Addition Of Expanded Graphite Research Articles

A Novel Paraffin Wax/Expanded Graphite/Bacterial Cellulose Powder Phase Change Materials for the Dependable Battery Safety Management

Although phase change materials (PCMs) exhibit effective performance in the thermal management of lithium-ion batteries (LIBs), their development is limited by low thermal conductivity and susceptibility to leakage during the solid–liquid phase transition. To address these challenges and enhance thermal management capabilities, this study introduces a novel composite phase change material (CPCM) synthesized by physically mixing paraffin (PA), expanded graphite (EG), and bacterial cellulose (BC). The thermal performance of CPCMs with varying BC proportions is evaluated, and their impact on temperature control in battery thermal management systems (BTMS) is assessed. The results show that the addition of EG and BC significantly improves the thermal conductivity of the CPCM, reaching a value of 1.39 W·m−1·K−1. This also enhances the uniformity of temperature distribution within the battery module and reduces CPCM leakage. By comparing temperature variations within the battery module under different operating conditions, it was found that the intricate network structure of the CPCM promotes uniform temperature distribution, effectively mitigating temperature rise. Consequently, the maximum temperature and maximum temperature difference within the battery module were maintained below 47 °C and 4 °C, respectively. Compared to a system without phase change material at a 3C discharge rate, the maximum cell temperature, maximum module temperature, and maximum temperature difference were reduced by 32.38%, 26.92%, and 34.94%, respectively. These findings provide valuable insights for the design and optimization of BTMS.

Facile synthesis and electrochemical properties of sheet-rod-sheet structured NiCo2S4/EG/Ti3C2Tx nanocomposites

Electrode materials with outstanding stability and electrochemical activity are ideal for high-performance supercapacitors. Herein, we developed a simple two-step method for fabricating NiCo2S4/EG/Ti3C2Tx nanocomposites with a sheet(2D)-rod(1D)-sheet(2D) structure. The NiCo2S4 rods were embedded into the expanded graphite (EG) sheets via an in-situ hydrothermal method, then the Ti3C2Tx sheets were assembled with NiCo2S4/EG by an electrostatic self-assembly method. The obtained NiCo2S4/EG/Ti3C2Tx nanocomposites exhibited a synergistic effect among the components. The addition of EG inhibited the volumetric effect of NiCo2S4 during charging and discharging processes, while the high conductivity of Ti3C2Tx promoted charges transfer. The rod-like structure of NiCo2S4 effectively inhibited the self-stacking of Ti3C2Tx sheets. Consequently, the optimized composite exhibited an excellent specific capacitance of 1837.9 F·g−1 at a current density of 1 A·g−1. Additionally, the composite electrode exhibited a capacitance retention of 73.5 % during 10,000 charging-discharging cycles at a current density of 20 A·g−1.

Tailoring mechanical and tribological properties of oscillatory pressure sintered binderless WC ceramics with expanded graphite addition

The fracture toughness and wear resistance of WC-based ceramics are crucial factors that determine their subsequent applications. In this study, the mechanical and tribological properties of expanded graphite (EG) reinforced WC ceramics consolidated by oscillatory pressure sintering (OPS) were investigated. The results demonstrated that the combination of dynamic pressure and EG had a synergistic effect, resulting in a much higher relative density of 0.2 wt% EG/WC ceramics reaching up to 99.78%. Simultaneously, 0.2 wt% EG/WC ceramics demonstrated a reduced grain size, with fracture toughness, flexural strength and wear rate reaching 7.54 MPa m1/2, 1262 MPa and 2.16 × 10−7 mm3·N−1·m−1, respectively. EG was present in the form of graphene nanoplatelets (GNPs) within WC ceramics. The primary toughening mechanisms involved the bridging and pulling out of GNPs, as well as the generation of microcracks induced by GNPs. Additionally, the exceptional thermal conductivity of GNPs can facilitate heat dissipation and reduce thermal damage. The wear resistance of WC-EG ceramics was primarily enhanced through improving overall mechanical properties and decreasing the occurrence of oxidation and adhesive wear.

