Zone Drawing Research Articles

Swollen-state polymerization of poly(ethylene terephthalate) in fibre form

The swollen-state polymerization of poly(ethylene terephthalate) in fibre form was performed in hydrogenated terphenyl as the swelling solvent. Ultra-high-molecular-weight poly(ethylene terephthalate) (CHMW-PET) fibre with an intrinsic viscosity of 3–4dl g−1 (Mn = 2–3 × 105) was obtained. The polymerization rate of as-spun PET fibres in the swollen state was greater than that of PET granules in the swollen state. It was clarified that the polymerization rate was related to the chain mobility of the starting materials. The chain mobility was influenced by various conditions, such as changing rigidity of the segments during copolymerization, the chain orientation of the starting fibre before swollen-state polymerization and the temperature of pretreatment with the solvent. Pretreatment with solvent before polymerization was effective in increasing the chain mobility. The relation between chain mobility and polymerization rate was examined by wide-angle X-ray diffraction, density, differential scanning calorimetry, solvent content and viscoelastic measurements. Undrawn UHMW-PET fibres could be drawn 10 times or more by the zone drawing technique in spite of their high crystallinity, and the drawn fibre showed high tensile strength (12 g d−1) and high modulus (240 g d−1).

Supermolecular structure of oriented and semicrystalline poly(ethylene terephthalate) as revealed by the electron density correlation function from small-angle X-ray scattering studies

Small-angle X-ray scattering (SAXS) is employed to study the supermolecular structure of uniaxially oriented and semicrystalline poly(ethylene terephthalate) (PET) samples. By means of a multistep zone drawing procedure carried out at different temperatures and loading conditions an extraordinarily high chain orientation is achieved. Using the electron density correlation function obtained from the Fourier transformed experimental scattering intensity, structure parameters such as the most probable long period, the average lamellar thickness, and the volume crystallinity are determined. By obtaining these parameters from only one experiment one can neglect possible effects from a combination of methods and thus gain new insights into the structure formation process under drawing.

Effect of zone annealing on LARC‐CPI thermoplastic polyimide

AbstractMechanical properties and structure were studied for undrawn and zone‐drawn films of LARC‐CPI thermoplastic polyimide. The dynamic modulus of undrawn glassy material ranged from about 1.8 to 4.3 GPa, depending upon the degree of crystallinity. After zone drawing to draw ratio of 3.6–4.0, the dynamic glassy modulus was increased to a maximum of 9.5 GPa. The highest moduli were attained in samples that were multiply zone‐drawn. The maximum‐achievable draw ratio increased with the maximum drawing temperature, but the semicrystalline nature of the starting material limited the ultimate drawability. For the first time, highly oriented crystalline films were obtained for X‐ray diffraction and preliminary crystal structure analysis. The crystal lattice was fit to the orthorhombic crystal system, and the results indicate that the lattice parameters are a = 8.0 ± 0.2 Å, b = 5.9 ± 0.2 Å, and c = 36.5 ± 0.3 Å. The value of the c‐axis lattice parameter is very close to the fully extended chain length of the monomer repeat unit. © 1994 John Wiley & Sons, Inc.

Zone drawn NEW‐TPI thermoplastic polyimide and its blends with Xydar liquid crystalline polymer

AbstractIn this work we report the effects of single stage zone drawing on the properties of NEW‐TPI thermoplastic polyimide homopolymer, and its blends with Amoco's Xydar liquid crystalline polymer. Zone drawing was performed first on homopolymer NEW‐TPI films to determine the effect of load weight, heater speed, and drawing temperature on the attainable draw ratio. Degree of crystallinity and chain orientation increase as the draw ratio increases for NEW‐TPI. Blends of NEW‐TPI/Xydar compositions 90/10 and 70/30 were studied next. In blends, the Xydar component is not molecularly dispersed, and is initially preferentially oriented along the machine direction during the film processing stage. Xydar acts as a nucleation site and lowers the temperature for crystallization of the NEW‐TPI from the rubbery amorphous state. Zone drawing was performed either parallel or perpendicular to Xydar's initial preferred orientation direction. Blends with lower Xydar fraction could be zone‐drawn to higher ratios. Zone drawing perpendicular to Xydar's initial orientation direction also resulted in increased draw ratio. Dynamic mechanical properties of the zone drawn materials were studied. In homopolymer NEW‐TPI, dynamic modulus increased by a factor of two to 4.0 GPa in zone drawn films, largely as a result of the formation of oriented crystallites. In the blends, the modulus parallel to Xydar's initial orientation direction was greater than that in the transverse direction. Depending upon composition and test direction, zone drawing increased the dynamic moduli of the blends from 1.5 up to 2.7 times, in the temperature range from 150°C to 300°C.

