Biopolymer for reduction of cotton flammability
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Cotton is an extensively utilized natural textile fiber but its applicability is negatively influenced by high flammability due to its cellulosic nature. Cotton ignites very easily with a rapid flame spread and quickly consumes as fuel ensuing perilous fires that can cause huge materials loss and fatal accidents. The desire to improve flame retardant properties of cellulosic textile materials for the reduction of fire hazards has been a major preoccupation over the years for the safety of ultimate consumers under many circumstances. However, most of the high-performing flame retardants for cellulosic textile products have been banned or limited from industrial/commercial use facing several changes and challenges of health issues and environmental concerns. Due to these considerations, researchers and manufacturers have been deploying their endeavors to find, design, and develop some efficient but more environmentally benign specialty flame retardant finishing materials/products for cellulosic textile substrates to reduce their flame vulnerabilities. Contextually, in recent years, bio-based natural and renewable materials/products, i.e., biopolymers have become of growing interest and gained significant importance because of their environmental friendliness. The focal intent of the present work was to scrutinize the applications of a biopolymer, i.e., bovine milk casein (bovine milk protein; a phosphoprotein) on cotton fabrics as green and environment-friendly flame retardant finishing material to provide an attractive solution for the valorization of the dairy industry by utilization of its by-product or waste in the improvement of flame retardant performance, char formation, and intumescence effect of cotton fabrics. Casein was applied on cotton fabrics just as it alone and in combination with other environment-friendly materials (such as ammonium polyphosphate and polyvinyl alcohol) for synergistic/hybrid effects in different concentrations through non-hazardous aqueous solvents/solutions and simple industrial applicable textile finishing techniques/methods (such as roller padding, roller coating, and electrospray coating). Physiological comfort, mechanical properties, and washing durability accompanying flame retardancy and thermal properties of cotton fabrics finished with casein and casein-based synergistic/hybrid systems were also perused. Different kinds of measurements, characterization, and testing techniques were employed on control and finished cotton fabrics to determine, investigate and evaluate the different parameters, features, and properties such as surface properties (surface morphology, surface chemical structure, elemental contents analysis), thermal properties (thermo-oxidative stability, flame retardancy, limiting oxygen index, radiant heat resistance, intumescent system performance), comfort properties (air permeability, water vapor permeability, thermal conductivity, bending rigidity) mechanical properties (tensile performance, tear performance), and durability properties (durability to washing) according to feasible standard test methods. Results were analyzed, interpreted, discussed, and concluded to study and investigate causes with logical reasons for observance of different functional properties. Casein finished cotton fabrics demonstrated, slow flame propagation as also revealed from the image analysis data of burn length and burn area, and enhancement in limiting oxygen index, producing a higher amount of thermally stable char residues. Casein was ascertained to develop flame retardant intumescent systems in combined applications with other synergistic chemicals/compounds. Cotton fabrics indicated stronger sensitization of cellulose decomposition and exhibited higher thermo-oxidative stability properties after treatments with casein macromolecules alone and in combination with other thermally stable and phosphorous-rich flame retardant compounds.