Search

In this article, we present an experimental design methodology for studying the effect of the draw ratio on the physical properties of nylon 6 fibers on hot multistage drawing. A response surface methodology involving D-optimal design was used for the modeling and optimization. According to the analysis of variance results, the proposed models could be used to navigate the design space. We found that the responses of the tenacity and initial modulus were very sensitive to the factor of the second-stage draw ratio, and the shrinkage response was governed by the factor of the third-stage draw ratio. The results show a good agreement between the experimental and model predictions with high correlation coefficients. The operation conditions for obtaining the drawn yarn with the highest tenacity and initial modulus and low shrinkage are proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1337-1344, 2013

The drawing and ultimate tenacity proper- ties of the Polyamide 6 (PA6)/Attapulgite (ATP) compos- ite fiber specimens prepared at varying modified ATP (mATP) contents and drawing condition were systemati- cally investigated. As evidenced by Fourier transform infrared (FTIR) and morphological analysis, demarcated translucent resins were found firmly attached on the surfa- ces of ATP nanofibers. The specific surface areas of the mATP specimens reached a maximum value at 381 m 2 /g as the weight ratios of silane coupling agents to ATP nanofibers reached an optimum value at 1.0. The percent- age crystallinity and melt shear viscosity values measured at varying shear rates of PA6x(mATP)y specimens increased consistently as their mATP contents increased. In contrast, melting temperatures of PA6x(mATP)y speci- mens reduced slightly as their mATP contents increased. At a fixed drawing temperature and rate, the achievable draw ratio (Dra) values of PA6x(mATP)y as-spun fiber specimens approach a maximum value, as their mATP contents are close to the 0.2 wt % optimum value. The maximum Dra values obtained for PA699.8(mATP)0.2 as- spun fiber specimens reached another maximum, when their drawing temperatures and rates approached the opti- mum values at 120 � C and 50 mm/min, respectively. At a fixed draw ratio, the tenacity values of PA6x(mATP)y drawn fiber specimens drawn at the optimum drawing temperature and rate reached a maximum value, as their mATP contents approached the 0.2 wt % optimum value. Possible reasons accounting for the interesting morpholog- ical, specific surface area, drawing, orientation, and ultimate tenacity properties found for the PA6x(mATP)y fiber specimens are proposed. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 126: 1906-1916, 2012

In this study, we investigated the effect of tensile properties of poly(ethylene naphthalate) (PEN) yarns on the ballistic performance of woven and nonwoven soft and composite armors. The results of ballistic tests of PEN armors were compared with Kevlar 49 armors as a reference. Based on these results, the Cunniff's equation was revised by removing the fiber elongation at break to predict the relationship between tensile properties and ballistic performances of PEN fibers. The calculations showed that by increasing tenacity of PEN fibers from 8.5 g/den (commercial product) to 12.5 g/den (strongest up to date PEN fibers produced by a novel melt spinning process discovered by our research group), the weight ratio of PEN to Kevlar 49 decreased from 1.8 to 1.35 with the same ballistic performance. Contrary to the results of the soft armors, composite armors made of high modulus PEN woven fabric showed a 17% lower ballistic resistance compared to the composite armor made of low modulus PEN woven fabric. The results of ballistic tests indicated that high tenacity PEN fibers produced in this research could have potential in soft and composite armors, and high velocity impact applications or improve performance of PEN in its current applications. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This article reports a study of multi-stage polypropylene fiber drawing (stretching) as a continuous, but independent stage of the overall fiber-forming process. The fibers were drawn according to a factorial experimental design, once appropriate spinning conditions had been devised. The structures of the drawn fibers were studied using wide-angle X-ray diffraction and birefringence measurements. In addition, the fibers were characterized with respect to filament tenacity, elongation to break, specific secant modulus, and extent of shrinkage at 130°C. All these properties were quantitatively assessed as responses to nine specially selected process control parameters in the drawing equipment. For every property analyzed, the temperatures of the hot plates in the draw frame were found to exert no significant influence, whereas the temperatures of the initial rollers were in most cases significant. Furthermore, the speed of the final roller also played an influential role, and a number of interactions between process parameters were identified as significant. Explanations are advanced for the parts played by significant process parameters on the properties of the drawn fibers. The article also demonstrates the advantages of factorial experimental design in determining correct settings for process parameters to give drawn fibers with the properties desired. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

In this study, we examined the effect of alkali treatment and its variables, namely, the time (2, 4, 6, or 8 h) and the concentration of alkali (1, 5, or 17.5% w/w), on the linear density, strength, and stress-relaxation properties of jute fiber. It was demonstrated that this kind of treatment led to the creation of several voids and fiber fibrillation. Properties were measured for the alkali-treated and dewaxed fibers. The linear density and tenacity of the fibers were reduced at higher alkali concentration and at longer dipping times. The strength increased with treatment with mild alkali and decreased with treatment with the strong alkali. A very low alkali treatment (1%) rendered low relaxation. At a 5% alkali concentration, interfibrillar matrix softening also played an important role and was prominent in the stress-relaxation behavior. The stress-relaxation value was much higher in the fibers treated with 17.5% NaOH compared to the dewaxed fibers; this was probably due to a loss in the fibrillar arrangement. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