Preparation and properties of three-dimensional continuous network reinforced Graphite/SiC ceramic composite insulation materials

Addressing the challenge of existing insulation materials struggling to achieve the synergy of lightweight construction, high strength, and low thermal conductivity, this paper presents a method based on multi-material assembly technology to achieve a controlled composite of a three-dimensional continuous silicon carbide network and graphite matrix. Following an examination of the impact of various forming densities and the addition of expandable graphite on the thermal conductivity and compressive strength of graphite/SiC composites, the study explored the effects of different "enhancement network" topologies on the properties of these composites. The investigation demonstrates that adjusting the forming density and incorporating expandable graphite enable regulation of both the porosity and closed porosity of the composites, thereby controlling their compressive strength and thermal conductivity. Additionally, the construction of a three-dimensional continuous SiC network structure within the graphite matrix significantly enhances the compressive strength of the composites, with only a slight increase in thermal conductivity. A graphite/SiC composite thermal insulation material was ultimately developed, boasting a density of merely 1.1 g/cm³, a low thermal conductivity of 1.847 W/m·K, and an impressive compressive strength reaching 15.627 MPa. Its overall performance surpasses that of water-glass sand, making it a promising candidate for various applications in the foundry industry as a thermal insulation material.

Preparation and thermal performance study of a novel hydrated salt composite PCM for space heating

In order to effectively address the mismatch between thermal energy supply and demand in buildings, latent heat storage (LHS) based on phase change material (PCM) stands out as a key technology. While hydrated salt has emerged as a promising PCM, it encounters common issues such as substantial supercooling, phase separation, and low thermal conductivity, hindering its development. To mitigate these limitations, this study focused on modifying Ba(OH)2·8H2O by incorporating various nucleating agents and thickening agents to reduce supercooling, enhancing the composite PCM's thermal properties by introducing expanded graphite (EG) to elevate thermal conductivity. Subsequently, the thermal stability of the PCM was evaluated through accelerated thermal cycling tests, encompassing the assessment of critical thermal parameters, including supercooling degree, enthalpy, and thermal conductivity of the composite PCM. Experimental findings unveiled the effectiveness of incorporating 2 wt% BaCl2·2H2O and 1 wt% CMC to Ba(OH)2·8H2O, effectively diminishing the supercooling degree from 14 °C to 1.42 °C. Further integration of 3.5 wt% EG led to a substantial decrease in the supercooling degree to 0.24 °C. Simultaneously, the addition of EG resulted in an improvement in thermal conductivity, elevating it from 0.62 W/(m·K) to 1.03 W/(m·K), while the enthalpy decreased from 283.68 J/g to 252.81 J/g. Notably, the composite PCM exhibited notable thermal reliability with a latent heat drop of 15.9 % following 1000 accelerated cycles of testing. Moreover, the composite PCM demonstrated superior thermal storage density, measuring at 2.36 times that of traditional paraffin wax, yet with a thermal storage cost merely a quarter of paraffin wax, rendering it more favorable for extensive deployment in building energy systems.

Development of bio-based flexible phase change materials utilizing lauric acid for battery thermal management systems

Lithium-ion batteries, serving as the cornerstone of electric vehicles, generate significant thermal output during their operation. This underscores the imperative need for the implementation of an appropriate battery thermal management system (BTMS). Extensive attention has been directed towards thermal-induced flexible phase change material (FPCM) within the domain of BTMS. However, it is notable that the predominant choice in contemporary practice for FPCM in BTMS remains paraffin (PA)-based, sourced from petroleum origins. This study utilizes an environmentally friendly bio-based phase change material (PCM), lauric acid (LA), to fabricate FPCM. The FPCM is skillfully crafted through the incorporation of styrene-ethylene-propylene-styrene (SEPS) and expanded graphite (EG) as supporting materials, forming the LA/SEPS/EG composite phase change material (CPCM). The addition of EG increases the thermal conductivity of CPCM by 4.97 times and enhances the leakage resistance. Furthermore, comprehensive assessments were conducted to evaluate the thermal performance, thermally induced flexibility, heat storage, release characteristics, and cyclic stability of the fabricated FPCM. In the battery discharge tests conducted at 2C/3C/4C rates, the battery containing FPCM consistently maintained its maximum temperature below 50 °C, with a minimal temperature difference of <1 °C, showcasing excellent thermal management performance.

