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Melt Spinning (melt + spinning)
Terms modified by Melt Spinning Selected AbstractsMelt Spinning of Bacterial Aliphatic Polyester Using Reactive Extrusion for Improvement of CrystallizationMACROMOLECULAR BIOSCIENCE, Issue 6 2007Roland Vogel Abstract This paper reports on an attempt to use reactive extrusion with peroxide as a comfortable pathway for improvement of the crystallization of poly(3-hydroxybutyrate) in a melt spinning process. At first, rheological and thermal properties of the modified melts are determined in order to assess the effect of nucleation. Then spinning tests are carried out. Molecular weights and molecular weight distributions of the spun fibers are determined by chromatographic methods. Average crystallite size is measured by wide angle X-ray scattering. Thermal and textile properties of the spun PHB fibers are also determined. An estimation of the improvement of the crystallization in the spinline and of the inhibition of the secondary crystallization in the fibers from the use of the described way of reactive extrusion is given. [source] Syndiotactic poly(propylene)/organoclay nanocomposite fibers: influence of the nano-filler and the compatibilizer on the fiber propertiesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 5 2005Zita Mlynar, íková Abstract Melt spinning of nanocomposites prepared from syndiotactic poly(propylene) (sPP) and organolayered silicate (M-ODA), containing bound octadecyl ammonium chains, was investigated. The influence of the nano-filler reinforcement and the role of the addition of maleic anhydride grafted isotactic poly(propylene) (iPP-g-MA) as compatibilizer with respect to the fiber proportion was examined. The presence of nano-filler, the drawing ratio, and the compatibilizer addition afforded increased tenacity of the fibers. Only in the presence of the compatibilizer high drawing ratio of the sPP nanocomposite fibers was achieved. Transmission electron microscopy (TEM) was applied to monitor morphology development during nanocomposite fiber spinning in the presence and the absence of the compatibilizer. Copyright © 2005 John Wiley & Sons, Ltd. [source] Raman spectroscopy for spinline crystallinity measurements.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Abstract The original Doufas,McHugh two-phase microstructural/constitutive model for stress-induced crystallization is expanded to polyolefin systems and validated for its predictive capability of online Raman crystallinity and spinline tension data for two Dow homopolymer polypropylene resins. The material parameters,inputs to the model,are obtained from laboratory-scale material characterization data, that is, oscillatory dynamic shear, rheotens (melt extensional rheology), and differential scanning calorimetry data. The same set of two stress-induced crystallization material/molecular parameters are capable of predicting the crystallinity profiles along the spinline and fiber tension very well overall for a variety of industrial fabrication conditions. The model is capable of predicting the freeze point, which is shown, for the first time, to correlate very well with the measured stick point (i.e., the point in the spinline at which the fiber bundle converts from a solid-like state to a liquid-like state and sticks to a solid object such as a glass rod). The model quantitatively captures the effects of the take-up speed, throughput, and melt flow rate on the crystallization rate of polypropylene due to stress-induced crystallization effects. This validated modeling approach has been used to guide fiber spinning for rapid product development. The original Doufas,McHugh stress-induced crystallization model is shown to be numerically robust for the simulation of steady polypropylene melt spinning over a wide range of processing conditions without issues of discontinuities due to the onset of the two-phase constitutive formulation downstream of the die face, at which crystallization more realistically begins. Because of the capturing of the physics of polypropylene fiber spinning and the very good model predictive power, the approximations of the original Doufas,McHugh model are asserted to be reasonable. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Raman spectroscopy for spinline crystallinity measurements.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Abstract Online Raman spectra, obtained at different points along the spinline during the melt spinning of polypropylene homopolymer (hPP) fibers, are presented. The percentage crystallinity corresponding to each spectrum was determined from the normalized intensity of the 809-cm,1 Raman band. A calibration curve for propylene crystallinity was established offline with compression-molded films and fibers spun under different processing conditions. Several hPPs and propylene,ethylene copolymers (with 5,15% ethylene) were used to cover a wide calibration range for propylene crystallinity (9.5,60.9%) with an R2 value of 0.989. This calibration curve was subsequently used to predict the polypropylene crystallinity in the spinline as a function of distance from the spinneret. Under identical conditions of quench and throughput, at a fixed point along the spinline, the overall crystallinity developed in the fiber was found to increase with an increase in the spinning speed. As the spinning speed increased, the point of the onset of crystallization moved closer to the spinneret. The rise in crystallinity was more gradual, at 750 m/min as opposed to 1500 m/min. Increasing the throughput at constant spinning speed was found to decrease the rate of crystallization because of a decrease in the spinline stress. At a fixed distance from the spinneret under identical conditions of quench and spinning speed, fibers spun at a higher throughput showed less overall crystallinity. The onset and rate of crystallization was found to be faster in the lower melt index H502-25RG resin as compared to the 5D49 resin under the spinning conditions explored. The experimental data presented here were used to validate fundamental fiber-spinning models (see part II of this series of articles). The validated models and experimental observations can be used to guide the fiber spinning of isotactic polypropylene for rapid product development. