以鸡蛋壳为致孔剂制备多孔海藻酸钠水凝胶小球及其性能

Preparation and Properties of Porous Sodium Alginate Hydrogel Pellets Using Egg Shell as Pore-causing Agent

以海藻酸钠(SA)、聚乙烯醇(PVA)为原料,鸡蛋壳粉末为致孔剂制备得到了多孔SA/PVA水凝胶小球,以溶胀率为主要指标,通过单因素条件实验对不同鸡蛋壳质量分数、盐酸浓度、SA/PVA质量比和交联方式等因素进行优化,确定了水凝胶小球的最佳制备条件。通过对其结构、形貌的表征,探讨了其结构与性能的关系。实验结果表明,各因素对水凝胶小球的微观形貌及溶胀率等均有一定影响,随着致孔剂用量和盐酸浓度的增大,水凝胶小球的溶胀率均呈现先增大后减小的趋势;而SA与PVA质量比不但会影响水凝胶小球的成球性能,也会影响小球孔结构;当鸡蛋壳质量分数为20%、盐酸浓度为1 mol/L、SA/PVA的质量比为1∶1.5以及采用化学交联法时,制备得到的水凝胶小球溶胀率最大,为1 033.21%,扫描电镜观察到在该条件下制备得到的小球表面具有丰富、连接紧密且稳定的多孔结构,孔形状规则且分布均匀,便于水分子在更多的渠道迅速通过,使得溶胀性能有较大改善。通过红外光谱分析揭示了交联机理:经化学交联后,Ca^(2+)与SA中的—COO—形成络合,硼酸根离子与PVA交联,形成双重交联结构。通过热失重分析表明,最佳制备条件下的水凝胶小球的质量损失最大时的温度为440℃,相较于SA、PVA和鸡蛋壳粉末均有较大提高,表明耐热性能得到了改善。研究为以鸡蛋壳粉末为致孔剂制备多孔水凝胶材料提供了一定的理论和实验基础。

Using sodium alginate(SA)and polyvinyl alcohol(PVA)as raw materials and egg shell powder as pore-causing agent,porous SA/PVA hydrogel pellets were prepared.With swelling rate as the main index,the factors,such as,the mass fraction of the egg shell,acid concentration,SA/PVA mass ratio and cross-linking method were optimized through single-factor experiments.The optimum preparation conditions of hydrogel pellets were determined.Through the characterization of its structure and morphology,the relationship between its structure and properties was discussed.The experimental results show that all the factors have certain effects on the micromorphology and swelling rate of the hydrogel pellets.As the addition of pore-forming agent and acid concentration increase,the swelling ratio of hydrogel pellets shows an initial increase followed by a decrease.Furthermore,the mass ratio of SA to PVA not only affects the sphericity of the hydrogel beads,but also influences the pore structure of the beads.When the mass fraction of the egg shell is 20%,the conditions of acid concentration is 1 mol/L and SA/PVA mass ratio is 1∶1.5,the hydrogel pellets are prepared by chemical crosslinking method,the highest swelling rate 1 033.21%could be obtained.It is observed by scanning electron microscope that the surface of the beads prepared under these conditions has abundant,tightly connected and stable porous structures,with regular pore shape and uniform distribution,which facilitates the rapid passage of water molecules in more channels.The cross-linking mechanism is revealed by infrared spectrum analysis:after chemical cross-linking,Ca~(2+) forms complexation with —COO— in SA,and borate ion crosslinks with PVA to form a double cross-linked structure.The thermogravimetric analysis shows that the temperature which the mass loss of the hydrogel pellets under the optimum preparation condition is the highest 440 ℃ and the heat resistance of the hydrogel pellets under the optimum preparation conditions is improved greatly.The research provides a theoretical and experimental basis for preparing porous hydrogels using egg shell powder as a new pore-causing agent.