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As wearable and flexible electronic devices continue to miniaturize and operate at higher frequencies, there is an urgent demand for polymer films that offer a high electromagnetic interference (EMI) shielding efficiency and effective thermal management capabilities, particularly under extreme environmental conditions. Conductive inks are extensively utilized in polymeric electromagnetic interference shielding coatings. However, the extensive utilization of organic solvents can lead to environmental pollution. Herein, we proposed a multifunctional conductive composite ink comprising waterborne polyurethane (WPU), silver nanosheets (AgNS) and heat-treated MXene, using deionized water as solvent. Inspired by the advantage of the unique "brick-mortar" layered structure, we fabricated a multifunctional flexible composite film with large size, high electrical conductivity, and good mechanical flexibility by blade coating, which has scalable manufacturing prospects for industrialization. The resultant films achieve a remarkable EMI SE of 87.3 dB at only 78 μm thickness and impressive mechanical fastness and chemical durability to various organic solvents. Meanwhile, the resultant composites also present a desirable Joule heating temperature (117 °C) and anisotropic thermal conductivity due to the compact and highly aligned morphology. In summary, our simple preparation technology and excellent comprehensive performance of composite inks have great potential in advanced thermal management and wearable electromagnetic protection devices. [ABSTRACT FROM AUTHOR]

With the rapid development of wireless communication and electronic equipment, there is an urgent need for lightweight and compressible electromagnetic interference (EMI) shielding materials to solve the increasingly serious problem of electromagnetic pollution. Graphene (GP) is widely used in functional materials with excellent electromagnetic interference shielding properties due to its large aspect ratio and specific surface area. Hierarchical structure attached by GP is constructed in melamine foams (MF) with the assistance of sodium alginate (SA) through simple impregnation and freeze-drying methods. Benefiting from such unique hierarchical porous structure, the composite foam achieves a high electrical conductivity of 39.1 S/m and an exceptional electromagnetic interference (EMI) shielding effectiveness (EMI SE) of 45.8 dB in the range of X-band (8.2–12.4 GHz) at only 2 mm thickness, resulting in a significant EMI shielding effectiveness as 3541.7 dB cm2 g–1. In addition, SA endows the improved compressive strength of MF with less effect on the resilience of MF due to the supporting effect of SA. The prepared foams show superior thermal stability, making it possible to expand the range of applications. This work fabricated highly efficient EMI shielding materials for reducing electromagnetic pollution, while also broadening the application areas of EMI shielding materials in complex environments. [ABSTRACT FROM AUTHOR]

The application of polyvinyl alcohol (PVA) films is still restricted due to their poor hydrophilicity, mechanical strength, and thermal stability. To improve these properties, a teardrop-shaped hollow polystyrene (HPS) nanoparticle was prepared in this work and further applied as the reinforcing nanomaterial. Herein, a teardrop-shaped silica nanoparticle was first used as the hard template; polystyrene was in situ-synthesized on the surface of teardrop-shaped silica, followed by the etching of the silica template. By tuning the synthesis parameters (e.g., styrene concentration and etching time), the optimal structure of HPS was obtained; subsequently, HPS was mixed with PVA by a solution-mixing method, which in turn produced the PVA-based synthetic foam film. Using optimal synthesis parameters of HPS and its loadings, the obtained syntactic foam films exhibited high transparency, excellent mechanical strength and toughness, and good thermal stability. Compared to pure PVA film, the tensile strength and toughness of PVA-based syntactic foam films containing 1.0 wt % HPS were improved by about 55 and 77%, respectively; the glass transition temperature and onset decomposition temperature of PVA-based syntactic foam films increased to about 32 and 66 °C, respectively. The research exemplifies the great promise of HPS toward practical application in polymer syntactic foams. [ABSTRACT FROM AUTHOR]

The introduction of wide-band semiconductor devices has led to the development of electronic components with a high degree of integration and power density. The use of dielectric polymers can guarantee the performance of electronic components while maximizing their operational reliability. However, this polymer performance is often enhanced at the expense of its electrical insulation properties and processability. Herein, we report the synthesis of epoxy resin composites filled with boron nitride nanosheets (BNNSs) functionalized with copper nanowires (Cu NWs). Through encapsulation within a polydopamine coating, Cu NWs and BNNSs exhibit excellent electrical insulation properties and high dispersion, and their 1D and 2D interconnected networks enable effective charge and heat transfer. Hence, these epoxy resin composites showed a thermal conductivity of 1.2 W/m K at a filler loading rate of 26 wt %, marking a staggering 486% increase compared to pure epoxy resin. These composites also showed low dielectric loss, enhanced electrical insulation properties, matched thermal expansion coefficients, and low water absorption. Experimental analyses and simulations indicated that the composites had strong heat dissipation capability, meeting the technical specifications for electronic packaging materials, and are thus expected to find use in electronic device packaging. [ABSTRACT FROM AUTHOR]

With the development of renewable energy resources, polymer-based dielectric materials, as key components in energy storage devices with optimized dielectric property, high-temperature stability, and good processibility, are highly demanded. In this study, p-phenylenediamine (PPD)-modified and l-ascorbic acid (LAA)-reduced graphene oxide (NH2-CRG) nanosheets with significant chemical functionalization and significantly improved dispersity were prepared. Also, polyimide was chosen to be the polymer matrix due to its high-temperature resistance, chemical inertness, and excellent mechanical property. By incorporating NH2-CRG into the PI polymer matrix via in situ polymerization, 0.8 wt % NH2-CRG/PI composite material with a dielectric constant as high as 839 and a breakdown strength of 80 kV·mm–1 was obtained. Meanwhile, the 5 wt % weight loss temperature of 0.8 wt % NH2-CRG/PI witnessed a 17.6 °C increase compared to pure PI. This work provided a promising strategy to prepare graphene-based materials for high-dielectric applications and a realizable process of fabricating polymer-based dielectric composite materials. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) possess the potential to regulate temperature by utilizing their thermal properties to absorb and release heat. Nevertheless, the application of PCMs in thermal management is constrained by issues such as liquid leakage and limited flexibility. In this study, we propose a novel approach to address these challenges by incorporating a pore structure within nanofibers to confine the crystallization of phase change molecules, thereby enhancing the flexibility of the composite material. Additionally, inspired by the adaptive mechanisms observed in plants, we have developed a form stable PCM based on polyether, which effectively mitigates the issue of liquid leakage at higher temperatures. Despite being a solid-liquid PCM at its core, this material exhibits molecular-scale flow and macroscopic shape stability as a result of intermolecular forces. The composite film material possesses remarkable flexibility, efficient thermal management capabilities, adjustable phase transition temperature, and the ability to undergo repeated processing and utilization. Consequently, it holds promising potential for applications in personal thermal energy management.