Microfibrillar reinforced composites from binary and ternary blends of polyesters and nylon 6

Binary (1:1 by weight) and ternary (1:1:1 by weight) blends of poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), and Nylon 6 (PA 6) as well as the homopolymers are extruded as strips and ultraquenched from the melt. After zone drawing and additional annealing at T a = 220 or 240°C for 5 or 25 h with fixed ends in vacuum, the samples are studied by DSC, WAXS, solubility, and mechanical testing. It is found that all components in the blends are oriented and perfection of the structure is observed at T a = 220°C.

Microfibrillar reinforced composite from drawn poly(ethylene terephthalate)/nylon-6 blend

Homopolymer poly(ethylene terephthalate) (PET) and nylon-6 (PA-6) and a blend (1:1 by weight) of these polymers, are each extruded as strips and ultraquenched from the melt. After zone drawing and additional annealing at temperatures, T a, of 220 or 240°C for 5 or 25 h in vacuum, the samples are studied by differential scanning calorimetry, small-angle and wide-angle X-ray scattering, and mechanical testing. It is found that all components in the blend are oriented and that the perfection of the structure develops with increasing T a up to 220°C. At T a = 240°C, isotropization of the PA-6 component is observed, while the orientation of the PET is preserved. A microfibrillar reinforced composite is obtained, with mechanical properties as high as those of glass-fibre-reinforced nylons and surprisingly large (about 100 ×) deformability. It is shown that during thermal treatment for longer time, in addition to physical processes (crystallization and relaxation), chemical interactions (additional condensation and exchange reactions) take place at the interfaces, resulting in the formation of PET-PA-6 block copolymers playing the role of compatibilizers. Further interaction between PET (partially) and PA-6 (completely) amorphous phases leads ultimately to the involvement of the entire amount of PA-6 in the block copolymers, thus converting the starting PA-6 matrix of the microfibrillar reinforced composite into a PET-PA-6 copolymer matrix.

Birefringence and orientation of polyethylene zone-drawn under various thermomechanical conditions

In this paper, the influence of deformation and thermomechanical drawing conditions on the development of birefringence and orientation in high-density polyethylene during zone drawing is described. The orientation process of the crystalline phase does not proceed uniformly with deformation and is complete at lower draw ratios, while orientation of the amorphous phase increases continuously up to the highest draw ratios. The maximum birefringence considerably exceeds that of a polyethylene crystal (as high as 0.081) and the amorphous orientation almost approaches that of the crystalline phase. This indicates that the zone-drawing technique is highly effective in producing orientation. The birefringence is affected simultaneously by drawing stress and temperature; at higher temperatures and lower stresses, softening effects predominate, while in the opposite case stiffening effects become operative. The occurrence of both factors is regulated by the time of thermal exposure in the heating zone.

Microfibrillar reinforcement of polymer blends

The mechanical behaviour and morphology of films prepared from poly(ethylene terephthalate), poly(butylene terephthalate) and polyamide-6 blends subjected to zone drawing and annealing with fixed ends are studied. It is established that as a result of simultaneous physical (crystallization, relaxation, partial melting) and chemical (solid state exchange reactions and condensation) processes substantial structural changes take place in the blends which affect their mechanical properties.

Preparation of high modulus and high strength PEEK film by the zone drawing/annealing method

In order to prepare poly(ether ether ketone) films with high modulus and high strength, the zone drawing/annealing method was used. The maximum dynamic modulus at room temperature was 13.3 GPa, which is 4.4 times that of a commercially available PEEK film. The modulus also remained at a high level even at elevated temperatures. For example, these were 12 GPa at 100°C, 7 GPa at 200°C, and 5 GPa at 300°C. The zone drawn/zone annealed films indicated a double orientation. The present paper discusses the characteristic of the zone drawing/annealing method, the determination of suitable conditions for zone drawing and zone annealing, and the changes in superstructure and mechanical properties with processing.

Preparation of ultra‐high modulus polyvinyl alcohol fibers by the zone‐drawing method

AbstractThe zone‐drawing method has been applied to prepare ultra‐high modulus polyvinyl alcohol fibers. First, the suitable temperature for zone‐drawing was decided. In the first zone drawing, when drawing temperature was as high as near melting point, the highest draw ratio and modulus were obtained. The modulus was further increased by repeating zone drawing and heat treatment. In this study, the highest dynamic moduli were 115 GPa at room temperature and 42 GPa at 200°C. The fiber has a sharp melting peak that appeared at 246°C and a small peak at 260°C in the DSC curve.

