Baljinder Kandola

Fire accidents are a significant cause of fatalities and property damage worldwide, with flammable textiles, especially cotton, posing a notable risk due to their widespread use and high susceptibility to ignition. To address this issue, we developed an innovative, environmentally friendly fire-retardant coating, inspired by traditional Indian practices of applying mud (clay) coatings in homes for enhanced safety. Our dual-layer coating consists of a primary layer of amino clay (AC) providing initial protection, and a secondary layer of copper phytate, which can be easily applied using a simple dip-coating technique. The coated cotton achieves a remarkable limiting oxygen index (LOI) of 61.3 %, signifying substantial fire resistance. Furthermore, in vertical flammability tests, the treated cotton immediately self-extinguishes upon ignition with no afterglow, demonstrating its high efficacy in fire prevention. This study highlights the potential of our coating to contribute to sustainable and economical fire safety solutions, aligning with global needs for enhanced fire protection in textile applications.
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•For the first time, an amino clay (AC)-based fire-retardant coating is reported.•A combination of amino clay and copper phytate is used through the dip-coating method to create a fire-retardant coating for textiles.•The coated cotton achieves a remarkable limiting oxygen index (LOI) of 61.3 %, signifying substantial fire resistance.

Fire sensors offer an effective strategy for mitigating fire hazards. This work reports the development of self-sensing glass fibre–reinforced composites (GFRCs) by incorporating a graphene oxide (GO)–aramid sensing layer into their structure. Two sensor configurations were explored: GO–coated aramid webs (GO–AW) and GO–aramid nanofibre films (GO–ANF). These sensors function via the thermal reduction of GO to conductive reduced graphene oxide (rGO) under heat or flame, enabling rapid (<1 s) fire detection and real-time wireless alerts via an IoT–enabled system. The GO–AW web strip, patterned with conductive ink electrodes and embedded in a GFRC laminate, effectively responded to both conductive (direct contact) and radiative (external heat flux) heat, acting as a robust pre–fire sensing material. Integration with an ESP32 microcontroller enabled wireless, real–time monitoring and instant alerts, ensuring practical applicability in fire–safety–critical environments. Furthermore, the incorporation of GO–AW enhanced the thermal and mechanical properties of the composite, with the flexural modulus increasing from 3.1 to 6.5 GPa and the glass transition temperature from 86 °C to 94 °C. The presence of GO–AW in the GFRC also reduced flammability of the composite, indicated by reduction in the peak and total heat release rate by 22 and 45 %, respectively in cone calorimetric experiments. Overall, the integration of GO–AW not only imparted fire-sensing functionality but also improved the composite's structural integrity and flame retardancy, demonstrating broad potential for structural and industrial applications.

This study has investigated the impact of fire retardants in carbon fibre-reinforced epoxy composites (CFRC) on physico-mechanical and oxidative properties of carbon fibres after exposure of CFRCs to high temperatures and fire. Three fire retardants were chosen based on their activity in condensed phase (ammonium polyphosphate, APP) and/or vapour phase (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, DOPO, and resorcinol bis-(diphenyl phosphate), RDP). The composites were subjected to high heat fluxes (75–116 kWm-2) and fire using a cone calorimeter and propane burner. Post-exposure, the carbon fibres extracted from different plies were analysed for surface oxidation, mass loss, diameter reduction, and changes in tensile and electrical properties. Carbon fibres exhibited differing degrees of oxidation across the plies, with surface ply fibres showing greater oxidation and diameter reductions, while underlying plies experienced limited oxidation due to restricted oxygen access. The charred residues from fire-retarded samples (residue levels: APP > RDP > DOPO > control) adhered to the fibres, reducing oxidation and preserving tensile properties. However, the charred residues increased the electrical conductivity of the carbon fibres. This analysis has enabled the evaluation of each retardant's effectiveness.

