Eco-friendly and Sustainable Flame-Retardant Finished Fabric
Samin Yeasar
B.Sc. in Textile Engineering
Department of Apparel Engineering
Textile Engineering College, Zorarganj, Chattogram
1. Introduction
Cotton, a popular natural textile fiber, is unfortunately extremely flammable, posing significant risks to life and property. Cotton’s cellulose thermal degradation begins around 300-400°C, resulting in the formation of highly flammable products such as levoglucosan, which further fuels combustion. Historically, flame retardants were classified into halogen-based, organophosphorus-based, inorganic metallic oxide-based, and nitrogen-based categories.
Conventional flame retardants, such as halogen-based compounds and certain phosphorus-based retardants (for example, Pyrovatex CP), have been restricted or prohibited due to their toxicity, formaldehyde release, or the generation of large amounts of smoke and corrosive gases when burned. These concerns have highlighted the critical need for the development of environmentally friendly, formaldehyde-free, and halogen-free flame-retardant finishing agents for textiles.
The goal is to improve fire safety while also ensuring that textile products are safe for human contact and have low environmental impact. This article describes the methodologies, findings, and conclusions of studies that focus on sustainable and environmentally friendly approaches to imparting flame-retardant finished fabric, which are frequently combined with additional functional properties such as hydrophobicity and antimicrobial characteristics.
2. Methodology
The general methodology for developing eco-friendly and sustainable flame-retardant finished fabric entails selecting non-toxic flame-retardant agents, applying them to fabric substrates using conventional textile finishing techniques, and then conducting extensive characterization.
2.1 Materials
| Material Types | Materials Name | Description |
| Fabric Substrate | Cotton | Cotton fabric is frequently used as a substrate due to its wide availability and inherent flammability. Fabrics can be used in their raw, pre-treated, or dyed states.
|
| Eco-friendly Flame-Retardant Agents | Diammonium Phosphate Octadecyl Citrate | Stearic acid, citric acid, and diammonium hydrogen phosphate are used to synthesize a flame retardant that is free of fluorine and formaldehyde. |
| Ammonium Polyphosphate | Modified ammonium polyphosphate is an intumescent flame retardant that is halogen-free and formaldehyde-free. It is commonly grafted onto cotton fabrics.
| |
| Inorganic and Organic Salt Mixtures and Phosphate-Structured Compounds | To improve flame resistance, various formulations containing these components are used, including commercial phosphate-structured flame retardants.
| |
| Natural Structured Flame Retardant | A water-based, cost-effective liquid blend derived from a mineral formula obtained from limestone. | |
| Chitosan Phosphate, Nano Titanium Dioxide, and Butane Tetracarboxylic Acid | This combination is used as an environmentally friendly finishing agent with flame-retardant and antibacterial properties. Titanium tetraisopropoxide is used in the sol-gel method to create nano titanium dioxide particles. | |
| Crosslinking Agents and Catalysts | Dicyandiamide, Butane tetracarboxylic acid | Dicyandiamide acts as a catalyst, grafting ammonium polyphosphate onto cotton fabrics via phosphorus-oxygen-carbon bonds. Butane tetracarboxylic acid also acts as a crosslinking agent, improving cotton’s structural stability. |
3. Fabric Finishing Process
3.1 Pad–Dry–Cure Method
Because of its uniformity and industrial feasibility, the pad-dry-cure method is commonly used to apply eco-friendly flame-retardant finishes.
3.1.1 Solution Preparation
The flame-retardant solution is created by combining the selected agents with auxiliary chemicals in an aqueous medium.
3.1.2 Diammonium Phosphate Octadecyl Citrate System
The solution is prepared with concentrations of 4%, 8%, 12%, and 16% (weight per volume). Polyacrylic acid and sodium hypophosphite are used as crosslinking agents and initiators, respectively. All components are dissolved in distilled water and stirred until a homogeneous solution is formed.
3.1.3 Modified Ammonium Polyphosphate System
Ammonium polyphosphate is applied at 30% of the fabric’s weight. Dicyandiamide serves as a crosslinking agent. The treatment solution is prepared by dissolving both components in distilled water.
3.1.4 Chitosan Phosphate, Nano Titanium Dioxide, and Butane Tetracarboxylic Acid System
Typical formulations include 2.0% chitosan phosphate, 3.0% butane tetracarboxylic acid, and 0.5%, 1.0%, 1.5%, or 2.0% nano titanium dioxide evenly dispersed in water.
3.1.5 Padding
Fabric samples are immersed in the prepared flame-retardant solution for about 2 minutes to allow complete absorption. The fabric is then passed through a two-roll padding machine with a pressure of two bars, resulting in an approximately 80% uniform wet pickup.
3.1.6 Drying
The padded fabric is dried at 100°C for 5 minutes to remove moisture without starting the curing process.
3.1.7 Curing
The dried fabric is cured for 3 minutes at 150°C to chemically adhere to the flame retardant.
- Diammonium phosphate octadecyl citrate develops carbon-oxygen-carbon bonds with cellulose.
