Increasing Draw Ratio Research Articles

Phase Structure of Acrylic Fibers Processed with Ionic Liquid as Solvent

The acrylic fibers were prepared by dry-jet wet spinning technology from polyacrylinitrile (PAN) /1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solution for the investigation of phase structure changing with drawing in boiling water. The DMA, WAXD and stress-strain measurements were conducted. It is shown that only a single Tg was observed from DMA and the paracrystalline structure was shown from WAXD. Although the the crystallinity and orientation increased with increasing draw ratio, the high crystallinity of the pre-drawn fiber indicates that the ordered structure was formed in the pre-drawn fiber by the high pre-drawn ratio (3.5) during the dry-jet wet spinning from high-viscosity PAN/[BMIM]Cl solution. It is also found that the initial modulus, ultimate elongation and tenacity increased with the increase of draw ratio.

Structure and physical properties of gelatin fibers prepared by gel‐spinning in ethylene glycol

AbstractGelatin fibers were produced by gel‐spinning using ethylene glycol as the solvent. Gelation conditions, drawing temperature, and draw ratio were studied. Physical properties of the fibers were characterized by mechanical tests, thermal analysis, X‐ray diffractometry, and scanning electron microscopy. The mechanical strength of the fibers increased with increased draw ratio. The gelatin fiber prepared by extrusion of the gelatin (15 wt %)/ethylene glycol into methanol at −20°C and drawn up to seven times its original length at 5°C had the highest tensile strength (405 MPa), a Young's modulus of 11 GPa, and a storage modulus of 7.9 GPa at 200°C. Remarkable differences were observed between the morphology of the undrawn and the drawn fibers. The results show that a gelatin fiber with very good mechanical properties can be prepared using ethylene glycol as the dispersion medium. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Effect of spandex filament draw ratio on elastic core spun yarn properties in friction spinning

The aim of the present study is to produce elastic core/cotton spun yarns in a friction spinning (Dref-II) system and then to investigate the effect of spandex filament draw ratio on the physical and mechanical properties of produced yarns. First, a positive feed device was designed and developed to adjust the spandex draw ratio and then mounted on the friction spinning machine. To maintain a constant yarn count at various draw ratios, the proportion of cotton sheath fibers should be increased. The yarns with larger proportions of cotton fibers showed lower twist. The elastic core spun yarns have lower hairiness in comparison with 100% cotton yarns in the present experiments. The theoretical and experimental results indicate that the tenacity of elastic core spun yarn increases as the spandex draw ratio increases. While the elongation of the elastic core spun yarns is the same as 100% cotton yarn at low spandex draw ratios of less than 3.75, when the spandex draw ratios exceed 3.75, the elongation of the elastic core spun yarn increases sharply.

Preparation and properties of polyamide 6 fibers prepared by the gel spinning method

AbstractPolyamide 6 (PA6) fibers were prepared by CaCl2 complexation and the gel spinning technique. PA6 was partially complexed with CaCl2 for the purpose of suppressing interchain amide group hydrogen bonding. The fibers were characterized with scanning electron microscopy, X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy. In the gel spinning process, a mixed tetrachloroethane and chloroform solution was chosen as the coagulation bath after a comparison of different types of solutions. From our investigation of the morphology, structure, and mechanical properties of gel‐spun and hot‐drawn fibers, it was indicated that the modulus and tensile strength increased with increasing draw ratio, the orientation of the fibers was improved, and the cross section of the PA6 gel fibers became more smooth and tight. The results from the XRD, DSC, and FTIR tests indicated that calcium metal cations complexed with the carbonyl oxygen atoms of PA6. The maximum modulus and tensile strength values obtained in this study were 28.8 GPa and 413 MPa, respectively, at a draw ratio of 8. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Mechanical properties and morphology of hot drawn polyacrylonitrile nanofibrous yarn

AbstractIn this study PAN nanofibrous yarn was produced by two‐nozzle conjugated electrospinning method. The nanofibrous yarns were drawn continuously in boiling water with drawing ratios of 1, 2, 3, and 4. The morphology of drawn yarns was investigated by scanning electron microscopy and tested for tensile properties as well as untreated yarn. The results showed that the nanofiber alignment in the yarn axis direction, the tensile strength, and tensile modulus of yarn increases as a result of drawing while the tensile strain and work of rapture decrease. X‐ray diffraction patterns of the produced yarns were analyzed as well. It was found that crystallinity index increases as the draw ratio increases. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Morphology, Chain Dynamics, and Domain Sizes in Highly Drawn Gel-Spun Ultrahigh Molecular Weight Polyethylene Fibers at the Final Stages of Drawing by SAXS, WAXS, and 1H Solid-State NMR

