One‐pot synthesis of aluminum phosphate‐supported, chitosan‐linked expandable graphite as a novel flame retardant for textile

Although cotton is the most common polymer in daily life, its limited use is due to its propensity to catch fire. To solve this issue, we developed an innovative flame‐retardant aluminum phosphate‐supported, chitosan‐linked expandable graphite composite (CAlPEG). The CAlPEG was synthesized by the reaction of natural graphite, aluminum phosphate, and chitosan biopolymer in a one‐pot method. When CAlPEG was coated with cotton fabric and exposed to continuous flame, the fabric did not catch fire up to 760 s, whereas only expandable graphite (EG), aluminum phosphate (AIP), and CS, coated cotton fabric burned within 20 s. Flame‐retardant proficiency of CAlPEG‐coated cloth was confirmed by flame tests such as a limiting oxygen index (LOI) and vertical flammability test. The blank cotton has 17% LOI and is completely burnt out. On the other hand, the as‐prepared composite has a 43% LOI rating, which denotes a high level of flame retardancy. The VFT test result showed the formation of a 3 cm char, which confirms the flame‐retardant material possesses self‐extinguishing qualities. The article develops a new method for utilizing bioresources such as chitosan and offers fresh perspectives on the environmentally friendly synthesis of phosphorylated EG‐linked chitosan on the AlPO4 matrix. Natural graphite is first transformed into expandable graphite in a one‐pot process using an acid mixture, such as ortho‐phosphoric acid and nitric acid. Chitosan and aluminum phosphate are added to the same pot and heated overnight to create a CAlPEG composite, which is then used as a flame retardant (FR) in cotton fabric. The composite has excellent flame resistance as demonstrated by factors like its high limiting oxygen index (LOI) value (43%) compared with ordinary cotton's low LOI value (17%), its shorter char length (3 cm) in VFT compared with blank cotton. It sustained even in contact with the flame for 760 s. This illustrates the future expansion of the cotton application using this FR.