This study is carried out to examine the effects of simultaneous dyeing and antimicrobial finishing of wool yarns. Wool yarns were dyed with acid dye along with colloidal silver nanoparticles through the exhaustion method in a one-bath. Different concentrations of nanosilver were examined to evaluate its influences on the color and the antibacterial properties of the yarns. The antibacterial property of the sample has been tested by a Gram-negative bacterium Escherichia coli and a Gram-positive bacterium Staphylococcus aureus. Also, the tenacity of wool yarns, color, and rubbing fastness of the dyed yarns has been measured. The color fastness against washing and antibacterial property of the dyed yarns after 10 laundering cycles was also considered. The fiber morphology was studied by SEM pattern, EDX, and X-ray diffractometer. The results showed that the wool yarns dyed with acid dye along with 25 ppm of silver nanoparticles exhibited a very good antimicrobial effect even after 10 laundering cycles on S. aureus while the rubbing fastness remained unchanged, and the color fastness and tenacity were even improved. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Melt spinning and pump speed conditions are described for five samples of staple polypropylene PP fibers of different fineness. The influence of fiber fineness or denier on the physical characteristics of staple PP fibers spun at different pump speeds was studied. Optical ani- sotropy was measured using two-beam interference mi- croscopy. Enthalpy and degree of crystallinity were measured using differential scanning calorimetry tech- nique for studied fibers. The relation between the fiber di- ameter, crimp ratio, tenacity, and degree of orientation with the fiber denier are given. A selection of microinter- ferograms of fibers is given for illustration. V C 2009 Wiley

Polylactide stereocopolymer multifilament fibers were prepared by wet spinning and subsequent hot drawing. The stereocopolymers were poly-(L,D-lactide) [P(L,D)LA], L/D ratio 96/4, and poly-(L,DL-lactide) [P(L,DL)LA], L/DL ratio 70/30. They were dissolved in dichloromethane and coagulated in a spin bath containing ethanol. The hot-drawing temperature was 65°C. The draw ratios (DR) were upto 4.5 to the P(L,D)LA 96/4 filaments and upto 3 to the P(L,DL)LA 70/30 filaments. Wet spinning decreased crystallinities of both copolymers. Hot drawing increased the crystallinity of the P(L,D)LA 96/4 filament but not to the level of the original copolymer, whereas the as-spun and the hot-drawn P(L,DL)LA 70/30 filaments were amorphous. The filament diameter, tenacity, Young's modulus, and elongation at break were dependent on the DR. The maximum tenacity (285 MPa) and Young's modulus (2.0 GPa) were achieved with the P(L,D)LA 96/4 filament at the DR of 4.5. Respectively, the maximum tenacity of the hot-drawn P(L,DL)LA 70/30 filament was 175 MPa and Young's modulus 1.3 GPa at the DR of 3. Hot drawing slowed down in vitro degradation rate of both stereocopolymer filaments. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

The conditions for producing nanocomposite fibers composed of calcium alginate, containing a hydroxyapatite nanoadditive were devised and the rheological, sorptive, and strength properties of these fibers, as well as their porous and supramolecular structure were subjected to analysis. It has been concluded that the presence of the HAp nanoadditive in the material of alginate fibers decreases their susceptibility to distortion in the drawing stage, which results in their tenacity properties being lower by 2cN/tex than of the fibers with no nanoadditive. The obtained nanocomposite fibers are characterised by a tenacity value exceeding 26 cN/tex, accompanied by high sorptive and water-retention properties of 90% and the even distribution of the nanoadditive on the fiber surface. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Poly(L,D-lactide) [P(L,D)LA], LL/D ratio 96/4, and poly(L,DL-lactide) [P(L,DL)LA], L/DL ratio 70/30, multifilament fibers were prepared by wet-spinning and the effects of the spin draw ratio and the coagulant on the morphological, thermal, and mechanical properties of the filaments were studied. The hydrolytic degradation of filaments was studied in vitro. The filament diameter and the mechanical properties of filaments were highly dependent on the spin draw ratio, whereas the coagulant had no or minor effect. The filament diameters were in the range of 11–36 μm and the maximum tenacity of 150 MPa was obtained at the spin draw ratio of 7.0 for both copolymers. The copolymer had the main importance on the crystallinity of filaments, but it was also affected by the duration of the coagulation process. The crystallinities of P(L,D)LA 96/4 filaments were in the range of 5–16%, whereas P(L,DL)LA 70/30 filaments were totally amorphous. The degree of crystallinity had effect on the hydrolytic degradation of filaments. The tenacity loss of P(L,D)LA 96/4 filaments was about 10% and that of P(L,DL)LA 70/30 filaments was as high as 50% after 24 weeks in vitro. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The authors determined conditions for manufacturing PAN precursor fibers containing a system of two nanoadditives, montmorillonite (MMT), and hydroxyapatite (HAp) in their structure. The PAN precursor fibers thus obtained are characterized by a tenacity of more than 30 cN/tex and a total volume of pores at the level of 0.29 cm3/g. Furthermore, it was found that the use of nanoadditives entails the remodeling of the paracrystalline structure of PAN fibers into a strictly crystalline one. This is accompanied by a decrease in spacing between MMT layers combined with their partial exfoliation. The fibers thus obtained, after being carbonized, will be used for medical applications. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

