| Fluorescence fiber is a prominent product because it can appear a specific colorunder the irradiation of a special light (such as UV light). The research anddevelopment of fluorescent fiber is one of key research field of functional fibers. Atpresent, the fluorescent fibers are mostly prepared from petroleum-based polymermaterials. With the increasing shortage of non-renewable petroleum resources,bio-based polymer material such as polylactic acid (PLA) has attracted more andmore attention because of its renewable, biodegradable and eco-friendly advantages.In recent years, numerous researches have been carried out on the functionalization ofPLA fiber, such as flame retardant, amphiphilic, antimicrobial or electrical conductivePLA fiber, whereas few works have been reported on the fluorescent PLA fiber.Therefore, the development of fluorescent PLA fiber will positively improve theadditional value and expand the application fields of PLA fiber. What’s more, asystemic comparison of different polymer-based fluorescent fiber is conducive to thecomprehensive study of the fluorescent fiber.In this thesis, the fluorescent PLA fiber was successfully prepared by melt spinningfor the first time, and filled the gaps of PLA material in the field of fluorescenceanti-counterfeiting. Moreover, the fluorescent fibers based on polypropylene (PP),polyamide6(PA6) and polyethylene terephthalate (PET) were also prepared,respectively. The structure and properties of petroleum-based PP and bio-based PLAfluorescent fibers were investigated in detail, and the acid&alkali resistance andanti-UV properties of fluorescent PLA fiber were discussed. In additional, theproperties of four kinds of polymer-based fluorescent fibers were comparedcomprehensively.Firstly, the fluorescent powder was treated with coupling agent andpetroleum-based PP fluorescent fiber was prepared by melt spinning. SEMphotographs showed that the average size of the fluorescent powder was slightlylarger and the distribution was more uniform after coupling agent treatment.Compared with the fluorescent powder without treatment, the compatibility betweenfluorescent powder and matrix could be improved by the coupling agent treatment,and PP fluorescent fiber exhibited better mechanical properties and fluorescence properties. With the increasing mass fraction of fluorescent powder, theagglomeration of the fluorescent powder in the fiber increased, and the surfacemorphology of fluorescent PP fiber was destroyed, and the tensile strength of the fiberdecreased. Moreover, fluorescence spectra and quantum yields results showed that thefluorescence intensity of the fluorescent PP fiber increased with the increasing massfraction of fluorescent powder, whereas the fluorescence intensity of fiber didn’t showa linear relation with the mass fraction of fluorescent powder. In addition, confocallaser scanning microscopy can be used well to simulate the3D distribution offluorescent powder among the fibers. The results proved that fluorescent powdercould be dispersed more uniformly in the matrix by the addition of compatibilizer-maleic anhydride grafted polypropylene (MAPP), whereas MAPP had no obviousimpact on tensile strength and fluorescence intensity of fluorescent PP fiber.Furthermore, the fluorescent PLA fiber was prepared successfully by optimizingmelt spinning parameters, and the effects of mass fraction of fluorescent powder anddraw ratio on the structure and the properties of the fluorescent PLA fiber wereinvestigated, respectively. The results showed that with the increasing mass fraction offluorescent powder, the relative fluorescence intensity of PLA fiber increasedgradually, whereas morphology of PLA fiber was destroyed gradually, both thecrystallinity and mechanical properties of fluorescent PLA fiber showed thedecreasing trend. With the increase of draw ratio, the fiber diameter became smaller,the tensile strength of fiber increased gradually, and the relative fluorescence intensityof PLA fiber increased firstly and then decreased. In addition, the L16(54) orthogonaltable was chosen to analyze the acid and alkali resistance of the fluorescent PLAfibers by considering three factors: pH, temperature and processing time. The resultsof range analysis and variance analysis showed that the mechanical properties offluorescent PLA fiber were significantly influenced by temperature, but not affectedby pH and processing time. With the increasing of temperature, the tensile strength ofthe fiber decreased. When the temperture was higher than Tg, the morphology of fiberwas seriously damaged. In addition, pH, temperature and processing time had nosignificant influence on fluorescence intensity of fluorescent PLA fiber, and the PLAfiber exhibited good acid/alkali resistance and heat resistance in terms of fluorescenceproperties. Moreover, the effect of UV illumination time on the properties offluorescent PLA fiber was investigated, and the results showed that the fluorescentPLA fiber showed good anti-UV properties. With the increase of UV illumination time, the mechanical properties and fluorescence properties of PLA fiber decreasedslightly.Based on the above work, four kinds of polymer-based fluorescent fibers (PLA, PP,PA6, PET) were compared comprehensively. The energy consumption of thecomposite processing of PLA materials is the lowest in the categories of chemicalfibers. When the mass fraction of fluorescent powder was5%, PET fluorescent fibershowed the highest thermal decomposition temperature; PA6fluorescent fiberexhibited the highest tensile strength; PLA fluorescent fiber had the best whiteness;and PP fluorescent fiber showed the highest fluorescence intensity and transparency.By the comprehensive analysis and comparison from the point of views of theapplication fields, cost and environmental sustainablity, PLA material showed widerapplication fileds, more environmentally friendly and more conducive to thesustainable development although its lower industrial level and higher cost. Therefore,the fluorescent PLA fiber has the excellent development potential. |
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