EG-based coatings for flame retardance of shape stabilized phase change materials

Application of Polyethylene Glycol-Based Flame-Retardant Phase Change Materials in the Thermal Management of Lithium-Ion Batteries

Composite phase change materials commonly exhibit drawbacks, such as low thermal conductivity, flammability, and potential leakage. This study focuses on the development of a novel flame-retardant phase change material (RPCM). The material's characteristics and its application in the thermal management of lithium-ion batteries are investigated. Polyethylene glycol (PEG) serves as the medium for phase change; expanded graphite (EG) and multi-walled carbon nanotubes (MWCNT) are incorporated. Moreover, an intumescent flame retardant (IFR) system based on ammonium polyphosphate (APP) is constructed, aided by the inclusion of bio-based flame-retardant chitosan (CS) and barium phytate (PA-Ba), which can improve the flame retardancy of the material. Experimental results demonstrate that the RPCM, containing 15% IFR content, exhibits outstanding flame retardancy, achieving a V-0 flame retardant rating in vertical combustion tests. Moreover, the material exhibits excellent thermomechanical properties and thermal stability. Notably, the material's thermal conductivity is 558% higher than that of pure PEG. After 2C and 3C high-rate discharge cycles, the highest temperature reached by the battery module cooled with RPCM is 18.71 °C lower than that of natural air-cooling; the material significantly reduces the temperature difference within the module by 62.7%, which achieves efficient and safe thermal management.

Effects of expandable graphite on the flame-retardant and mechanical performances of rigid polyurethane foams

Polyurethane foams (PUFs) are found everywhere in our daily life, but they suffer from poor fire resistance. In this study, expansible graphite (EG) as flame retardant was incorporated into PUFs to improve material fire resistance. With the presence of EGs in the PU matrix, bubble size in PUF became smaller as confirmed by the scanning electron microscopy. The mass density of PUFs is directly proportional to the content of EG additive. The compression strengths of EG0/PUF and EG30/PUF decrease from 0.51 MPa to 0.29 MPa. The Fourier transform infrared spectroscopy (FTIR) analysis of RPUFs showed that the addition of EGs did not change the functional group structures of RPUFs. Thermo-gravimetric analysis (TGA) testing results showed that the carbon residue weight of EG30/PUF is higher than other PU composite foams. The combination of TGA and FTIR indicated that the EG addition did not change the thermal decomposition products of EG0/PUF, but effectively inhibited its thermal decomposition rate. Cone calorimeter combustion tests indicated that the peak of the heat release rate of EG30/PUF significantly decreased to 100.5 kW m^-2compared to 390.6 kW m^-2for EG0/PUF. The ignition time of EG/PUF composites also increased from 2 s to 11 s with incorporation of 30 wt% EGs. The limiting oxygen index (LOI) and UL-94 standard tests show that the LOI of EG30/PUF can reach 55 vol%, and go through V-0 level. This study showed that adding EG into PU foams could significantly improve the thermal stability and flame retardancy properties of EG/PUF composites without significantly sacrificing material compression strength. The research results provide useful guidelines on industrial production and applications of PUFs.

Investigation of Fire Protection Performance and Mechanical Properties of Thin-Ply Bio-Epoxy Composites

Hybrid composites composed of bio-based thin-ply carbon fibre prepreg and flame-retardant mats (E20MI) have been produced to investigate the effects of laminate design on their fire protection performance and mechanical properties. These flame-retardant mats rely primarily on expandable graphite, mineral wool and glass fibre to generate a thermal barrier that releases incombustible gasses and protects the underlying material. A flame retardant (FR) mat is incorporated into the carbon fibre bio-based polymeric laminate and the relationship between the fire protection properties and mechanical properties is investigated. Hybrid composite laminates containing FR mats either at the exterior surfaces or embedded 2-plies deep have been tested by the limited oxygen index (LOI), vertical burning test and cone calorimetry. The addition of the surface or embedded E20MI flame retardant mats resulted in an improvement from a base line of 33.1% to 47.5% and 45.8%, respectively. All laminates passed the vertical burning test standard of FAR 25.853. Cone calorimeter data revealed an increase in the time to ignition (TTI) for the hybrid composites containing the FR mat, while the peak of heat release rate (PHRR) and total heat release (TTR) were greatly reduced. Furthermore, the maximum average rate of heat emission (MARHE) values indicated that both composites with flame retardant mats had achieved the requirements of EN 45545-2. However, the tensile strengths of laminates with surface or embedded flame-retardant mats were reduced from 1215.94 MPa to 885.92 MPa and 975.48 MPa, respectively. Similarly, the bending strength was reduced from 836.41 MPa to 767.03 MPa and 811.36 MPa, respectively.

