Environmentally Benign Phytic Acid-Based Nanocoating for Multifunctional Flame-Retardant/Antibacterial Cotton

Abstract

Environmentally benign layer-by-layer (LbL) deposition was used to obtain flame-retardant and antimicrobial cotton. Cotton was coated with 8, 10, and 12 phytic acid (PA) and chitosan (CH)-urea bilayers (BL) and then immersed into copper (II) sulfate (CuSO4) solution. Our findings were that 12 BL of PA/CH-urea + Cu2+ were able to stop flame on cotton during vertical flammability testing (VFT) with a limiting oxygen index (LOI) value of 26%. Microscale combustion calorimeter (MCC) data showed a reduction of peak heat release rates (pHRR) of more than 61%, while the reduction of total heat release (THR) was more than 54%, relative to untreated cotton. TG-IR analysis of 12 BL-treated cotton showed the release of water, methane, carbon dioxide, carbon monoxide, and aldehydes, while by adding Cu2+ ions, the treated cotton produces a lower amount of methane. Treated cotton also showed no levoglucosan. The intumescent behavior of the treatment was indicated by the bubbled structure of the post-burn char. Antibacterial testing showed a 100% reduction of Klebsiella pneumoniae and Staphylococcus aureus. In this study, cotton was successfully functionalized with a multifunctional ecologically benign flame-retardant and antibacterial nanocoating, by means of LbL deposition.

Biorenewable Polyelectrolyte Nanocoating for Flame-Retardant Cotton-Based Paper

“…The second stage (300–380 °C) involves dehydration and decomposition reactions of cellulose, which produce nonflammable gases, aliphatic char, and levoglucosane. The third step, around 490 °C, is attributed to the conversion of aliphatic char into aromatics, producing CO and CO 2 due to simultaneous carbonization. , The coating decreases the degradation temperature of the raw paper from 343 to 329 °C. This earlier onset of decomposition ( T onset = 329 °C) is due to the activation of the instumescent ingredients, which form a char layer that suppresses combustion and protects the underlying material from the flame .…”

“…Intumescent coatings constructed via LbL assembly are known for imparting FR behavior on cellulosic material, including cotton fabric and wood. − An effective intumescent system contains an acid source, a blowing agent, and a carbon source, which react upon heating to form an insulating and protective char layer on the surface of the substrate . Renewable and environmentally benign intumescent systems have previously been deposited on cotton fabric by coupling cationic chitosan (CH) and anionic phytic acid (PA) .…”

Layer-by-Layer Deposition: A Promising Environmentally Benign Flame-Retardant Treatment for Cotton, Polyester, Polyamide and Blended Textiles

“…CH-U/PA decreased the decomposition rate of cotton by generating more non-flammable gases (e.g., CO, CO2, NOx) instead of highly flammable levoglucosane, which diluted the concentration of the combustible gases and absorbs heat, causing bubbling. At the same time, urea catalyzed the reaction of PA, as well as the decomposition of cellulose at lower temperature, thus forming intumescent char, which acted as a physical barrier that blocked heat and oxygen [104]. The thermogravimetric analysis (TGA) showed an increase in char with the increase in bilayers at 650 • C (from 1.2% for untreated cotton to 7.0% for 8 BLs and 14.1% for 10, 12 and 15 BLs), as well as the reduction in degradation temperatures, as shown in Figure 4 [92].…”

“…CH-U/PA decreased the decomposition rate of cotton by generating more non-flammable gases (e.g., CO, CO 2 , NO x ) instead of highly flammable levoglucosane, which diluted the concentration of the combustible gases and absorbs heat, causing bubbling. At the same time, urea catalyzed the reaction of PA, as well as the decomposition of cellulose at lower temperature, thus forming intumescent char, which acted as a physical barrier that blocked heat and oxygen [104].…”

“…The results showed that cotton treated with 12 BLs self-extinguished the flame in VFTs (char length, 6.5 cm), with an LOI value of 26% and a reduction in pHRR by 62% and in THR by 54%. The resulting cotton killed almost 100% of bacteria [104].…”