Effect of zinc oxide on flame retardant finishing of plasma pre-treated cotton fabric

An organic phosphorus compound (flame retardant agent, FR) in combination with a melamine resin (crosslinking agent, CL), phosphoric acid (catalyst, PA) and zinc oxide (co-catalyst, ZnO/nano-ZnO) imparted effective and durable flame retardant properties. Also, atmospheric pressure plasma jet was applied as pre-treatment to improve post-finishing (flame retardant finishing) on cotton fabrics. In the present paper, surface morphology, chemical structure analysis, combustibility and mechanical properties of plasma pre-treated cotton fabrics subjected to flame-retardant treatment were investigated. Surface morphology of treated cotton specimens showed roughened and wrinkled fabric surface with high deposition of the flame retardant finishing agent, which was caused by the plasma etching effect and attack of acidic FR. The FTIR-ATR spectra for the treated cotton specimens showed some new characteristic peaks in chemical structure, interpreted as carbonyl bands, OH stretching vibration, COO⁻ stretching vibration, CH₂ rocking band and CH₃ asymmetric and CH₂ symmetric stretching. Moreover, FR-CL-PA-treated specimens showed remarkable flame-retardant property, which was further improved by the plasma pre-treatment and ZnO/nano-ZnO co-catalyst. However, flame-retardant-treated cotton specimens had poor mechanical strength when compared with control sample, resulting from side effects of the crosslinking agent used, while plasma pre-treatment and ZnO/nano-ZnO co-catalyst may compensate for the reduction in tensile and tearing strength caused by flame-retardant agents.