Ultradrawing behavior of one- and two-stage drawn gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends

The ultradrawing behavior of gel films of plain ultrahigh molecular weight polyethylene (UHMWPE) and UHMWPE/low molecular weight polyethylene (LMWPE) blends was investigated using one- and two-stage drawing processes. The drawability of these gel films were found to depend significantly on the temperatures used in the one- and two-stage drawing processes. The critical draw ratio (λ_c) of each gel film prepared near its critical concentration was found to approach a maximum value, when the gel film was drawn at an “optimum” temperature ranging from 95 to 105°C. At each drawing temperature, the one-stage drawn gel films exhibited an abrupt change in their birefringence and thermal properties as their draw ratios reached about 40. In contrast, the critical draw ratios of the two-stage drawn gel films can be further improved to be higher than those of the corresponding single-stage drawn gel films, in which the two-stage drawn gel films were drawn at another “optimum” temperature in the second drawing stage after they had been drawn at 95°C to a draw ratio of 40 in the first drawing stage. These interesting phenomena were investigated in terms of the reduced viscosities of the solutions, thermal analysis, birefringence, and tensile properties of the drawn and undrawn gel films. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 149–159, 1998     

Ultradrawing properties of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends prepared at various formation temperatures

The ultradrawing behavior of ultrahigh‐molecular‐weight polyethylene/low‐molecular‐weight polyethylene film specimens prepared at various concentrations and formation temperatures was studied. The critical draw ratio (D_rc) of UL_?0.7 film specimens was found to depend significantly on the formation temperature used to prepare the film specimens. At any fixed drawing temperature, the D_rc values of UL_?0.7 specimens prepared at various formation temperatures increased significantly as the formation temperatures were reduced. In fact, with an optimum drawing temperature of 95°C, the D_rc values of UL_?0.7 specimens prepared at a formation temperature of 0°C reached 488, about 50% higher than that of UL_?0.7 specimens prepared at a formation temperature of 95°C. These interesting phenomena were investigated in terms of the thermal, birefringence, and tensile properties of these undrawn and drawn UL_?0.7 specimens. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3728–3738, 2003     

Ultradrawing properties of ultrahigh‐ molecular‐weight polyethylene/carbon nanotube fibers prepared at various formation temperatures

The influence of formation temperature on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/carbon nanotube (UHMWPE/CNT) fiber specimens is investigated. Gel solutions of UHMWPE/CNT with various CNT contents were gel‐spun at the optimum concentration and temperature but were cooled at varying formation temperatures in order to improve the ultradrawing and tensile properties of the UHMWPE/CNT composite fibers. The achievable draw ratio (D_ra) values of UHMWPE/CNT as‐prepared fibers reach a maximum when they are prepared with the optimum CNT content and formation temperature. The D_ra value of UHMWPE/CNT as‐prepared fibers produced using the optimum CNT content and formation temperature is about 33% higher than that of UHMWPE as‐prepared fibers produced using the optimum concentration and formation temperature. The percentage crystallinity (W_c) and melting temperature (T_m) of UHMWPE/CNT as‐prepared fiber specimens increase significantly as the formation temperature increases. In contrast, W_c increases but T_m decreases significantly as the CNT content increases. Dynamic mechanical analysis of UHMWPE and UHMWPE/CNT fiber specimens exhibits particularly high α‐transition and low β‐transition, wherein the peak temperatures of α‐transition and β‐transition increase dramatically as the formation temperature increases and/or CNT content decreases. In order to understand these interesting drawing, thermal and dynamic mechanical properties of the UHMWPE and UHMWPE/CNT as‐prepared fiber specimens, birefringence, morphological and tensile studies of as‐prepared and drawn fibers were carried out. Possible mechanisms accounting for these interesting properties are proposed. Copyright © 2010 Society of Chemical Industry     

Effect of the ultradrawing behavior of gel films of ultrahigh‐molecular‐weight polyethylene and low‐molecular‐weight polyethylene blends on their physical properties