The photooxidative degradation of acrylic fibers was investigated with two different fiber-spinning processes, that is, dry spinning and wet spinning. Several analytical methods were used in this study: viscometry, X-ray diffraction, Fourier transform infrared spectroscopy, optical measurements, and mechanical testing. Viscometry was used to determine the molecular weight as a monitoring factor for degradation. X-ray diagrams showed lower changes in the crystallinity of wet-spun fibers during a weathering process by irradiation. The results from mechanical testing indicated that the tenacity of dry-spun fibers had less deterioration than that of wet-spun fibers. Degraded wet-spun and dry-spun fibers showed similar trends in optical and spectroscopy analysis. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

As pilling in textiles originates from many factors, the kinetic of pilling formation play an important role in the investigation and approaches of pilling. The single jersey-knitted lyocell fabrics were treated with different alkaline solution concentrations and submitted to Rapid Pilling Test—a wet-state Martindale test for cellulosic fabrics performed with increasing abrasion cycles. After each type of cycles, the pilling density was microscopically counted, and then pilling was visually rated. The changes in fiber properties were followed by water retention values (WRV), fibers swelling, fiber wet abrasion resistance (NSF), and fibers tenacity/elongation in wet and in dry states. The kinetics of pill formation—quantified by pills/cm2—occurred in the following steps: pills are promptly formed at first abrasion cycles, reached the pill plateau cycles, and are self-removed from the fabric surface. The untreated and alkali-treated lyocell fabrics followed a similar trend of pill formation. However, the pilling propensity is distinct depending on the concentrations. The changes in the swollen state of fiber properties and fiber–fiber friction mainly determined the pill kinetics in lyocell fabrics. The kinetic model aims to figure out the pilling mechanism and the appropriate treatment for pilling resistance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The ability of polylactide (PLA) to retain its mechanical properties after repeated cleanings at various pH levels, washing temperatures, and drying conditions has been studied. One of the problems with PLA is its poor resistance to hydrolysis, especially under alkaline conditions. In this study, PLA fabrics were sent through 50 cleaning cycles with different pH levels (8 or 10), washing temperatures (35 or 55°C), and drying conditions (air dry at 21°C/65% relative humidity or tumble dry at 50 or 70°C). The retention percentages of the breaking tenacity, breaking elongation, and modulus of the PLA yarns were measured after every 10 cleaning cycles. A pH of 8 gave greater breaking tenacity, breaking elongation, and modulus retention than pH 10. Washing PLA at 35°C and air drying it at 21°C resulted in greater modulus retention than washing and drying at higher temperatures. Hydrolysis of the polymer was the main cause of the loss in mechanical properties. Equations were developed to predict the retention percentage of the breaking tenacity, breaking elongation, and modulus based on the pH, number of cleaning cycles, and washing and drying temperatures. Recommendations for appropriate conditions for the cleaning of PLA fabrics that result in greater mechanical property retention are given. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Polyglycolic acid (PGA) fibers were prepared by melt-spinning process in this report. The effects of spinning parameters, such as windup rates and drawn ratio, on the mechanical properties of the fibers were discussed by analyzing the internal stress of as-spun fibers, axial sound velocity, fiber tenacity, etc. The results showed that windup rate had a slight effect on the macromolecular orientation degree of the as-spun fibers, which was quite unusual for melt spinning, whereas, the subsequent drawing process effectively increased the macromolecular orientation degree of the PGA fibers and consequently increased the tensile strength of the fibers. Low internal stress of as-spun fibers obtained at lower windup rate led to higher drawing ratio, and the drawn fibers possessed relatively excellent mechanical properties. As a contrast, higher windup rate resulted in the strong internal stress of the as-spun fibers, which had a negative influence on the drawing process, and so the tensile strength of the drawn fibers was relatively poor. Therefore, PGA fiber with perfect mechanical performance could be prepared at the technical parameters of lower windup rate and higher drawing multiples as well as slow drawing rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Cationic dyeable polycaproamide (CD-PCA) and cationic dyeable poly(trimethylene terephthalate) (CD-PTT) polymers were extruded (in ratios 75/25, 50/50, and 25/75) from one melt twin-screw extruders to prepare three CD-PCA/CD-PTT polyblended polymers and then spin fibers. This work examines the rheology, thermal characteristics, crystallinity, tenacity, density, and miscibility parameter μ value of CD-PCA/CD-PTT polyblended polymers and fibers using gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, potentiometer, rheometer, the density gradient analysis, wide-angle X-ray diffraction, and extension stress–strain measurement. The melting behavior of CD-PCA/CD-PTT polyblended polymers revealed negative-deviation blends (NDB). The 50/50 blend of CD-PCA/CD-PTT had the lowest melt viscosity. The experimental DSC results demonstrated that CD-PCA and CD-PTT molecules constituted an immiscible system. In particular, CD-PCA, CD-PTT, and their polyblended fibers yielded a double endothermic peak. The tenacity of CD-PCA/CD-PTT polyblended fibers initially declined and then increased as the CD-PTT content increased. The crystallinities and densities of CD-PCA/CD-PTT polyblended fibers were linearly related to the blend ratio. The values of the miscibility parameter μ for all CD-PCA/CD-PTT samples were under zero, revealing electrostatic repulsion between CD-PCA and CD-PTT molecules. All experimental data supported the immiscibility of CD-PCA/CD-PTT polyblended fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

