductivity, but this difficulty can be resolved using proper effective thermal diffusivity values. • Proposing an iterative evaluation procedure for the Guyer-Krumhansl equation. • Determining the effective thermal parameters of metal matrix synthetic foams. • Correlating the Fourier and Guyer-Krumhansl parameters. • Comparing the effective thermal conductivity estimations to the measured one. [ABSTRACT FROM AUTHOR]

Most of the thermal characterization methods using a uniform heating of a surface (Guarded Hot Plate, Transient Hot Plate, Fluxmeter Method) assume 1D transfer in the measurement area and neglect the in-plane heat transfer in the heating element. This results in limitations regarding the time interval for estimation, the thickness of samples or the possibility of simultaneously measuring thermal conductivity and capacity. To overcome these limits, a new 3D transient analytical model suited to isotropic materials and taking into account the convective lateral heat losses on the periphery of the samples as well as the 3D heat transfers in the heating element has been developed. It is first presented and then validated by comparison with 3D numerical simulations carried out with COMSOL. A study of the reduced sensitivities of the measured temperature to the various parameters and parameters estimations carried out on simulations obtained with the 3D model enable us to define an optimal estimation process. Finally, transient hot plate experiments were carried out on five extruded polystyrene samples with thickness ranging from 9.1 mm to 49.8 mm and on samples of PVC foam, PVC and of the reference anisotropic material IRMM-440. The results validate the theoretical study with a deviation lower than 5% compared to the known values of the thermal conductivity for the isotropic materials when using the 3D model, while the deviation may reach 77% using the1D model for the thickest sample of extruded polystyrene. The deviation reaches 11% for the thermal conductivity of IRMM-440 showing the need for a model taking into account the anisotropy for this type of materials. • 1D heat transfer is most often assumed in thermal characterization methods using plane source. • Experimental devices to ensure a 1D heat transfer are complex. • A 3D analytical model is developed for transient plane source methods. • The accuracy of thermal properties estimation using this 3D model is demonstrated. [ABSTRACT FROM AUTHOR]

Graphene promises considerable application potentials in improving the thermal conductivity of polymeric composites due to its superior intrinsic thermal conductivity. However, the simple incorporation of graphene in polymeric composites usually fails to meet the requirements for simultaneously high thermal conductivity and electrical insulation. Herein, an epoxy-based composite with excellent thermal conductivity and electrical insulation has been produced by introducing a long-range ordered carbon/graphene/MgO ternary foam (CGMF) via surface modification and ice template method. The heat conduction shortcut provided by the vertically aligned structure of CGMF endows the composites with excellent thermal conductivity of 4.87 Wm−1K−1 (through-plane) at 12.96 vol% filler loading. Meanwhile, the barrier of MgO and PVA to the electron transmission in CGMF results in the composite with high surface electrical resistivity and volume electrical resistivity, which satisfies the requirement of electrical insulation. This work provides valuable insights into the fabrication of highly thermal conductive & electrically insulating composites. [ABSTRACT FROM AUTHOR]

Ultra-lightweight foam concrete (ULFC) is a relatively new construction material that has gained attention recently due to its unique properties. This material is not very heavy and low-density, making it easy to form into different shapes and sizes. Its excellent thermal insulation makes it popular for building walls, roofs, and floors. This review paper provides an in-depth examination of the properties and characteristics of ULFC. Its composition typically consists of cement, water, foam, additives, and the various manufacturing methods used to produce it—the mechanical properties of ULFC, including its compressive strength. The density of ULFC can vary greatly, usually falling between 100 and 600 kg/m3. The diversity of this can be affected by different factors, such as the kind and number of additives applied and the methods of foaming and thickening employed. The paper highlights the various applications of ULFC in the construction industry. Its use is as a TC material, which can help reduce heating and cooling costs; as a structural material, it can help reduce dead loads of structures. The review paper also discusses the challenges associated with ULFC production, including foam stability. Foam insulation concrete emits 302–508 kg CO 2 per cubic meter, primarily due to Portland cement, but enhances building energy efficiency, reducing household CO 2 emissions, while advanced recycled insulation materials offer superior thermal and acoustic properties with lower environmental impact. Additionally, we examine the current research on ULFC and suggest potential avenues for future investigation. This paper aims to introduce and put forward a range of cutting-edge and original recommendations and informative guidelines, with the ultimate objective of directing and shaping future research endeavors that focus on effectively exploiting and utilizing ultra-light foamed concrete. • Utilisation of Ultra-light foamed concrete for sustainable construction. • Mechanical properties and thermal insulation perspective incorporating Ultra-light foamed concrete. • The density of ULFC materials compared with normal concrete. • Microstructures properties of concrete incorporated with ULFC. • Recommendations and observations are advanced for future research in ULFC. [ABSTRACT FROM AUTHOR]