Zone drawing and mechanical relaxation of poly(vinylidene fluoride)

AbstractPoly(vinylidene fluoride), PVF2, has been zone drawn to extensions up to 7 times. Well oriented β phase tapes are produced when the draw neck moved out of the hot zone, at extensions over six times and zone temperatures =<155°C. Other conditions give α phase tapes. The dynamic mechanical spectra of highly drawn PVF2 is exactly the same for both phases, with Tg at −25°C and a sharp rise in tan δ at 50°C. Isotropic α and β phase sheets gave different mechanical spectra, but with similar features at different strengths. As the isotropic sheets were prepared in very different ways, no specific features of the spectra could be assigned to the different phases.

A new analytical method for the optimization of thermomechanical conditions in zone drawing and its application to polyethylene

Abstract An original method of zone drawing of polymers at constant load and a procedure for the optimization of thermomechanical conditions (stress, temperature) are suggested, allowing high draw ratios and favorable strength values to be obtained. The temperature (or stress) range of necking has been determined in a nonisothermal and in an isothermal regime. The advantage of the method consists in that the increasing orientation in the neck starting from the initiation point and up to fracture allows the morphology and properties to be quickly examined, depending on the varying thermomechanical conditions in different regions of the neck. At a high temperature and low load the mechanism of oriented crystallization from melt becomes operative; in opposite cases, orientation of the solid state takes place. It is shown that in the nonisothermal regime an increased rate of heating allows extreme draw ratios (up to ca. 150) to be obtained, approximately twice as high as those obtained in the isothermal regime. This is interpreted as a gradual improvement of the oriented structure by recrystallization during extension and by a quick fixation on cooling below the zone.

Investigations on supermolecular structure of poly(ethylene terephthalate) samples of higher modulus

The supermolecular structure of higher modulus poly(ethylene terephthalate) (PET) samples obtained by means of multi-stage combined cold drawing/hot zone drawing procedures is characterized using WAXS, SAXS and mechanical methods. The direct separate determination of crystallite sizes and lattice distortions using a single line method has been applied for the first time to high modulus PET samples. Influences of supermolecular structure on the axial elastic modulus and on a limitation in preparing high modulus PET samples are discussed.

Preparation of ultra-high modulus polyethylene films by the zone-annealing method

The zone-annealing method has been used to prepare uniaxially oriented ultra-high modulus polyethylene films from single crystal mats of ultra-high molecular weight polyethylene. The maximum dynamic modulus and tensile strength at room temperature of superdrawn films were 232 and 6 GPa, respectively. The present paper discusses the advantages of the zone-annealing method, the determination of the optimum conditions for zone drawing and zone annealing, and the changes in superstructure and mechanical properties with processing.

Structure and properties of crystalline polymer fibers

Most polymer fibers studied by TEM have been semi-crystalline or more recently liquid crystalline, both because the majority of technically interesting fibers are ordered and because scientific interest lies in the polymer morphology. The obvious common feature of fibers is that they are "fibrous" that is to say, they have long and narrow features aligned along the fiber direction. The basic unit obtained by a very local deformation of a crystal is called a micro-fibri l . [1,2] Fibrils may or may not be clear in the TEM, either because the structure itself is not well defined or because of superposition of several small fibrils within the sample.The large plastic deformation in fiber drawing will make any heterogeneity in the material appear fibrous. While zone drawing gels of poly(vinyl alcohol) recently we obtained porous fibers when residual ethylene glycol solvent boiled at just below the draw temperature.

High modulus poly (vinyl alcohol) fibers by zone drawing

Dried gel films of poly (vinyl alcohol) were drawn at high temperature using zone heating devices. Hot air zones 5 and 10 mm wide were used to draw the gels to draw ratios up to λ = 23 × at 200 °C. A 3.2 mm wide heated bar in direct contact with the specimen enabled use of drawing temperatures up to 235°C and resulted in draw ratios of 25-38 ×. Drawn films had a highly fibrous nature, were well oriented, and contained crystals about 10 nm long. Gel permeation chromatography studies of the material before and after drawing showed that drawing at high temperatures caused some changes in molecular weight and dispersity. Storage moduli of the fibers increased with draw ratio, reaching a high of 59 GPa at 31× but, in general, leveled off at high A. Low draw ratio (10-15 ×) fibers drawn in the 5 mm air zone had moduli comparable to high draw ratio (25-38 ×) fibers drawn with the high-temperature contact heater (20-60 GPa). Retraction studies showed that low modulus fibers, even those highly drawn, had low effective molecular extension. Drying the fibers increased both their room temperature modulus and glass transition temperature.

Relationship between piezoelectricity and superstructure in highly oriented poly(vinylidene fluoride) film prepared by zone drawing

AbstractThe oriented superstructure of poly(vinylidene fluoride) is controlled by using a forced‐quenching type of zone drawing apparatus. Systematic variation of the weight fraction χ(I) of form‐I crystals and the orientation function fa of amorphous chains shows that the piezoelectricity increases with increasing χ(I) and fa. A change in the state of molecular aggregation during poling is also effective in increasing the piezoelectricity and the orientation of the crystal b axis along the poling direction. Equations relating piezoelectricity to the form‐I crystallinity, the orientation of amorphous chains, and the orientation of the crystal b axis along the poling direction are derived. These are based on a mechanical model having regions of taut tie molecules in parallel with composite regions consisting of crystalline and amorphous blocks in series.