We developed and elaborated manufacturing conditions for the production of alginic acid fibers with high sorption properties. The fibers' tenacity obtained at a level of 16 cN/tex is suitable for textile processing these fibers, and will make it possible to produce a new generation of highly absorptive dressing materials. The presence of acid groups in the fiber-forming material allows us to use them for the addition of new generation antibiotics, which makes it possible to extend the antibacterial effects of these fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The strength properties of fibers made from polyimideamide (PIA) nanocomposite were investigated and the effect of the presence of MMT in the fiber-forming polymer on the porous structure and supermolecular structure of fibers was analyzed. It was found that lower strength properties (tenacity, elongation at break) of PIA nanocomposite fibers, as compared with those ones of fibers without montmorillonite (MMT), are connected with a lower deformability of the polymer during drawing stage and the collapse of MMT galleries, confirmed by WAXS investigations. This results in the formation of agglomerates that are weakly connected with the fiber-forming polymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 339–344, 2007

The structural parameters and strength properties of three types of new-generation precursor polyacrylonitrile fibers are comparatively analyzed. These fibers, after the carbonization process, can be used as implants supporting the process of bone reconstruction. They are characterized by a high tenacity ranging from 21 to 41 cN/tex. Tests and measurements have shown that the presence of nanoadditives causes a clear increase in the degree of fiber crystallinity. Moreover, the tenacity of the fibers can be considerably increased by the grinding of nanoadditive agglomerates with ultrasound. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

This study was undertaken to investigate the effect of enzymatic pretreatment of cotton (polysaccharides) fibers on the properties of resulting nonwoven fabric. Enzymatic treatment is known to improve the esthetical properties of fabrics but will likely lead to a reduction in strength. In the case of nonwovens the strength loss can be even more drastic as cellulase may attack bonded areas of the fabric. In this work, raw and bleached cotton fibers were treated with enzyme solutions prior to fabric formation to avoid possible damage to the bonded areas and improve strength retention. These fibers were first modified with commercially available whole cellulases and monocomponent endoglucanase enzyme solutions. Then they were formed into a fabric and bonded via hydroentangling. Parameters such as bending modulus, fabric tenacity, fiber strength, length and reducing power were measured for each sample. The pretreatment of cotton fibers prior to fabric formation showed that the resulting nonwovens could be stronger and more drapeable than the same fabric composed of untreated fibers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The microstructural transformation of wool fiber during the stretching process was investigated by the tensile tests and TEM micrograph observation. The results showed that water breaks some of the hydrogen bonds in the fiber, whereas the sodium bisulfite solution breaks some of the disulphide crosslinks between the peptide molecules, then the wool fiber is easy to be stretched. Two types of transformations were found during the stretching process, that is, the slippage of molecule chains or microstructural elements and the αβ transformation. The αβ transformation is dominant, in particular, during the low stretching rate process. In addition, the stretching slenderization tends to increase the tenacity of wool fiber and decrease its extension at break. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 816–822, 2007

Laboratory-accelerated degradation tests have been conducted to understand the stability of high tenacity poly(ethylene terephthalate) (PET) as a result of exposure to stressful chemical environments when used as an implantable prosthesis. The experiments were conducted at 40°C to mimic normal physiological conditions. At various time intervals, samples were collected and evaluated for weight loss (%), mechanical properties, and changes in the surface structure. The mechanical properties that were specifically observed include: breaking load, tenacity, breaking strain, work of rupture, and modulus. For all PET fibers loss of work of rupture was the highest. An empirical formula was developed to estimate degradation behavior over time, though such a prediction cannot be verified without further research and observation. The transverse cracks formed on the stressed samples beyond the critical load in an alkaline environment at 40°C are similar to those found on the PET prosthetic grafts. The cracks in the experimental samples at 40°C and those recovered from human bodies both appear more ‘corallite in structures’ versus those at room temperature. Therefore, it is concluded that the arterial stress that the PET prosthetic graft encountered inside the human body was higher than the yield load of the fiber. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4814–4822, 2006