Preparation and thermal property enhancement of sodium acetate trihydrate-lithium chloride-potassium chloride expanded graphite composite phase change materials

Phase change materials (PCMs) present promising solutions for enhancing energy efficiency in solar heat pump systems. In our study, we have innovatively developed a composite PCMs (CPCMs) by combining sodium acetate trihydrate (CH3COONa·3H2O, SAT), lithium chloride (LiCl), potassium chloride (KCl), and incorporating expanded graphite (EG). This addition of high thermal conductivity EG was aimed at bolstering the CPCM's thermal stability. Our findings reveal that SAT-LiCl-KCl/EG CPCMs, with 14 wt% EG, significantly enhances thermal energy storage performance while preserving the fundamental phase change characteristics. The resulting CPCMs demonstrates a phase transition temperature of 49.3 °C and a latent heat of 196.4 J/g, ideally suited to meet the demands of hot water heat pump systems operating in the 45–50 °C range. Notably, the thermal conductivity of this CPCMs, following the incorporation of 14 wt% EG, registers at 4.54 W/(m K), representing a remarkable 10.6-fold increase compared to the SAT-LiCl-KCl ternary eutectic salt. To ensure long-term stability, secondary encapsulation with a thermally conductive sealant was applied. Subsequent tests involved subjecting the CPCM to 3000 heating/cooling cycles, resulting in minimal deviations, with the phase transition temperature shifting by approximately 1 °C and a modest 6 % reduction in latent heat of phase transition. These outcomes underscore the robustness and reliability of our developed composite phase change materials.

Bio‐based rigid polyurethane foam composites reinforced with flame retardants: From synthesis to performance evaluation

AbstractThe building and construction industry is under increasing pressure to make insulation materials greener, more sustainable, and less flammable. In this study, sugar beet pulp was liquified under the optimized liquefaction conditions and used as the source of bio‐polyol (SBpol) in the production of bio‐based rigid polyurethane foam (sPUF). In order to improve the flame retardancy, sPUF composites were prepared with the addition of flame retardants; expandable graphite (EG) and/or dimethyl methyl phosphonate (DMMP). The bio‐polyol was used at a fixed ratio of 50 php in sPUF composites whereas the total ratio of flame retardants was fixed at 20 php. The effects of the ratio of EG and/or DMMP on the morphological, physicomechanical, thermal, and flame retardant properties of sPUF composites were evaluated. Although the thermal conductivity values of flame retardant added sPUF composites were increased in comparison to the petroleum‐based foam, the compressive strength values were decreased as the amount of DMMP increased in the flame retardant formulation. Thermogravimetric analysis showed that the onset of decomposition of 20 php DMMP‐containing sPUF composite decreased to 168.3°C. Although the limiting oxygen index (LOI) value of the petroleum‐based PUF was as low as 19.7%, the LOI value of the sPUF/10E/10D foam increased to 24.9% (by about 26%). According to the cone calorimeter results, the peak heat release rate (pHRR) of sPUF was much higher than the petroleum‐based foam. The incorporation of both DMMP and EG could further improve the flame retardant properties. The pHRR value of sPUF/10E/10D was 28.1% lower than that of sPUF. The results have shown that flame retardancy of sPUF composites could be improved by the addition of EG which acts in the condensed phase and DMMP, which acts mainly in the gas phase during burning. Flame retardant incorporated sPUF composites are considered as promising materials for use in insulation applications.

Preparation and characterization of lauric acid-stearic acid/fumed silica/expanded graphite thermally conductive enhanced composites

