| Lyocell fiber is a new regenerated cellulose fiber in this century,and the production process is green and pollution-free.Lyocell fiber has been widely used in production and life because of its good comfort and permeability,excellent dry and wet strength and environmental friendliness.However,like most polymer materials,Lyocell fiber and its products are very easy to burn and have high fire risk.Therefore,the flame retardant finishing of Lyocell products to improve its safety and expand its application range is of great significance.In the first part of this paper,a halogen-free durable phosphorus nitrogen flame retardant(PNDDEU)was prepared with dimethylol dihydroxy ethylene urea as the main raw material.Lyocell fabric with good flame retardancy(FR-lyocell)was obtained by the modification of dipping-drying-baking method.The results showed that PNDDEU was successfully synthesized and connected with the fabric through chemical bonds.The limiting oxygen index(LOI)of FR-lyocell fabric was 35.4%,and the LOI was still 33.6% after 30 laundering cycles with water,indicating that FR-lyocell fabric has certain flame retardant durability.Under nitrogen atmosphere,the char residue of FR-Lyocell fabric at 800℃ increased to 38.2 wt%.The peak heat release rate(p HRR)of FR-lyocell fabric decreased by 91.43%,and the total heat release(THR)decreased by 78.18%.PNDDEU played synergistic flame retardant effect in condensed phase and gas phase,showing good flame retardancy.In the second part of this paper,a flame retardant(APDN)containing phosphorus,nitrogen and sulfur was synthesized by using the raw materials of thiourea,glyoxal,formaldehyde,phosphoric acid and urea,which was then used to treat Lyocell fabric by dipping-drying-baking method to obtain excellent flame retardant Lyocell fabric(FR-lyocell).The results showed that APDN was successfully prepared and phosphorus,nitrogen and sulfur were introduced into the fabric.The LOI of treated Lyocell fabric before and after 30 laundering cycles with water was 37.7% and 30.1%respectively,demonstrating that the fabric had good flame retardant effect and water washing resistance.Under nitrogen,the char residue of the modified fabric at 800℃was 42.1 wt%.The p HRR and THR of FR-lyocell fabric decreased by 92.67% and67.27%.APDN played a synergistic role in condensed phase and gas phase,and the modified fabric had outstanding flame retardancy. |