In this study, a new type of highly porous ceramic was successfully fabricated from α-Al 2 O 3 whiskers and nano-sized Al 2 O 3 particle slurry by vacuum infiltration with the subsequent annealing in air. It was found that with an increase in the alumina slurry amount or sintering temperature, the porosity of the foam ceramic decreased while its compressive strength increased. The optimal alumina slurry content and sintering temperature were equal to 4 g, and 1350 °C, respectively. The as-synthesised porous foam ceramic exhibited a low density of 0.65 g/cm3, high porosity of 83.51%, high compressive strength of 3.84 MPa, and low thermal conductivity of 1.37 W/m⋅K at room temperature, suggesting its potential applications in high-temperature gas filtration and thermal insulation materials. [ABSTRACT FROM AUTHOR]

In this paper, 3D-SiC network skeleton with different structures was successfully constructed by regulating the microstructure of SiC foam ceramic struts via polyurethane replication technology combined with reactive infiltration of Si and solid-state sintering. Then, SiC/Al composites with 3D-interpenetrated network structure (3D-SiC/Al) were fabricated via vacuum pressure infiltration of Al alloy into the 3D-SiC skeleton, for application as electronic packaging. The effects of different skeleton structures on the thermal conductivity (TC), coefficient of thermal expansion (CTE), and flexural strength of the composites were investigated in detail. Furthermore, representative volume element (RVE) models of the 3D-SiC/Al composites were developed and their heat transfer properties and dimensional stability were also comparatively analyzed by finite element (FE) simulations. The results showed that the 3D-SiC/Al composites exhibited high TC of 196 W/m·K, low CTE of 8.03 × 10−6 K−1, and excellent flexural strength of 272 MPa. Low thermal deformation parameter (TDP) and Ashby map demonstrated that the synergistic effect of a complete 3D network skeleton and a clean well-bonded interface in the 3D-SiC/Al composites facilitated the integration of low CTE and high TC even at a low SiC content of 30 vol%. The FE results revealed a 63.5 % reduction in thermal stress and nearly an order of magnitude increase in heat flux for the RVE model of 3D-SiC (30 vol%)/Al composite compared to the RVE model of SiC P (60 vol%)/Al composite. This work provides a novel and scalable method for designing and synthesizing various composites for electronic packaging. [ABSTRACT FROM AUTHOR]

[Display omitted] • Calcination to generate spider web-like distribution of SiC whiskers to control electrical and thermal conductivity. • SiC/C foam with maximum EAB of 6.9 GHz, perfect C-band coverage. • SiC/C foam combines thermal conductivity, Joule heating, mid-temperature microwave absorption and compression to support repeated mid-temperature heating. • SiC/C closed cell foam has potential for large-scale industrial application. Microwave-absorbing materials (MAMs) for applications such as aircraft protective layers and ship side panels often need to take into account the actual working conditions. Conventional MAMs are often difficult to take into account special functional requirements such as mechanics, high temperature, de-icing, etc. Therefore, there is an urgent need to develop MAMs with harsh environmental adaptability and multifunctional requirements. Here, we utilize SiO 2 microspheres and phenolic resin to prepare precursor foams, and through calcination, we have prepared closed-cell SiC/C foam composites with both microwave absorption properties, mechanical properties and thermal properties. The effective absorption bandwidth (EAB) of the samples is up to 6.9 GHz at a thickness of 7.3 mm, which can satisfy the perfect coverage of the C-band, and can be further broadened by structural design. The samples can satisfy the full coverage of the X-band at 200 °C. The samples have loaded properties, and the maximum compressive strength of the samples is up to 10.5 mm. The samples are loaded with a maximum compression strength of 8 MPa, support repeated medium-temperature heating, and maintain a compression performance of 5.7 MPa after heating. The samples have good thermal conductivity and Joule thermal properties, and the surface temperature can be rapidly increased under the condition of applying a heat source or applying a low pressure to cope with the cold and humid working conditions. The composites in this paper are simple to prepare and have the potential for mass production. [ABSTRACT FROM AUTHOR]