Morphology, phase composition, and molecular mobility for a series of semicommercial gel-spun UHMWPE fibers were studied using a combination of WAXS, SAXS, and 1H solid-state NMR methods. The fibers show uncommon for this type of fibers decrease in the break load with increasing draw ratio, whereas their modulus and the tenacity reach very high ultimate values. The X-ray and NMR methods have provided complementary information about the fiber morphology and structural reorganizations occurring at the final stage of the fiber drawing. The results suggest that the fiber morphology can be described by a mixture of crystalline fibrils with long period of ∼35–45 nm, as shown by SAXS, and large, so-called, chain-extended crystals. The presence of large crystals with embedded defects is shown by NMR. The drawing causes increase in the crystallinity from ∼89 to ∼96 wt % and in chain orientation, while the long period of fibrils and the break load of fibers surprisingly decrease. The decrease in the long period wit...

Mechanical properties, structure analysis and enzymatic degradation of uniaxially cold-drawn films of poly[( R)-3-hydroxybutyrate- co-4-hydroxybutyrate

Poly[( R)-3-hydroxybutyrate- co-4-hydroxybutyrate] (P(3HB- co-4HB)) films were prepared by uniaxial cold-drawing from an amorphous preform at a temperature below, but close to the glass transition temperature. Molecular and highly-ordered structures and physical properties of cold-drawn films were investigated by tensile testing, wide-angle X-ray diffraction and small-angle X-ray scattering. Enzymatic degradation of P(3HB- co-4HB) films was performed using an extracellular polyhydroxybutyrate depolymerase purified from Ralstonia pickettii T1. Tensile strength, elongation to break and Young’s modulus of P(3HB- co-4HB) with cold-drawn ratio 1200% reached 290 MPa, 58% and 2.8 GPa, respectively. X-ray fibre diagrams of cold-drawn P(3HB- co-4HB) films showed a strong reflection on the equatorial line, indicating a planar zigzag conformation ( β-form) together with 2 1 helix conformation ( α-form). The β-form seems to contribute to the high tensile strength, and a new mechanism of generation of the β-form is proposed. The enzymatic degradation rate increased with increasing draw ratio, and increased greatly with increasing 4HB content.

Frequency response analysis of nonisothermal film blowing process using transient simulations

AbstractFrequency response of the nonisothermal viscoelastic film blowing process to the ongoing sinusoidal disturbances has been investigated using transient simulation techniques. Of the many state variables exhibiting resonant peaks with the input frequency, amplitude ratio of the film cross‐sectional area at the freezeline height has been used as an indicator of the process sensitivity. The effects of operating conditions and viscoelasticity on the sensitivity have been scrutinized around the middle point of three multiple steady states under the given conditions. The sensitivity results have been interpreted through their correlation with results from linear stability analysis. Increasing draw ratio generally makes the system more sensitive to sinusoidal disturbances, whereas the cooling induces more sensitive or less sensitive system, according to the location of a steady state. Also, the viscoelasticity makes the system of extensional thickening fluids more sensitive at low Deborah number and less sensitive at high Deborah number. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Properties and structure of MWNTs/cellulose composite fibers prepared by Lyocell process

AbstractLyocell fiber is a new kind of regenerated cellulose fiber and expected to replace the Rayon fiber to be not only used in the textile field but also used in the fields of industry and aerospace after being modified. In this work, the multi‐walled carbon nanotubes (MWNTs)/Lyocell composite fibers were prepared under different draw ratios by dry‐wet spinning and their electrical properties, mechanical properties, and structure were investigated. It was found that an appropriate amount of MWNTs could be dispersed homogeneously in the Lyocell matrix and could improve the mechanical and thermal properties of composite fiber. The results of wide angle X‐ray diffraction (WAXD) showed that the MWNTs in the composite fiber almost aligned along the axis of the fibers and the orientation of MWNTs increased with the increasing draw ratio. Furthermore, it was found that more MWNTs content and lower draw ratio could improve the electrical conductance of the composite fiber. The composite fiber containing 5 wt % MWNTs has a volume conductivity of 8.8 × 10−4 S/cm, which is five orders higher than that of pure Lyocell fiber. These results indicate that the MWNTs/Lyocell composite fiber has potential applications in the areas of precursor of carbon fiber and conductive fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Influence of Hot Multistage Drawing on Structure and Mechanical Properties of Nylon 6 Multifilament Yarn

The effect of hot multistage drawing conditions on the structure and properties of nylon 6 fibers was investigated by varying second stage draw ratio. Total draw ratio was changed from 3.3 to 5.775 to clarify the structural changes in nylon 6 fiber at a broad range of draw ratio. The structural development of the fibers was studied with FTIR spectroscopy, differential scanning calorimetry (DSC), optical microscopy, and tensile testing. A continuous drop of the γ crystalline form content is observed as a function of draw ratio, in parallel with an increased content of α crystalline phase. The γ crystalline phase vanished completely at draw ratio of 4.62. Increasing draw ratio caused an increase in birefringence and no significant change occurred in crystallinity for the drawn nylon 6 fibers. Deformation behavior of drawn nylon 6 fibers has been explained in terms of applied thermal treatment and mechanical deformations which occurred in each step of multistage drawing.