A polarized light source covering a wide wavelength range is required in applications across diverse fields, including optical communication, photonics, spectroscopy, and imaging. For practical applications, high degrees of polarization and thermal performance are needed to ensure the stability of the radiation intensity and low energy consumption. Here, we achieved efficient emission of highly polarized and broadband thermal radiation from a suspended aligned carbon nanotube film. The anisotropic nature of the film, combined with the suspension, led to a high degree of linear polarization (∼0.9) and great thermal performance. Furthermore, we performed time-resolved measurements of thermal emission from the film, revealing a fast time response of approximately a few microseconds. We also obtained visible light emission from the device and analyzed the film's mechanical breakdown behavior to improve the emission intensity. Finally, we demonstrated that suspended devices with a constriction geometry can enhance the heating performance. These results show that carbon nanotube film-based devices, as electrically driven thermal emitters of polarized radiation, can play an important role for future development in optoelectronics and spectroscopy.

Carbon nanotubes (CNTs) hold great promise in next-generation sensors because of their remarkable physical properties. Yet, maintaining precise stacking configurations of CNTs to make full use of their remarkable properties is challenging because of their susceptibility to spontaneous reconstruction. Inspired by the weaving technology, we propose a CNT-graphene nanoribbon hybrid woven model that can maintain the specific structure of CNTs to achieve their elaborately designed function. In this study, comprehensive molecular dynamics simulations are carried out to investigate the thermal stability of the CNT-graphene hybrid woven model, as well as their potential for pressure sensing applications by utilizing the unique response of thermal transport to mechanical deformation at heterojunctions. The thermal stability is sensitive to the size of the graphene nanoribbon, and the woven structure remains stable from 200-500 K when its width is greater than 2.0 nm. Moreover, it is exciting that the sensors are effective at predicting the shapes of externally loaded objects through the analysis of the thermal conductivity distribution, which can be derived from the relationship between the thermal conduction and the pressure. Our findings shed light on the bottom-up functional design of nanomaterials and expand wider applications of high-performance nanosensors in other related fields.

NaCl-MgCl 2 -CaCl 2 eutectic ternary chloride salts are potential heat transfer and storage materials for high-temperature thermal energy storage. In this study, first-principles molecular dynamics simulation results were used as a data set to develop an interatomic potential for ternary chloride salts using a neural network machine learning method. Deep potential molecular dynamics (DPMD) simulations were performed to predict the microstructure and thermophysical properties of the NaCl-MgCl 2 -CaCl 2 ternary salt. This work reveals that DPMD simulations can accurately calculate the microstructure and thermophysical properties of ternary chloride salts. The association strength of chloride ions and cations follows the order of Mg 2+ > Ca 2+ > Na + , and the coordination number decreases gradually with increasing temperature, indicating a progressively looser and more disordered molten structure. Furthermore, thermophysical properties, such as density, specific heat capacity, thermal conductivity, and viscosity, are in good agreement with the experimental measurements. Machine learning molecular dynamics will provide a feasible multivariate molten salt exploration method for the design of next-generation solar power plants and thermal energy storage systems.

Single-wall carbon nanotubes (SWCNTs) with excellent physicochemical properties are considered a promising candidate for the electrical and mechanical reinforcements of polymers. However, the poor dispersion of SWCNTs in plastics seriously limits their application and their achieved performance enhancement. Here, we coat a freestanding, highly conductive SWCNT film onto the surface of a polyethylene terephthalate (PET) film by a hot-pressing method. Due to the uniform SWCNT network structure and strong interfacial interaction, the SWCNT/PET hybrid film showed notably enhanced electrical and mechanical properties even though with a very low SWCNT weight fraction of 0.066%. The surface square resistance of the SWCNT/PET film decreased to 120-140 Ω/□ from 10 16 Ω. In addition, Young's modulus and tensile strength of the SWCNT/PET film reached 4.6 GPa and 148 MPa, which are 31.3 and 24.4%, respectively, higher than the pure PET film. The SWCNT/PET film shows excellent mechanical durability and thermal stability, demonstrating its potential use as an antistatic material.

This study provides an effective interface modification strategy for preparing graphene-based composite. Urethane-functionalized graphene oxide (FGO) was prepared by in situ polymerization and then was incorporated into a polyurethane binder (PUB) matrix to fabricate composites. The surface chemical composition and structural properties of FGO were systematically characterized by a series of measurements. It was found that urethane chains were covalently attached onto the graphene oxide surface, and the FGO possessed a comparatively regular lamellar structure and a larger interlayer distance. Additionally, amphipathic urethane chains on the FGO sheets not only improved the compatibility and interfacial interaction between the stiff FGO and the soft PUB matrix, but also alleviated the modulus mismatch between them. The most effective improvements in mechanical and thermal transport properties were achieved when 0.5 wt % FGO was incorporated into the PUB matrix, leading to improvement of tensile strength, elongation at break, and thermal conductivity by 23.4%, 12.1%, and 61.5%, respectively, in comparison with the neat PUB matrix. We expect that this work will have potential applications in functional composite coatings. [ABSTRACT FROM AUTHOR]

Tungsten tetraboride alloys with Y, Sc, Gd, Tb, Dy, Ho, and Er were prepared by arc-melting and investigated for their thermal stability and mechanical properties. The phase composition and purity were confirmed by powder X-ray diffraction (PXRD) and energy dispersive X-ray spectroscopy (EDS). In all cases, except for Sc, a change to a "dendritic" morphology was observed. For alloys with Sc, the metal boride and boron grains became smaller; however, no patterning was observed. This shows that tuning the composition of the alloys of WB4 with transition metals and lanthanides results in a modification of the morphology leading to patterning and smaller grains that enhance mechanical and thermal properties. For alloys of WB4 with Y, Sc, Gd, Dy, Tb, Ho, and Er, an increase in hardness to 50.2 ± 2.4, 48.9 ± 2.5, 48.0 ± 2.1, 46.3 ± 2.6, 48.5 ± 2.3, 46.4 ± 3.4, and 47.2 ± 2.9 GPa at low load, respectively, compared to 41.2 ± 1.4 GPa for WB4 is observed. Moreover, the alloys of WB4 with Y, Sc, and Gd showed an increase in oxidation resistance from ~450 °C for WB4 to ~470, ~525, and 465 °C, respectively. [ABSTRACT FROM AUTHOR]