Fatty acid and fatty acid blend phase change materials (PCM) have issues with easy leakage and low thermal conductivity in thermal storage and exothermic processes. To overcome this issue, a novel low-temperature composite material, Lauric acid - stearic acid - fumed silica - expanded graphite (LA-SA-FS-EG), was fabricated by vacuum impregnation technique using lauric acid-stearic acid (LA-SA) as the phase change material (PCM), fumed silica (FS) as the support material, and expanded graphite (EG) as the thermal conductive material. Leakage tests indicated that the maximum adsorption of LA-SA by fumed silica was 75 wt%. Scanning electron microscopy (SEM) was employed to observe the microscopic morphology of the composites. The crystal structure and chemical composition of the composites were analyzed by X-ray diffraction (XRD) and Fourier infrared spectroscopy (FT-IR). The differential scanning calorimeter (DSC) data indicates that the melting temperatures of LA-SA-FS-EG 3 %, 5 % and 7 % were 33.38 °C, 33.32 °C and 33.13 °C respectively, with melting latent heats of 110.8 J/g, 114.3 J/g and 119.9 J/g, respectively. The thermal conductivity of LA-SA-FS-EG 7 % is improved by 454 % compared to the LA-SA-FS composite without the addition of EG. LA-SA-FS-EG7% composite showed excellent heat storage capacity. LA-SA-FS-EG7% has a 46.1 % increase in heat storage rate and a 59.4 % increase in thermal release rate compared to LA-SA-FS composite. Notably, the LA-SA-FS-EG7% composite retains good thermal properties even after 1000 heating and cooling cycles. Consequently, the LA-SA-FS-EG7% composites produced have potential applications in thermal energy storage and building energy efficiency.

Design of a stearic acid/boron nitride/expanded graphite multifiller synergistic composite phase change material for thermal energy storage

• Stearic acid was encapsulated by various fillers. • A shape-stabilized composite phase change material was prepared. • Thermal and cycling stability of the prepared composite are excellent. • Thermal conductivity of the prepared composite is 6.349 W•m −1 •K −1 . In order to solve the problems of low thermal conductivity and easy liquid leakage of a stearic acid (SA), the composite phase change material(PCM) was prepared by adding boron nitride (BN) and expanded graphite (EG) to melted SA, and its thermal conductivity, crystal structure, chemical stability, thermal stability, cycle stability, leakage characteristics, heat storage/release characteristics, and temperature response characteristics were characterized. The results showed that the addition of BN and EG significantly improved the thermal conductivity of the material, and they efficiently adsorbed melted SA. The maximum load of SA was 76 wt. % and there was almost no liquid leakage. Moreover, the melting enthalpy and temperature were 154.20 J • g − 1 and 67.85°C, respectively. Compared with pure SA, the SA/BN/EG composite showed a lower melting temperature and a higher freezing temperature. In addition, when the mass fraction of BN and EG was 12 wt. %, the thermal conductivity of the composite was 6.349 W • m −1 • K −1 , which was 18.619 times that of SA. More importantly, the composite showed good stability for 50 cycles of heating and cooling, and the SA / BN / EG-12 hardly decomposes below 200°C, which implies that the working performance of the composite PCM is relatively stable within the temperature range of 100°C. Therefore, the composite can exhibit excellent thermal stability in the field of building heating.

Investigation of novel expandable polystyrene/alumina aerogel composite thermal insulation material

Expandable polystyrene (EPS) foam is one of the most commonly used building thermal insulation materials due to its low thermal conductivity, apparent density as well and low cost. However, its high flammability and the release of a large number of toxic gases during combustion hinder its application. In this paper, using EPS foam and alumina aerogel (Al2O3) as insulation components, epoxy resin (EP) as a binder, and expandable graphite (EG) and ammonium polyphosphate (APP) as composite flame-retardant, a novel organic-inorganic composite thermal insulation material (EPS-AEA) was designed and fabricated. Experiment results showed that adding Al2O3 to EPS could further reduce the thermal conductivity of the obtained composite, and improve its mechanical properties. The addition of EG and APP composite flame-retardant could markedly enhance flame-retardant performance. With the addition of 4.17% Al2O3, and 50% EG/APP (1/1 mass ratio), the obtained EPS-AEA-1/1 composite showed superior fire resistance (reaching UL-94 V-0 rating and limiting oxygen index (LOI of 40.6%), high thermal insulation (thermal conductivity of 0.0487 W/(m·K)and applicable mechanical properties. In addition, EPS-AEA had excellent anti-hygroscopic properties (moisture ab-desorption rate within 0.5%) and fairly low toxic gas emissions during combustion, indicating its potential in practical application.

Optimization of Thermal Conductivity and Tensile Properties of High-Density Polyethylene by Addition of Expanded Graphite and Boron Nitride.

