Preparation And Characterization Of Esterified Sodium Alginate Fibers

Alginate is a natural polysaccharide carbohydrate,a good biocompatible and biodegradable material without toxicity or immunogenicity.However,the production and application of alginate fibers are quite limited and mainly used in the special areas like medical dressing due to its low mechanical strength,brittleness and poor resistance to acid and alkali,which is because the molecular chains with low ionic cross-liking bond energy in alginate fibers are rigid,hard to dissolve and stretch.This paper is intend to improve the dyeing properties of alginate fiber,mechanical properties and to expand the application fields of alginic acid and its derivative by grafting flexible macromolecule of polyethylene glycol(PEG)with functional groups onto the molecular chains of sodium alginate.This research was made mainly by two methods to realize alginic acid esterification modification.The first one is that sodium alginate sulfate was prepared using NaAlg as the raw material,amino three sulfonic acid sodium as esterification agent.The UV spectrophotometer was used to determine the grafting rate of alginate sulfate,The effects of the factors such as the ratio of the sulfonate mass,the temperature of esterification,the esterification time and the pH on the grafting yield were analyzed by orthogonal experiment.The best process parameters were determined as follows: The sulfonated mass ratio was 2:3,the esterification temperature was 60 C,the esterification time was 3h,the esterification of pH was 8,the highest degree of esterification was 1.13%.The thermal stability of alginate sulfate was better.Sodium alginate sulfate was prepared by wetting spinning,which was dyed by the cationic red dye.The results showed that the NaAlg molecule was successfully grafted with the sulfate radical,which increased the adsorption of cationic red.The second one is that Alginic acid glycol ester was prepared using NaAlg as the raw material,PEG with different molecular weight as graft monomer,1-ethyl-3-(3-dimethyl amino propyl)-ethylcarbodiimide hydrochloride(EDC-HCl)as coupling agent,4-dimethyl amino pyridine(DMAP)as catalysts.The effects of factors as monomer molar ratio,reaction time and reaction temperature on the grafting rate were studied by single factor variables.Results showed that the molar ratio of sodium alginate to polyethylene glycol was 1:1,thereaction time was 24 h,the reaction temperature was 60 C,and the amount of benzene sulfonic acid was 0.324 g,the highest grafting rate was 0.98%.The chemical structure was characterized by infrared spectroscopy(FTIR)and nuclear magnetic resonance spectroscopy(HNMR).The results showed that new ester stretching vibration peak of Polyethylene glycol alginate appeared at 1689cm-1,indicating that the PEG was successfully grafted onto the molecular chains of alginate.Alginic acid polyethylene glycol ester fiber was prepared by wetting spinning.The effects of the factors such as the spinning solution concentration,coagulation bath concentration,extrusion rate and draft ratio were analyzed,and we found that when the spinning concentration was 3%,coagulation bath concentration was 5%,spinning speed was 27s-1,drafting ratio was 2 times,fiber mechanical properties were the best with the maximum mechanical strength about 1.59 cN/dtex.The alginate ester fiber was characterized by using differential scanning calorimetry(DSC),thermal gravimetric analysis(TGA)and single fiber strength tester,and the results turned out that Polyethylene glycol alginate had relatively good thermal stability,heat-resistant temperature reached 280?,the lower the molecular weight of PEG was,the easier alginate carboxyl was to be introduced to form ester,thus forming a network structure or a closed cyclic compounds.SEM photographs showed that smoothness of the fiber surface was increased by introducing PEG.