| Konjac glucomannan (KGM), a natural polysaccharide with good biodegradability, hasattracted an ever-increasing attention due to its excellent water retention, thickening, gellingalong with outstanding film forming ability as well as some other unique physical and chemicalproperties. However, the range of its applications has been severely limited resulting from itsshortcomings such as lower solubility, higher viscosity, poorer fluidity and hydrosol stability. Inthis paper, a natural nano-clay, attapulgite (AT), was introduced for the modification of KGM bysolution blending, which was different from conventional chemical modifications or blendingwith other natural or synthetic polymers. The rheological behavior of KGM/AT blend solutionswas studied in order to investigate the dispersion and movement of AT nano-rods. Meanwhile,the overall performances of KGM/AT nanocomposites were researched in detail. Besides, wetspinning simulated by using a syringe was carried out to explore the spinnability of KGM/ATblend solutions. Furthermore, the properties of KGM/AT fibers had also been conducted apreliminary study.The dynamic rheological properties of KGM/AT blend solutions showed that AT with arod-like structure similar to the rigid segments of liquid crystal moleculas was sensitive to theshear stress and their volume effect was helpful to reduce the intermolecular hydrogen bondingsof KGM, which contribute to the disentanglement and orientation of KGM molecules, leading tolower viscosity of blend solutions. Nevertheless, the blend solutions were seemed to be moreheterogeneous in internal structure with the increase of AT nano-rods and their structure stabilitywas influenced by AT nano-rods to a certain extent from the rheological perspective, whichdiscouraged the spinnability for KGM/AT fibers. Therefore, the contents of AT nano-rods in theKGM solution have to be controlled under a certain range.According to the characterization of morphology and structure of KGM/AT nanocomposites,it was found that the appropriate amount of AT nano-rods could be dispersed uniformly withsingle crystal state in the matrix of KGM and the closely combined interface was formedbetween these two components. In contrast, excessive AT nano-rods were easily to aggregate, inducing an irregular distribution in the matrix. A certain interaction such as hydrogen bondingcan be produced between AT and KGM. In addition, the crystallinity of KGM was slightlyincreased with the addition of AT, whereas the crystal form of KGM remained the same. Basedon the test results, it was also found that the rigidity of KGM/AT nanocomposites was enhancedcompared to the pure KGM and the storage modulus reached a maximum with2%AT loadings.Correspondingly, the mechanical properties of KGM/AT nanocomposites were significantlyimproved. The maximal tensile strength and initial modulus was increased by40%and53%,respectively, in contrast to pure KGM. Moreover, the highest initial temperature of thermaldecomposition as well as the temperature of maximum thermo-gracimetric rate increased by27℃and33℃respectively, indicating that the KGM/AT nanocomposites had higher thermalstability. The degree of swelling of KGM/AT nanocomposites decreased with the increasing ofAT nano-rods, to a certain extent, showing that the water resistance of composites was improved.It was believed that KGM/AT solutions had certain spinnability in the95%alcoholcoagulation bath according to the wet spinning experiment simulated by using a syringe.However, irregular structures such as weak-links, defects, increased at higher AT loadings. ATnano-rods at the right amount was beneficial to the orientation of KGM molecules in the draftingprogress, enhancing the mechanical properties of KGM fibers. Furthermore, the water absorptionof KGM fibers could be improved at lower AT loadings, accompany with the highest waterabsorbing capability increasing by nearly50%. |
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