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Influence of different functionalized multiwall carbon nanotubes on the mechanical properties of poly(ethylene terephthalate) fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Liming Shen Abstract Master batches with four different kinds of functionalized multiwall carbon nanotubes (MWCTs) were prepared through the mixing of MWCTs with poly(ethylene terephthalate) (PET) (0.01 : 0.99 w/w) in trifluoroacetic acid/dichloromethane mixed solvents (0.7 : 0.3 v/v) followed by the removal of the solvents in the mixture by flocculation. The results of scanning electron microscopy showed that a good dispersion of MWCTs in PET was achieved. The reinforced fibers were fabricated by the melt spinning of PET chips with small amounts of the master batch and then further postdrawing. The optimal spinning conditions for the reinforcement of fibers were a 0.6-mm spinneret hole and a 250 m/min wind-up speed. Among the four master batches, the fibers obtained from PET/master batch B made by acid-treatment had the highest enhancement of mechanical properties. For a 0.02 wt % loading of acid-treated MWCT, the breaking strength of the PET/master batch B composite fibers increased by 36.9% (from 4.45 to 6.09 cN/dtex), and the initial modulus increased by 41.2% (from 80.7 to 113.9 cN/dtex). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Manufacturing, mechanical characterization, and in vitro performance of bioactive glass 13,93 fibersJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006E. Pirhonen Abstract Fibers were manufactured from the bioactive glass 13,93 by melt spinning. The fibers were further characterized by measuring their tensile and flexural strength, and their in vitro performance was characterized by immersing them in simulated body fluid, which analyzed changes in their mass, their flexural strength, and surface reactions. The strength of glass fibers is highly dependent on fiber diameter, test method, and possible surface flaws, for example, cracks due to abrasion. In this study, the thinnest fibers (diameter between 24 and 33 ,m) possessed the highest average tensile strength of 861 MPa. The flexural strength was initially 1353.5 MPa and it remained at that level for 2 weeks. The Weibull modulus for both tensile and flexural strength values was initially about 2.1. The flexural strength started to decrease and was only ,20% of the initial strength after 5 weeks. During the weeks 5,40, only a slight decrease was detected. The flexural modulus decreased steadily from 68 to 40 GPa during this period. The weight of the samples initially decreased due to leaching of ions and further started to increase due to precipitation of calcium phosphate on the fiber surfaces. The mass change of the bioactive glass fibers was dependent on the surface area rather than initial weight of the sample. The compositional analysis of the fiber surface after 24 h and 5 weeks immersion did confirm the initial leaching of ions and later the precipitation of a calcium phosphate layer on the bioactive glass 13,93 fiber surface in vitro. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Draw ratio enhancement in nonisothermal melt spinningAICHE JOURNAL, Issue 3 2009Balram Suman Abstract Nonisothermal melt spinning of materials having a step-like viscosity variation with temperature is studied in this work. A set of nonlinear equations is used to describe the fiber behavior and to obtain the draw ratio, the square of the ratio of the fiber diameter at the entrance to that at the exit of the fiber-spinning device. The fluid-flow equation is based on a slender-jet approximation, and external heating and cooling have been accounted for with a one-dimensional model in order to obtain the fiber temperature and viscosity along the fiber length. The model is similar to that used by Wylie et al. (J Fluid Mech. 2007;570:1,16) but accounts for inertia, shear stress at the fiber surface, surface tension, gravity, cooling, and larger heating rates. Steady-state analysis reveals that the draw ratio increases with an increase in the pulling force, passes through a maximum, and then starts increasing again, resulting in three possible pulling forces for the same draw ratio. However, linear stability analysis reveals that depending on the strength of heating and/or cooling, at most two of the steady states are stable. The stability analysis also predicts complicated oscillatory and nonoscillatory dynamical behavior as the pulling force varies. Nonlinear simulations reveal that an unstable system always tends to limit-cycle behavior. Systems predicted as stable by the linear stability analysis are also stable for large-amplitude perturbations. External heating is found to dramatically enhance the draw ratio of the melt-spinning process. The addition of a cooling section suppresses the draw ratio, but this can be compensated for with a higher heating strength. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Effect of non-isothermal oriented crystallization on the velocity and elongational viscosity profiles during the melt spinning of high density polyethylene fibersPOLYMER ENGINEERING & SCIENCE, Issue 7 2001A. Makradi Based on the experimental data of spine line temperature and percent crystallization, a time-integral constitutive equation has been used together with the degree of phase transformation theory to predict the velocity and elongational viscosity profiles. For the velocity profile, our predicted results are compared to experimental data and good agreement is found. Under a drawing force, the elongational viscosity profile shows a stress softening due to the molecular alignment; then the fiber hardens close to the take-up point, owing to filament crystallization. [source] In vitro hydrolytic degradation of centrifugally spun polyhydroxybutyrate,pectin composite fibresPOLYMER INTERNATIONAL, Issue 12 2009L John R Foster Abstract BACKGROUND: Centrifugal spinning is a novel fibre-forming process that readily permits the incorporation of additives while avoiding the thermal damage often associated with conventional melt spinning. Centrifugal spinning of a viscous solution of poly(3-hydroxybutyrate) (PHB) mixed with pectin was used to fabricate a range of fibres containing different concentrations of this biologically active agent. The influence of this blending on fibre morphology and in vitro degradation in an accelerated hydrolytic model at 70 °C and pH of 10.6 is reported. RESULTS: Blending influenced the physiochemical properties of the fibres, and this significantly affected the degradation profile of both the fibre and its PHB constituent. A greater influence on degradation was exerted by the type of pectin and its degree of esterification than by variations in its loading. CONCLUSION: Centrifugal spinning permits the fabrication of composite fibrous matrices from PHB and pectin. Incorporation of the polysaccharide into the fibres can be used to manipulate degradation behaviour and demonstrates a model for doping of matrices with active biological constituents. The unique features of the centrifugal spinning process, as illustrated by the structure of the fibres and the degradation profiles, suggest possible applications of centrifugally spun biopolymers as wound scaffolding devices and in tissue engineering. Copyright © 2009 Society of Chemical Industry [source] | ||||||||||