The effects of catalyst on the molecular weight, chemical structure, and yellowness of isosorbide-based polycarbonate (ISB-PC) in the melt-transesterification and polycondensation stages were investigated. Results showed that the high steric hindrance and intramolecular hydrogen bonding of the endohydroxyl group (endo--OH) of ISB enabled its reactivity to be lower than that of the exohydroxyl group (exo--OH). We also found that the reactivity of endo--OH with diphenyl carbonate can be preferentially activated by strong electrophilic catalysts, and that the configuration of the ISB-PC chain strongly depended on the reactivity balance between endo--OH and exo--OH. Various catalysts with different coordinate capacities, acidity coefficients, and radius of metal ion were further tested. Catalysts with a calcium or zinc ion showed a higher reactivity of endo--OH than exo--OH, resulting in a high glass-transition temperature of ISB-PCs. Results suggested as well that the thermal stability of ISB-PC may be correlated to the amount of OH groups at the chain ends, whereas its yellowness mainly arose from 1,4-sorbitan due to the hydrolysis of ISB. [ABSTRACT FROM AUTHOR]

This paper presents the effect of end groups, chain structure, and stereocomplexation on the microparticle and nanoparticle morphology and thermal properties of the supramolecular triblock copolyesters. Therefore, the series of the triblock copolymers composed of l,l- and d,d-lactide, trimethylene carbonate (TMC), and e-caprolactone (CL) with isopropyl (iPr) or 2-ureido-4-[1H]-pyrimidinone (UPy) end groups at both chain ends were synthesized. In addition, these copolymers were intermoleculary stereocomplexed by polylactide (PLA) blocks with an opposite configuration of repeating units to promote their self-assembly in various organic solvents. The combination of two noncovalent interactions of the end groups and PLA enantiomeric chains leads to stronger interactions between macromolecules and allows for alteration of their segmental mobility. The simple tuning of the copolymer microstructure and functionality induced the self-assembly of macromolecules at liquid/liquid interfaces, which consequently leads to their phase separation in the form of particles with diameters ranging from 0.1 µm to 10 µm. This control is essential for their potential applications in the biomedical field, where biocompatible and well-defined microparticles and nanoparticles are highly desirable. [ABSTRACT FROM AUTHOR]

The effect of phenolic hydroxyl bearing naphthoxazines as catalysts for the ring-opening polymerization (ROP) of simple 1,3-benzoxazines was investigated. The latent catalytic role of napthoxazines in the curing process of the mixtures was demonstrated by DSC and FT-IR investigations. It was found that phenolic naphthoxazines cause clear reduction in ROP temperature, particularly when electron-withdrawing groups are attached and an onset ROP temperature as low as 169 °C is attained. Thermal properties of the final polymers were also analyzed, and no significant effect of naphthoxazines on the thermal stability of the cured polybenzoxazines was observed. [ABSTRACT FROM AUTHOR]

Ion transport in polymerized ionic liquids (poly-ILs) occurs via a fundamentally different mechanism than in monomeric ionic liquids, and recently progress has been made toward understanding ion conduction in poly-ILs. To gain insight into the nature of ionic conductivity in ionic polymers, we investigate the physical properties of the trisaminocyclopropenium (TAC) ion, as it is an aromatic carbocation with unique structural and electronic properties. Herein, we characterize the thermal properties, local morphology, and dielectric response of a series of monomeric and polymeric TAC ionic liquids with different counterions. We have found that the extent of a "superionic" mechanism depends on the nature of the ion pair and can result in anomalously high conductivity at the calorimetric Tg. Our results suggest that the molecular volumes of the cationic and anionic species are important parameters that impact ion conductivity in polymerized ionic liquids. [ABSTRACT FROM AUTHOR]

Chemically cross-linked elastomers are an important class of polymeric materials with excellent temperature and solvent resistance. However, nearly all elastomers are petroleum-derived and persist in the environment or in landfills long after they are discarded; this work strives to address these issues by demonstrating the synthesis of renewable, enzymatically hydrolyzable, and mechanically competitive polyester elastomers. The elastomers described were synthesized using a novel bis(β-lactone) cross-linker and star-shaped, hydroxylterminated poly(γ-methyl-ε-caprolactone). Using model compounds, we determined that the bis(β-lactone) cross-linker undergoes acyl bond cleavage to afford β-hydroxyesters at the junctions. The mechanical properties of the cross-linked materials were tunable and competitive with a commodity rubber band. Furthermore, the elastomers demonstrated high thermal stability and a low glass transition (-50 °C), indicating a wide range of use temperatures. The polyester networks were also subjected to enzymatic hydrolysis experiments to investigate the potential for these materials to biodegrade in natural environments. We found that they readily hydrolyzed at neutral pH and environmentally relevant temperatures (2-40 °C); complete hydrolysis was achieved in all cases at temperature-dependent rates. The results presented in this work exemplify the development of high performance yet sustainable alternatives to conventional elastomers. [ABSTRACT FROM AUTHOR]

This work takes advantage of the unique thermally reversible dissociation/association feature of C-ON bonds in alkoxyamine (Diol) to facilitate the reprocessability of poly(butyl methanol methacrylate) (PBMM) rubber with excellent thermal and mechanical properties. Isocyanate groups were incorporated into the PBMM backbone and then reacted with hydroxyl groups in Diol to obtain cross-linked PBMM rubber. Although its cross-linking degree is slightly lower than the conventional cross-linked rubber by an irreversible cross-linker (Dieg), it shows a higher tensile strength and elongation at break. Its decomposition temperature is about 50 °C higher than PBMM cross-linked by Dieg. Furthermore, the dissociation of C-ON bond at high temperature can break the cross-linking network of PBMM rubber to form a flowable and reprocessable melt and show an excellent ability of reshaping and healing; the association of thermally reversible C-ON bond can completely recover the cross-linking network and mechanical properties at a low temperature. [ABSTRACT FROM AUTHOR]