This study examined the effect of the ultradrawing behavior of gel film specimens of ultrahigh‐molecular‐weight polyethylene (UHMWPE) and UHMWPE/low‐molecular‐weight polyethylene (LMWPE) blends on their physical properties. The concentration of a gel film approximated its critical concentration at a fixed drawing temperature; its achievable draw ratio was higher than that of other blend specimens with various concentrations. Noticeably, when about 5 wt % LMWPE was added to a UHMWPE/LMWPE gel film specimen, the achievable draw ratio of the gel film increased, and this contributed to an apparent promoting effect on its anticreeping properties and thermal stability. Therefore, when UL_B?0.9 was drawn to a draw ratio of 300, the anticreeping behavior was improved to less than 0.026%/day. Moreover, with respect to the thermal stability, when the same specimen was drawn to a draw ratio of 300, the retention capability of its storage modulus could resist a high temperature of 150°C, which was obviously much higher than the temperature of an undrawn gel film specimen (70°C). To study these interesting behaviors further, this study systematically investigated the gel solution viscosities, anticreeping properties, dynamic mechanical properties, thermal properties, molecular orientations, and mechanical properties of undrawn and drawn UHMWPE/LMWPE gel film specimens. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Ultradrawing behavior of gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends at varying drawing conditions

A systematic study of the influence of the drawing temperature and rate on the ultradrawing properties of film samples prepared from gel solutions of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends is reported. At a fixed drawing rate, the achievable draw ratios reached a maximum value when each film specimen was drawn at a temperature near its optimum temperature (T_op). It is interesting to note that the T_op values of each film sample increased consistently with the drawing rate. The achievable draw ratio of each film sample drawn at a constant rate and a temperature near T_op is referred to as the D_raop, which reached another maximum value as the drawing rates approached an optimum value. Dynamic mechanical analysis of the film sample exhibited an extraordinary high transition peaked at temperature near 95°C, which is again very close to the T_op value found for the film sample drawn at a relatively low rate. On the other hand, the birefringence values and tensile strengths of the film specimen were found to improve significantly with the draw ratios, although the improvement of these properties reduced significantly at high draw ratios. Moreover, both the drawing temperature and rate showed beneficial influence on the birefringence, and tensile strengths of the drawn film specimens. Possible mechanisms accounting for these interesting deformation properties are suggested.     

Ultradrawing properties of ultrahigh‐molecular‐weight polyethylene/attapulgite fibers

An investigation of the influence of the contents of original and modified attapulgite (ATP) on the ultradrawing properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE)/ATP (FA_x) and UHMWPE/modified ATP (FA_mx) as‐prepared fibers is reported. Similar to what is found for the orientation factor values, the achievable draw ratios (D_ra) of the FA_x and FA_mx as‐prepared fibers approach a maximum value as the original ATP and/or modified ATP contents reach their corresponding optimum values. The maximum D_ra value obtained for FA_mx as‐prepared fiber specimens is significantly higher than that for FA_x as‐prepared fiber specimens prepared at the optimum original ATP content. Similar to what is found for the orientation factors and achievable drawing properties, the tensile strength (σ_f) and initial modulus (E) of both drawn F₂A_x and F₂A_mx fiber series specimens with a fixed draw ratio reach maximum values as the original and/or modified ATP contents approach the optimum values, respectively. The σ_f and E values of the F₂A_mx fiber specimens are always significantly higher than those of the corresponding F₂A_x fiber specimens prepared at the same draw ratios and ATP contents but without being modified. To understand the interesting ultradrawing, orientation and tensile properties of FA_x and FA_mx fiber specimens, Fourier transform infrared spectral, specific surface area, transmission electron microscopic and elemental analyses of the original and modified ATPs were performed. Copyright © 2012 Society of Chemical Industry     

Solid‐state compaction and drawing of nascent reactor powders of ultra‐high‐molecular‐weight polyethylene

The continuous production of ultra‐high‐molecular‐weight polyethylene (UHMWPE) filaments was studied by the direct roll forming of nascent reactor powders followed by subsequent multistage orientation drawing below their melting points. The UHMWPE reactor powders used in this study were prepared by the polymerization of ethylene in the presence of soluble magnesium complexes, and they exhibited high yield even at low reaction temperatures. The unique, microporous powder morphology contributed to the successful compaction of the UHMWPE powders into coherent tapes below their melting temperatures. The small‐angle X‐ray scattering study of the compacted tapes revealed that folded‐chain crystals with a relatively long‐range order were formed during the compaction and were transformed into extended‐chain crystals as the draw ratio increased. Our results also reveal that the drawability and tensile and thermal properties of the filaments depended sensitively on both the polymerization and solid‐state processing conditions. The fiber drawn to a total draw ratio of 90 in the study had a tensile strength of 2.5 GPa and a tensile modulus of 130 GPa. Finally, the solid‐state drawn UHMWPE filaments were treated with O₂ plasma, and the enhancement of the interfacial shear strength by the surface treatment is presented. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 718–730, 2005     

