| Polysaccharide is naturally ubiquitous biological macromolecules widely applied in food,chemical,and pharmaceutical industries.As main components of polymer materials,performances of polysaccharide can be enhanced via inter or intra molecular interaction to broaden its use.Konjac glucomannan(KGM)is one of the most promising and abundant source of renewable natural polysaccharide polymer.It can produce a strong synergy by intermolecular hydrogen bonds with such macromolecular polysaccharide as xanthan gum,gellan gum,and curdlan,by which the rheology,film-formation and gel performances are improved.Welan gum(WG)is a novel microbial polysaccharide with excellent rheological property,thermal stability,pH stability and consistency.The KGM/WG compound system was prepared by physical blending in this study,and the rheological properties,film-forming properties and gel properties were investigated by modern polymer research methods,to provide instructions for the further application of KGM/WG blended materials.The main findings were summarized as follow:(1)Study on the rheological properties of KGM/WG compound system.Static rheological studies showed that the viscosity of KGM/WG compound system decreased with the increase of shear rate,exhibiting a typical pseudoplastic.KGM/WG compound system was highly concentration-dependent as the higher concentration led to more obvious increase in viscosity.The effects of metal ions on compound system showed that K+ could enhance its viscosity,while Ca2+ and Fe3+decreased its viscosity and Fe3+ had more significant impact.Moreover,dynamic viscoelasticity test showed that compared with the pure KGM,the rheological properties and thermal stability of the compound system was obvious improved with adding a certain amount of WG.The sample KW8 had stronger intermolecular forces and the best rheological properties.(2)Study on the film-forming properties of KGM/WG compound system.The distinctive functional group showed no apparent change as no new group generated and no significant altering in chemical structure observed,suggested via UV-VIS and FT-IR.After blending,the intermolecular hydrogen bonds between polysaccharides were reinforced.Thermal characteristics indicated that blended film KW8 exhibited better compatibility and had the best thermal stability,indicating that adding a certain amount of WG could improve the thermal stability of KGM.The results of the properties of the film showed that adding a small amount of WG in KGM can significantly improve the properties of the films,especially the sample KW8.Generally,the KW8 compound film had the preferred performance with higher tensile strength,lower moisture absorption and water vapor transmission rate.(3)Study on the gel properties of KGM/WG compound system.The formation and thermal stability of the blended gel system were studied by employing methods of rheology,DSC,IR and other analytical instruments combined with molecular modeling.The results showed the occurrence of the blending gel point was delayed with the adding of WG.Pure KGM gel had a share-thinning phenomenon and poor thermal stability at low temperatures,while by adding WG,intermolecular hydrogen bonds could be formed between WG and deacetylated KGM,and thus improved resistance to low-temperature and thermal stability.Investigations on gel performance and scanning electron microscopy showed the adding of WG could make the complex system more uniform and the structure more complete,for the gel strength,elasticity and drainage rate had been improved,while the hardness was decreased.The FT-IR and the computer molecular simulation also indicated that the energy of position for system was decreased and was to being stable after the intermolecular hydrogen bond formed between the deacetylated KGM and WG. |
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