The freezing of supercooled water films on different substrates was investigated using a high-speed camera coupled to an optical microscope, obtaining details of the freezing process not described in the literature before. We observed the two well known freezing stages (fast dendritic growth and slow freezing of the water liquid left after the dendritic growth), but we separated the process into different phenomena that were studied separately: two-dimensional dendrite growth on the substrate interface, vertical dendrite growth, formation and evolution of ice domains, trapping of air bubbles and freezing of the water film surface. We found all of these processes to be dependent on both the supercooling temperature and the substrate used. Ice dendrite (or ice front) growth during the first stage was found to be dependent on thermal properties of the substrate but could not be unequivocally related to them. Finally, for low supercooling, a direct relationship was observed between the morphology of the dendrites formed in the first stage, which depends on the substrate, and the roughness and the shape of the surface of the ice, when freezing of the film was completed. This opens the possibility of using surfaces and coatings to control ice morphology beyond anti-icing properties. [ABSTRACT FROM AUTHOR]

Layered lithium transition metal oxides, in particular, NMCs (LiNixCoyMnzO2) represent a family of prominent lithium ion battery cathode materials with the potential to increase energy densities and lifetime, reduce costs, and improve safety for electric vehicles and grid storage. Our work has focused on various strategies to improve performance and to understand the limitations to these strategies, which include altering compositions, utilizing cation substitutions, and charging to higher than usual potentials in cells. Understanding the effects of these strategies on surface and bulk behavior and correlating structure-performance relationships advance our understanding of NMC materials. This also provides information relevant to the efficacy of various approaches toward ensuring reliable operation of these materials in batteries intended for demanding traction and grid storage applications. In this Account, we start by comparing NMCs to the isostructural LiCoO2 cathode, which is widely used in consumer batteries. Effects of changing the metal content (Ni, Mn, Co) upon structure and performance of NMCs are briefly discussed. Our early work on the effects of partial substitution of Al, Fe, and Ti for Co on the electrochemical and bulk structural properties is then covered. The original aim of this work was to reduce the Co content (and thus the raw materials cost) and to determine the effect of the substitutions on the electrochemical and bulk structural properties. More recently, we have turned to the application of synchrotron and advanced microscopy techniques to understand both bulk and surface characteristics of the NMCs. Via nanoscale-to-macroscale spectroscopy and atomically resolved imaging techniques, we were able to determine that the surfaces of NMC undergo heterogeneous reconstruction from a layered structure to rock salt under a variety of conditions. Interestingly, formation of rock salt also occurs under abuse conditions. The surface structural and chemical changes affect the charge distribution, the charge compensation mechanisms, and ultimately, the battery performance. Surface reconstruction, cathode/electrolyte interface layer formation, and oxygen loss are intimately related, making it difficult to disentangle the effects of each of these phenomena. They are driven by the different redox activities of Ni and O on the surface and in the bulk; there is a greater tendency for charge compensation to occur on oxygen anions at particle surfaces rather than on Ni, whereas the Ni in the bulk is more redox active than on the surface. Finally, our latest research efforts are directed toward understanding the thermal properties of NMCs, which is highly relevant to their safety in operating cells. [ABSTRACT FROM AUTHOR]

Luminescent molecular thermometers have attracted great attention due to their potential application for temperature detection in special environments. By a very simple one-step method, we have synthesized one novel cuprous compound, [I@Cu8(HMTZ)(MTZ)7]·MeCN·2H2O (I@Cu8), which consists of an infrequent octatomic [I@Cu8S8] ring. Importantly, compound I@Cu8 features dual-emitting behavior and shows successive visual luminescent emissions varying from green, to yellow, to orange, and then to red in the temperature range of 80-300 K, suggesting potential application for a luminescent molecular thermometer. [ABSTRACT FROM AUTHOR]

Heat dissipation is an increasingly critical technological challenge in modern electronics and photonics as devices continue to shrink to the nanoscale. To address this challenge, high thermal conductivity materials that can efficiently dissipate heat from hot spots and improve device performance are urgently needed. Boron phosphide is a unique high thermal conductivity and refractory material with exceptional chemical inertness, hardness, and high thermal stability, which holds high promises for many practical applications. So far, however, challenges with boron phosphide synthesis and characterization have hampered the understanding of its fundamental properties and potential applications. Here, we describe a systematic thermal transport study based on a synergistic synthesis-experimental-modeling approach: we have chemically synthesized high-quality boron phosphide single crystals and measured their thermal conductivity as a record-high 460 W/mK at room temperature. Through nanoscale ballistic transport, we have, for the first time, mapped the phonon spectra of boron phosphide and experimentally measured its phonon mean free-path spectra with consideration of both natural and isotope-pure abundances. We have also measured the temperature- and size-dependent thermal conductivity and performed corresponding calculations by solving the three-dimensional and spectral-dependent phonon Boltzmann transport equation using the variance-reduced Monte Carlo method. The experimental results are in good agreement with that predicted by multiscale simulations and density functional theory, which together quantify the heat conduction through the phonon mode dependent scattering process. Our finding underscores the promise of boron phosphide as a high thermal conductivity material for a wide range of applications, including thermal management and energy regulation, and provides a detailed, microscopic-level understanding of the phonon spectra and thermal transport mechanisms of boron phosphide. The present study paves the way toward the establishment of a new framework, based on the phonon spectra–material structure relationship, for the rational design of high thermal conductivity materials and nano- to multiscale devices. [ABSTRACT FROM AUTHOR]

Starch aerogels were prepared via dissolution in water (thermomechanical treatment), retrogradation, solvent exchange, and drying with supercritical CO2. Amylose content in starches was varied from 0 to 100%. The aerogels' bulk density, morphology, specific surface area, thermal conductivity, and mechanical properties under compression were investigated. Pea starch aerogels had one of the highest specific surface area and lowest density and thermal conductivity (0.021-0.023 W/m·K), with the latter indicating that a new thermal superinsulation material was obtained. A detailed study of the influence of processing parameters on pea starch aerogels properties showed the importance of retrogradation time which decreases specific surface area and increases mechanical properties and thermal conductivity. Finally, a comparison of starch aerogel thermal conductivity with that of other bioaerogels is performed. [ABSTRACT FROM AUTHOR]