For polymer foams, a high expansion rate is often required to obtain a low thermal conductivity. However, polymer foams with high expansion ratio faces a difficulty of shape recovery. In this work, polystyrene (PS)/polymethyl methacrylate (PMMA)/carbon nanotubes (CNTs) composite foams were prepared by the synergy of ultrasound and H 2 O in supercritical carbon dioxide (scCO 2) foaming. The introduction of ultrasound and H 2 O is beneficial to improving expansion ratio. CNTs can enhance the melt strength of PS/PMMA, which also absorb part of the thermal radiation. Therefore, the PS/PMMA/CNTs foams with 0.5 wt% CNTs exhibits the high expansion ratio (80.7 times), low thermal conductivity (25.98 mW/mK) and 100% compression recovery in water at 85 °C after one compression. In addition, with the increasing of filler contents, the reusability of the foam is further improved. After ten compressions, the PS/PMMA/CNTs foams with 2 wt% CNTs still achieve the 99% recovery. This work provides a new way to prepare polymer foams with super-insulation and reusability. [Display omitted] [ABSTRACT FROM AUTHOR]

Polymeric syntactic foams (PSF) are a kind of composite material, which consists of a polymer matrix reinforced by hollow thin wall glass micro-spheres. Because of their low density, low moisture absorption, relatively high specific strength and stiffness, PSF are often employed in aerospace and submarine applications in which they are subjected to a wide range of temperature conditions. Due to the temperature sensitivity of the polymer matrix, the physical and mechanical behaviour of PSFs is highly sensitive to temperature variations. Besides, their dynamic response is significantly affected by the strain rate. This research investigates the temperature and strain rate dependence of the mechanical behaviour of polyurethane, epoxy and nylon syntactic foams under compressive and tensile loads. The selected materials have in common that their mechanical characteristics, thermal properties, and dimensional stability make them suitable for both impact engineering and thermoforming applications. The experimental results, acquired over a temperature range from −25 °C to 100 °C at low and high strain rates, reveal a clear interplay between temperature and strain rate effects on the mechanical behaviour of the materials under investigation. This synergy is observed to vary based on both the matrix material and the loading mode. Notably, the rate dependency of polyurethane and nylon syntactic foams is significantly influenced by the testing temperature during compression, while in tension the influence of the temperature on the rate dependency is moderate or negligible. In contrast, the rate dependency of the epoxy syntactic foam remains largely unaffected by the testing temperature. Deformation and failure mechanisms were analysed by examining the failure surface of the tested samples using SEM micrographs. • A method to measure the dynamic response of polymeric syntactic foams is presented. • The interaction between the effects of temperature and strain rate is investigated. • The examined foams are characterised by a noticeable strength asymmetry. • The variation of strength and energy absorption in diverse conditions is examined. • The failure mechanisms of the materials is analysed via SEM micrographs. [ABSTRACT FROM AUTHOR]

• Unidirectional anisotropic PIAs have been prepared by freeze-drying. • The PIA shows excellent thermal stability and stable mechanical behavior. • The u -PIA-6 exhibits great strength, which is over twice as high as that of the TEEK-HH at 177 °C with a similar density. • The u -PIA shows great thermal insulation properties in anisotropic. Polyimide aerogels (PIAs) are the new type of high-performance lightweight material that combines the excellent thermal and mechanical behavior of polyimides with the highly porous and lightweight properties of aerogels. PIAs can meet the increasing material requirements of high-tech fields such as the aerospace and transportation industries. This study reports a series of all-aromatic anisotropic polyimide aerogels (p-phenylenediamine (PDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA)) with unprecedented behavior. These PIAs were synthesized using a random or unidirectional freeze-drying method followed by thermal imidization of the precursor solution. Their mechanical and thermal conductivity performance were anisotropic (u -PIA-8 strength: 1.86 and 0.14 MPa, thermal conductivity: 62.9 and 50.1 mW·m−1·K−1 along the axial and radial direction, respectively). Furthermore, the PIAs possessed excellent compression behavior in a wide temperature range from 25 °C to 316 °C, with a compressive strength over twice that of the commercial polyimide foam TEEK-HH (u -PIA-6 strength: 0.83 and 0.32 MPa at 177 and 316 °C, TEEK-HH strength: 0.31 MPa at 177 °C). These aerogels also demonstrated good thermal insulation performance after being held at 300 °C for 20 min (u -PIA-8: 76.3 °C at 25 mm). These highly anisotropic aerogels exhibit flexible thermal protection properties that extend the potential use of PIAs to applications such as high-temperature-resistant rocket fairings, sandwich structures, and arc-shaped structures for aerobats or the automobile industry. [ABSTRACT FROM AUTHOR]