Due to its mechanical, rheological, and chemical properties, high-density polyethylene (HDPE) is commonly used as a material for producing the pipes for transport of various media. Low thermal conductivity (0.4 W/mK) narrows down the usage of HDPE in the heat exchanger systems. The main goal of the work is to reduce the vertical depth of the HDPE pipe buried in the borehole by increasing the thermal conductivity of the material. This property can be improved by adding certain additives to the pure HDPE matrix. Composites made of HDPE with metallic and non-metallic additives show increased thermal conductivity several times compared to the thermal conductivity of pure HDPE. Those additives affect the mechanical properties too, by enhancing or degrading them. In this research, the thermal conductivity and tensile properties of composite made of HDPE matrix and two types of additives, expanded graphite (EG) and boron nitride (BN), were tested. Micro-sized particles of EG and two different sizes of BN particles, micro and nano, were used to produce composite. The objective behind utilizing composite materials featuring dual additives is twofold: firstly, to enhance thermal properties, and secondly, to improve mechanical properties when compared with the pure HDPE. As anticipated, the thermal conductivity of the composites exhibited an eightfold rise in comparison to the pure HDPE. The tensile modulus experienced augmentation across all variations of additive ratios within the composites, albeit with a marginal reduction in tensile strength. This implies that the composite retains a value similar to pure HDPE in terms of tensile strength. Apart from the enhancement observed in all the aforementioned properties, the most significant downside of these composites pertains to their strain at yield, which experienced a reduction, declining from the initial 8.5% found in pure HDPE to a range spanning from 6.6% to 1.8%, dependent upon the specific additive ratios and the size of the BN particles.

Preparation and thermal properties of LiNO3-NaNO3-NaCl/EG composite heat storage material

Nitrate phase change materials (PCM) have important applications in the field of thermal energy storage, but their latent heat value is relatively low. A novel LiNO3-NaNO3-NaCl ternary molten salt with high latent heat was prepared and studied. LiNO3-NaNO3-NaCl/expanded graphite (EG) composite phase change material (CPCM) was prepared by using high thermal conductivity EG as the carrier adsorption material. The performance of PCM and CPCM were tested and analyzed. Compared with LiNO3-NaNO3, the newly prepared ternary nitrate-chloride mixed molten salt has a lower phase change temperature, a higher latent heat value, and a higher thermal decomposition temperature. At the same time, the supercooling degree of LiNO3-NaNO3-NaCl is about half lower than that of LiNO3-NaNO3. There is no chemical reaction between different molten salts or between mixed molten salts and EG. The mixed molten salt is uniformly dispersed into the pore structure of EG, and no agglomeration occurs. Both LiNO3-NaNO3-NaCl and LiNO3-NaNO3-NaCl/EG have good cyclic thermal stability. The addition of EG greatly improves the thermal conductivity of LiNO3-NaNO3-NaCl. When the addition ratio of EG is 20%, the thermal conductivity of ternary molten salt increases from 1.378 to 5.453 W/m·K. The phase change materials added with EG still have high latent heat of phase change. The results show that LiNO3-NaNO3-NaCl/EG has broad application prospects in medium temperature heat storage.

Highly thermally conductive polyamide 6 composites with favorable mechanical properties, processability and low water absorption using a hybrid filling of short carbon fiber, flake graphite and expanded graphite

Abstract It is a challenge to maintain the mechanical properties and processability of thermally conductive polymer composites in the presence of high filling of heat conductive filler. An optimized hybrid filler system composed of flake graphite (FG), expanded graphite (EG) and short carbon fiber (CF) was introduced into PA6 matrix. The addition of EG to PA6 was found to be more effective in improving its thermal conductivity, while the addition of FG maintained favorable processability due to its lubrication effect. Furthermore, the hybrid filling of FG and EG has a synergistic effect on the enhancement of thermal conductivity. The ternary filling of FG, EG and CF produced highly heat conductive PA6 composites with high strength, favorable processability, and low water absorption. The thermal conductivity of 10CF/20FG/10EG/PA6 composite reached 3.45 W/m k, which is 12.3 times of pure PA6. Additionally, the flexural strength increased to 110 MPa, which is 37 % higher than that of pure PA6, and the water absorption was reduced to one quarter that of pure PA6.