Layered two-anion compounds are of interest for their diverse electronic properties. The modular nature of their layered structures offers opportunities for the construction of complex stackings used to introduce or tune functionality, but the accessible layer combinations are limited by the crystal chemistries of the available anions. We present a layered three-anion material, Bi4O4Cu1.7Se2.7Cl0.3, which adopts a new structure type composed of alternately stacked BiOCuSe and Bi2O2Se-like units. This structure is accessed by inclusion of three chemically distinct anions, which are accommodated by aliovalently substituted Bi2O2Se0.7Cl0.3 blocks coupled to Cu-deficient Bi2O2Cu1.7Se2 blocks, producing a formal charge modulation along the stacking direction. The hypothetical parent phase Bi4O4Cu2Se3 is unstable with respect to its charge-neutral stoichiometric building blocks. The complex layer stacking confers excellent thermal properties upon Bi4O4Cu1.7Se2.7Cl0.3: a room-temperature thermal conductivity (κ) of 0.4(1) W/ mK was measured on a pellet with preferred crystallite orientation along the stacking axis, with perpendicular measurement indicating it is also highly anisotropic. This κ value lies in the ultralow regime and is smaller than those of both BiOCuSe and Bi2O2Se. Bi4O4Cu1.7Se2.7Cl0.3 behaves like a charge-balanced semiconductor with a narrow band gap. The chemical diversity offered by the additional anion allows the integration of two common structural units in a single phase by the simultaneous and coupled creation of charge-balancing defects in each of the units. [ABSTRACT FROM AUTHOR]

Highly efficient organic light-emitting diodes are in urgent demand in applications of new generation full-color displays and solid-state lighting sources. The limitation of device performance is greatly affected by extrinsic and intrinsic elements of the light out-coupling process. By elaborately designing emitters as sticklike molecules, horizontal orientation ratios in the range of 86-93% were realized to intrinsically increase the out-coupling factor of electroluminescence devices. These elongated compounds are inclined to lie parallel to substrate in vacuum-deposited thin solid films and regularize their transition dipole moments in a major degree. As consequences of such desirable molecule arrangement, remarkable external quantum efficiencies near 21% for pure blue devices, close to 30% for sky-blue devices, and over 35% for greenish blue devices were respectively achieved. A compatible strategy on devising high-performance emitters for organic electroluminescence is advocated herein. [ABSTRACT FROM AUTHOR]

Organic neutral π-monoradicals are promising semiconductors with balanced ambipolar carriertransport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(α) and SOMO(β), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits wellbalanced ambipolar carrier transport properties. [ABSTRACT FROM AUTHOR]

This work is on in the volumetric and thermal properties of brines in the quinary Na–K–Ca–Mg–Cl–H2O chemical system. Its objective is twofold. First, by acquiring original data for temperatures ranging from 278.15 to 353.15 K and ionic strengths ranging from 1.3 to 5.1 mol·kg-1 it aimed to add to the experimental data set, usually acquired only at high ionic strengths or at 298.15 K. Experimental solution density was measured using a vibrating-tube densitometer with relative uncertainty, Δρ/ρ, better than 6 × 10-6. This property, combined with volumetric heat capacity measurements, provided the isobaric heat capacity of solution determined with a mean relative deviation better than 0.3%. Second, we used PhreeSCALE software to compute the density and heat capacity of the chemical system of interest, simultaneously applying the Pitzer and the Helgeson–Kirkham–Flowers (HKF) equations. We propose a new set of specific interaction parameters so that published and newly measured experimental data can be described accurately. We show that only binary interaction parameters are necessary and that ternary interaction parameters could be set to zero. [ABSTRACT FROM AUTHOR]

New experimental data on the thermal conductivity of trans-1-chloro-3,3,3-trifluoropropene (R1233zd(E)) are reported that allow the development of wide-range correlations. These new experimental data, covering a temperature range of 204 to 453 K at pressures from 0.1 to 67 MPa, are used to develop a correlation for the thermal conductivity. The experimental data reported here have an uncertainty of 1% for liquid and supercritical (density > 700 kg·m-3), 1.5% for vapor and supercritical (pressure ≥ 1 MPa and density < 200 kg·m-3), 3% for supercritical (200 kg·m-3 ≤ density ≤ 700 kg·m-3), and 3% vapor and supercritical (pressure <1 MPa). On the basis of the uncertainty of and comparisons with the present data, the thermal-conductivity correlation for R1233zd(E) is estimated to have a relative expanded uncertainty ranging at a 95% confidence level from 1% to 4% depending on the temperature and pressure with larger uncertainties in the critical region. [ABSTRACT FROM AUTHOR]

In this work, the effects of noble metal (Au and Pt) incorporation into black phosphorus (BP) were first investigated. Several important sensing results were observed as a result of the incorporation of Au or Pt into the BP surface. First, prior to incorporation, pristine BP only detects paramagnetic molecules, e.g., NO2 or NO. However, after incorporation with Pt, low concentration of H2 can be detected with high response amplitude. Furthermore, the H2 sensing performance reported in this study was found to be most sensitive as compared with that observed for a previously reported 2D H2 gas sensor. The second significant result was obtained after incorporation with Au, where the work function of BP was varied by the transfer of electrons from the Au nanoparticles, thereby inducing the effects of n-doping on p-type pristine BP. Accordingly, the response behavior of BP to oxidizing gas changed from a p-type response (negative resistance variation) to an n-type response (positive resistance variation). In addition, a highly stable, low noise baseline was achieved in the Au-incorporated BP channel material. Finally, because of the high chemical and ambient stability of the Au or Pt, the synthesized Au- or Pt-incorporated BP systems exhibited long-term stability, which is difficult to achieve when using other doping strategies. Overall, a significant step was taken toward the efficient control of the electrical/chemical sensitization level of BP and significant enhancement of superior chemical sensing performance of BP. [ABSTRACT FROM AUTHOR]

A new type of semicrystalline vitrimer was prepared via the incorporation of glycerol into the amorphous phase of poly(butylene terephthalate) (PBT) by solid-state (co)polymerization (SSP). A near quantitative incorporation of the glycerol was confirmed by NMR spectroscopy. Wide-angle X-ray diffraction, differential scanning calorimetry (DSC), and temperature-modulated DSC showed that the PBT/glycerol-based vitrimers maintain the crystallization characteristics of normal PBT. By a change in the cross-link density of the PBT/glycerol-based vitrimers, a wide range of thermal, rheological and mechanical properties were obtained; e.g., the rubbery plateau modulus at 270 °C could be tuned from 0.07 to 3 MPa. The characteristic vitrimer behavior was demonstrated by stress relaxation and oscillatory frequency sweep experiments. In addition, these semicrystalline vitrimers can be recycled multiple times by compression molding without a substantial loss in dynamic mechanical and thermal properties. [ABSTRACT FROM AUTHOR]

