Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of v...Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions, The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process.展开更多
Barium ferrite micro/nano fibers were successfully prepared via the electrostatic spinning by using dimethyl formamide（DMF） as the solvent, and poly vinyl pyrrolidone（PVP） as the spinning auxiliaries. Effects of s...Barium ferrite micro/nano fibers were successfully prepared via the electrostatic spinning by using dimethyl formamide（DMF） as the solvent, and poly vinyl pyrrolidone（PVP） as the spinning auxiliaries. Effects of strontium substitution on the structure, morphology, and magnetic properties were investigated by scanning electron microscope（SEM）, X-ray diffraction analysis（XRD）, and vibration sample magnetometer（VSM）. XRD patterns of the samples confirm that pure barium ferrite fibers form, and the Sr substitution makes the main peaks（110）,（107）, and（114） move to right slightly. Also, the FE-SEM images show that the Sr substituted fibers can keep complete fibrous morphology. Moreover, the VSM results demonstrate that the saturation magnetization can reach 56.7 emu/g when the fibers are calcined at 800℃.展开更多
It is highly desirable to develop fiber materials with high strength and toughness while increasing fiber strength always results in a decrease in toughness.Spider silk is a natural fiber material with an excellent co...It is highly desirable to develop fiber materials with high strength and toughness while increasing fiber strength always results in a decrease in toughness.Spider silk is a natural fiber material with an excellent combination of high strength and toughness,which is produced from the spinning dope solution by gelation and drawing spinning process.This encourages people to prepare artificial fibers by mimicking the material,structure,and spinning of natural spider silk.In this review,we first summarized the preparation of artificial spider silk prepared via such a gelation process from different types of materials,including nonrecombinant proteins,recombinant proteins,polypeptides,synthetic polymers,and polymer nanocomposites.In addition,different spinning approaches for spinning artificial spider silk are also summarized.In the third section,some novel application scenarios of the artificial spider silk were summarized,such as artificial muscles,sensing,and smart fibers.展开更多
基金This work was financially supported by the National Natural Science Foundation of China(Nos.20204007,50390090,20490220,10590355)the Doctoral Foundation of National Education Committee of China(No.20030248008)the 863 Project of China(No.2002AA336120).
文摘Finite element method is used to simulate the high-speed melt spinning process, based on the equation system proposed by Doufas et al. Calculation predicts a neck-like deformation, as well as the related profiles of velocity, diameter, temperature, chain orientation, and crystallinity in the fiber spinning process. Considering combined effects on the process such as flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity, the simulated material flow behaviors are consistent with those observed for semi-crystalline polymers under various spinning conditions, The structure change of polymer coils in the necking region described by the evolution of conformation tensor is also investigated. Based on the relaxation mechanism of macromolecules in flow field different types of morphology change of polymer chains before and in the neck are proposed, giving a complete prospect of structure evolution and crystallization of semi-crystalline polymer in the high speed fiber spinning process.
基金Funded by the Qilu Program in Shandong University and the Natural Science Foundation of Shandong Province(ZR2014EMM001)
文摘Barium ferrite micro/nano fibers were successfully prepared via the electrostatic spinning by using dimethyl formamide（DMF） as the solvent, and poly vinyl pyrrolidone（PVP） as the spinning auxiliaries. Effects of strontium substitution on the structure, morphology, and magnetic properties were investigated by scanning electron microscope（SEM）, X-ray diffraction analysis（XRD）, and vibration sample magnetometer（VSM）. XRD patterns of the samples confirm that pure barium ferrite fibers form, and the Sr substitution makes the main peaks（110）,（107）, and（114） move to right slightly. Also, the FE-SEM images show that the Sr substituted fibers can keep complete fibrous morphology. Moreover, the VSM results demonstrate that the saturation magnetization can reach 56.7 emu/g when the fibers are calcined at 800℃.
基金This study was supported by the National Key Research and Development Program of China(Nos.2019YFE0119600,2022YFB3807103)the National Natural Science Foundation of China(Nos.52090034,52225306,51973093,and 51773094)+4 种基金Frontiers Science Center for New Organic Matter,Nankai University(No.63181206)the National Special Support Plan for High-Level Talents People(No.C041800902)the Science Foundation for Distinguished Young Scholars of Tianjin(No.18JCJQJC46600)the Fundamental Research Funds for the Central Universities(No.63171219)the Operation Huiyan(No.62502510601).
文摘It is highly desirable to develop fiber materials with high strength and toughness while increasing fiber strength always results in a decrease in toughness.Spider silk is a natural fiber material with an excellent combination of high strength and toughness,which is produced from the spinning dope solution by gelation and drawing spinning process.This encourages people to prepare artificial fibers by mimicking the material,structure,and spinning of natural spider silk.In this review,we first summarized the preparation of artificial spider silk prepared via such a gelation process from different types of materials,including nonrecombinant proteins,recombinant proteins,polypeptides,synthetic polymers,and polymer nanocomposites.In addition,different spinning approaches for spinning artificial spider silk are also summarized.In the third section,some novel application scenarios of the artificial spider silk were summarized,such as artificial muscles,sensing,and smart fibers.
