Polyester is one of the most extensively utilized products of the 21st century, and textiles made from this material have high durability and flexibility. To improve flame retardancy and thermal conductivity, graphene or chemicals can be distributed as fillers in polymeric frameworks and deposited on textile fibers. This article covers the importance of making fabrics flame-retardant and novel approaches being excessively researched.
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The Need for Flame-Retardant Fabrics
Polyester (PET) fabric is a versatile synthetic material with excellent abrasion, corrosion resistance, and light resistance. However, PET fabric is combustible, with a limiting oxygen index (LOI) of only approximately 21%. The ignition process creates lethal fumes and a significant number of particulates.
A low LOI value indicates that a substance is highly flammable, and the lower inherent LOI value of PET substances necessitates the implementation of flame-retardant technology. This is a key reason why the scientific community is focused on the development of ecologically sustainable flame-retardant techniques for fabrics.
Advantages of Graphene Material
Owing primarily to distinct nano-effects, inorganic nanoparticles have been exploited in the domain of flame-resistant textiles. Graphene is a 2D substance with sp2-hybridization and unique characteristics.
A three-dimensional graphene counterpart, graphene aerogel (GA), is a novel form of carbon polymer. It possesses several exceptional qualities, including ultra-light density (10 mg/cm-3), superior compressibility (>90%), low thermal conductivity (0.01 W/(m K)), and high flame retardancy.
How GA-Ammonium Poly-Phosphate (APP) Functions
Graphene aerogel (GA) and GA-based APP (GA-APP) embedded aerogel flame retardants have been principally investigated to obtain high-efficiency flame retardancy for PET textiles.
GAs adsorb tiny organic molecules produced by polymer burning and create a 3D carbon skeleton to inhibit material ignition and promote carbon layer development.
APP is inorganic phosphorus that contains nitrogen and phosphorus flame retardant materials and has the benefits of low cost, strong thermal durability, a high phosphorus concentration, and no harmful gases.
Limitations and Disadvantages of Flame Suppressants
Although these substances are being researched extensively, flame retardant technologies are currently being called into question concerning ecological sustainability, synthetic toxicological tolerance, efficacy, and affordability. Most notably, the high cost of the technology is a major hurdle in its marketability.
Latest Research Findings
A team of researchers from China has published a new paper titled “Progress in Organic Coatings” which is focused on the sustainable growth of composite aerogels (GA-APP) directly on fabric surfaces via the process of hydrothermal reduction.
The scientists utilized scanning electron microscopy (SEM) for morphological studies. The GA itself had a dense permeable framework with varying pore diameters. The GA-APP particles were also discovered to have a system model made up of graphene sheets and tiny APP fragments.
The XPS examination of the GA-APP compound revealed that the powder contains five types of elements: C (78.3%), O (18.8%), N (1.6%), P (0.3%), and Si (1.0%).
The LOI and vertical burning tests were two major metrics used to assess cloth flame retardancy. The LOI of GA/PET (S-1) increased to 32.1%, indicating that the introduction of GA enhanced the LOI of PET material.
When the flame retardant load remained the same, the LOI number of the GA-APP/PET fabric increased to 34.1%, and the vertical combustion test was cleared with a B1 grade. During the vertical combustion test, the GA-APP/PET fabric demonstrated a clear self-extinguishing event after combustion, with no melt decrease with flame.
A CONE test was performed to simulate the real-life efficacy of the fabric. The inclusion of GA-APP dramatically lowered the fabric's PHRR, THR, and other statistics. When compared to pure PET fabric and GA/PET fabric, the PHRR value was lowered to 25.4 kW/m2, which is 82.8% and 24.2% lower, respectively.
Is Flame Retardant PET Fabric Water Resistant?
To assess the longevity of flame-retardant PET textiles, fabric specimens were washed periodically before and after flame-retardant treatment, and the variations in mass loss and LOI value of the fabric were examined.
The LOI rating after washing did not change significantly. The LOI value dropped, but the quality remained good enough to meet the flame-retardant and water-resistant standards.
Utilization of Machine Learning to Optimize Flame Retardancy
The journal ACS Applied Mat. Interfaces have published novel research focused on the utilization of novel data-driven and modern AI technology for the development of highly flame-suppressant polymeric fabrics.
The researchers employed machine learning to examine empirical values and promote the creation of novel flame-retardant polymers. To investigate the link between the limit oxygen index (LOI) and components, 20 composites were synthesized and a simple expression for the LOI was established utilizing the sure independence screening and sparsifying operator (SISSO).
According to the researchers, a simple yet effective structure of nano-graphene oxide (GO) wrapped micro zinc hydroxystannate (ZHS) is a revolutionary flame retardant chemical to increase flame retardancy and mechanical capabilities.
Plasma Surface Treatment and UV-Curing for Flame Retardancy
Another article published in the journal Progress in Organic Coatings focused on a continual immersion and ultraviolet (UV) curing technique used to create a covering for polyester materials that was flame retardant, anti-drip, and wash-resistant.
To begin with, the exterior of the polyester fabric was prepared with plasma to provide additional grafting opportunities. Following that, the flame retardant UV coating was applied.
The impact length of polyester with the coating was lowered from 300 mm of immaculate PET to 100 mm with no leaking in a vertical burn test. In the Micro-Scale Combustion Calorimetry (MCC) test, the Peak Heat Release Rate (PHRR) and Total Heat Rate (THR) of modified PET were reduced by 43.3% and 22.2%, respectively, indicating outstanding thermal resilience and flame retardant qualities.
To summarize, graphene and other flame retardant materials are being researched to rapidly commercialize novel modified fabrics. Graphene, owing to its advantages and carbon framework, is an essential substance, and its composite aerogel has been shown by researchers to be very useful in the enhancement of flame retardant properties.
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References and Further Reading
Qi, L. et. al. (2022). Durable flame retardant and dip-resistant coating of polyester fabrics by plasma surface treatment and UV-curing. Progress in Organic Coatings, 172, 107066. Available at: https://doi.org/10.1016/j.porgcoat.2022.107066
Wang, H. et al. (2022). A novel flame-retardant system toward polyester fabrics: flame retardant, anti-dripping and smoke suppression. J Polym Res. 29. 180. Available at: https://doi.org/10.1007/s10965-022-02961-3
Attia, N. et. al. (2021). Recent advances in graphene sheets as new generation of flame retardant materials. Materials Science and Engineering: B, 274, 115460. Available at: https://doi.org/10.1016/j.mseb.2021.115460
Chen, F. et. al. (2021). Machine learning and structural design to optimize the flame retardancy of polymer nanocomposites with graphene oxide hydrogen bonded zinc hydroxystannate. ACS Applied Materials & Interfaces. 13(45). 53425-53438. Available at: https://doi.org/10.1021/acsami.1c12767
Xue, B. (2022). Effect of a graphene-APP composite aerogel coating on the polyester fabric for outstanding flammability. Progress in Organic Coatings, 172, 107130. Available at: https://doi.org/10.1016/j.porgcoat.2022.107130
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