An eco-friendly and durable multifunctional cotton fabric incorporating ZnO and a branched polymer

In this study, we investigated a two-step method of preparing cotton fabrics with flame retardancy and UV-blocking properties. This method involved the in situ deposition of ZnO nanoparticles (NPs) and the synthesis of a phosphorus ammonium salt. The application of ZnO NPs on cotton fabrics was achieved by an in situ ammonia-smoking method with zinc acetate and ammonia. A hyperbranched polyphosphate ammonium salt (FHPOPN) was synthesized for application to the cotton fabrics after the ammonia-smoked finish was applied. This research mainly focused on the fire-resistance and UV-blocking performance of cotton fabrics. The treated cotton fabrics were observed by scanning electron microscopy (SEM). The Fourier transform infrared (FTIR) spectroscopy results showed that ZnO NPs were successfully deposited in the fabric and that FHPOPN was bound to the fabric by covalent bonds. The flame retardancy and UV-protection properties of the treated cotton fabrics were studied. The effect of the zinc acetate concentration on the fire resistance and UV-blocking performance of the fabrics was investigated. The cotton fabrics treated with 70 g/L zinc acetate and 160 g/L FHPOPN obtained excellent flame retardancy with a char length of  57 mm and an limited oxygen index (LOI) value of 36.4%. The peak heat release rate and the total heat release of the ZnO/FHPOPN-treated samples were  26 kW/m² and 4.4 MJ/m², respectively, which were slightly lower than those of the FHPOPN-treated samples and much lower than those of the control cotton fabric sample. Furthermore, the thermogravimetric analyses of ZnO/FHPOPN-treated cotton fabric showed a char yield of 33.3% at 800 °C, whereas FHPOPN-treated cotton fabrics had a 29.7% char yield. The ZnO/FHPOPN-treated cotton fabric exhibited effective UV-protection properties with a UPF value of 224.80. These results demonstrated that the ZnO/FHPOPN-treated fabric had excellent flame retardancy, washability and UV-protection performance and revealed the importance of ZnO NPs in enhancing the flame retardancy and UV-blocking of performance cotton fabrics.

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