| Lyocell fiber, a new kind of regenerated cellulose fiber, is known as "green fiber" due to its simple processing, environmental friendly and inexhaustible raw materials. However, Lyocell fiber belongs tocellulose fiber, which is not melted after being heated, and the flame is burning fast. The characteristics of flammable limit its application in some fields. Therefore, it is very necessary to seek an effective reasonable flame retardant method on Lyocell fiber.The flame retardant Lyocell fibers were preparedby immersed in a finish solution containing a flame retardant agent of 2-carboxyethyl phenyl phosphonic acid(CEPPA) or N-Methylol dimethyl phosphono propionamide(MDPA), then passed through a laboratory padder with two dips and two nips, and treated at certain conditiongs in this paper. The effect of the flame retardant concentration, microwave time, baking temperature and time on the structure and properties of Lyocell fiber had been studied.In this paper, the flame retardant of CEPPA was firstly grafted to Lyocell fiber,and the structure and properties of flame retardant fiber were studied. The results showed that the crystallinity of the fiber treated by CEPPA changed little, moisture absorption decreased, cracks and grooves arose on the surface of the fiber. With the increase of CEPPA concentration, tmicrowave processing time, baking temperature and time, the P content and limit oxygen index(LOI) of the fiber increased, but the mechanical properties of fiber decreased. When the flame retardant concentration of CEPPA was 8%, 480 W microwave treatment 3min, bake at 160℃ for 5min, the mechanical property of the fiber caused little damage and the content of the flame retardant grafted to fiber is relatively high. The residual amount of fiber after thermal weight loss increased from 4.73% to 13.09%, and LOI increased from 18.5% to 24.5%. So the flame retardant properties of Lyocell fiber had been improved obviously.In order to further improve the flame retardant properties of Lyocell fiber, the flame retardant MDPA was selected to treat Lyocell fiber, and the effects of MDPA treatment on the structure and properties of flame retardant fiber were also investigated. The crystallinity and the moisture absorption properties of the treated fiber had no obvious changes, and the photo of SEM showed that Wrinkles arose on the surface of the fiber. Similar to CEPPA treatment, the P content and limit oxygen index(LOI) of the fiber increased with the increase of MDPA concentration, microwave processing time, baking temperature and time, but the mechanical properties of fiber decreased. When the flame retardant concentration of MDPA was 40%, 320 W microwave treatment for 3min, bake at 160 ℃ for 5min, the comprehensive properties of the fiber is best.. The residual amount of fiber after thermal weight loss increased from 4.73% to 21.48%, the maximum heat release rate of the fiber was obviously decreased and LOI reached more than 33%, which showed that the Lyocell fiber treated under the above conditions has a good effect of flame retardant. In addition, the fiber still had better effect of flame retardant after washed 30 times.On the basis of the above research, the dry and wet Lyocell fiber prepared in our laboratory were further treated by CEPPA and MDPA separately. The content of flame retardant, mechanical properties and thermal stability of the obtained flame retardant fibers were compared. It was found that the flame retardant effect of wet fiber is better than that of dry fiber. Compared with the dry Lyocell fiber, the residual amount after thermal weight loss of wet Lyocell fiber treated with CEPPA and MDPA increased by 3.83%and 14.13%, respectively, and the LOI value is higher than that of dry Lyocell fiber. Therefore, Lyocell fiber with better flame retardant effect could be obtained by treating wet Lyocell fiber with CEPPA and MDPA. |
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