Polyamide 56 (PA56) fibers were prepared by one‐step melt spinning and drawing process. The effects of draw ratio and draw temperature on the structure and properties of PA56 fibers were ...investigated. Both α‐like‐ and γ‐crystalline phases were formed in PA56 fibers. An increase in the draw ratio at a given draw temperature leads to the significantly increase in crystallinity, chain orientation, and the content of the α‐like crystalline phase in the resultant PA56 fibers. The crystallinity and orientation parameters of the PA56 fibers increase with draw temperature in the range of 130–190°C. The PA56 α‐like crystalline phase is unfavorable at a higher draw temperature. The optimal process parameters for PA56 fibers with good mechanical properties are at draw ratio above 3 and with a draw temperature in the range of 150–190°C.
Textiles have a very long history, but they are far from becoming outdated. They gain new importance in technical applications, and man-made fibers are at the center of this ongoing innovation. The ...development of high-tech textiles relies on enhancements of fiber raw materials and processing techniques. Today, melt spinning of polymers is the most commonly used method for manufacturing commercial fibers, due to the simplicity of the production line, high spinning velocities, low production cost and environmental friendliness. Topics covered in this review are established and novel polymers, additives and processes used in melt spinning. In addition, fundamental questions regarding fiber morphologies, structure-property relationships, as well as flow and draw instabilities are addressed. Multicomponent melt-spinning, where several functionalities can be combined in one fiber, is also discussed. Finally, textile applications and melt-spun fiber specialties are presented, which emphasize how ongoing research efforts keep the high value of fibers and textiles alive.
The (Sm,Zr)(Fe,Co)5 alloys were prepared by the melt-spinning technique and subsequent annealing. The substitution of Zr for Sm stabilized the SmFe5 phase and resulted in a small increase in ...coercivity, while the substitution of Co for Fe also stabilized the SmFe5 phase and produced a slightly higher increase in coercivity. The substitution of both Zr for Sm and Co for Fe not only stabilized the SmFe5 phase but also significantly increased the coercivity. The (Sm,Zr)(Fe,Co)5 alloy with the optimal annealing temperature and composition exhibited a high coercivity of 4.75 kOe without nitrogenation.
•The addition of Zr to the SmFe5 alloy stabilized the SmFe5 phase.•The addition of Co to the SmFe5 alloy also stabilized the SmFe5 phase.•The addition of both Zr and Co to the SmFe5 alloy resulted in an increase in coercivity.•The (Sm,Zr)(Fe,Co)5 alloy exhibited high coercivity without nitrogenation.
In this study, the electrical conductivity of melt spun composites consisting of PMMA containing both aligned carbon fibers (CF) and carbon black (CB) has been investigated. A broad range of ...composite compositions (up to 50 vol % CF and 20 vol % CB) was studied. The percolation thresholds of binary PMMA/CF and PMMA/CB composites were determined to 31.8 and 3.9 vol %, respectively. Experimental conductivity contour plots for PMMA/CF/CB ternary composites were presented for the first time. Additionally, based on a model for predicting the percolation threshold of ternary composites, a novel equation was proposed to predict the conductivity of ternary composites, showing results in agreement with corresponding experimental data. Finally, two mechanical contour plots for elastic modulus and tensile strength were presented, showing how the decreasing tensile strength and increasing E-modulus of the PMMA/CF/CB ternary composites was depending on the CB and CF filling fractions. The systematic measurements and novel equations presented in this work are especially valuable when designing ternary conductive polymer composites with two different fillers.
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•Boron addition slows down the formation of 1:12 structure in melt-spun alloys.•Zr addition speeds up the formation of 1:12 structure in melt-spun alloys.•Together, B and Zr increase ...coercivity of annealed melt-spun alloys.•Coercivity of bulk magnets was 5.4 kOe with a temperature coefficient of −0.25%/°C.