Overhauser dynamic nuclear polarization (ODNP) is investigated at a moderately low field (1.2 T) for natural abundance 13C NMR of small molecules in solution state at room temperature. It is shown that ODNP transferred from ¹H to 13C by NMR coherence transfer is in general significantly more efficient than direct ODNP of 13C. Compared to direct 13C ODNP, we demonstrate over 4-fold higher 13C sensitivity (signal-to-noise ratio, SNR), achieved in one-eighth of the measurement time by transferred ODNP (t-ODNP). Compared to the 13C signal arising from Boltzmann equilibrium in a fixed measurement time, this is equivalent to about 1500-fold enhancement of 13C signal by t-ODNP, as against a direct 13C ODNP signal enhancement of about 45-fold, both at a moderate ESR saturation factor of about 0.25. This owes in part to the short polarization times characteristic of ¹H. Typically, t-ODNP reflects the essentially uniform ODNP enhancements of all protons in a molecule. Although the purpose of this work is to establish the superiority of t-ODNP vis-à-vis direct 13C ODNP, a comparison is also made of the SNR in t-ODNP experiments with standard high resolution NMR as well. Finally, the potential of t-ODNP experiments for 2D heteronuclear correlation spectroscopy of small molecules is demonstrated in 2D ¹H–13C HETCOR experiments at natural abundance, with decoupling in both dimensions. [ABSTRACT FROM AUTHOR]

We report the results of atomistic molecular dynamics simulations informed by quantum-mechanically parametrized force fields, which identify the mechanisms underlying ion motion and diffusivities in poly(1-butyl-3-vinylimidazolium-hexafluorophosphate) polymerized ionic liquid (polyIL) electrolytes. Our results demonstrate that anion transport in polyILs occurs through a mechanism involving intra- and intermolecular ion hopping through formation and breaking of ion-associations involving four polymerized cationic monomers bonded to two different polymer chains. The resulting ion mobilities are directly correlated to the average lifetimes of the ion-associations. Such a trend is demonstrated to contrast with the behavior in pure ILs, wherein structural relaxations and the associated times are dominant mechanism. Our results establish the basis for experimental findings that reported ion transport in polyILs to be decoupled from polymer segmental relaxations. [ABSTRACT FROM AUTHOR]

The coupled heat and mass transfer that occurs in evaporation is of interest in a large number of fields such as evaporative cooling, distillation, drying, coating, printing, crystallization, welding, atmospheric processes, and pool fires. The temperature jump that occurs at an evaporating interface is of central importance to understanding this complex process. Over the past three decades, thermocouples have been widely used to measure the interfacial temperature jumps at a liquid-vapor interface during evaporation. However, the reliability of these measurements has not been investigated so far. In this study, a numerical simulation of a thermocouple when it measures the interfacial temperatures at a liquid-vapor interface is conducted to understand the possible effects of the thermocouple on the measured temperature and features in the temperature profile. The differential equations of heat transfer in the solid and fluids as well as the momentum transfer in the fluids are coupled together and solved numerically subject to appropriate boundary conditions between the solid and fluids. The results of the numerical simulation showed that while thermocouples can measure the interfacial temperatures in the liquid correctly, they fail to read the actual interfacial temperatures in the vapor. As the results of our numerical study suggest, the temperature jumps at a liquid-vapor interface measured experimentally by using a thermocouple are larger than what really exists at the interface. For a typical experimental study of evaporation of water at low pressure, it was found that the temperature jumps measured by a thermocouple are overestimated by almost 50%. However, the revised temperature jumps are still in agreement with the statistical rate theory of interfacial transport. As well as addressing the specific application of the liquid-vapor temperature jump, this paper provides significant insight into the role that heat transfer plays in the operation of thermocouples in general. [ABSTRACT FROM AUTHOR]

GeTe and its derivatives constituting Pb-free elements have been well known as potential thermoelectric materials for the last five decades, which offer paramount technological importance. The main constraint in the way of optimizing thermoelectric performance of GeTe is the high lattice thermal conductivity (κlat). Herein, we demonstrate low κlat (~0.7 W/m·K) and a significantly high thermoelectric figure of merit (ZT = 2.1 at 630 K) in the Sb-doped pseudoternary (GeTe)1-2x(GeSe)x(GeS)x system by two-step strategies. The (GeTe)1-2x(GeSe)x(GeS)x system provides an excellent podium to investigate competition between an entropy-driven solid solution and enthalpy-driven phase separation. In the first step, small concentrations of Se and S were substituted simultaneously in the position of Te in GeTe to reduce the κlat by phonon scattering due to mass fluctuations and point defects. When the Se/S concentration increases significantly, the system deviates from a solid solution, and phase separation of the GeS1-xSex (5-20 μm) precipitates in the GeTe1-xSex matrix occurs, which does not participate in phonon scattering. In the second stage, κlat of the optimized sample is further reduced to 0.7 W/m·K by Sb alloying and spark plasma sintering (SPS), which introduce additional phonon scattering centers such as excess solid solution point defects and grain boundaries. The low κlat in Sb-doped (GeTe)1-2x(GeSe)x(GeS)x is attributed to phonon scattering by entropically driven solid solution point defects rather than conventional endotaxial nanostructuring. As a consequence, the SPS-processed Ge0.9Sb0.1Te0.9Se0.05S0.05 sample exhibits a remarkably high ZT of 2.1 at 630 K, which is reproducible and stable over temperature cycles. Moreover, Sb-doped (GeTe)1-2x(GeSe)x(GeS)x exhibits significantly higher Vickers microhardness (mechanical stability) compared to that of pristine GeTe. [ABSTRACT FROM AUTHOR]

The development of metal-free organic room-temperature phosphorescent (RTP) materials is promising but challenging, because spin-orbit coupling is less efficient without heavy metals such as platinum and palladium. Here, we present a novel amorphous copolymer composed of 2-bromocarbazole phosphor and acrylamide on its side chains, which can engender blue-purple phosphorescence emission with high quantum yield at room temperature. The polymer matrices of acrylamide and the hydrogen bonding in the polymeric chain system can effectively help to inhibit nonradiative transition process and, hence, strengthen the phosphorescent emission. The molar ratio of the 2-bromocarbazole phosphor and acrylamide remarkably influences the RTP emission intensities and quantum yields of the polymers. The high amount of phosphor will weaken the rigidity of the polymers and the shielding effect from oxygen, thus leading to a decrease in their RTP emission, while a low concentration of the phosphor will also weaken their RTP emission intensity. Furthermore, RTP intensity of the amorphous polymer is responsive to humidity, because the hydrogen bonding in the polymeric chain system can be broken by water, which makes it applicable in the area of encryption. [ABSTRACT FROM AUTHOR]

