Preparation Of Cyclodextrin-based Polyrotaxane Flame Retardant Viscose Fibers

Viscose fiber belongs to the cellulose fiber,due to its excellent properties such as good moisture absorption,breathability,anti-static and easy dyeing,it is widely used in clothing,furniture,packaging and other fields.However,viscose fibers are extremely flammable and their limiting oxygen index（LOI）is only 19%.More than 94%of house fire incidents are reported to be fiber-related.Therefore,the improvement of the flame retardant properties of viscose fibers has become an urgent concern for the current research workers.The flame retardant viscose fibers prepared by the traditional industry using physical blending will shed the flame retardant after several washes,resulting in the loss of the flame retardant properties of the viscose fibers.This paper mainly use cyclodextrin（CD）as raw material to synthesize two different flame retardant viscose fibers using supramolecular self-assembly technology,and improve the interaction force between flame retardant and fiber through intermolecular self-assembly,so as to enhance the flame retardancy and durability of the fiber.To achieve the research objectives of this thesis,specific experimental work was designed and carried out as follows:（1）The large component flame retardants（PR-DPCP）were synthesized fromβ-cyclodextrin（β-CD）,polyetheramine（PPG-NH₂）,2-iodobenzoic acid（IBX）and diphenyl chlorophosphate（DPCP）.The structures of the reaction intermediates and PR-DPCP were characterized by ~1H NMR,FTIR,XPS,and the thermal stability of different ratios of flame retardants was investigated.The results showed that the thermal stability performance of PR-DPCP was optimal at the ratio of 21:14.The optimal synthesis process of PR-DPCP was also investigated.The results showed that under the optimal synthesis process conditions,the feeding ratio[n（Polyrotaxane）:n（diphenyl chlorophosphate）]was 1:209,the reaction temperature was chosen as 50℃,and the reaction time was 4 h.Under the conditions of this synthesis process,the yield of PR-DPCP was 70.7%.（2）Flame retardant viscose fibers were prepared by wet spinning using PR-DPCP in physical blending.The FTIR and SEM analysis confirmed that PR-DPCP successfully entered into the interior of the fiber.Thermal stability,flame retardancy and durability of flame retardant fibers were studied by thermogravimetric analysis（TG）,differential scanning calorimetry（DSC）,combustion in air,cone calorimetry（MC）,limiting oxygen index（LOI）and water washing test.The results showed that the flame retardant viscose fiber had a high residual carbon rate（23.5%）and excellent flame retardant properties（LOI value of 30.1%）as well as strong washing durability at 600℃.Raman spectroscopy demonstrates that viscose fibers form a dense charcoal layer after combustion,which effectively isolates oxygen and heat transfer and fully protects the fiber interior.（3）A supramolecular flame retardant（PPR-DPCP）was synthesized in three steps usingα-cyclodextrin（α-CD）,dicarbonylimidazole（CDI）,polyethylene glycol（PEG）,and diphenyl chlorophosphate as raw materials,and the flame retardant viscose fiber was prepared by physical blending with viscose stock.The modified fibers were tested by TG,DSC and Micro Cone Calorimeter（MCC）,which showed that the initial decomposition temperature of the modified fibers was advanced by 60℃,the amount of carbon residue was increased by 10%,the total heat release（THR）was decreased by 38%,the LOI value was increased to 31%,and the LOI value could still be maintained at 29.5%after washing,and the mass change before and after washing was≤1%,which showed excellent flame retardant durability.