Lyocell fabric samples were pretreated with NaOH and KOH and resin finished. The treated samples were tested to determine the influence of alkali pretreatments on the tenacity, abrasion resistance, and crease recovery of resin-finished lyocell. Alkali pretreatments resulted in a higher surface concentration of the crosslinking reagent in fabrics, leading to lowered crease recovery and abrasion resistance. The pretreatments also exerted a deleterious influence on the tensile strength in resin-finished samples. However, the differential distribution of crosslinking reagent within the textile structure does not appear to be the only factor responsible for the changes observed in substrate properties; other factors also appear to be responsible for the results observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3596–3601, 2006

The dry-jet-wet spinning process was employed to spin poly(lactic acid)(PLA) fiber by the phase inversion technique using chloroform and methanol as solvent and nonsolvent, respectively, for PLA. The as spun fiber was subjected to two-stage hot drawing to study the effect of various process parameters, such as take-up speed, drawing temperature, and heat-setting temperature on the fiber structural properties. The take-up speed had a pronounced influence on the maximum draw ratio of the fiber. The optimum drawing temperature was observed to be 90°C to get a fiber with the tenacity of 0.6 GPa for the draw ratio of 8. The heat-setting temperature had a pronounced effect on fiber properties.

Poly(1-oxotrimethylene) (ECO) was dissolved in an aqueous composite metal salt solution, and the ECO solution was heated at different temperatures and then used for wet spinning. Within a certain heating time, ECO fibers with a tenacity of 17.6 cN/dtex (2.3 GPa) or greater were successfully produced through hot drawing 16–17 times after drying. Over a certain heating time, however, the strength of the ECO fibers drastically decreased. A higher heating temperature shortened the heating time at which the drastic decrease in the maximum tenacity began. On the basis of ultraviolet measurements of the undrawn fibers, heating ECO in the aqueous composite metal salt solution promoted the thermal degradation of ECO because of aldol condensation or Paal–Knorr furan synthesis. The thermal degradation due to these intermolecular or intramolecular crosslinking reactions was resistant to the molecular orientation of ECO by the hot drawing of the undrawn fibers and reduced the strength of the ECO fibers by producing defects in the filament. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3358–3363, 2006

Cationic dyeable poly(ethylene terephthalate) (CD-PET) and metallocene isotactic polypropylene (m-iPP) polymers were extruded (in the proportions of 75/25, 50/50, 25/75) from two melt twin-screw extruders to prepare CD-PET/m-iPP (and m-iPP/CD-PET)-conjugated fibers of the island-in-sea type. This study investigated the thermal behavior and mechanical and morphological characteristics of the conjugated fibers using DSC, TGA, WAXD, melting viscosity rheometer, density indicator, tenacity measurement, and a polarizing microscope. Melting behavior of CD-PET/m-iPP polyblended polymers exhibited negative-deviation blends (NDB) and the 50/50 blend showed a minimum value of the melt viscosity. Experimental results of the DSC indicated CD-PET and m-iPP molecules formed a partial miscible system. The tenacity of CD-PET/m-iPP-conjugated fibers decreased initially and then increased as the m-iPP content increased. Crystallinities and densities of CD-PET/m-iPP-conjugated fibers presented a linear relation with the blend ratio. On the morphological observation, it was revealed that the blends were in a dispersed phase structure. In this study, the CD-PET microfibers were successfully produced with enhanced diameters (from 2.2 to 2.5 μm). Additionally, m-iPP colored fibers (m-iPP fibers covered with CD-PET polymer) were also successfully prepared. Meanwhile, the presence of PP-graft-MA compatibilizer improved the tenacity considerably. Blends with 10 wt % compatibilizer exhibited maximum improvement in the tenacity for m-iPP colored fibers. The dye exhaustions of various fabrics followed the order: m-iPP colored fibers > conventional CD-PET fibers > CD-PET microfibers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5396–5405, 2006

In the previous work (S. Kiantash, MS Thesis, Amirkabir University of Technology, Textile Engineering Department, Tehran, Iran, 2002), the possibility of producing filament yarns from used PET bottles was investigated and the production was successfully carried out. To improve physical properties and to have a detailed understanding of the molecular structure, spinning variables such as the take-up speed (one of the most influencing factors) should be varied and studied. In the present work, continuous filament yarns from virgin PET chips and used PET bottles were produced at the two take-up speeds of 2500 and 3000 m/min. Optical birefringence, crystallinity (obtained from three methods including density, calorimetry, and FTIR), tenacity, breaking elongation, initial modulus, and shrinkage of yarns were measured and compared. Optical birefringence and crystallinity (obtained from all three methods) of used samples show higher values compared with those of virgin samples produced at both take-up speeds. Consequently, the tenacity of used samples is higher and breaking elongation is lower. Generally, samples having bigger crystallinity present higher initial modulus and smaller shrinkage. However, results of initial modulus and shrinkage do not correspond to this assumption. As it was predicted, increasing the take-up speed resulted in an increase in the optical birefringence, crystallinity, tenacity, and initial modulus and a reduction in the breaking elongation of both virgin and used samples. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3972–3975, 2007

