Regenerated Cellulose Fibers From Waste Cotton Fabrics Directly Dissolved In Aqueous Phosphoric Acid

In today’s fast and fashionable consumption concept,the speed of clothing renewal is accelerated.The life of clothes is shortened and the utilization rate is very low after being discarded.Most of them are incinerated or landfilled together with domestic garbage,which not only wastes resources,but also pollutes the environment.At present,the recycling technology of polyester fabric is mature,but the recycling technology of waste cotton fabric needs to be developed urgently.In this paper,waste cotton fabric was dissolved in 85wt% phosphoric acid aqueous solution,a good solvent of cellulose,at room temperature,and the dissolving conditions were controlled to avoid excessive degradation of cellulose to prepare spinning solution with proper viscosity.Regenerated cellulose fiber was prepared by wet spinning,and the microstructure and mechanical properties of the fiber were adjusted and optimized by changing the coagulation bath.polypyrrole was deposited on the regenerated fiber as the substrate to realize conductive functionalization,and the application performance of conductive regenerated cellulose fiber was preliminarily explored.The main work is as follows:(1)The dissolving conditions of waste cotton fabrics were discussed,and different cellulose spinning solutions were prepared by changing the content of cellulose and the types of waste cotton fabrics.The dissolution time of different cellulose contents,rheological properties of spinning solution and polymerization degree of regenerated cellulose were studied.The results showed that waste cotton fabrics could be completely dissolved by phosphoric acid solution at 30℃.When the cellulose concentration increased from 1% to 5%,the dissolution time increased from 1h to 4h,and the viscosity of spinning solution gradually increased,and all kinds of spinning solutions showed shear thinning phenomenon.The effects of cellulose content in spinning solution and spinning conditions on the structure and properties of regenerated fibers were discussed.The results showed that with the increase of cellulose content in spinning solution,the strength and strain of regenerated fiber increased gradually.The cross-sectional morphology and strength of regenerated fibers in different coagulation baths are different.The strength of regenerated fibers using 50% ethanol as coagulation bath is up to 140 MPa,and coagulation bath has no effect on the crystal form of regenerated fibers.By changing the temperature of the coagulation bath,when the temperature of the coagulation bath drops to 0℃,the strength can reach 160 MPa.Low temperature can slow down the double diffusion of phosphoric acid and spinning solution,and the structure of regenerated fiber is more uniform.Changing the drawing ratio of regenerated fiber can improve the orientation and crystallinity of regenerated fiber,and affect the mechanical properties of regenerated fiber.After a low draft ratio of 1.4,the strength of the fiber is increased by 30%.In order to show that phosphoric acid has good solubility for all kinds of waste cotton fabrics,waste cotton with different colors was dissolved and regenerated.The results showed that all kinds of waste cotton fabrics could be completely dissolved within 4h,and the strength of regenerated fibers was similar to that of colorless fibers,and the K/S was high,which indicated that phosphoric acid could be used for the dissolution and regeneration of all kinds of waste cotton fabrics.(2)Using regenerated fiber as the substrate,we tried to endow the regenerated fiber with electrical conductivity by pyrrole polymerization,studied the effects of different preparation conditions on the properties and structure of pyrrole conductive fiber,and explored its electrothermal properties.The results show that when the molar ratio of pyrrole to ferric chloride is 1:1 and the polymerization time is 48 h,the electrical conductivity of regenerated fiber is the best,which is 566S/m.SEM,IR and Raman spectra proved that pyrrole was deposited on the fiber.After the fiber was polymerized with pyrrole,its mechanical strength increased and its elongation decreased.The change of the resistance of conductive fiber with temperature is preliminarily explored.The resistance of conductive fiber will decrease with the increase of temperature.After 7 cycles at 50℃,the change rule of resistance is similar and the stability is good.The electric heating performance of conductive fiber is preliminarily explored.At low voltage of 3V,the conductive fiber can reach 37℃,which is similar to human body temperature.It can be used to electrically heat textiles in the future.