| Lyocell fiber is a new kind of regenerated cellulose fiber with lots of excellent properties. Lyocell process is an eco-friendly technology because the nontoxic NMMO solvent used is almost all completely recycled. In recent years, numerous researches have been carried out on the functionalization of Lyocell fiber, and there are some reports on Lyocell fibers with hydrophilic, antibacterial, colored, electrical conductive properties, whereas a few works have been reported on the luminescent Lyocell fiber.Luminescent fiber is a kind of functional fiber which can emit transient or continuous light in the general or special lighting conditions (such as irradiated by UV or visible light). According to the difference of the excitation irradiation, luminescent fiber can be divided into two types:fluorescent fiber and long afterglow luminescent fiber (light-storing fiber or luminescent fiber). Fluorescent fiber can appear a specific color under the irradiation of a special light (such as UV light), so it can be widely used in the field of security. Long afterglow luminescent fiber can absorb the visible light and then store the energy. After the removal of the light source, the energy is released as visible light which leads to a long lasting afterglow in the darkness. Therefore it can be widely used in the fields of fire-fighting equipment, safety instruction and traffic signs.At present, luminescent fibers based on PP, polyester matrix have been successfully prepared. As the most abundant natural resources, cellulose has more advantages as the matrix of luminescent fiber. Lyocell process is a relatively simple and environmentally friendly method with relatively low processing temperature, and it is a totally directly physical dissolving process allowing for modifications of Lyocell fiber. Therefore, the use of the Lyocell process and cellulose will undoubtedly promote the development of cellulose functional materials.In this thesis, Lyocell process was used to prepare fluorescent fiber and long afterglow luminescent fiber by integrating ZnS:Cu UV-excitable fluorescent powder or rare-earth luminescent strontium aluminate (SrAl2O4:Eu,Dy) into cellulose, respectively. The coupling agent was used to modify the functional powder, and then fluorescent fiber and long afterglow luminescent fiber were spun by the dry-jet wet spinning process with a single filament spinning device, and the structure and properties of the both fibers were investigated in detail.The fluorescent Lyocell fiber was studied firstly. The characterization of the physical and chemical properties of fluorescent powder confirmed that it had strong absorption in the UV band. After excitation, the emission spectrum consists of two broad band peaked at450and526nm (maximum at526nm), indicating the fluorescent powder would show yellow-green under UV light. The IR results showed that the chemical structure of the fluorescent powder changed after treated with titanate coupling agent, indicating there are chemical bonds combinations for the coupling agent in the surface of fluorescent powder. After the treatment of the titanate coupling agent, the apparent viscosity of the spinning dopes was decreased, and the fluorescent powder could be dispersed more uniformly in Lyocell fibers. Moreover, the fluorescent properties of fibers were improved significantly, and the tensile strength of fibers showed little change although the degree of crystallinity of fibers was decreased slightly by the coupling agent treatment of fluorescent powder. In addition, the rheological properties of spinning dope with different fluorescent powder contents were studied. The results showed that the apparent viscosity of the fluorescent powder/Lyocell spinning dope was decreased firstly and then increased with the increase of fluorescent powder content, and the spinning dope showed the minimum apparent viscosity when the content of fluorescent powder was3%. With the increase of fluorescent powder content, the surface of the fiber became rough and the agglomeration of the fluorescent powder in the fibers was increased, which leads to the decrease of tensile strength and the degree of crystallinity of the fluorescent fibers, whereas the thermal performance of fibers did not change. Fluorescent Lyocell fibers with different content of fluorescent powder have the same emission peaks at450and526nm with fluorescent powder, and the position of main peak didn’t shift, the strongest emission light at526nm confirmed that the fibers could present green-yellow when exposed to the UV light (365nm). With the increase of fluorescent powder content, the emission intensity of the fluorescent Lyocell fiber was improved, but the emission efficiency of the fiber gradually reduced.The long afterglow luminescent Lyocell fiber was also investigated in this thesis. The physical and chemical properties of fluorescence powder were studied firstly. XRD results showed that the main crystalline phase of luminescent powder is SrAl2O4and it can emit green light with an emission peak at510nm. Based on the previous chapter, three kind of coupling agents were used to modify the luminescent powder and the change of sedimentation properties of luminescent powder in aqueous NMMO solution was compared, and then a suitable titanate coupling agent (TC-311) was chosen to improve the dispersion stability of luminescent powder in NMMO solution. After the treatment of coupling agent, the tensile strength of luminescent Lyocell fibers was improved, whereas the thermal decomposition temperature of fibers was decreased slightly by the addition of luminescent powder. With the increase of luminescent powder content, the agglomeration of the luminescent powder in the fibers was increased, which leads to the decrease of tensile strength and the degree of crystallinity of the luminescent fibers. In addition, the emission peak of green luminescent Lyocell fiber was located at510nm, which show good consistency with the rare-earth luminescent strontium aluminate. The afterglow decay curves of luminescent Lyocell fiber showed a basic law of exponential model attenuation, and the decay process of fibers include rapid and slow decay processes, which conforms to the basic rule of the long afterglow powder. With the increase of luminescent powder content, the initial luminescent intensity and the afterglow decay properties of fibers were improved and afterglow duration was extended. The analysis of excitation time showed it need only six minutes to reach the maximum luminous intensity of luminescent fiber.Based on the above work, acid-alkaline resistance and water proof properties of both fibers were further investigated. The results showed that acid-base solutions had a little effect on the tensile strength of the fluorescent Lyocell fiber, but an intense effect on the luminescent Lyocell fiber. The degree of influence varied with the acid-alkaline types, the acid solutions had a stronger effect than alkali solution on the tensile strength and strong acid-base solution showed more obvious influence than weak acid-base solution. After acid-base treatment, fluorescence performance of fluorescent Lyocell fibers had a little change, and the emission peak of fluorescent fibers remained at526nm and present yellow-green light under UV light (365nm). Moreover, luminescent powders are sensitive to acid-base solution, which lead to some voids and cracks on the surface of luminescent Lyocell fibers. After hydrochloric acid (HCl) and alkali solutions treatment, the emission peak of luminescent Lyocell fibers shifted to shorter wavelength and the luminescent intensity was decreased significantly. However, the emission peak of fibers kept unchanged after acetic acid treatment. In this experimental range, two kinds of luminescent fibers showed excellent durability to water, which indicated the fluorescent Lyocell fibers and long afterglow luminescent Lyocell fiber with anti-water performance were successfully prepared based on Lyocell process. |
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