Preparation of high-modulus and high-strength poly(ethylene terephthalate) fiber by zone annealing

To prepare high-modulus and high-strength PET fiber, a new method using zone drawing and zone annealing has been studied. The apparatus used for this method is the usual tensile tester equipped with a band heater 2 mm wide and a sample holder which can apply a high tension to the fiber. The experimental procedure consists of two stages: zone drawing and zone annealing. The zone drawing was done on the original as-spun fiber in order to produce a fiber with as high an orientation and as low a crystallinity as possible. The zone-drawn fiber was subsequently zone annealed under high tension by moving the band heater from one end to the other of the fiber at a temperature above the crystallization temperature at a considerably low moving speed. In spite of the simple apparatus and procedure, Young's modulus of the fiber obtained was 19.4 × 1010 dyn/cm2, which is comparable to the maximum value of the high-tenacity PET filament commercially available. In order to elucidate the change in the superstructure with zone drawing or zone annealing, optical, x-ray, IR, DSC, and dynamic mechanical measurements were performed. It is suggested that the zone-annealed fiber consists of almost perfectly oriented crystallites and fully extended amorphous chains.

Preparation of ultrahigh modulus isotactic polypropylene by means of zone drawing

AbstractHighly oriented isotactic polypropylene with ultrahigh modulus was prepared by means of the zone drawing method proposed by Kiho and Asai. This method features heating a limited portion of the sample. The maximum value of modulus attained was 15 GPa, which corresponds to about half the crystal modulus along the molecular axis evaluated by the x‐ray method. Such an ultrahigh modulus was obtained for a sample of medium molecular weight by inducing necking in the heater and subsequently cooling the sample at lower temperature. The loss tangent peak with the initiation of micro‐Brownian motion of amorphous chains became progressively smaller and broadened more at higher temperatures with increasing draw ratio. Orientation function of the crystal c‐axis increased with draw ratio λ in the region below λ = 9, but reached a constant value, 0.995, in the region above λ = 9. The modulus increased with draw ratio in all ranges of the draw ratio.

1. An account of a remarkable aurora borealis seen at Montreal on the 13th of August 1849

The author having witnessed a singular aurora on the 13th of August, in this communication gives a description of the phænomenon. He states that, on the evening in question, the whole northern hemisphere was screened by thick dark clouds, which, though very small, were closely packed together. Shortly after sunset (7 h 34 m ) it became quite dark, and at 8 o’clock the existence of the meteor was indicated by a mellow luminous tinge which appeared through the openings of the clouds in the north. About half-past eight a similar luminous glow was observed through the clouds which were fast disappearing in a heavy dew. This light appeared like a belt of 2° broad, extending across the sky from a point almost due east directly to the west, and reaching within 5° or 6° of the horizon. As the clouds disappeared, which they did very rapidly, the true character of the aurora became more perfectly developed. In the north the usual dark arch from which the columns of light ordinarily appear to issue, was for the greater part of the time wanting; and the luminous columns seemed to rise from the earth, extending upwards occasionally to the pole star, beyond which no trace of them was visible. A brown vapoury cloud, the only one now visible, extended along the horizon from N. N. E. to a few points south of east, and maintained apparently a motionless position, the lower part appearing to rest upon the earth, and the upper edges, which seemed uniform, rose about 6° above the horizon. Immediately in the east, and apparently issuing from this cloud, rose the belt or zone of light already noticed, forming a magnificent arch. The light emitted from this zone was of a milky whiteness, and the matter of it seemed to be much more compact than any portion of an aurora ever seen by the author; but immediately in the zenith, where it intersected the Milky Way, it appeared to be far less compact. At this point, where alone motion was observable, a constant current was seen, presenting the appearance of light fleecy clouds driven by a strong wind, and following each other in such close succession as to appear in contact. This stream of the aurora was maintained undiminished for more than an hour, during which time the eastern part of the zone did not appear to lose either in volume or brilliancy, nor did the western seem to gain in either of these respects. After an hour, the dark cloud seemed to diminish slowly, and with it the zone began to lose its brilliancy. In about another hour this cloud and also the zone, which throughout had maintained apparent contact with it, vanished. The conclusion, that the dark cloud served the purpose of a conductor and fed the zone drawing off the matter of the aurora from the north, seemed to the author inevitable. The cloud did not appear to him to be more than forty or fifty miles distant. In conclusion he remarks that none of the prismatic tints were observable on this occasion.