This study investigates the mechanism of charring of a hydroxypropyl-modified lignin (TcC) and its 50:50 wt% blend with a bio-based polyamide (PA1010). Potential applications are in carbon fibre and activated carbon production. Thermogravimetric analysis (TGA) coupled with Fourier transform infrared (FTIR) spectroscopy revealed that the blend’s thermal stability up to 500°C was lower than expected based on the TGA profiles of the individual components. However, above 500°C, the blend exhibited improved thermal stability. Isothermal pyrolysis was conducted at temperatures between 300°C to 800°C in 50°C intervals. Chars were characterized using FTIR, scanning electron microscopy (SEM), and porosity measurements. There is no evidence of covalent bond formation between the two degrading polymers in the blend. However the melting of PA1010, which surrounds the lignin particles, at 180°C and the relatively high thermal stability of the molten PA1010 up to 400°C, leads to delayed but extended initial thermal dehydration and decarboxylation of the lignin. This results in enhanced aromatization and increased thermal stability of the lignin above 500°C, contributing to enhanced char formation (20.8 % compared to a theoretical value of 17.5 %, calculated form the averaged sum of the chars from its components). These findings indicate the suitability of the blend for carbon fibre formation. However, the reduced porosity of the blend’s char (0.5 %), compared to that of lignin alone (4.7 %), indicates that the blend is not suitable for producing an activated carbon. This latter aspect will be discussed in a forthcoming publication.
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•Lignin/PA1010 blend less stable than lignin, but produces more char than expected.•No chemical, only physical interactions between lignin and PA1010 during pyrolysis.•Molten PA1010 encapsulates lignin, promoting aromatisation and char formation.•Blend a suitable precursor for carbon fibre, but for high-porosity activated carbon.

The thermal stability of melt-spun hydroxypropyl–modified lignin/polyamide (PA1010) 50:50 wt% blended precursor fibres, crucial for the thermal stabilisation stage in carbon fibre production, was enhanced by pre-treating the fibres with a graphene oxide (GO) suspension, synthesized via the modified Hummers method. This pre-treatment allowed the fibres to be subsequently thermally stabilised at a faster heating rate of 20 °C/min, compared to the typical 0.1–0.25 °C/min used for lignin-based fibres, thereby reducing overall thermal stabilisation time from 29 h to 2.5 h. The stabilised filaments were successfully carbonised at 950 °C, yielding coherent, void-free carbon fibres without inter-filament fusion. The tensile modulus of GO-treated filaments improved from 1.3 GPa to 2.3 GPa after thermal stabilisation. However, derived carbon fibres were brittle in nature. Various characterisation techniques, including DSC, TGA, FTIR, SEM-EDX, AFM, XPS, and tensile testing, were used to analyze the physico-chemical changes. DSC showed that GO improved the polycrystallinity of the precursor filaments and contributed to the formation of a three-dimensional cross-linked network during heat stabilisation, suppressing the PA melt endotherm. TGA confirmed that GO-treated filaments had higher char yields (∼40 %) than untreated fibres (∼30 %), further supporting GO-induced crosslinking reactions. FTIR, SEM-EDX, and AFM confirmed an even GO coating. A study of GO pre-treatment variables suggested that a reduction in GO concentration is required to reduce resulting carbon fibre brittleness at the expense of increased thermal stabilisation time.

This review explores the advancements in MXene-based nanomaterials as flame-retardant additives for polymers and composites, driven by increasing fire safety demands across industries. It highlights the critical role of flame-retardant materials in mitigating fire hazards in structures, electronics, transportation, and textiles, emphasizing the need for innovative solutions due to stricter safety regulations. MXenes, a class of two-dimensional nanomaterials with unique structural properties such as high surface area, tunable composition, and superior thermal stability, are presented as promising candidates. The review discusses various synthesis and incorporation techniques for MXenes in polymer matrices, showcasing improvements in flame retardancy, mechanical properties, and thermal stability. Additionally, it emphasizes the multifunctionality of MXenes, which offer conductivity, electromagnetic shielding, and mechanical reinforcement alongside flame suppression. In conclusion, the review underscores MXenes' potential to address challenges in flame-retardant materials, advocating for further research to optimize their applications and explore synergies with other agents to enhance safety and sustainability in engineering materials.

This work reports the qualitative and quantitative identification of volatile products from thermal and thermo-oxidative decompositions of different epoxy resins to allow selection of the particular chemical species most likely to be detectable in situ by infrared and chemical sensors. Thermogravimetry coupled with Fourier transform infrared analysis (TGA-FTIR) has been carried out on three resins at heating rates ranging from 20 to 70 °C/min in increments of 10 °C/min to understand the effects of the severities of different heating environments. Pyrolysis-FTIR has been conducted to complement the TGA-FTIR study under static atmospheric conditions hence revealing the volatile production under oxidative conditions. While the evolution of water, CO2, phenolic, carbonyl, aliphatic, aromatic and N-containing species could be observed in all resin types, the intensities and times of evolution of different components varied. Higher heating rates resulted in the evolution of volatiles occurring earlier and at greater intensities, but with a lower total amount of each product being evolved. From detection of CO, CO2 and aliphatic hydrocarbons in early stages of resin decomposition, i.e., prior to ignition, it can be inferred that sensors detecting these gases could be deployed in composites to provide a warning of any potential fires.