Polyimide (PI) foams possess excellent mechanical properties, high-temperature resistance, and other unique properties, which facilitate impact in aerospace, automotive, and microelectronics industries. However, when they are used as lightweight insulation structural layers for high-temperature carbon fiber reinforced composites, improvement in thermal-insulating properties and temperature resistance of PI foams without compromising the flexibility in extreme environments is a challenging task. In this study, the flexible blocks were linked into rigid polymeric structures to fabricate a thermoplastic structure through a simple aqueous strategy to construct hydrogen-bonding networks. Thus, with a low shrinkage of 8.42%, an ultrahigh compressive modulus of 11.17 MPa, and a specific modulus of 81.03 MPa cm3 g−1 was successfully achieved. Benefitting from the formation of ultra-strong network backbones, foams showed excellent thermal-insulating properties and temperature resistance. The robust porous material with thermal-insulating properties (0.0481 W m−1 K−1) exhibited a compression modulus of 4.21 MPa after heat treatment at 300 °C and maintained 91% strength retention, thus it can be used as lightweight heat-insulation composite sandwich structures up to 300 °C. The copolymer foam obtained by using 30 mol% flexible blocks reserves its high flexibility undergoing only 10% dimensional changes after 40,000 compression-release cycles. The lightweight thermoplastic PI foams with flexibility, thermal-insulating properties, and temperature resistance can be used for high-temperature lightweight composite sandwich structures in aeronautics and space exploration. Preparing flexible thermoplastic polyimide foams with exceptional mechanical, thermal insulating properties, and temperature resistance through a simple aqueous strategy. [Display omitted] [ABSTRACT FROM AUTHOR]

Ethylene vinyl acetate copolymer blends (EVA-B), with vinyl acetate set at 19 % and 28 % by weight (wt%), were mixed with EVA waste (EVA-w), (a reticulated and micronized ethylene vinyl acetate copolymer) from injection branches and defective midsoles. The EVA-B/EVA-w composites were prepared with 15, 25, and 35 per hundred rubber (phr) EVA-w using a Banbury mixer to mix all components. Afterwards, the mixture was submitted to compression molding to obtain expanded EVA-B/EVA-w composite plates. A standard compound, provided by a Brazilian footwear industry (EVA-ref), was used as reference for thermal and mechanical property comparisons. During the thermal analysis, when increasing the EVA-w content, a delay in the deacetylation of the EVA-B composites in relation to the EVA-ref was observed. There was also an increase in the maximum degradation rate temperature and a reduction in loss of mass in the first decomposition event. In the second event, the maximum temperature did not vary in the composites with EVA-w added as compared to the EVA-ref. The residue content increased at 600 °C, indicating that EVA-w acts as a filler for EVA-B. The mechanical properties evaluated were hardness, tension at break, elongation at break, tear strength, compression set, and shrinkage. Addition of EVA-w to the composites (comparing 15 phr–35 phr) increased tear strength properties by 4 %, (EVA-w acts as a nucleation cell agent, increasing the EVA foam cell density). However, shrinkage increased by roughly 35 % above the specifications for footwear applications. Hardness increased by 5 %, tensile strength increased by 10 %, and elongation at break decreased by roughly 4 %. The compression set property increased by nearly 5 % with the EVA-w content (due to decreasing matrix elongation). Thus, EVA-w acts as a reinforcement filler for EVA-B. A statistical study based on composite performance indices for the mechanical properties, and a cost analysis was performed. Except for the average linear shrinkage (35 phr EVA-w composite), all other studied composites met the mechanical property specifications for sports shoe midsoles. The best combination for process performance and cost analysis was for the EVA-w composite at 25 phr. Cleaner and sustainable production of a Brazilian footwear industry was evaluated EVA-w of injection branches and defective midsoles was assessed EVA-w of 15, 25 and 35 phr effect on thermal and mechanical properties of EVA was analyzed Process performance and cost analysis showed EVA-w at 25 phr as the best setup [ABSTRACT FROM AUTHOR]

New organic-inorganic polyurethane-based hybrids with enhanced mechanical properties and thermal insulation properties are reported. Polyurethane-based hybrids are characterized by the intimate interactions of their inorganic and organic co-networks and prepared by sol-gel approach, have exhibited properties exceeding those of polyurethane foams, e.g. enhanced thermal stability, durability and thermal insulating effectiveness. However, mechanical properties have previously been poor. Here, new porous organic-inorganic materials consisting of a polyurethane network modified by in-situ formation of aerogel-like polysiloxane domains, were developed. They exhibit a multiscale-porosity which enhances the insulation, mechanical and thermal properties. The synthesis was performed through a novel stepwise process consisting of: preparation of a siloxane precursor based on methyl-triethoxysilane and tetraethoxysilane; functionalization of traditional polyol for polyurethane foams with 3-(triethoxysilanepropyl)isocyanate as coupling agent; use of suitable catalysts and silicone surfactants; and foaming with methylene-di-isocyanate compound. The siloxane precursors and coupling agent led to formation of "aerogel-like" polysiloxane domains within the walls and struts of the polyurethane foams. The synthesis method enabled increased incorporation of the "aerogel-like" polysiloxane structures into the foams, compared to literature, with 20 wt% SiO 2 , reducing thermal conductivity of the hybrid foams 30% compared with pristine polyurethane, in addition to significant improvement in thermal stability and mechanical properties. [Display omitted] [ABSTRACT FROM AUTHOR]