Influence of Drawing Conditions on the Ultradrawing Properties of Film Specimens of Ultrahigh Molecular Weight Polyethylene and Low Molecular Weight Polyethylene Blends

The influence of the drawing temperature and rate on the ultradrawing properties and deformation mechanisms of a series of film specimens prepared from varying concentrations of gel solutions of ultrahigh molecular weight polyethylene (UHMWPE) and low molecular weight polyethylene (LMWPE) blends is reported. The maximum achievable draw ratio was obtained when each UHMWPE/LMWPE film specimen was drawn at an optimum temperature (T _op), wherein the T _op values of each UHMWPE/LMWPE film specimen increased consistently with the drawing rate. The temperature dependence of the apparent elongational viscosity (_a) revealed two distinguishable intervals with different activation energies. Coincidentally, the transition temperature (T _r) obtained from the intersection of the two straight lines drawn parallel to the two distinct intervals is approximately equal to the T _op value found for the film sample drawn at the same rate. Dynamic mechanical analysis of the film samples exhibited an extraordinary high transition peaked at temperatures near 95–115C, which are again very close to the T _op and T _r values found for the film samples drawn at varying rates, and increases significantly with the testing frequencies. Possible mechanisms accounting for these interesting deformations, temperature dependence of the apparent elongational viscosity and dynamic mechanical properties are suggested in this study.     

Syndiotacticity‐rich ultrahigh molecular‐weight poly(vinyl alcohol) film. I. Determination of optimum polymer concentration by zone‐drawing method in film preparation

A new method using a simple zone‐drawing technique has been suggested for determining the optimum initial concentration of a polymer solution that has suitable macromolecular entanglements. This method was developed to replace the incorrect inherent viscosity‐measuring method for syndiotacticity‐rich (syndiotactic diad content of 63.4%) ultrahigh molecular‐weight (number‐average degree of polymerization of 12,300) (UHMW) poly(vinyl alcohol) (PVA) solution. Syndiotacticity‐rich UHMW PVA films were prepared from dimethyl sulfoxide (DMSO) solutions with different initial concentrations: of 0.1, 0.2, 0.3, 0.4, and 0.5 g/dL. In order to investigate the drawing behavior of the syndiotacticity‐rich UHMW PVA films with different solution concentrations, the films were drawn under various zone‐drawing conditions. Through a series of experiments, it was discovered that the initial concentration of PVA solution in DMSO caused significant changes in the draw ratio of the syndiotacticity‐rich UHMW PVA film. That is, the one‐step and maximum zone draw ratios of the film at an initial concentration of 0.3 g/dL exhibited its maximum values and gradually decreased at higher or lower concentrations. Thus, it was disclosed that the initial concentration of 0.3 g/dL is the optimum polymer concentration to produce a maximum draw ratio in this work. Based on the above results, it may be concluded that the optimum concentration of the initial PVA solution can be determined directly by measuring the zone draw ratio. The draw ratio, birefringence, crystallinity, degree of crystal orientation, tensile strength, and tensile modulus of the maximum drawn PVA film were 32.9, 0.0449, 0.61, 0.991, 1.91, and 46.2 GPa, respectively. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 123–134, 2000     

Roller drawing of ultrahigh molecular weight polyethylene

The roller drawing of ultrahigh molecular weight polyethylene (UHMW-PE) sheets were carried out in the roller temperature T_r range of 100–140°C. In addition to the roller drawing in the solid state (T_r = 100°C), we attempted to crystallize the molten UHMW-PE sheet under the roller-drawing process (T_r = 100–140°C). The tensile and dynamic viscoelastic properties, the molecular orientation, and the microstructure of the roller-drawn UHMW-PE sheets were investigated. The mechanical properties of UHMW-PE sheets were much improved by crystallization during the roller drawing process at T_r = 140°C. The sheets roller-drawn at T_r = 135 and 140°C exhibited c-axis orientation to the draw direction and (100) alignment in the sheet plane. However, at T_r = 100°C the elastic motion of the amorphous chains induces the twinnings of lattice, which enhances the transition to the (110) alignment in the sheet plane. The dynamic storage modulus below γ-dispersion temperature showed good correlation with crystallinity and orientation functions, while taut tie molecules and thick crystallites play an important role in the storage modulus above γ-dipersion temperature.     

