Przeglądaj {{ collection }} wg Autor "Salaün, Fabien"

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Effects of the alginate and CACL2 concentrations imparting mechanical and morphological properties of wet spun filaments
(Wydawnictwo Politechniki Łódzkiej, 2022) Erard, Annaëlle; Cayla, Aurélie; Salaün, Fabien
Alginate fibers were used essentially in wound dressing due to his biocompatibility and were prepared by the wet-spinning process using a sodium alginate solution and a calcium chloride solution (CaCl2) as a coagulation bath. The effects of the wet-spinning solvent, coagulating solution, and polymer concentration on corresponding fiber structure were addressed to achieve homogeneous fibers with controlled morphology and suitable mechanical properties. Fiber average diameter, surface state, and fiber homogeneity were assessed by optical and scanning electron microscopies to screen the influence of the formulation and process parameters on the morphological characteristics of the fibers. Furthermore, mechanical properties were studied after determining the monofilament finesses. At an alginate concentration of 8 wt.%, the tenacity and elongation at break of the resulting alginate fibers are the best results. Finally, preliminary studies demonstrated that optimization of CaCl2 concentration and coagulation time resulted in improved fiber regularity and mechanical properties. Thus, optimization of the process and formulation parameters were obtained for a concentration of 8 wt.% alginate, 1 wt.% CaCl2, and a coagulation time of 5 minutes. The resulting spun fibers had an average tenacity of 11 cN/Tex and an average elongation at break of 24%. This is promising for the wet spinning process which can modify the fibers properties.
Optimization of the fiber/matrix interface and integration of a photochromic molecule in the fiber/matrix system
(Wydawnictwo Politechniki Łódzkiej, 2022) Aden, Mahad Barre; Rault, François; Salaün, Fabien
Molecules and supramolecular that are capable of undergoing structural rearrangements when subjected to an external stimulus have attracted a great deal of attention as they can represent a new way to design smart textiles. Azobenzenes are stable molecules in both the isomeric states, i.e., open and closed forms. By mimicking nature, one of the most significant challenges in the realization of switches is to integrate multiple and independent reactive units in a single molecular system allowing to couple a photochromic activity with a mechanical activity to obtain a photo mechanically activatable system. Among the different inputs, photons have been considered as one of the most promising for application in the textile field. This study aims to explore the possible ways to integrate a diarylethene (DTE) either in the core of the fiber or on its surface to create a photoactive textile structure. The integration of DTE by melt spinning into a poly (methyl methacrylate) matrix has demonstrated the feasibility of the process. Nevertheless, even if a photosensitive effect has been observed, the low quantity of molecules coupled with the thermal constraints do not make this process feasible on a larger scale. To overcome this problem, it was considered to integrate the DTE in a functional coating formulation by dispersing them in a polyurethane matrix with a coating step. This part of the study focuses mainly on the fiber/matrix adhesion mechanisms to determine the best couples in terms of adhesion. The results obtained after the pull-out test showed that the polyamide/polyurethane couple has the highest work of adhesion compared to the polypropylene or polyethylene terephthalate ones.
Preparation of PVDF nanofibers by optimizing solvent properties: improved solvent viscosity and evaporation rate
(Wydawnictwo Politechniki Łódzkiej, 2022) He, Zhongchen; Rault, François; Mohsenzadeh, Elham; Lewandowski, Maryline; Salaün, Fabien
PVDF nanofibers have been intensively investigated in wearable energy harvesting because of their flexibility and piezoelectric properties. In this study, we prepared PVDF nanofibers by the electrospinning method. Different solvents like DMF and DMF/acetone with the ratio of 6/4, 5/5, and 4/6 were selected to adjust the solvent properties. SEM, FTIR, and DSC characterizations were used to characterize the morphology, structure, and β phase content of PVDF nanofibers. The results demonstrate that the electrospun PVDF nanofibers produced by using DMF/acetone have predominantly a fibre structure and increased β phase compared to electrospun samples using DMF alone as solvent. PVDF nanofibers fabricated by using DMF/acetone with a ratio of 4/6 exhibit the maximum content of β phase and the highest value of piezoelectric coefficient (d33).