Study On Extraction Of Agar From Gracilaria Lemaneiformis And Wet Spinning Process

As a kind of natural high molecular polysaccharide extracted from red algae,agar has been widely used in biomedical,food and beverage industries because of its excellent gelation and biodegradability.In recent years,agar fiber,as a new type of seaweed fiber,has shown great potential in textile,medical and other fields due to its rich sources and good biocompatibility.However,until now there has been no extraction technology specifically applied in the field of agar spinning.To address this problem,we put forward a environmental protection and energy saving extraction process suitable for wet spinning,and improved the wet spinning process by changing the spinning solution and coagulation bath,and discussed the influence of different treatments on the properties of agar fiber.1.A new extraction process without alkali treatment was used to extract agar from Gracilaria lemaneiformis and obtain agar fiber by wet spinning.FTIR,GPC,DLS and Zeta potential tests were used to characterize the properties of the agar and the spinning solution respectively.The results showed that alkali-free agar had the highest molecular weight（75567 Da）and the content of sulfate group was also higher.The particle size distribution of spinning solution by alkali-free agar was uniform,which was suitable for wet spinning.The properties of the fiber were characterized by SEM,XRD and tensile test.The results showed that the agar fiber fabricated by wet spinning with the new extraction process had high breaking strength（0.63±0.06 c N/dtex）and elongation at break（38.89±13.90%）.The new process didn’t need alkali pretreatment step,and simplifies the process,and the yield was 37.5±1.4%,much higher than that of the traditional extraction process,and the new process is more suitable for spinning because of its high sulfate group content,high molecular weight.2.In order to increase fiber strength and make fiber preparation more environmentally friendly,this study proposed the wet spinning process of introducing Ba²⁺metal ion pre-crosslinking into the spinning solution,and using deionized water instead of barium chloride solution as coagulation bath,successfully prepared the fiber with good splitting effect and excellent mechanical properties.The rheological properties,zeta potential and particle size distribution of the spinning solution were analyzed.The results showed that Ba²⁺introduced into the spinning solution increased the viscosity of the spinning solution.Ba²⁺bonded with the charged groups in the molecule,which made the molecular chain arrangement more ordered and was conducive to the gelation transformation of the spinning solution.The properties of the agar fiber were characterized.The test results showed that the metal ion precrosslinked agar fiber had better morphology and higher mechanical strength（0.71±0.14 c N/dtex）.In addition,the use of deionized water instead of barium chloride solution as coagulation bath reduces drug consumption,making coagulation bath more conducive to treatment and recycling.3.AGF-Ca and AGF-Al fibers were prepared by wet spinning by introducing non-toxic and environmentally friendly Ca²⁺and Al³⁺ions into the coagulation bath.AGF-Ca and AGF-Al both maintained good morphology and mechanical strength,especially AGF-Al had a certain flame retardant ability.The experimental results showed that the mechanical strength of AGF-Ca and AGF-Al was 0.63±0.14 c N/dtex and 0.65±0.09c N/dtex,respectively,which were better than that of AGF-Ba（0.61±0.15 c N/dtex）.The LOI value of AGF-Al is 25.60,which is much higher than that of AGF-Ba（LOI=19.00）.