Rare-earth-lean Sm(Fe,Co,Ti)12 alloys with the ThMn12 crystal structure and less than one Ti atom per formula unit have the potential of exceptionally powerful permanent magnets, but all prior attempts to develop high coercivity in bulk alloys, especially coercivity combined with crystallographic texture, have fallen short of the expectations. This study was aimed at improvement of the currently best Sm(Fe,Co,Ti)12 magnets prepared through melt-spinning which are inherently isotropic. Modifications of the alloys with B and Zr, already demonstrated in earlier studies to be effective separately, have been implemented simultaneously. A systematic study of Sm1.1-x(Fe,Co)11.3-yTi0.7By alloys melt-spun at a tangential speed of 50 m/s and annealed at 600–950 °C allowed for monitoring the continuous evolution of the two consecutive crystal structures, those of the TbCu7 and ThMn12 types. Zirconium was found to facilitate the formation of the 1:12 structure at the expense of the 1:7, whereas boron has the opposite effect, at certain concentrations completely suppressing the 1:12. When the two alloying elements are introduced simultaneously, they inhibit growth of the 1:12 crystallites at annealing temperatures higher than 800 °C, thus allowing for the development of a higher coercivity. Because of instrumental limitations, bulk magnets were prepared through a two-step process – compaction of the melt-spun ribbons at 650 °C and additional treatment at a higher temperature – and they were characterized by a reduced, 90–93%, density. Nevertheless, an isotropic Sm0.9Zr0.2(Fe,Co)10.8Ti0.7B0.5 magnet exhibited fair values of the remanence (7.4 kG), maximum energy product (8.5 MGOe) and coercivity (5.4 kOe), as well as high Curie temperature of 525 °C and remarkably small temperature coefficient of the coercivity, −0.25%/°C.
The adverse effect of draw-down ratio (DDR) during melt-spinning of mesophase pitch on resulting properties of carbon fibers (CFs) is reported. Precursor fibers were obtained using spinneret ...capillaries of various diameters. For CFs with equivalent diameters (ranging between 8 and 13 μm), the tensile strength of CFs increased from 1.4 to 2.3 GPa as the DDR of precursor fibers decreased from 189 to 14. This is contrary to that observed for CFs derived from polyacrylonitrile precursor, where strength increases with increasing precursor fiber DDR. Raman spectroscopy revealed an inverse relationship between pitch fiber DDR and CF coherence length (increase from 58 to 85 nm when DDR decreased from 189 to 14). Further, x-ray diffraction results confirm a larger CF crystalline orientation with decreasing DDR. Thus, a smaller DDR during mesophase spinning could facilitate intra-crystalline graphitic-plane orientation and decrease defects in the inter-crystalline regions along fiber axis in resulting CFs, leading to increased strength (a defect-controlled property). Thus, while it is generally known that tensile strength increases with decreasing CF diameter, for mesophase pitch-based carbon fibers this relationship is not fully valid if the diameter reduction is obtained by merely increasing the draw-down ratio of precursor fibers during melt-spinning.
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Lightweight, easy recyclability and improved bonding can be achieved by self-reinforced polymer composites (SPC). However, the mechanical properties of SPC are usually limited. This paper describes ...the incorporation of graphene platelets (GNP) into polypropylene (PP) to produce PP/GNP SPC. PP/GNP fibers were firstly prepared by melt compounding and spinning, and then PP/GNP SPC were produced by film stacking. The thermal, mechanical, and morphological properties of the produced samples were characterized via DSC, WAXD, tensile test, peeling test, optical microscopy, and SEM. The combination of film stacking technology of SPC and nanotechnology of graphene enhanced the mechanical properties significantly. The tensile strength, tensile modulus, and interfacial strength of PP SPC with only 0.062 wt% GNP were increased by 117, 116, and 116%, respectively. The reinforcement is attributed to the high intrinsic mechanical properties of GNP and the self-reinforced mechanism. The spinning promotes the alignment of GNP, and the compaction process induces the in-plane orientation of GNP. In addition, a small number of GNP do not increase the cost significantly.
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•Polypropylene/graphene platelets single-polymer composites (PP/GNP SPC) were prepared.•Compared with pure PP, 117% and 116% increases of tensile strength and modulus were obtained by the PP/0.062 wt% GNP SPC.•Compared with PP SPCs, 116% increase of interfacial strength was obtained by the PP/0.062 wt% GNP SPC.•Graphene nanotechnology and self-reinforced mechanism enhanced the mechanical properties of the PP/GNP SPC.
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