We present a theoretical study of electronic and thermal transport in polycrystalline heterostructures combining graphene (G) and hexagonal boron nitride (hBN) grains of varying size and distribution. By increasing the hBN grain density from a few percent to 100%, the system evolves from a good conductor to an insulator, with the mobility dropping by orders of magnitude and the sheet resistance reaching the MΩ regime. The Seebeck coefficient is suppressed above 40% mixing, while the thermal conductivity of polycrystalline hBN is found to be on the order of 30-120 Wm-1 K-1. These results, agreeing with available experimental data, provide guidelines for tuning G-hBN properties in the context of two-dimensional materials engineering. In particular, while we proved that both electrical and thermal properties are largely affected by morphological features (e.g., by the grain size and composition), we find in all cases that nanometer-sized polycrystalline G-hBN heterostructures are not good thermoelectric materials. [ABSTRACT FROM AUTHOR]

The isobaric and isochoric heat capacities of seven 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides, two 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imides, and two bis(1-alkyl-3-methylimidazolium) tetrathiocyanatocobaltates were determined at atmospheric pressure in the temperature range from 293.15 to 323.15 K. The isobaric heat capacities were determined by means of differential scanning calorimetry, whereas isochoric heat capacities were determined along with isothermal compressibilities indirectly by means of the acoustic method from the speed of sound and density measurements. Based on the experimental data, as expected, the isobaric heat capacity increases linearly with increasing alkyl chain length in the cation of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides and no odd and even carbon number effect is observed. After critical comparison of the obtained data with the available literature data, the most reliable values are recommended. It has been also shown that, although the COSMOthermX calculations underestimated the isobaric heat capacity values whatever the temperature and the ionic liquid structure, the approach used during this work may be applied to estimate physical properties of non-single-charged ions as well. Additionally, based on the speeds of sound the thermal conductivities were calculated using a modified Bridgman relation. [ABSTRACT FROM AUTHOR]

Understanding the temperature dependency of triplet-triplet annihilation upconversion (TTA-UC) is important for optimizing biological applications of upconversion. Here the temperature dependency of red-to-blue TTA-UC is reported in a variety of neutral PEGylated phospholipid liposomes. In these systems a delicate balance between lateral diffusion rate of the dyes, annihilator aggregation, and sensitizer self-quenching leads to a volcano plot, with the maximum upconversion intensity occurring near the main order-disorder transition temperature of the lipid membrane. [ABSTRACT FROM AUTHOR]

Low-dimensional carbon allotropes, from fullerenes, carbon nanotubes, to graphene, have been broadly explored due to their outstanding and special properties. However, there exist significant challenges in retaining such properties of basic building blocks when scaling them up to three-dimensional materials and structures for many technological applications. Here we show theoretically the atomistic structure of a stable three-dimensional carbon honeycomb (C-honeycomb) structure with superb mechanical and thermal properties. A combination of sp2 bonding in the wall and sp3 bonding in the triple junction of C-honeycomb is the key to retain the stability of C-honeycomb. The specific strength could be the best in structural carbon materials, and this strength remains at a high level but tunable with different cell sizes. C-honeycomb is also found to have a very high thermal conductivity, for example, >100 W/mK along the axis of the hexagonal cell with a density only ~0.4 g/cm3. Because of the low density and high thermal conductivity, the specific thermal conductivity of C-honeycombs is larger than most engineering materials, including metals and high thermal conductivity semiconductors, as well as lightweight CNT arrays and graphene-based nanocomposites. Such high specific strength, high thermal conductivity, and anomalous Poisson's effect in C-honeycomb render it appealing for the use in various engineering practices. [ABSTRACT FROM AUTHOR]

The purpose of this study is to determine how certain model compounds, representing in this case ink and typical coating components, interact in increasingly complex mixtures by evaluating their response to thermal treatment. Such materials are also used in many other chemical and industrial products and processes other than printing, such that the mechanisms are universally applicable. Thermogravimetric analysis (TgA) and differential scanning calorimetry (DSC) are techniques considered here as potential tools for the analysis. Fourier transform infrared (FTIR) spectrometry is used to characterize the model compounds and to provide a characteristic of the change undergone by some model compound mixtures after thermal exposure in TgA. To visualize the thermal data so as to combine the TgA and DSC measurements into a single comprehensible observation, a representation has been devised for the specific case of material evaporation and the respective observed specific evaporation energy, whereby the specific gravimetric change (TgA) and specific energy (DSC) ratios are calculated. By adopting this combinational representation, it is possible to clarify if there are observable interactions between studied model components. It is to be supposed that the thermal behavior of solvent in a given mixture will reflect, for instance, the ease with which an ink will set and dry to form a nonsmearing print, thus improving the efficiency of this and similar such processes. Additionally, any evidence of newly formed compounds, or material loss, resulting from thermal treatment during processing may affect product performance and ultimately recyclability or waste management. [ABSTRACT FROM AUTHOR]

A quantitative structure-activity relationship model has been constructed by artificial neural networks for estimation of melting temperature (T m) of molecular cocrystals (CCs). On the basis of a literature analysis using SciFinder and Cambridge Structural Database softwares, a database has been created of CCs for four active pharmaceutical ingredients, namely, caffeine, theophylline (THP), nicotinamide (NA), and isonicotinamide (INA). In total, of 61 CCs were included: 14-CAF, 9-THP, 29-INA, and 9-NA. A good correlation was obtained with ANNs to quantify the T m of the CCs with respect to various coformers. The training process was completed with an average relative error of 2.38%, whereas the relative error for the validation set was 2.89%. On the basis of a literature analysis using Scifinder and Cambridge Structural Database softwares, a database has been created of over 61 cocrystals for four active pharmaceutical ingredient, namely, caffeine, theophylline, nicotinamide, and isonicotinamide. An estimation of melting point of the cocrystals is made possible by performing a quantitative structure-activity relationship using the artificial neural network programs as a main tool. [ABSTRACT FROM AUTHOR]

We report that K2Bi8Se13 exhibits multiple conduction bands that lie close in energy and can be activated through doping, leading to a highly enhanced Seebeck coefficient and a high power factor with elevated temperature. Meanwhile, the large unit cell, complex low symmetry crystal structure, and nondirectional bonding lead to the very low lattice thermal conductivity of K2Bi8Se13, ranging between 0.42 and 0.20 W m-1 K-1 in the temperature interval 300-873 K. Experimentally, we further support the low thermal conductivity of K2Bi8Se13 using phonon velocity measurements; the results show a low average phonon velocity (1605 ms-1), small Young's modulus (37.1 GPa), large Grüneisen parameter (1.71), and low Debye temperature (154 K). A detailed investigation of the microstructure and defects was carried out using electron diffraction and transmission microscopy which reveal the presence of a K2.5Bi8.5Se14 minor phase intergrown along the side of the K2Bi8Se13 phase. The combination of enhanced power factor and low thermal conductivity results in a high ZT value of ~1.3 at 873 K in electron doped K2Bi8Se13 material. [ABSTRACT FROM AUTHOR]

