Abstract
Flame retardant behaviour was imparted using the layer-by layer assemblies of phosphorus rich casein milk protein with eco-friendly inorganic chemicals on cotton fabrics. The cotton twill fabrics were prepared using two solutions; a mixture of positively charged branched polyethylenimine (BPEI) with urea and diammonium phosphate (DAP), and negatively charged casein. Layer-by-layer assemblies for flame retardant properties were applied using the pad-dry-cure method, and each coating formula was rotated for 20 bi-layers. The effectiveness to resist flame spread on treated fabrics was evaluated using vertical (ASTM D6413-08) and 45° angle flammability test (ASTM D1230-01) methods. In most case, char lengths of fabrics that passed the vertical flammability tests were less than 50% of the original length, and after-flame and after-glow times were less than one second. Thermal properties were tested the extent of char produced by untreated and treated fabrics at 600°C by thermogravimetric analysis (TGA). Micro-scale combustion calorimeter (MCC) and Limiting oxygen indices (LOI, ASTM D2863-09) were also assessed. All untreated fabrics showed LOI values of about 21% oxygen in nitrogen. LOI values for the treated casein with BPEI/urea/DAP fabrics were greater than 29-34% between 5.80-9.59 add on wt%. Their structural characterizations were revealed by TGA/FT-IR and SEM methods. The treated fabrics exhibited improved thermal stability, as evidenced by increased ignition times and lower heat release rates. The results of this study show that flame retardant nanocoatings can be readily applied to textile fabrics using a continuous process that is ideal for commercial and industrial applications.
Highlights
Cotton fiber is broadly used to produce clothing, home furnishings, and various industrial products, such as medical supplies, industrial fiber, and canvases
branched polyethylenimine (BPEI)/urea/diammonium phosphate (DAP) solution, which passed through a roller, immediately followed by immersion of the fabrics in the 1.5 wt% Casein solution, which passed through a roller
Formulation and percent add on values following wet pickup, drying, curing, and reconditioning of 20 bilayer coated mercerized twill fabric samples are shown in Table 1. 20 bilayers (BL) casein−BPEI/urea/DAP coatings solutions were prepared as following: 1.5% casein solution in deionized water and 1.5% BPEI, 10% urea and 10% DAP in deionized water (CM-10 sample); 1.5% casein solution in deionized water and 1.5% BPEI, 15% urea and 15% DAP in deionized water (CM-15 sample); 1.5% casein solution in deionized water and 1.5% BPEI, 20% urea and 20% DAP in deionized water (CM-20 sample)
Summary
Cotton fiber is broadly used to produce clothing, home furnishings, and various industrial products, such as medical supplies, industrial fiber, and canvases. The nanocoating of textile materials to impart flame retardancy is a relatively new field, and the use of LBL technology to modify the surfaces of textile fabrics and fibers has been widely studied in recent years, the overall process is still not well understood. An attempt was made to improve the flame retardancy of cotton fabrics by the deposition of multilayer films containing BPEI, DAP, urea, and casein nanoparticles using a newly developed continuous LBL self-assisted process. The imparted flame retardancy of the cotton fabrics with the deposited casein nanolayers was tested using thermogravimetric analysis (TGA), limiting oxygen index (LOI, ASTM D2863-09) [30], 45° angle (clothing textiles test, ASTM D1230-01) [31], vertical flammability testing (ASTM D6413-11), and microscale combustion calorimeter (MCC) [32]. Scanning electron microscopy (SEM) measurements were performed to verify the presence of the deposited nanolayers and study the morphology of the various nanocoatings
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