Investigation of the ultradrawing properties of gel spun fibers of ultra‐high molecular weight polyethylene/carbon nanotube blends

The carbon nanotubes (CNTs) contents, ultrahigh‐molecular‐weight polyethylene (UHMWPE) concentrations and temperatures of UHMWPE, and CNTs added gel solutions exhibited significant influence on their rheological and spinning properties and the drawability of the corresponding UHMWPE/CNTs as‐prepared fibers. Tremendously high shear viscosities (ηs) of UHMWPE gel solutions were found as the temperatures reached 140°C, at which their ηs values approached the maximum. After adding CNTs, the ηs values of UHMWPE/CNTs gel solutions increase significantly and reach a maximum value as the CNTs contents increase up to a specific value. At each spinning temperature, the achievable draw ratios obtained for UHMWPE as‐prepared fibers prepared near the optimum concentration are significantly higher than those of UHMWPE as‐prepared fibers prepared at other concentrations. After addition of CNTs, the achievable draw ratios of UHMWPE/CNTs as‐prepared fibers prepared near the optimum concentration improve consistently and reach a maximum value as their CNTs contents increase up to an optimum value. To understand these interesting drawing properties of the UHMWPE and UHMWPE/CNTs as‐prepared fibers, the birefringence, thermal, morphological, and tensile properties of the as‐prepared and drawn fibers were investigated. Possible mechanisms accounting for these interesting properties are proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Conditions of homogeneous deformation of poly(ethylene terephthalate) films during uniaxially drawing

Amorphous poly(ethylene terephthalate) film was uniaxially drawn over a wide range of temperatures from below to above the T_g at a constant strain rate. The geometry of the deformation in macroscopic dimensions of the sample demonstrates that homogeneous deformation can be obtained when the drawing temperature (T_def) is not lower than 69°C. The change of the cold crystallization peak temperature (T_cc) and crystallinity determined by differential scanning calorimetry and density measurement, respectively, were studied in terms of the T_def and the draw ratio (λ). The orientation, relaxation, and crystallization during drawing were investigated as a function of T_def as well as of λ. The results suggest that 69°C is the critical temperature at which the sample with the highest orientation and the least slippage of the molecular chain and without obvious crystallization can be obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2044–2048, 2000     

Effects of zone drawing on the structure of metallocene polyethylene

The influence of zone drawing on bulk properties and structure of metallocene polyethylene (m‐PE) is reported. Two different m‐PE materials were subjected to tensile stresses above the yield point by zone drawing in the temperature range from 50 to 100°C. Drawn materials were characterized by using small‐ and wide‐angle X‐ray scattering (SAXS, WAXS), molecular retraction, and small‐angle light scattering (SALS). Structural changes were studied as a function of drawing temperature, engineering stress, and draw ratio. WAXS showed strong crystalline orientation in drawn samples, and only the orthorhombic crystal modification was observed. SAXS showed lamellar orientation in drawn samples. At low drawing temperatures of 50 or 60°C, draw ratio increased as a step function of stress. There is a stress barrier, which must be exceeded before high‐draw ratios can be achieved at these temperatures. At drawing temperatures of 70°C or above, the barrier stress is low enough that draw ratio increases nearly linearly as a function of stress. Below the stress barrier, spherulitic structure is observed by small‐angle light scattering (SALS). Elongation occurs via deformation of the interspherulitic amorphous phase. Molecular retraction was low for these samples, indicating mostly plastic deformation of the amorphous material. Above the stress barrier, SALS showed that spherulites are destroyed. Elongation occurs via deformation of the intraspherulitic amorphous phase. Molecular retraction for these samples was high, indicating elastic deformation of the amorphous material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3492–3504, 2001     

Characterization of polyethylene terephthalate films drawn in hot water

Sorbed water molecules in PET (around 1% in mass) lead to classic plasticizing effects, basically evidenced by a decrease of the glass transition (T_g) and of the cold crystallisation (T_c) temperatures with increasing water content. During drawing of dry PET film and depending on the draw ratio, the initial amorphous phase is oriented at first, then a strain‐induced crystallisation appears. This work deals with the conjugate effects of drawing and water sorption in PET films drawn in hot water. Differential scanning calorimetry and birefringence measurements shown that drawing performed in hot water leads to modifications of T_g and T_c without modification of the degree of crystallinity. Moreover, the formation of water clusters is observed when the strain‐induced crystalline phase occurs.     