NaNO3-KNO3/EG/Al2O3 shape-stable phase change materials for thermal energy storage over a wide temperature range: Sintering temperature study

The coefficient of thermal expansion of inorganic salts increases with increasing temperature. The sintering temperature may affect the properties of the shape-stable phase change materials (SSPCMs). We study the SSPCMs with NaNO3-KNO3 as the phase change material and Al2O3 and expanded graphite (EG) as the skeletal support materials (SSMs) to achieve thermal energy storage over a wide temperature range. The effects of different sintering temperatures on the SSMs content, thermal conductivity and compressive strength of SSPCMs were studied. The results showed that as the sintering temperature increased, more SSMs were required to support the SSPCMs. The maximum NaNO3-KNO3 mass percentages of the SSPCMs sintered at 300 °C and 450 °C were 82.8 wt% and 66.4 wt%, respectively. Samples with application temperatures higher than the sintering temperature may have problems stabilizing the shape. Sintering temperature had little influence on the thermal conductivity of the same SSPCMs. However, the compressive strength of the SSPCMs decreased with increasing sintering temperature. The addition of EG decreases the decomposition temperature of the composite and limits its application temperature range. The SSPCM-10/30 sintered at 450 ℃ showed good chemical stability performance, and the latent heat decreased from 56.01 J/g to 53.44 J/g. The compressive strength dropped from 30.7 MPa to 25.17 MPa before and after 20 cycles due to larger internal gaps and did not change much after 20 cycles.

Performance Analysis of Loose-Fill Thermal Insulation from Wood Scobs Coated with Liquid Glass, Tung Oil, and Expandable Graphite Mixture.

The current study presents the results of monitoring the behavior of loose-fill thermal insulating material for buildings made of wood scobs (WS), which were coated with one, two, and three component-based coatings from liquid glass (LG), tung oil (TO), and expandable graphite (EG). The thermal conductivity of samples in the dry state and under normal laboratory conditions, short-term water absorption by partial immersion, surface wettability, and water vapor permeability were evaluated, and regression equations describing the variations in numerical values of specified properties under different amounts of each coating component were presented. It was shown that LG and TO act as hydrophobic layers that, in conjunction, reduce water absorption by a maximum of 274%, have a contact angle equal to 86°, and lower thermal conductivity by 55% in the dry state due to the specifics of the layer formed on the surface of WS. The addition of EG to LG coating resulted in insignificantly changed water absorption and thermal conductivity values, indicating the potential of this material to be used to improve the fire resistance of wood-based composites in the future. The results showed that the three-component layer of LG/TO/EG reduces water absorption by a maximum of 72%, increases thermal conductivity in the dry state by a minimum of 0.4%, and increases the contact angle to 81° at 100 wt.% LG. The changes in water vapor permeability of all compositions were determined to be insignificant.

Synthesis and characterization of polyethylene

A combined intumescent flame retardant expandable graphite (EG), with an initial expansion temperature of 155°C and expansion volume of 515 mL g-1, was successfully prepared based on a chemical intercalation method of material graphite under oxidation of KMnO4, intercalation of H2SO4 and Na4B2O7· 10H2O at the mass ratio C : KMnO4 : H2SO4 (98%) : Na4B2O7· 10H2O of 1.0 : 0.4 : 5.5 : 0.6 (H2SO4 diluted to a mass concentration of 80-wt. % before reaction), and characterized by expansion volume (EV), initial expansion temperature, X-ray diffraction (XRD). The flame retarding and thermal properties of LLDPE/EG and LLDPE/EG/APP composites (LLDPE-Linear low-density polyethylene; APP-ammonium polyphosphate) were investigated and characterized by limiting oxygen index (LOI), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric (TG) and differential thermal analysis (DTA). The results showed that addition of EG (30-wt. %) increased the LOI of 70LLDPE/30EG composite to 28.4 %. Even more, the synergistic effect of 20% EG together with 10% APP improved the LOI of 70LLDPE/20EG/10APP composite to 30.5%. At the same time, temperatures corresponding to a 1% weight loss and a maximum weight loss rate increased at about 50°C and 2°C, respectively. The 70LLDPE/10APP/20EG composite exhibited higher flame retardancy even at a lower residual char than 70LLDPE/30EG specimen. The intercalated borate was more effectual in improving the flame retardancy than the direct additive of Na4B2O7· 10H2O.