High Modulus high tenacity polypropylene filaments have been prepared by drawing them on a heater with a gradient of temperature. The thermal properties have been analyzed, and the effects of nature of the gradient and end temperatures on thermal properties of the filament have been investigated for such filaments. Low shrinkage values even at 150°C, high retention of storage modulus in dynamic mechanical analyses and very low change in length in thermomechanical analyses have been the characteristic of the gradient drawn filaments. The filaments have high crystallinity, crystal perfection, and crystal orientation. In addition, the reported process has the advantage of being continuous in nature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 838–842, 2006

This investigation considers a quantitative procedure for determining the values of critical process parameters in melt spinning to optimize the qualities of denier, tenacity, breaking elongation, and denier variance in as-spun polypropylene yarn. An orthogonal array in the Taguchi method defines the minimum set of parameter-level combinations that are experimentally tested. The significant process parameters, namely the third extruder barrel temperature, spinning temperature, metering pump speed, and take-up velocity, are identified on the basis of the analysis of variance and F test. After a confirmation experiment is conducted to ensure the reproducibility of the experimental results, the back-propagation neural network establishes a continuous system linking 10 process parameters and four qualities. The technique for order preference by similarity to an ideal solution can be used to obtain a performance measure for assessing multiple qualities. The genetic algorithm attempts to find parameter values for optimizing the quality performance, including the denier, tenacity, breaking elongation, and denier variance. Finally, the experimental results demonstrate that the smallest denier, largest tenacity, smallest breaking elongation, and second smallest denier variance of as-spun polypropylene yarn can be achieved with the proposed approach in melt spinning. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2532–2541, 2006

Tensile properties are important basic characteristics of materials and influence their end-use and performance. More importantly, in the case of leather due to end-use applications such as shoe uppers, automotive and furniture upholstery, mechanical properties such as tenacity are of extreme importance. Therefore, fundamental studies on the tensile properties of leather are needed. In this study, an attempt has been made to examine the effect of gauge length (GL) on the tensile properties of shoe upper leather. Two different specimens in the form of rectangular and dumbbell shapes have been cut from parallel and perpendicular directions to the body axis of the leather and have been tested. Results showed that the maximum breaking load and the percentage extension at break decreased with the increase in GL. Rectangular specimens showed a 30% decrease in maximum breaking load and a 13% decrease in percentage extension at break, while dumbbell specimens showed reductions in the order of 28 and 6%, respectively, as the GL increased from 9.53 cm to 23.5 cm. Highly varying supramolecular architecture of the collagen matrix and the frictional slippage caused by the free ends present in the collagen fibrils, which induce a weak-link effect similar to the one found in cotton fibers and yarns, are considered to be the probable reasons for this behavior. A limited scanning electron microscopic study has been undertaken to pictorially represent the breakage of leather at different GLs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1202–1209, 2006

Investigated in the present study are the physical properties, morphology, and structure of PP/N6 alloy filaments (10, 20 wt % N6) made with or without PP-g-MAH as compatibilizer. The alloy filaments produced at the take-up speeds of 300 and 800 m/min were drawn with draw ratio of 3.5 and 2, respectively. Stress–strain curves of PP and alloy filaments show ductile and brittle behavior, respectively. It is suggested that the brittle behavior of alloy filaments is due to the presence of microvoids or micropores at the interface of PP and N6; these lead to stress concentration and thus to a decrease in tenacity, modulus, and elongation at break. Effects of the blending of N6 with PP on birefringence and crystalline and amorphous orientation factors of the composite filaments are studied. The amorphous orientation factor, fam, of PP was found to increase with an increase in the amount of N6. The alloy filaments behaved like isostrain materials and most of the force in spinning and drawing was born by the PP phase. The presence of N6 fibrils helped to orient PP chain molecules in amorphous regions. However, the crystalline factor, fc, of PP decreased with the increase in nylon fraction. This means the presence of the crystals of N6 caused a decrease in the orientation of the PP crystals. LSCM micrographs of the filament showed the presence of matrix–fibril morphology with the N6 fibrils oriented along the axis. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 532–544, 2005

Polypropylene (PP) filaments are prepared by blending two different molecular weight components of PP. A melt-spinning process to produce filaments includes mixing of components, extrusion, and two-stage drawing, followed by a unique Gradient Drawing™ process. Blending results in highly deformable as-spun filaments with high draw ratios. For 90:10 blends of PP samples with melt flow indexes of 35 and 3, a high level of crystallinity and crystalline and amorphous orientations are obtained. A sonic modulus of 28 GPa, dynamic modulus of 20 GPa, tensile modulus of 16 GPa, and tenacity of 667 MPa are achieved. These samples are dimensionally stable up to ∼100°C. All steps in the production of the filaments are continuous. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1021–1028, 2005

The drawing behavior and mechanical properties of as-spun and highly oriented nylon 66 fibers drawn in supercritical carbon dioxide (SCCO2) were investigated. Conditions including different temperatures, CO2 pressures, and plasticizers with different polarity were systematically studied. Results indicate that CO2 is an efficient plasticizer for as-spun nylon 66 fibers as shown by decreases in the draw stress. In contrast, CO2 shows only a slight influence on the drawability of highly oriented nylon 66 fiber. The effect of other plasticizers such as water, methanol, and ethanol on the drawability of nylon 66 fibers is very similar to that of CO2. Tenacity and modulus of one-stage drawn fibers were less than 0.8 and 5.0 GPa, respectively. Fibers with the highest tenacity and modulus, 0.96/5.04 and 1.06/5.04 GPa, were obtained by two-stage drawing in SCCO2 from as-spun and drawn nylon 66 fibers, respectively. The main reason for the extremely low draw ratios (

