Study On The Preparation, Structure And Performance Of Reinforced Modified Alginate Fiber

Alginate fiber prepared by wet spinning method has been used in the fields of medical treatment,cosmetic skin care,textile and industry as medical dressing,drug carrier,cosmetic mask,and metal ion adsorption material due to its high moisture absorption and excellent biodegradability.However,the strength of alginate fiber is low due to the particularity of the egg-shell structure in alginate fiber,and ion exchange reaction is easily taken place between calcium ions of alginate fiber with sodium ions in the salt solution,causing poor resistance,which limits the widespread application of alginate fiber.In this paper,to improve the strength of alginate fiber,the physical blending and chemical crosslinking method were used to modify the alginate fibers,and the influence of different process conditions on the mechanical properties of the alginate fiber was studied,the structure and properties of modified alginate fiber were characterized by Fourier transform infrared spectroscopy（FTIR）,X-ray diffraction（XRD）,Scanning Electron Microscopy（SEM）,Thermogravimetric Analysis（TGA）.The research content mainly includes the following three parts:（1）Preparation of hydroxypropyl cellulose（HPC）,hydroxypropyl methylcellulose（HPMC）modified alginate fibersThe HPC and HPMC with good water solubility and film forming property were physically blended with sodium alginate to prepare HPC and HPMC modified alginate fibers with different blending ratios.FTIR showed that the peaks of associative hydroxyl group of modified alginate fibers moved to higher wave number than that of alginate fiber,indicating that the hydrogen bonding association between HPC,HPMC and alginate calcium macromolecule was enhanced.The appearance of new peaks and the disappearance of old peaks in the XRD spectrum of modified alginate fibers proved that there was an interaction between the components of the modified alginate fibers,which changed the original crystal structure of the alginate fibers.SEM showed that the surface stripes of modified alginate fibers became wider,the grooves deepened,and irregular jagged stripes appeared on the cross section,roughness of surface and tensile section of blended fibers got significantly increased.The thermal stability and water absorption of HPC and HPMC modified alginate fibers were improved compared with alginate fiber.Adding a certain amount of HPC and HPMC can improve the mechanical properties of alginate fiber.When the relative amounts of HPC were 4%and 8%,the breaking elongation and breaking strength of HPC modified alginate fibers reached the maximum value.The breaking elongation of HPMC modified alginate fibers maximized and the breaking strength decreased slightly,when the ratio of SA to HPMC was 9:1.（2）Preparation of glutaraldehyde crosslinked alginate fibers and HPC modified alginate fibersGlutaraldehyde is a highly effective aldehyde crosslinking agent.To further enhance the breaking strength of fibers,glutaraldehyde crosslinked alginate fiber and HPC modified alginate fiber were prepared by crosslinking reaction between glutaraldehyde and alginate fiber,HPC modified alginate fiber,under the catalysis of hydrochloric acid.The influences of the concentration of glutaraldehyde and the time of crosslinking on the mechanical properties of alginate fibers were explored.The appearance of-CH₂ stretching vibration peak in the infrared spectrum of crosslinked alginate fibers proved that the crosslinking reaction between glutaraldehyde and alginate fiber occurred.Based on the mechanical properties of the crosslinked fibers,the optimal preparation conditions for glutaraldehyde crosslinked alginate fiber and HPC modified alginate fiber were:the crosslinking temperature was 45℃,the pH was 4 to 5,the volume fraction of glutaraldehyde was 8%,and the crosslinking time was 2 h.At this time,the breaking strength of the crosslinked fibers reached its maximum.The breaking strength of the crosslinked alginate fibers and HPC modified alginate fibers increased by 73%and 106%respectively,but the elongation at break decreased.XRD spectrum showed that the intensity of the diffraction peak of the crosslinked alginate fibers increased,the content of the crystalline phase of the crosslinked fiber increased,which was beneficial to improve the crystalline properties of the alginate fiber.The roughness of surface and tensile section of crosslinked fibers got significantly increased.The TG curve showed that the 5%thermal weight loss temperatures of the crosslinked fibers were higher than those of un-crosslinked fibers,proving that the thermal stability of the glutaraldehyde crosslinked fiber was improved.The swelling degree of the crosslinked fibers in the salt solution was significantly lower than that of un-crosslinked fibers,and the salt resistance of the crosslinked fiber was improved.（3）Preparation of BTCA crosslinked alginate fibersBTCA crosslinked alginate fibers was prepared by using BTCA as the crosslinking agent to chemical crosslink the alginate fibers.The influences of the concentration of BTCA and crosslinking temperature on the amount of carboxyl groups of alginate fibers,the conversion rate of-COOH and the mechanical properties of alginate fibers were investigated.Experimental results showed that elevated temperature and suitable concentration of BTCA were conducive to the esterification reaction between BTCA and alginate fibers.The optimal esterification conditions were:crosslinking temperature was160℃,the concentration of BTCA was 1%,crosslinking time was 3 min,then the breaking strength of crosslinked alginate fiber reached the maximum value,which was 82%higher than that of un-crosslinked alginate fibers.