Preparation,Properties And Application Of Alginate Helical Fiber

Sodium alginate(SA),extracted from brown algae,is a polyelectrolyte type block polymer with irregular arrangement.At the same time,SA possesses the merits of good biocompatibility,excellent degradability,low cost and non-toxicity.It has a wide scope of applications such as healthcare,textile,and tissue engineering.Currently,for sodium alginate,there are three commonly used spinning methods,namely wet spinning,microfluid spinning and electrospinning.Among them,the most commonly used spinning method for SA is wet spinning.The coagulating bath used is mostly calcium chloride solution.The G units of alginate macromolecule can form"egg box"structure with calcium ions,thus obtaining the calcium alginate fiber with stable structure.Alginate fibers prepared by wet spinning are hard and brittle with low strength.In order to solve this defect,improving the mechanical properties of pure alginate fibers is a research focus recently.The common methods to improve mechanical properties of alginate are the use of different crosslinking agent(e.g.covalent citric acid and glutaraldehyde,etc.)and to blend with other material(e.g.chitosan and graphene,etc.).The main mechanism is to improve the crystalline region of the final product and enhance the intermolecular or intramolecular bonding effects.Nevertheless,due to the presence of other substances,these substances may remain in the final sample,thereby leading to a risk of affecting the reaction of the organism.Therefore,the improvement of alginate structure would contribute to enhancing the mechanical properties of the fibers,and finally improving the biocompatibility and biodegradability of the product.Furthermore,with introducing helical structure and stretching oriented alginate polymer chain segment,the mechanical properties of alginate fibers are improved and enhanced.For single fiber,the mechanical property is the best when adding 20 twists.The average tensile strength and toughness of single fiber are 55.23±5.17 MPa(0.552 c N/dtex)and 6.64±1.15 KJ·m^-3.Compared with no twisting of single fiber,it increased by 112.83%and155.38%,respectively.For bundle fibers,the mechanical property is the best when adding 80twists and soaking in calcium ion solution.The average tensile strength and toughness are 22.29±3.72 MPa(0.223 c N/dtex)and 8.01±0.75 KJ·m^-3,respectively.Compared with no twisting,they increased by 185.04%and 215.35%,respectively.The results showed that the helical structure is effective to improve the mechanical properties of pure alginate fibers.Then,four various aqueous solutions with the same concentration of metal ions(Ca²⁺,Zn²⁺,Ba²⁺,Fe³⁺)were prepared,and alginate fibers with 80 twists were soaked after natural drying.Eventually,the alginate–metal ion fibers were obtained.The results of EDS and mechanical properties showed that alginate was successfully combined with metal ions.In addition,the maximum tensile strength of ferric alginate fiber is 31.89±2.57 MPa(0.319 c N/dtex).The maximum toughness of calcium alginate fiber is 8.01±0.75 KJ·m^-3.FT-IR spectra showed that the alginate chains formed chelate coordination bonds with all metal ions.By toughening SA double network hydrogel and suturing medical bandage with calcium alginate fiber of 80 twists,the pure alginate fibers with helical structure may be used as toughening materials in the field of tissue engineering in the future.