Alginate-based Aerogels:Preparation, Reinforcement And Hydrophobic Modification

Aerogel materials, which use natural ploysaccharide as main resource, have a number of merits such as biocompativility, nontoxicity and biodegradability. In this paper, alginate aerogels were prepared by using sodium alginate (SA) as main body and CaCO3-GDL as the binary crosslinking agent, as well as employing freeze-drying technology. Although gel process was mild and easy to control hydrogel formation by this method, aerogel’s application was limited due to the weak mechanical property. To improve the mechanical properties, N,N-methylenebisacrylamide (MBA) and carboxymethylcellulose (CMC) were introduced into the alginate hydrogel matrix as reinforcing agents, respectively. Meanwhile, the impacts of SA concentration and crosslinking agent on the density, volume shrinkage and compression strength of the aerogels were investigated.The results showed that the density of alginate aerogels was in the range of0.023-0.086g/cm3, and the compression strength increased with increasing SA concentration and crosslinking agent content. The compression strengths of the obtained SA, SA-MBA and SA-CMC aerogels were up to40KPa,80KPa and100KPa, respectively. Therefore, it is indicated that the MBA and CMC excel good reinforcement. According to the SEM images, unexpected numerous nanofibers existed through the network of the SA-MBA aerogel and fixed as pillars, which supported the structure of aerogel effectively. The SA-CMC aerogel, with adding of CMC, exhibited smooth membrane layers that could also enhance the structure.To further improve the application limitation that resultis from hydrophilic property, this work adopted CCl4cold plasma technology to conduct hydrophobic modification. The surface properties of alginate aerogels were converted successfully from hydrophilicity to hydrophobicity. Significantly, the high value129°of contact angle was reached by SA-MBA aerogel after modificated by the plasma at discharge power50W and duration12min. Based on this finding, the oil absorption of modified aerogels in different oil substance, including peanut oil, methyl silicone oil, vacuum pump oil and liquid paraffin, were observed. These modified aerogels exhibited higher oil absorbency which were2-4times more than that of unmodified aerogels. Moreover, the modified aerogels showed high oil retention (>72%for methyl silicone oil and>89%for others). At this point, the hydrophobic alginate-based aerogels showed potentials in oil absorption fields. The above hydrophobic modification mechanism was also discussed on the basis of analyses of XPS and FT-IR spectrum. At the last chapter, the insulation property of alginate-based aerogels was explored preliminarily. The thermal conductivity measurement showed that the value was as low as0.029W/m·K, which was lower than that of common rubber and plastic insulating materials (about0.038W/m·K). It means alginate aerogels exhibit excellent insulation property. Overall, the favorable insulation capability enables the alginate-based aerogels to be potentially applied in insulating material fields.