Recent Progress in Polymer-Based Building Materials

With the development of human society, the requirements for building materials are becoming higher. The development of polymer materials and their application in the field of architecture have greatly enhanced and broadened the functions of building materials. With the development of material science and technology, many functional materials have been developed. Polymer materials have many excellent properties compared with inorganic materials, and they can also be improved to enhance functional properties by blending or adding various additives (such as flame retardants, antistatic agents, and antioxidants). In this paper, polymer-based building materials are introduced with three classes according to the applications, that is, substrates, coatings, and binders, and their recent signs of progress in the preparations and applications are carefully demonstrated.

Flame Retardant Paraffin-Based Shape-Stabilized Phase Change Material via Expandable Graphite-Based Flame-Retardant Coating

Shape-stabilized phase change material (SSPCM) is a promising thermal energy storage material in energy-saving buildings. However, its flammability leads to a fire risk. The conventional bulk addition method has a limited flame-retardant effect. Herein, a series of surface coatings with various flame retardants were introduced to improve flame retardance of SSPCM. The results showed that all of the coatings had flame-retardant effects on SSPCM; In particular, the EG coating performed the best: the horizontal burning time was the longest, the limiting oxygen index was above 30%, the V0 classification was obtained, the peak heat release rate was sharply decreased from 1137.0 to 392.5 kW/m² and the burning process was prolonged with the least total smoke production. The flame-retardant mechanism was discussed. As paraffin easily evaporated from the SSPCM at a moderate temperature, it caused flames. After being surface coated, the EG-based coatings first hindered the volatilization of paraffin at a moderate temperature, then expanded and formed thick porous carbon layers at a high temperature to block the transfer of combustibles, oxygen and heat between the bulk and the environment. Therefore, the surface coating strategy achieved a desirable flame-retardant level with fewer flame retardants.

Preparation, characterization, and thermal properties of novel fire-resistant microencapsulated phase change materials based on paraffin and a polystyrene shell

Paraffin and paraffin mixtures that are preferred as phase change materials in many thermal energy storage applications are highly flammable. Microencapsulation of paraffin in a polymeric shell can decrease flammability, however, breaking of the shell under fire conditions can still cause a high risk. In the current paper, microencapsulated paraffin with a polystyrene shell is prepared and halogen-free flame retardants (ortho-phosphoric acid and pentaerythritol) were applied with the novel approach of direct incorporation during the microencapsulation process. Thermal energy storage and fire retardancy properties were characterized before and after fire-retardant addition. The fire behavior of samples in concrete blocks was determined with standardized methods in order to assess their suitability in building applications. ortho-Phosphoric acid as a flame retardant in microencapsulated phase change material was tested for the first time in this study. The results support that the improved flame retardancy and thermal energy storage properties were achieved with the incorporation of a flame retardant on microcapsules for energy storing concrete samples.

Flame retardancy properties of paraffin-based microcapsules were enhanced using halogen-free fire retardants. The reducing on the heat of combustion, and improving on noncombustibility properties and microencapsulation ratio were achieved.

Ecological Ammonium Thiocyanate-Modified Geopolymeric Coating for Flame-Retarding Plywood

An ecological ammonium thiocyanate (NH4SCN)-modified geopolymeric coating was facilely prepared for flame-retarding plywood. The effect of NH4SCN on the flame resistance was preliminarily investigated using cone calorimeter (CC), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermal gravimetry (TG). The results show that 1 wt.% NH4SCN as dopant is of paramount importance to generate a compact and continuous coating. The formation of a smooth, intact, and uniform-swelling siliceous layer during combustion facilitates enhanced fire resistance, evidenced by the increased fire performance index (FPI), reduced fire growth index (FGI), and 39.7% decreased value of peak heat release rate (pHRR), in comparison to those of the sample without NH4SCN. Because of the reducibility of O2-consuming NH4SCN, the compact shielding-layer containing carbonate and sulfate, as well as the release of NH3, the NH4SCN-modified geopolymeric coating exerts an enhancement on the flame-retardant efficiency.