Preparation Of Hydroxyethyl Cellulose(HEC) Fibers And Their Crosslinking

In recent years, with the decrease of non-renewable resources, the prospects of synthetic fibers were limited. The novel regenerated cellulose fibers are brought to the attention of people because of their regenerated ability, environment friendly and performance similar to cotton. It has found that the alkali soluble HEC solution owns a rather good spinnability, promising to be another kind of regenerated cellulose fibers. In order to improve the wet tensile properties of the HEC fibers, cross-linking treatment was used as post-treatment process and the glyoxalin was selected as crosslinking agent. The cross-linking mechanism was studied and the parameters of the reaction process were optimized. The HEC fibers with good wet strength were expected to be widely applied in the future.In this paper, the alkali soluble HEC was synthesized through gas-solid reaction route. Its spinning solution was prepared by dissolving HEC in8wt%NaOH aqueous solution, and the HEC fibers was manufactured through wet spinning process and H2SO4/Na2SO4aqueous solution was adopted as coagulant. By studying the coagulation rate of HEC gel solution of different concentration in different coagulation bath, the coagulation mechanism of HEC solution was roughly disclosed. It was confirmed that the coagulation process of HEC solution in H2SO4/Na2SO4aqueous solution was a double diffusion principle driven by chemical reaction process. The dependences of tensile properties of HEC fibers on drawing ratio of spinneret, the plastic stretching ratio, the different coagulation bath conditions and the coagulation bath temperature were carefully investigated. With increasing the drawing ratio of spinneret, the breaking strength of the HEC fibers was increased firstly and then declined while elongation at break of the fibers dropped With the increase of plastic stretching ratio, the elongation at break of HEC fibers was decreasing while the breaking strength was enhanced gradually. The breaking strength of the fibers reached the maximum of2.2cN/dtex under the optimum conditions. With elevating the temperature of coagulation bath,"channel" structure would be found on the surface of the prepared HEC fibers due to the fast coagulation rate. The crystalline structure of HEC fibers was changed from cellulose-Ⅰto cellulose-Ⅱ during the regeneration process. The crystallinity of the HEC fibers decreased gradually as increasing the temperature of coagulation bath.For the consideration of the practical application, the wet tensile properties of the HEC fibers should be improved. The glyoxal was used as a cross-linking agent for the HEC fibers during post-treatment process. The effects of reaction conditions on the tensile properties of the cross-linked fibers were exploited. Meanwhile, the reaction mechanism was referred to. The crosslinking of glyoxal with HEC fibers was confirmed by FT-IR analysis. Furthermore, the cross-linking reaction conditions were optimized, and its optimal parameters were summarized as followed:glyoxal concentration is about4%, the pH value is4, the reaction temperature is40℃and the running time is about30min. Under the optimal parameters, the wet tensile strength of the cross-linked fibers was increased by41.5%comparing to that of the uncross-linked fibers, while the elongation at break of the cross-linked fibers was decreased slightly, indicative of significant cross-linking role.The structure changes of the crosslinking and original HEC fibers were characterized by various measurement methods such as wide angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and swelling test. The results showed that the cross-linking reaction have not effects on the crystal form but crystallinity of HEC fibers, and it was increased18%compared to that of the original fibers. Thermal stability of the HEC fibers was also enhanced after the increase of the crystallinity of HEC fibers and the generation of mesh structure. It can be found from the SEM results that the anomalous tendency of HEC fibers was increased and there were more insoluble particles when compared with the no crosslinked fibers. The swelling tests can be another evidence of the occurrence of the crosslinking reaction. It has also found that the swelling degree of HEC fibers in water was decreased with heightening the concentration of the glyoxal solution. When glyoxal concentration reached a certain value, the swelling degree of HEC fibers approached a definite value where the cross-linking reaction kept the ultimate limit.