Flame-Retardant and Smoke-Suppressant Flexible Polyurethane Foams Based on Phosphorus-Containing Polyester Diols and Expandable Graphite

A liquid-phosphorus-containing polyester diol, PPE, was prepared via condensation polymerization using commercial reactive flame retardant 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phospha-phenanthrene-10-oxide, adipic acid, ethylene glycol, and 1,4-butanediol. PPE and/or expandable graphite (EG) were then incorporated into phosphorus-containing flame-retardant polyester-based flexible polyurethane foams (P-FPUFs). The structure and properties of the resultant P-FPUFs were characterized using scanning electron microscopy tensile measurements, limiting oxygen index (LOI), vertical burning tests, cone calorimeter tests, thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. Unlike the FPUF prepared using regular polyester polyol (R-FPUF), PPE increased the flexibility and elongation at break of the resultant forms. More importantly, the peak heat release rate (PHRR) and total heat release (THR) of P-FPUF were reduced by 18.6% and 16.3%, respectively, via gas-phase-dominated flame-retardant mechanisms, compared with those of R-FPUF. The addition of EG further reduced the peak smoke production release (PSR) and total smoke production (TSP) of the resultant FPUFs while increasing the LOI and char formation. Interestingly, it was observed that EG noticeably improved the residual quantity of phosphorus in the char residue. When the EG loading was 15 phr, the resulting FPUF (P-FPUF/15EG) attained a high LOI value (29.2%) and exhibited good anti-dripping performance. Meanwhile, the PHRR, THR, and TSP of P-FPUF/15EG were significantly decreased by 82.7%, 40.3%, and 83.4%, respectively, compared with those of P-FPUF. This superior flame-retardant performance can be attributed to the combination of the bi-phase flame-retardant behavior of PPE and condensed-phase flame-retardant characteristics of EG.

Study on the mechanism of expanded graphite to improve the fading resistance of the non-asbestos organic composite braking materials

To improve the anti-fading performance and braking reliability of non-asbestos organic composite braking materials (NAOCBM) and to decrease vehicle driving risks due to braking failure, we studied the addition of expanded graphite (EG) to NAOCBM. The properties were optimized when the EG dose was 4 wt%. The reason for improvement was that the local flexible internal stress due to graphite expansion at high braking temperature partially offset the crack expansion, and thereby significantly decreased the damages of delamination wear to braking materials and braking performances. These results uncover the mechanism of EG addition to the performance optimization of braking materials, and provide an effective method to improve the reliability of braking materials and to reduce the probability of traffic accidents.

Form-stable flexible composite multi-phase change material with high latent heat and enhanced thermal conductivity for thermal management

Form-stable flexible composite phase change materials (PCMs) are widely studied on the application of thermal management of batteries. Usually, the latent heat of composite PCMs is lower than that of pure PCMs due to the existence of additive materials. More composite PCMs are needed when their latent heat is too low to meet the requirements, which limits the development of the compact structure of the thermal management system. In this work, a novel paraffin (PA) -based composite multi-phase change material (m-PCM) with high latent heat was fabricated for thermal management. PA thickened by adding styrene ethylene butene styrene block copolymer (SEBS) and expanded graphite (EG) as enhanced thermal conductivity material were loaded in phase change polymer skeleton (PPS) synthesized from polyethylene glycol (PEG). One side, PPS not only played a role on preventing the leakage of paraffin as supporting material, but also provided the extra latent heat of phase change for the composite m-PCM. On the other side, SEBS was added by increasing the viscosity of PA to solve the problem of poor compatibility between the polymer skeleton and PA. Benefiting from the additional latent heat provided by PPS and the addition of EG, the composite m-PCM exhibited the phase change enthalpies as high as about 221.3 J·g−1 while ensuring the thermal conductivity as high as 1.46 W·m−1·K−1. When heated, the composite m-PCM exhibited the excellent shape-stability and flexibility. After 200 thermal cycles, the composite m-PCM performed the almost constant phase transition properties. The results demonstrate the composite m-PCM has extensive application prospects for efficient thermal management.