Spinning and drawing properties of ultrahigh‐molecular‐weight polyethylene fibers prepared at varying concentrations and temperatures

The concentrations and temperatures of ultrahigh‐molecular‐weight polyethylene (UHMWPE) gel solutions exhibited a significant influence on their rheological and spinning properties. The shear viscosities of UHMWPE solutions increased consistently with increasing concentrations at a constant temperature above 80°C. Tremendously high shear viscosities of UHMWPE gel solutions were found as the temperatures reached 120–140°C, at which their shear viscosity values approached the maximum. The spinnable solutions are those gel solutions with optimum shear viscosities and relatively good homogeneity in nature. Moreover, the gel solution concentrations and spinning temperatures exhibited a significant influence on the drawability and microstructure of the as‐spun fibers. At each spinning temperature, the achievable draw ratios obtained for as‐spun fibers prepared near the optimum concentration are significantly higher than those of as‐spun fibers prepared at other concentrations. The critical draw ratio of the as‐spun fiber prepared at the optimum concentration approached a maximum value, as the spinning temperature reached the optimum value of 150°C. Further investigations indicated that the best orientation of the precursors of shish‐kebab‐like entities, birefringence, crystallinity, thermal and tensile properties were always accompanied with the as‐spun fiber prepared at the optimum concentration and temperature. Similar to those found for the as‐spun fibers, the birefringence and tensile properties of the draw fibers prepared at the optimum condition were always higher than those of drawn fibers prepared at other conditions but stretched to the same draw ratio. Possible mechanisms accounting for these interesting phenomena are proposed.     

Preparation and characterization of novel ultra‐high molecular weight polyethylene composite fibers filled with nanosilica particles

Ultrahigh molecular weight polyethylene (UHMWPE)/nanosilica (F₂S_y) and UHMWPE/modified nanosilica (F₂S_mx‐y) as‐prepared fibers were prepared by spinning of F₂S_y and F₂S_mx‐y gel solutions, respectively. Modified nanosilica particles were prepared by grafting maleic anhydride grafted polyethylenes onto nanosilica particles. The achievable draw ratios (D_ra) of F₂S_y and F₂S_mx‐y as‐prepared fibers approached a maximal value as the original and modified nanosilica contents reached corresponding optimum values; the maximal D_ra value obtained for F₂S_mx‐y as‐prepared fiber specimens was significantly higher than that of the F₂S_y as‐prepared fiber specimens prepared at the optimum nanosilica content. The melting temperature and evaluated lamellar thickness values of F₂S_y and F₂S_mx‐y as‐prepared fiber series specimens decrease, but crystallinity values increase significantly, as their original and modified nanosilica contents respectively increase. Similar to the achievable drawing properties of the as‐prepared fibers, the orientation factor, tensile strength (σ_f) and initial modulus (E) values of both drawn F₂S_y and F₂S_mx‐y fiber series specimens with a fixed draw ratio reach a maximal value as the original and/or modified nanosilica contents approach the optimum values; the σ_f and E values of the drawn F₂S_mx‐y fiber specimens are significantly higher than those of the corresponding drawn F₂S_y fiber specimens prepared at the same draw ratios and nanosilica contents but without being modified. To understand the interesting ultradrawing, thermal, orientation and tensile properties of F₂S_y and F₂S_mx‐y fiber specimens, Fourier transform infrared, specific surface area and transmission electron microscopy analyses of the original and modified nanosilica were performed in this study. © 2012 Society of Chemical Industry     

Effect of zone drawing on the structure and properties of melt‐spun poly(trimethylene terephthalate) fiber