The wet spinning of chitosan fibers was studied with 2% acetic acid as the solvent, 10% aqueous sodium hydroxide as the nonsolvent, and a 4% chitosan solution as the polymer. This article describes the crosslinking of the chitosan fibers. Epichlorohydrin (ECH) was selected as a convenient base-catalyzed crosslinking agent. The coagulation and crosslinking of the chitosan fibers occurred simultaneously in the coagulation bath. In this study, we investigated the effect of the concentration of the crosslinking agent, ECH, in the spinning dope on the structural, thermal, morphological, and mechanical properties (e.g., the tenacity, elongation, and work of rupture) of chitosan fibers. The tenacity of the chitosan fibers, especially the wet tenacity, was improved by crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2054–2062, 2004

The correlation between the fiber structure and mechanical properties of two different poly(ethylene terephthalate) fiber types, that is, wool and cotton types produced by three producers, was studied. Fiber structure was determinedusing different analytical methods. Significant differences in the suprastructure of both types of conventional textile fibers were observed, although some slight variations in the structure existed between those fibers of the same type provided by different producers. A better-developed crystalline structure composed of bigger, more perfect, and more axially oriented crystallites was characterized for the cotton types of PET fibers. Crystallinity is higher, long periods are longer, and amorphous domains inside the long period cover bigger parts in this fiber type in comparison with the wool types of fibers. In addition, amorphous and average molecular orientation is higher. The better mechanical properties of cotton PET fiber types, as demonstrated by a higher breaking tenacity and modulus accompanied by a lower breaking elongation, are due to the observed structural characteristics.

The thermal degradation of jute and flax fibers under temperatures between 170 and 210°C for a maximum of 120 min was studied in detail. This article will analyze the effects of the thermal exposure on mechanical properties (tenacity) as well as on fiber fine structure (degree of polymerization and degree of crystallinity). It was found that temperatures below 170°C only slightly affects fiber properties, while temperatures above 170°C significantly dropped tenacity and degree of polymerization. Because of chain scissions, a slight increase in degree of crystallinity was observed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1417–1422, 2001

A possible method for recycling automobile and truck tires is to comminute them and incorporate the rubber particles in to cementitious mixtures for nonstructural applications. It was found that addition of rubber granules led to a decrease in compressive and flexural strengths of the mortar. The fracture behavior of cementitious paste containing untreated rubber particles showed particulate pull out characteristics and weak interface. The interfacial strength of rubber-cementitious composite can be improved upon chemical treatment of rubber by gamma mercapto trimethoxy silane coupling agent (GMPTS). The extent of interfacial bonding of rubber and cement was measured by peel strength analysis. The increased interfacial strength of the composite was found to play an important role in the ability of the composite to withstand postpeak loading and postpeak displacement. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 934–942, 2000

The preparation of fibers from aqueous urea–formaldehyde resins has been investigated; a dry spinning process has been developed based on the extrusion of catalyzed resin into a drying chamber at 180–220°C, producing a multifilament yarn at spinning speeds of up to 600 m/min. A range of UF filaments was produced with diameters between 10–70 μm; the tenacities of spun filaments were 6–10 cN/tex, initial moduli were 220–340 cN/tex, and elongation at break was 4–10%. The best tensile properties resulted from conditions that produced the smallest diameter fibers. Postspin heat treatment improved the tenacity to 14 cN/tex and the elongation to 20%. Spinnability improved with increased viscosity of the spinning solution and increased cell temperature, while tenacity and elongation increased with increasing cell temperature and spinning stretch. A correlation was found between TGA weight loss (between 105 and 200°C) and fiber tenacity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 64–74, 2000

The tensile properties of high-strength poly(vinyl alcohol) (PVA) fibers after heat treatment in air, water, and engine oil were studied. The results show that heat treatment in air, water, and engine oil have a different influence on the tensile properties of high-strength PVA fibers. After heat treatment in air, the fibers possess excellent heat stability of the tensile properties. But in water, especially in hot water, the tenacity, Young's modulus, and specific work of rupture of the fibers decrease, while the elongation at break of the fibers increases. Similarly, engine oil has a significant influence on the tensile properties of the fibers. When the temperature of engine oil is above 120°C, the tensile properties of the fibers decrease drastically. We also discuss the influence of heat, water, and engine oil on the tensile properties of high-strength PVA fibers in relation to the structure of the fibers.

