Research On The Reinforcement, Toughening And Modification Of Alginate Fiber And Its Structure And Performance

Alginate fiber has excellent properties such as high hygroscopicity,flame retardancy and biodegradability,and can be used in many fields,such as dressings for bandaging wounds and carriers for drug transportation.However,due to the particularity of its structure and poor mechanical property,alginate fiber is largely limited in application.In order to improve its mechanical property and maintain its excellent characteristic of green and environmental protection,the modified alginate fiber was prepared by wet spinning process with self-made cellulose nanocrystalline?CNC?and polyethylene glycol diglycidyl ether?PEGDE?.The modified alginate fiber was characterized by FTIR,SEM,XRD,TGA and single fiber strength meter,and the experimental results were analyzed and discussed to explore the best process conditions for improving the comprehensive mechanical properties of alginate fiber.The research mainly includes the following two aspects:?1?The preparation,structure and performance of CNC modified alginate fiberCNC has many excellent performance,such as large specific surface area,good biocompatibility,environmental friendliness,wide range of sources,and renewable,which has attracted much attention.In this paper,the CNC was prepared by acid hydrolysis of microcrystalline cellulose?MCC?.By laser particle size meter to test the particle size,using SEM and transmission electron microscopy?TEM?to observe the morphology,structure were characterized by using the XRD and FTIR.The results showed that the average particle size of the CNC was about 115.5 nm,reaching the nanometer level,and the polydispersity index?PDI?of particle size was 0.428,indicating that the particle size of the self-made CNC was uniform.The modified alginate fiber with different CNC contents were prepared by dispersing CNC in sodium alginate spinning solution with ultrasonic shaker,and then crosslinking with calcium ions in calcium chloride coagulation bath,and the structure of the modified alginate fiber was characterized.The FTIR spectrograms showed that a large number of hydrogen bonds were formed between CNC and sodium alginate molecules,which caused the stretching vibration band of-OH shifted to the low frequency direction and the band became wider.The SEM images of fiber tensile section showed that the section of pure alginate fiber was smooth and belonged to brittle fracture.However,with the increase of the amount of CNC,the sawtooth structure and stripes on the smooth fiber section increased,and the addition of CNC changed the deformation capacity of the alginate matrix.The TG curves showed that the thermal decomposition rate of modified alginate fiber increased slightly with the increase of CNC content in a certain range,but the mass retention rate increased.Based on the test the comprehensive mechanical properties of the fiber and the test results of other properties,the best preparation conditions was summarized as:sodium alginate solution concentration was5%?wt?,the concentration of the CNC was 8%?wt?,CaCl₂ concentration of coagulation bath was 5%?wt?,the temperature was at 25°C,to optimize the mechanical properties of modified alginate fiber.The breaking strength and elongation at break increased by 46.8%and 111.9%respectively.The water absorption performance of modified alginate fiber also increased from116.6%to 142.6%when the CNC concentration was 0.5%?wt?.?2?Preparation,structure and properties of PEGDE modified alginate fiberPolyethylene glycol diglycidyl ether?PEGDE?as a derivative of polyethylene glycol?PEG?,is a kind of common environmental crosslinking agent,but at this stage,the crosslinking reaction in the study requires in alkaline environment.In this paper,PEGDE was added to the sodium alginate spinning solution under neutral conditions.Under continuous mechanical stirring,the two were cross-linked,and then cross-linked with calcium ions in a calcium chloride coagulation bath.The effect of the amount of PEGDE on the structure and mechanical property of modified alginate fiber.The FTIR spectrograms showed that the characteristic absorption peak of PEGDE ternary ring epoxy group did not appear in the modified alginate fiber,indicating that the ring was completely opened during the reaction,and the crosslinking agent did not destroy the basic structure of the fiber.New absorption peaks were observed in the modified alginate fiber at 2921 cm^-1 and 2851 cm^-1,which was attributed to the asymmetric and symmetric stretching vibration of-CH₂,demonstrating that sodium alginate reacted with PEGDE.The XRD test showed that after cross-linking of PEGDE and SA,the entanglement of macromolecular chains increased,and the regularity of macromolecular chain of fiber after traction and stretching increased,which increased the crystallization performance of modified alginate fiber to some extent.The TG curves showed that after crosslinking by PEGDE,the maximum thermal decomposition temperature increased,the corresponding maximum thermal decomposition rate decreased,and the thermal stability of the modified alginate fiber improved.The optimum preparation conditions for obtaining PEGDE-modified alginate fiber are as follows:sodium alginate and PEGDE are reacted in a neutral pH,60°C environment for 5 h,and the ratio of quality of SA:PEGDE for100:20,to optimize the mechanical properties of modified alginate fiber which breaking strength was increased by about 78%,and the elongation at break was also increased by about114%.