Research On The Preparation Of Carrageenan Fiber Directly From Carrageenan Extract By Wet Spinning

The carrageenans are hydrophilic linear sulphated D-galactans extracted from various species of marine red algae.It has excellent properties such as emulsification,thickening,non-toxicity and stability.It is widely used in food,biology,chemical,pharmaceutical and other fields because of its abundant resource,non-pollution,biocompatibility and biodegradation.Carrageenan fiber is one kind of the seaweed fiber.Traditionally,the carrageenan fibers were prepared by process of extracting,drying,dissolving of carrageenan power and wet spinning process of fibers.In this thesis,carrageenan fibers were prepared by carrageenan solution directly from the extraction of Chondrus,without the steps of precipitation,and drying.The carrageenan fibers were prepared directly from the Chondrus extraction by syringe spinning,simulating the wet spinning process.Orthogonal test determine the optimum extraction process and carrageenan fibers were prepared by simulated wet spinning.The results showed that the optimum conditions were as follows:the concentration of NaOH,the temperature of water bath and the time of water bath were8%,95^oC and 2h,respectively.The carrageenan powder and extractions under these conditions were analyzed by zeta potential,NMR,Fourier transform infrared spectroscopy（FTIR）,dynamic light scattering（DLS）and gel permeation chromatography（GPC）.The results showed that the Chondrus contained mainly iota-carrageenan and the particle size distribution of the extraction was uniform with an average diameter of 218nm.The average molecular weight of the carrageenan in the extraction was 1.05×10⁶ g/mol,and the molecular weight distribution was narrow.Therefore the extraction was suitable for spinning directly.The physical and chemical properties of the carrageenan fibers prepared under the optimal conditions were characterized by scanning electron microscope（SEM）,FTIR and energy dispersive spectroscopy（EDS）.Through the above characterization methods we can deduce the formation mechanism of carrageenan fiber:the combination of sulfate ester in the carrageenan and barium ions in the coagulation to form a three-dimensional network structure,which laid a theoretical foundation for one-step to form fiber from Chondrus extraction.The carrageenan fibers were prepared directly from the Chondrus extraction by a small spinning machine and a wet spinning process.The properties of spinning solution and carrageenan fibers were characterized with DLS,SEM,tensile testing and EDS.The results showed that the extraction of Chondrus was a uniform liquid with good properties of a solution,which was suitable as a spinning solution.Compared with traditional process of preparing carrageenan fiber,the so prepared carrageenan fibers possessed good morphology and tensile properties.Study on the mechanism of NaOH dissolving carrageenan.In this research,the complete dissolution of carrageenan was realized by using NaOH aqueous solution and the corresponding mechanism was successfully revealed.The properties of carrageenan solution prepared in NaOH aqueous solution were comprehensively studied by gel temperature,differential scanning calorimetry and dynamic light scattering.The intra-and intermolecular interactions of carrageenan in NaOH/H₂O system were studied by a combination of NMR measurements(including ¹³C NMR and ²³Na NMR)and FTIR.The stability of carrageenan in NaOH aqueous solution was studied by the average molecular weight and viscosity determination.The results indicated that gel temperature and gel-sol transition temperature of carrageenan solution decrease with the dosage increasing of NaOH and a true and stable carrageenan solution was obtained by completely dissolving carrageenan in NaOH aqueous solution.The dissolution mechanism was that carrageenan chains were surrounded directly by NaOH hydrates to form hydrogen-bonded structure,leading to the good dissolution.