Melt‐spun poly(trimethylene terephthalate) (PTT) fibers were zone‐drawn and the structures and properties of the fibers were investigated in consideration of the spinning and zone‐drawing conditions. The draw ratio increased up to 4 with increasing drawing temperature to 180°C, at a maximum drawing stress of 220 MPa. Higher take‐up velocity gave lower drawability of the fiber. The PTT fiber taken up at 4000 rpm was hardly drawn, in spite of using maximum drawing stress, because a high degree of orientation had been achieved in the spinning procedure. However, an additional enhancement of birefringence was observed, indicating a further orientation of PTT molecules by zone drawing. The exotherm peak at 60°C disappeared and was shifted to a lower temperature with an increase in the take‐up velocity, which means that the orientation and crystallinity of the fiber increased. The d‐spacing of (002) plane increased with increasing take‐up velocity and draw ratio, whereas those of (010) and (001) planes decreased. In all cases, the crystal size increased with take‐up velocity and draw ratio. The cold‐drawn PTT fiber revealed a kink band structure, which disappeared as the drawing temperature was raised. The physical properties of zone‐drawn PTT fibers were improved as the draw ratio and take‐up velocity increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3471–3480, 2001     

Ultrahigh molecular weight polyethylene fibers prepared using conical dies with varying dimensions

Dimensions of conical dies were found to have a significant influence on thermal, morphological, orientation, ultradrawing, and dynamic mechanical properties of the as‐prepared and/or drawn ultrahigh molecular weight polyethylene (UHMWPE) fiber specimens prepared in this study. Many demarcated “micro‐fibrils” were found paralleling to fiber direction of the as‐prepared UHMWPE fiber specimens. The percentage crystallinity, melting temperatures, orientation factor (f_o) and achievable draw ratio (D_ra) values of each as‐prepared UHMWPE fiber specimen prepared at a fixed length of outlet land reach a maximum value, as the entry angles of the conical die approach the optimum value at 75°. The maximum f_o and D_ra values obtained for each F₂₀^75‐y as‐prepared fiber series specimens prepared using the optimum entry angle reach another maximum value as their length of outlet land approach the optimum value of 6.5 mm. The ultimate tensile strengths and moduli of the drawn UHMWPE fibers prepared at the optimum entry angle and length of outlet land are significantly higher than those of fibers prepared at other conditions but stretched to the same draw ratio. Possible reasons accounting for the above interesting properties were discussed in this study. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers     

Superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone‐drawn under critical necking tension

The superstructure and mechanical properties of poly(ethylene terephthalate) fibers zone‐drawn under a critical necking tension (σ_c) were studied. σ_c was defined as the minimum tension needed to generate a neck at a given drawing temperature (T_d) and was measured over a temperature range of 70–120°C. The σ_c value increased rapidly with decreasing T_d in the temperature range below 85°C, but the temperature dependence of σ_c was small above 85°C. The neck profile relied on T_d, becoming more shapely with decreasing T_d. A neck with a gradual decrease in diameter was observed in the fibers drawn at 100°C and above. The draw ratio increased significantly with increasing T_d above 90°C, but birefringence decreased. Density decreased gradually with increasing T_d, and fiber drawn at 120°C had a density of 1.347 g/cc. Wide‐angle X‐ray diffraction photographs of the fibers drawn at 100°C and below showed reflections due to crystallites, but a photograph of the fiber obtained at 120°C showed a ring‐like amorphous halo. The storage modulus (E′) at 25°C increased progressively with decreasing T_d, and the fiber drawn at 70°C had the maximum E′ value among the fibers drawn at a series of T_d's. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 179–185, 2002     

Viscoelastic properties and structure of the zone‐drawn polyaniline films

The zone‐drawing method was applied to chemically synthesized polyaniline cast films of emeraldine base under various applied tensions and drawing temperatures. The changes in the microstructure and viscoelastic properties of the resulting films were investigated. It was found that the microstructure was strongly affected by the drawing temperature (T_d). The crystallinity, crystallite size, and orientation factor of crystallites, respectively, attained 42%, 23 Å, and 0.975 for the film zone‐drawn at T_d = 170°C, whereas a further increase in the T_d brought about a decrease of these values. The viscoelastic measurements indicated that the dynamic storage modulus attained 12 GPa at room temperature and was 5 GPa at 280°C for the film zone‐drawn at T_d = 210°C, which was comparable to that of the typical engineering plastics. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 566–571, 2000