Herein, we designed wearable, flexible, highly sensitive textile-based pressure sensor assemblies utilizing a piezoresistive working mechanism. The sensor assemblies were constructed using a composite of coated cotton woven or polyester knitted fabric encapsulated and stitched between two layers of polypropylene spunbond nonwoven fabric embroidered with stainless steel yarn serving, creating a robust and integrated sensing structure. As a component of the sensor assemblies, the cotton and polyester fabrics were subjected to a series of surface modifications involving coating with silver nanoparticles, a silica xerogel film formation through a sol-gel process, application of polypyrrole via chemical oxidative polymerization, followed by deposition of a layer of carbon nanotubes and polydimethyl siloxane utilizing a dip-coating method. The sensor assemblies employing conductive polyester knitting fabrics demonstrate remarkable sensing capabilities, including an extensive sensing range of 0 kPa-225 kPa, high sensitivity values of 30 kPa−1, low detection limits of 125 Pa, fast response-recovery times of 120–80 ms and robust sensing stability exceeding 1000 cycles, respectively. Moreover, the sensor assemblies exhibited significant promise for real-time human motion monitoring, encompassing activities such as finger, wrist, elbow and knee bending; swallowing, walking and jumping. These sensor assemblies offer distinct advantages, including cost-effectiveness, ease of handling, straightforward production methods, and an environmentally friendly fabrication process.
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•Textile-based pressure sensors, utilizing piezoresistive principles were designed.•Conductive fabrics obtained by coating with AgNPs, silica film, PPy, CNTs and PDMS.•Sensor assemblies from conductive fabrics placed in between two layers of NW fabric.•Sensor assemblies exhibited excellent sensing properties.•Sensor assemblies presented great potential for monitoring human motion in real-time.

Carbon fibres have been produced from hydroxypropyl-modified lignin (TcC)/bio-based polyamide 1010 (PA1010) blended filaments. Two grades of PA1010, with different molecular weights and rheological properties, were used for blending with TcC. An oxidative thermal stabilisation step was used prior to carbonisation in an inert atmosphere to prevent the fusion of the filaments during the latter step. Thermal stabilisation was not possible using a one-step stabilisation process reported in the literature for lignin and other lignin/synthetic polymer blends. As a consequence, a cyclic process involving an additional isothermal phase at a lower temperature than the precursor filaments' melting point, was introduced to increase the cross-linking reactions between the lignin and polyamide. Thermally stabilised filaments were characterised by DSC, TGA, TGA-FTIR, ATR, and SEM techniques. Polymer rheology and heating rate used during thermal stabilisation influenced the thermal stabilisation process and mechanical properties of the derived filaments. Thermally stabilised filaments using optimised conditions (heating in the air atmosphere at 0.25 degree celsius/min to 180 degree celsius; isothermal for 1 h, cooling back down to ambient at 5 degrees C/min; heating to 250 degree celsius at 0.25 degree celsius/min, isothermal for 2 h) could be successfully carbonised. Carbon fibres produced had void-free morphologies and mechanical properties comparable to similarly thermally stabilised and carbonised polyacrylonitrile (PAN) filaments. (c) 2024 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/ )

This study examines the effects of heat and fire on the physical, mechanical and electrical properties of carbon fibre and those in carbon fibre reinforced composites (CFRCs). Carbon fibres were exposed to controlled heating (thermogravimetric analysis (TGA) and a tube furnace) in inert and air (oxygenated) environments and simulated fire (cone calorimetry at 35–75 kW m−2 and jet fire (propane burner) of 116 kW m−2) atmospheres. In inert atmospheres there was a minimal effect on the properties of carbon fibres, but in an oxygenated environment, significant oxidation began at temperatures ≥550 °C, resulting in a reduction in fibre diameter, which reduced further with increasing temperature and exposure duration. Tensile strength and electrical conductivity of carbon fibre decreased with reduction in fibre diameter. CFRCs exposed to 75 kW m−2 in a cone calorimeter and direct flame in a propane burner (116 kW m−2) showed varying degrees of oxidation in CFRC plies, with surface ply fibres experiencing more oxidation and consequent reductions in fibre diameter and tensile properties compared to fibres in underlying plies, where oxidation was limited due to restricted oxygen availability. Fibres exposed to the propane burner exhibited notable damage, including pitting and internal oxidation. Despite this, the overall electrical properties of residual carbon fibres did not significantly decrease, indicating that they still pose an electrical hazard if exposed during a high heat or fire event.