The Study On Degradation Prevention Of Sodium Alginate

Sodium alginate (NaAlg) degrades easily in producing and applying process becauseof the structure defect—the monomer is made up of indican bonds which degrade easily.Lots of studies have been done in degradation prevention but a right method to prevent thedegradation totally can not be found.The producing method of NaAlg with cellulase enzymolysis was firstly studied. Bysingle factor experiments, The effects of the varieties of factors on the final weight ofNaAlg were studied, including buffer quantity, enzyme quantity, reaction temperature,reaction time, pH and so on. Based on those, the perpendicular experiments were used tooptimize the technology. The optimum technical parameters were obtained: buffer quantity55ml, pH5.0, reaction temperature 45 ℃, reaction time 18h, 90μ/g seaweed of cellulose.Under these conditions 2.4g NaAlg can be extracted from 5g seaweed (dry mass).The cross-linked sodium alginate was prepared with mixed anhydride andepichlorohydrin. By single factor experiments, The effects of the varieties of factors on thefinal viscosity of NaAlg were studied, including cross-linked reagent mass, diluting times,reaction temperature, reaction time, pH and so on. Based on those, the perpendicularexperiments were used to optimize the synthesis technology. The optimum technicalparameters of epichlorohydrin cross-linked sodium alginate were obtained: cross-linkedreagent mass 10%, diluting times 35, reaction temperature 50℃, reaction time 5h, pH9.Under these conditions the viscosity of cross-linked product can reach 720cps which was3.5 times of the material. The optimum technical parameters of mixed anhydridecross-linked sodium alginate were also obtained: cross-linked reagent mass 5%, dilutingtimes 30, reaction temperature 55 ℃, reaction time 5.5h, pH10. Under these conditions theviscosity of cross-linked product can reach 430cps.The thermal degradation process of sodium alginate was researched with moderninstruments. It showed that the thermal dissociation of sodium alginate took place in threestages: the dehydration occured at 40~150℃, sodium alginate dissociated into intermediateat 220~260℃ and had been carbonized partly. The stability of cross-linked sodium alginatedeclined with the cross-linked reagent mass increasing. Sodium alginate had beencarbonized totally and the final product was sodium carbonate at 520~570℃ .The thermal properties when heating and cooling of material and cross-linked productwere discussed using Brabender. The curves of Brabender showed that the thermal gelstability declined with the cross-linked reagent increasing and the cold gel stabilityincreased. The aging and returning properties of cross-linked sodium alginate were worsethan the material.