Structure and properties influenced by heat setting technology of Lyocell filament
In view of the problem that the heat setting technology of Lyocell filament was not clear,Lyocell washed filaments were prepared by dry-jet wet spinning technology and the effects of heat setting tension,temperature and time on the mechanical properties and dimensional stability were investigated.The crystal,orientation and micropore structure of Lyocell filaments were analyzed by means of wide angle X-ray diffraction,small angle X-ray scattering and birefringence,and the relationship between structure and properties under heat setting was clarified.The results show that the moisture in the filaments can be removed when the washed filaments are heat-set at 100-130 ℃ for 3 min.During the heat setting process,the crystal structure of the filament changes little while the decrease of micropore size and the shrinkage of chain segments improve the densification and decrease the orientation degree.The mechanical properties cannot be weakened at the tension of 0.5-2.3 cN/dtcx and the thermal shrinkage is lower than 0.7％.The heat setting with tension inhibits the disorientation of the cellulose segments effectively and keeps high crystallinity and high orientation of Lyocell filament,which guarantee both mechanical properties and dimensional stability of Lyocell filament.
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