Studies On Phosphazene-derivative Flame-retardant Viscose Fiber

Viscose fiber is an important material in textile industry. Its main drawback is theeasy flammability. China contributes half of the output of viscose fiber around the world.However, there is no widely accepted solution to flame-retardant viscose fiber in China.Therefore, the produce of domestic flame-retardant viscose fiber is very important andmeaningful. In this study, two phosphazene derivatives were applied as flame-retardantagents. After-finishing method was employed to prepare flame-retardant viscose fiber.Flame retardancy, mechanical strength, thermal stability and thermal degradation of thefibers were studied systematically.Hexachlorocyclotriphosphazene (HCCTP) was used as raw material to synthesizeHexaaminocyclotriphosphazene (HACTP) and Triaminoethyoxylcyclotriphosphazene(TAECTP). Reaction processes were optimized, which indicated the appropriate reactiontime for HACTP was6h, and gave a yield of90.7%. The optimized HACCP toethanolamine ratio was1:9, which gave a yield of90.5%. Infrared spectrum (IR) showedthat both products were well substituted. Differential scanning calorimetry (DSC) andThermogravimetry (TG) tests indicated that thermal stability of the two flame-retardantagents was close to that of HCCTP.After-finishing method was applied to the preparation of flame-retardant viscosefibers using these two flame-retardant agents. Mathematic relation between theconcentration of the flame-retardant finishing solution and the weight gain of fiber wasestablished. Scanning electron microscope (SEM) images indicated that the fibers werecoated by flame-retardant agents in various degrees. Limiting oxygen index (LOI) testsgave a minimum LOI value of above33%, HACTP finished fibers obtained better flameretardancy than TAECTP fibers under the same concentration. The study of thermalstability of the fibers showed that the thermal decomposition of flame-retardant agentsaccelerated the char reaction of viscose fiber within170³00°C, and protection layer onthe surface of the fiber was formed. With the increase of flame-retardant content, drystrength, elongation at break and initial modulus of the fiber were decreased gradually. However, the strength loss of the fibers was less than20%, which was acceptable.Combined thermogravimetric and infrared analysis was employed to analyze the thermaldecomposition products of the flame-retardant viscose fibers. The results indicated that themajor product of the thermal decomposition was CO₂.