The mechanical response of syntactic foams comprising hollow thermoplastic microspheres (HTMs) embedded in a polyurethane matrix were experimentally examined under uniaxial compressive strain. Phenomenological strain energy models were subsequently developed to capture both the axial stress-strain and transverse strain response of the foams. HTM syntactic foams were found to exhibit increased small-strain stiffness with reduced density, revealing a highly-tuneable and extremely lightweight syntactic foam blend for applications. The foams were also found to become strongly compressible at large strains and possess a high threshold for plastic deformation, making them a robust alternative to hollow glass microsphere syntactic foams. The non-standard transverse strain relationship exhibited by HTM syntactic foams at high filling fractions was captured by Ogden-type strain energy models. The thermal characteristics of these syntactic foams were also explored with Differential Scanning Calorimetry testing which showed that HTMs have a negligible impact on the thermal characteristics of the matrix. [Display omitted] • This study experimentally describes how hollow thermoplastic microspheres impact the mechanical properties of polyurethane. • Testing is conducted to large compressive strains capturing both the uniaxial stress-strain and the transverse stretch. • Increased small-strain stiffness is observed with decreasing density, significantly enhancing the specific stiffness. • Phenomenological strain energy models are constructed that show the choice of Ogden-type model depends on filling fraction. • Exploratory results suggest hollow thermoplastic microspheres only minimally alter the thermal properties of the matrix. [ABSTRACT FROM AUTHOR]

• Highly porous Cu foams were used to improve the thermal conductivity of paraffin PCM. • Cu foams were fabricated by a simple solution combustion synthesis method. • The SCS condition was optimized for the ratio of copper nitrate oxidizer and starch fuel. • Paraffin was embedded in Cu foams to form PCM composites with improved heat transfer properties. Regardless of the high latent heat of organic phase change materials (PCMs) for thermal energy storage, their intrinsically low thermal conductivity has constrained their wide application. In order to improve the thermal conductivity of paraffin PCM, porous copper foams as supporting frameworks are fabricated by a simple solution combustion synthesis (SCS), using copper nitrate as oxidizer and starch as fuel. The SCS is conducted under inert atmosphere and the efficient exothermic reaction occurs at around 100 °C. At an optimal oxidant-fuel condition of 4.43 g copper nitrate to 2 g starch, a good porous copper scaffold is prepared, which is further shaped and sintered to form robust copper foams. Paraffin is infiltrated into the copper foams to form PCM composites and the thermophysical properties are analyzed. Due to the continuous copper skeleton as heat transfer path, the thermal conductivity of the composite is improved to 3.29 W m−1 K−1 from 0.25 W m−1 K−1 of pure paraffin. The enhanced heat transfer properties of PCM composites as-supported by the facilely SCS-derived copper foams can reinforce the application in solar thermal harvesting and thermal management. [ABSTRACT FROM AUTHOR]

Flexible polyurethane foams (FPUs) having polystyrene (PS) stabilized by silica gel or polystyrene-acrylonitrile (SAN) particles were synthesized employing polymer polyether polyols (PPPs). The filler and its content effect on physical, mechanical and thermal properties of FPUs were studied. The FPU thermal stability increased with PS content into PPP and no interaction filler-polymeric network was observed. Meanwhile, FPUs containing PS as filler were more thermally stable and mechanically resistant -except the elongation-than those from the commercial PPP containing SAN. Contrary to porosity and cell size, the density and hardness are function of the filler type and increase with the filler content although the hardness is practically constant from 10 wt%. Closed cell foams instead of tight foams were produced from filler contents higher than 15 wt%. Synthesized FPUs presented better hardness and density properties but worse mechanical properties than the commercial one. Finally, mechanical properties were similar than FPUs containing inorganic fillers. •Foams containing PPPs stabilized by silica gel were successfully synthesized. • The PPP with the smallest PS particles originated smaller and more homogeneous cell size. •PPP-PU showed higher thermal stability and hardness keeping the rest of properties •The maximum density value obtained was 41 kg/m3 employing 40 pph of PPP 43. •The PPP-PU foams satisfied the requirements to be applied in the automotive sector. [ABSTRACT FROM AUTHOR]