Digital holographic interferometry: Optomechanical properties of fibers

AbstractStudying polymer fiber's mechanical properties leads to an increased understanding of the behavior of polymeric structures. This will support the design of new synthetic fibers with improved properties. Thus, there is great interest in the exact knowledge of these properties. In this work, phase‐shifting digital holographic interferometry is used to investigate the variation of the optical properties of drawn polyvinylidene fluoride (PVDF) fiber. The study shows that the refractive index for light which is polarized in parallel direction to the fiber axis increases as the draw ratio increases. This implicates that the molecules become more oriented in this direction. However, the decrease in the values of the refractive index for light polarized perpendicular to the drawing direction reflects the reduced orientation of the molecules in this direction. This has been confirmed by studying the variation of the molecular orientation versus birefringence of the drawn PVDF fiber. Holograms and their relationship with the optomechanical parameters obtained are given for illustration. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Posttreatment of the dry-spun fibers obtained from regenerated silk fibroin aqueous solution in ethanol aqueous solution

Abstract

Study on the Structure and Property of Ultra-Fine Denier PET Full Drawing Yarn: Effect of Draw Ratio and Take-Up Velocity

The effect of draw ratio and take-up velocity on the structure and property of the ultra-fine denier PET full drawing yarn (PET-FDY) with monofilament linear density equal to 0.38dTex was studied in this paper. The crystalline structure and crystalline size were determined by XRD method and size was reduced with increase of draw ratio. The orientation of whole molecular chain was determined using sonic velocity method. The mechanical properties and boiling water shrinkage were also examined. Draw ratio had greater influence on the boiling water shrinkage than take-up velocity did.

Influence of Draw Ratio on Crystal Morphology and Structure of β-Form of Isotactic Polypropylene

The effects of the draw ratio (DR) on the polymorphic nature of β-iPP were investigated by polarized light microscopy (PLM), wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS) and differential scanning calorimeter (DSC). The iPP sheet is extruded through a slit die, and then the extruded sheets were hot stretched with the different draw ratio (DR). DSC and WAXD results indicate that the β-iPP content increase with DR increasing from 4.8 to 10.8. β-spherulites can be observed by PLM in the stretched specimen even at a lower DR (4.8). With increasing draw ratio, the relative amount of the β-cylindrites crystals gradually increased.

Structure and properties of highly oriented polyoxymethylene produced by hot stretching

Highly oriented self-reinforced polyoxymethylene (POM) was successfully fabricated through solid phase hot stretching technology. The tensile strength and modulus increased with draw ratio, which reached 900 MPa and 12 GPa, respectively at a high draw ratio of 900% without remarkable drop of the elongation at break. The structure and morphology of the drawn products were studied and the mechanical structure model of microfibril of POM was established. Raman spectral exhibited a low-frequency shift, which indicated two types of molecular chains with different response to the stress. During drawing, the spherulitic structure of POM was broken up and the mat texture crystals were formed. With the increase of draw ratio, the melting peak moved to high temperature and an additional shoulder peak ascribed to melting of highly chain-extended and oriented crystalline blocks was observed. X-ray diffraction showed that the crystallinity and orientation factor increased, while the grain size perpendicular to (1 0 0) crystal plane of POM decreased by drawing. The α relaxation peak corresponding to the glass transition temperature of POM ( T g) moved to high temperature with draw ratio. The section morphology of drawn POM exhibited a fibrillar structure which contributed to the significantly high tensile strength and modulus of the product.

Effect of Orientation on the Morphology and Mechanical Properties of PLA/Starch Composite Filaments

Polylactic acid (PLA)/starch fibers were produced by twin screw extrusion of PLA with granular or gelatinized starch/glycerol followed by drawing through a set of winders with an intermediate oven. At 30% starch, fibers drawn 2–5x were highly flexible (elongation 20–100%) while undrawn filaments were brittle (elongation 2–9%). Tensile strength and moduli increased with increasing draw ratio but decreased with increasing starch content. Mechanical properties were better for composites made with gelatinized starch/glycerol than granular starch. In conclusion, orientation greatly increases the flexibility of PLA/starch composites and this may be useful not only in fibers but also possibly in molded articles. Other advantages of starch addition could include fiber softness without added plasticizer, moisture/odor absorbency and as a carrier for active compounds.