Two-component fluorescent hydrogels have been discovered, containing the mixtures of naphthalene diimide (NDI)-conjugated peptide-functionalized bola-amphiphile and primary amines with long alkyl chains at physiological pH 7.46. The aggregation-induced enhanced emission associated with an NDI-appended peptide in aqueous medium is rare, as water is known to be a good quencher of fluorescence. In this study, an NDI-containing gelator peptide forms a highly fluorescent aggregate in aqueous medium. Absorption and emission spectroscopic techniques reveal the formation of J-aggregates among the chromophoric moieties in their aggregated state in aqueous medium. However, this NDI-containing peptide does not form any gel in aqueous medium. In the presence of the primary amines with long alkyl chains in the buffer solution, it forms two-component fluorescent hydrogels exhibiting bright yellow fluorescence under a UV lamp (365 nm). Probably, the acid-amine interaction between the amines and the bola-amphiphile triggers the gel formation, as evident from Fourier transform infrared data, indicating the presence of a carboxylate group (−COO-) and an ammonium species (NH3+) in the coassembled two-component gel system. Low- and wide-angle powder X-ray diffraction and small-angle X-ray scattering further support the fact that the coassembled state in the gel form is produced by the supramolecular interaction between the NDI-based bola-amphiphile and the long-chain amines. Field-emission scanning electron microscopy and high-resolution transmission electron microscopy images reveal that the π-conjugated coassembled hydrogels exhibit nanofibrillar network morphologies. Interestingly, the coassembled hydrogels exhibit an enhanced fluorescence emission, excited-state lifetime, and quantum yield when compared with those of the NDI-containing amphiphile alone in its self-assembled state in aqueous medium. Moreover, the thermal stability and mechanical strength of these gels have been successfully tuned by varying the alkyl chain length of the corresponding amine. Moreover, these NDI-peptide-conjugated soft materials exhibit semiconducting behavior in their respective coassembled states. This holds future promise to use these peptide-appended NDI-based coassembled soft materials for applications in optoelectronic and other devices. [ABSTRACT FROM AUTHOR]

Different thermodynamic properties of aqueous solutions of butyltriacetonediamine (BuTAD), unloaded and loaded with carbon dioxide, are studied experimentally. For unloaded mixtures of BuTAD and water, protonation equilibrium constants between 283 and 333 K and liquid-liquid equilibria between 313 and 353 K, including the lower critical point, are determined at atmospheric pressure. Furthermore, the solubility of carbon dioxide in aqueous solutions of BuTAD between 313 and 393 K is determined at low loadings with an analytic method based on headspace gas chromatography and at high loadings with a synthetic method using a high pressure view cell. In the loaded system, solid precipitation, liquid-liquid phase split, and the presence of metastable states are observed in certain ranges. The data is interesting for assessing the aqueous solution of BuTAD as solvent for carbon capture. A short-cut method is used for comparing the new solvent with an aqueous solution of monoethanolamine (MEA) with respect to the energy requirement of an absorption/desorption process for CO2 scrubbing. Furthermore, a new and simple gas chromatographic method for determining the loading with carbon dioxide of aqueous solutions of amines is described. [ABSTRACT FROM AUTHOR]

The combination of DOPO and 2-aminobenzothiazole (ABZ) was designed to develop P/N/S-containing flame retardant DOPO-ABZ, and its chemical structure was confirmed by HRMS, FTIR, and ¹H and 31P NMR. The reduced thermal stability of EP/DOPO-ABZ formulations was found through DSC and TGA, as compared to that of EP. Fire properties were evaluated by LOI, UL-94, and cone calorimeter tests, respectively. The results indicated that DOPO-ABZ imparted flame retardance to EP, and that EP/7.5 wt % DOPO-ABZ passed the V-0 rating, and acquired a LOI value of 33.5%; moreover, when the loading of DOPO-ABZ increased to 10 wt %, it could further suppress the heat release and smoke release of the curved epoxy resin. Finally, the flame-retardant mechanism was studied by TG-FTIR and py-GC/MS, disclosing that DOPO-ABZ exerted predominant gaseous-phase activity of fire inhibition via generating phosphorus-containing free radicals and nitrogen/sulfur-containing volatiles. [ABSTRACT FROM AUTHOR]

A novel branched poly(phosphonamidate-phosphonate) (BPPAPO) oligomer was synthesized from the polycondensation of phenylphosphonic dichloride and trihydroxymethylphosphine oxide followed by end-capping with aniline in a one-pot synthesis. BPPAPO exhibited excellent flame-retardant efficiency in epoxy resins (EP). With only 5.0 wt % loading, the EP composite reached UL-94 V-0 rating with a limiting oxygen index (LOI) value of 35.5%. BPPAPO catalyzed the early degradation of EP and promoted the formation of more char residue. Glass transition temperatures were partially lowered. When 7.5 wt % BPPAPO was incorporated, the peak heat release rate and total heat release were decreased by 66.2% and 37.3%, respectively, with a delayed ignition and the formation of a highly intumescent char residue. Combination of gas-phase and condensed-phase flame-retardant mechanisms was verified. [ABSTRACT FROM AUTHOR]

In this work, the investigation mainly focused on the synergistic effect of phosphorus-containing polyol (BHPP) and nitrogen-containing polyol (MADP) in improving the flame retardancy of EG/rigid polyurethane foam (RPUF). BHPP and MADP were synthesized through dehydrochlorination and Mannich reaction, respectively. The influence of the weight ratio of BHPP and MADP was studied by thermogravimetric analysis and limiting oxygen index (LOI) tests. The results demonstrated that the optimal weight percentage of BHPP and MADP in flame-retarding RPUF was 1/1. In addition, the incorporation of expandable graphite (EG) into the RPUF/BHPP/MADP system could greatly improve the flame-retardant properties of RPUF composites. When the content of EG was 15 wt %, LOI value of RPUF composites reached 33.5%. Furthermore, the value of the peak of the heat release rate was reduced by 52.4% compared to that of pristine RPUF. Based on the analysis and discussion, a condensed flame-retardant mechanism was primarily proposed. [ABSTRACT FROM AUTHOR]