- Ammonium polyphosphate develops phosphorus-oxygen-carbon bonds with cotton fibers.
- Butane tetracarboxylic acid forms ester bonds that link with cellulose’s hydroxyl groups.
4. Characterization and Performance Evaluation
4.1 Flame Retardancy Tests
| Flame Retardancy Tests | Description |
| Limiting Oxygen Index | Determines the minimum oxygen concentration required to sustain combustion. Higher values indicate improved flame retardancy. |
| Vertical Flame Spread Test | Evaluates after-flame time, after-glow time, and char length. Reduced char length and absence of ignition indicate effective flame resistance. |
| Microcalorimetry | Measures heat release rate and total heat release to assess combustion behavior. |
4.2 Durability Tests
| Durability Test | Description |
| Washing Durability | Flame-retardant performance is evaluated after 5, 20, and 50 laundering cycles. |
4.3 Fabric Characterization
Thermal behavior, surface morphology, chemical bonding, and crystalline structure are all evaluated using thermogravimetric analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction.
4.4 Additional Properties
Hydrophobicity is assessed through water contact angle measurements. Antimicrobial tests assess the ability to kill Staphylococcus aureus and Escherichia coli. Fabric quality is confirmed through measurements of whiteness, tensile strength, and bending length.
5. Results
5.1 Flame Retardancy Performance
A limiting oxygen index of 27.0% was attained by cotton fabric treated with 12% diammonium phosphate octadecyl citrate, as opposed to 18% for untreated cotton. The value was still 26.4% after 20 cycles of laundering. After washing, the char length decreased from 48 millimeters to 40 millimeters.
After 50 laundering cycles, the limiting oxygen index of cotton fabric grafted with 30% ammonium polyphosphate remained at 28.5%. Heat release values were considerably lower, and no after-flame or after-glow was seen.
Increased limiting oxygen index values and enhanced thermal stability were the outcomes of combining chitosan phosphate with nano titanium dioxide and butane tetracarboxylic acid. The system as a whole outperformed its individual parts.
Phosphate-based systems and naturally structured flame retardants both increased flame resistance; strong flame-retardant performance is indicated by shorter char lengths.
5.2 Multifunctional Properties
Cotton treated with diammonium phosphate octadecyl citrate showed superhydrophobic behavior, with a water contact angle of 151.9° at 12% concentration and 148.5° after 20 washing cycles.
Fabrics treated with nano titanium dioxide, chitosan phosphate, and diammonium phosphate octadecyl citrate showed antimicrobial activity. Ammonium polyphosphate treatments preserved acceptable bending length, tensile strength, and whiteness.
5.3 Flame Retardancy Mechanism
Cotton treated with ammonium polyphosphate had a greater char residue at 800°C according to thermogravimetric analysis. Heat transfer and oxygen diffusion are restricted by the resulting char layer, which functions as an intumescent barrier. Through cellulose crosslinking and barrier formation, butane tetracarboxylic acid, nano titanium dioxide, and chitosan phosphate improve thermal stability.
6. Conclusion
Sustainable and eco-friendly flame-retardant finishing techniques provide a workable way to increase fire safety while upholding environmental responsibility. Non-toxic flame-retardant systems significantly improved limiting oxygen index values, decreased char length, and strong washing durability.
Without sacrificing the mechanical integrity or aesthetic appeal of the fabric, these treatments frequently offer extra features like superhydrophobicity and antimicrobial activity. Stable char layer formation during combustion is the main flame-retardant mechanism.
Utilizing bio-based agents, nanoparticle-enhanced systems, and naturally structured flame retardants shows great promise for green chemistry solutions that promote safer and more sustainable textile production.
7. References
[1] El-Shafei, A., et al. “Eco-Friendly Finishing Agent for Cotton Fabrics to Improve Flame Retardant and Antibacterial Properties.” Carbohydrate Polymers, vol. 118, Mar. 2015, pp. 83–90. DOI.org (Crossref), https://doi.org/10.1016/j.carbpol.2014.11.007.
[2] Lu, Yi, et al. “An Eco-Friendly Intumescent Flame Retardant with High Efficiency and Durability for Cotton Fabric.” Cellulose, vol. 25, no. 9, Sept. 2018, pp. 5389–404. DOI.org (Crossref), https://doi.org/10.1007/s10570-018-1930-0.
[3] OmerogullariBasyigit, Zeynep, and Dilek Kut. “FORMALDEHYDE-FREE AND HALOGEN-FREE FLAME RETARDANT FINISHING ON COTTON FABRIC.” TekstilveKonfeksiyon, vol. 28, no. 4, Dec. 2018, pp. 287–93. DOI.org (Crossref), https://doi.org/10.32710/tekstilvekonfeksiyon.482884.
[4] Sharif, Rabia, et al. “One Pot Application of a Green Chemistry-Based Finish for Cotton Fabric, Providing Hydrophobic, Flame Retardant, and Antimicrobial Properties.” RSC Advances, vol. 14, no. 9, 2024, pp. 6146–55. DOI.org (Crossref), https://doi.org/10.1039/D3RA07931G.
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