Stretched Polyethylene Films Probed by Single Molecules

Stretched films of low-density polyethylene (LDPE) doped with 2.3,8.9-dibenzanthanthrene (DBATT) were studied using polarization-selective single-molecule spectroscopy at 1.8 K. By measuring the in-plane component of the electronic transition-dipole moments of individual chromophores, the alignment of dopant molecules is determined without averaging. The distributions of chromophore orientations reveal the presence of two fractions of dopant molecules: those oriented along the stretching direction and randomly oriented molecules. With increasing drawing ratio of the polyethylene films, the ratio of oriented to randomly oriented guest molecules increases, whereas the extent of chromophore orientation, that is, the width of the orientation distribution, remains the same. The results are consistent with the interpretation that oriented chromophores reside on the surfaces of polyethylene crystals, instead of in the amorphous polyethylene regions. Guest molecules in stretched polyethylene are oriented due to the alignment of the crystallites on which they are adsorbed. As such, the shape and width of the distributions of chromophore orientations are determined by the interaction of guest molecules with the crystal surfaces.

Structural Origins of Silk Piezoelectricity.

Uniaxially oriented, piezoelectric silk films were prepared by a two-step method that involved: (1) air drying aqueous, regenerated silk fibroin solutions into films, and (2) drawing the silk films to a desired draw ratio. The utility of two different drawing techniques, zone drawing and water immersion drawing were investigated for processing the silk for piezoelectric studies. Silk films zone drawn to a ratio of λ= 2.7 displayed relatively high dynamic shear piezoelectric coefficients of d(14) = -1.5 pC/N, corresponding to over two orders of magnitude increase in d(14) due to film drawing. A strong correlation was observed between the increase in the silk II, β-sheet content with increasing draw ratio measured by FTIR spectroscopy (C(β)∝ e(2.5) (λ)), the concomitant increasing degree of orientation of β-sheet crystals detected via WAXD (FWHM = 0.22° for λ= 2.7), and the improvement in silk piezoelectricity (d(14)∝ e(2.4) (λ)). Water immersion drawing led to a predominantly silk I structure with a low degree of orientation (FWHM = 75°) and a much weaker piezoelectric response compared to zone drawing. Similarly, increasing the β-sheet crystallinity without inducing crystal alignment, e.g. by methanol treatment, did not result in a significant enhancement of silk piezoelectricity. Overall, a combination of a high degree of silk II, β-sheet crystallinity and crystalline orientation are prerequisites for a strong piezoelectric effect in silk. Further understanding of the structural origins of silk piezoelectricity will provide important options for future biotechnological and biomedical applications of this protein.

Effect of the extensional flow on the properties of oriented nanocomposite films for twist wrapping

AbstractIn this study, we examined the mechanical behavior of nanocomposite films based on polyethylene (PE) and pristine PE films. The films were prepared by film blowing and were then cold‐drawn at low temperature. The experimental results show that cold drawing significantly enhanced the orientation; with increasing draw ratio (DR), the elastic modulus and tensile strength of the PE films strongly increased, particularly in the presence of the organoclay. To obtain polymeric films suitable for twist wrapping, the films must be sufficiently stiff so that no shrinkage or elastic recovery occur during or after twisting. The elongation at break and the yield strain sharply decreased with orientation, mainly in films upon drawing. According to the mechanical behavior, the twist angle increased with increasing DR and, particularly, with the addition of nanoclay, probably because of the applied DR, which reduced the nanoparticle size and, as a consequence, hindered the applied torsional elastic recovery. Therefore, the nanocomposite film with a higher DR was particularly suitable for twist‐wrapping applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Dynamic Mechanical and Perforation Impact Behavior of All-PP Composites Containing Beta-Nucleated Random PP Copolymer as Matrix and Stretched PP Homopolymer Tape as Reinforcement: Effect of Draw Ratio of the Tape

Cross-ply all-polypropylene (PP) composite laminates were prepared by hot consolidation after tape winding combined with film stacking. Alpha (α) PP tapes of different draw ratios (DR = 8 and 12), produced by online extrusion stretching, served as reinforcements. Beta (β)-nucleated random PP copolymer, introduced in the form of a film, composed the matrix. The E-modulus of the PP tapes increased whereas their density decreased with increasing DR. The volume fraction of the reinforcement and the void content were estimated using optical microscopic images. The all-PP composites were subjected to dynamic mechanical thermal analysis, flexural, and instrumented falling weight impact tests. It was found that with increasing draw ratio of the α-PP tapes, the stiffness, strength, and perforation resistance of the composites were improved.