The tensile stress–strain and recovery behavior of all the four commercial varieties of Indian silk fibers, namely Mulberry, Tasar, Eri, and Muga, have been studied along with their structures. Compared to the non-Mulberry silk fibers, Mulberry silk fiber is much finer and has crystallites of smaller size, higher molecular orientation, and a more compact overall packing of molecules. These structural differences have been shown to result in (1) the presence of a distinct yield and a yield plateau in non-Mulberry silk and their absence in Mulberry silk, and (2) relatively higher initial modulus and tenacity along with lower elongation-to-break and toughness and superior elstic recovery behavior of mulberry silk compared to non-Mulberry silk. It is also observed that fine silk fibers have a relatively more ordered and compact structure with higher orientation compared to their coarse counterparts, and this gives rise to higher initial modulus and higher strength in the finer fibers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2418–2429, 2000

Superabsorbent filament fibers based on sodium alginate were prepared using glutaraldehyde as a crosslinking agent. Alginate was extruded into an aqueous hydrochloric acid coagulation bath to form continuous alginic acid gel fibers via a wet-spinning method. The alginic acid gel fibers were dehydrated by exchanging water with dioxane, crosslinked, then neutralized for better absorbency. Crosslinked alginate filaments exhibited a high saline solution and synthetic urine absorbencies, maintaining the integrity of the fiber structure. Maximum synthetic urine absorbency was obtained with the fiber crosslinked at a lower glutaraldehyde concentration compared with that required for maximum saline solution absorbency. This appears to be due to the crosslinking effect of calcium ions in the synthetic urine solution being absorbed. Strain and tenacity of the crosslinked alginate fibers decreased with an increasing amount of glutaraldehyde used in the crosslinking reaction. The decrease in tenacity was not significant while the strain showed an extensive decrease. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1797–1804, 2000

LaRC-IA polyimide fibers were extruded from the melt and drawn. The fibers were characterized by sonic pulse propagation, polarized optical microscopy, calorimetric analysis, X-ray diffraction, and tensile testing. When the amorphous, essentially isotropic, as-extruded filaments were heated slowly in a calorimeter, no “cold” crystallization could be detected. However, when these filaments were drawn at temperatures above the Tg of the polymer, they crystallized rapidly to produce oriented semicrystalline structures. The consequent increases in modulus and strength were significant, with the properties reaching the levels of commercial fibers of intermediate tenacity. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 1215–1222, 1999

The fibrillar and the lamellar structures in a range of poly(ethylene terephthalate) fibers were studied by small-angle X-ray scattering. The intensity maxima in the lamellar peaks lie on a curve that can be described as an ellipse. Therefore, the two-dimensional images were analyzed in elliptical coordinates. The dimensions of the coherently diffracting lamellar stack, the dimensions of the fibrils, the interfibrillar spacing, and the orientation of the lamellar surfaces were measured in addition to the lamellar spacing. The orientation of the lamellar planes and the size of the lamellar stacks had a better correlation with mechanical properties of the fibers than did the lamellar spacing. In particular, longer and wider lamellar stacks reduced fiber shrinkage, as did the closer alignment of the lamellar normal to the fiber axis. These structural features were also associated with lower tenacity. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2527–2538, 1998

Jute and flax fibers were improved under UV radiation using methyl methacrylate (MMA) mixed with methanol (MeOH). There was a 30% enhancement of tenacity for these fibers against 3–8% grafting of MMA with the fibers. Incorporation of 1% of one of the additives 2-ethyl hexyl acrylate (EHA), urea (U), or N-vinylpyrrolidone to MMA + MeOH solution increased the grafting very slightly and enhanced the tenacity of jute by 110% and flax by 50%. Enhancement of elongation of the treated fibers was up to 30%. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 843–848, 1998

A series of Polyamide 4.6/6 textile fibers spun according to different technologies, high-speed spinning, and the spin drawing, was investigated by 13C-NMR, ultrasonic, optical, WAXS, and DSC measurements. It was shown from the determination of the chain orientational order parameters and the DSC results that in the as-spun textile fibers two different crystallization modes occur, i.e., up to spinning speeds of 3500 m/min spherulites and orientationally ordered crystallites are present at the same time. With increasing fiber spinning speeds, the orientationally ordered crystallites grow at the expense of the spherulitic structures. At spinning speeds beyond 3500 m/min the spherulites vanish completely and only the orientationally ordered crystallites are observable and the tenacity increases. The drawn fibers only show a fibril-like structure and spherulites do not occur. Accordingly the drawn fibers have a higher level of tenacity. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 377–385, 1997

The orientation of the noncrystalline (amorphous) phase in poly(ethylene terephthalate) fibers is analyzed by separating the amorphous scattering in the wide-angle x-ray diffraction patterns into isotropic and anisotropic components. Two parameters are used to characterize the amorphous orientation—the fraction of the anisotropic component and its degree of orientation. The x-ray amorphous orientation parameters are compared with the sonic modulus and the birefringence values. Our results illustrate that the intrinsic birefringence of the amorphous phase is not “intrinsic” but depends on its density. The role of the oriented amorphous phase in determining the strength (tenacity) and the dimensional stability (shrinkage) of the fibers is discussed. We conclude that although amorphous orientation determines the shrinkage, other factors such as the connectivity between the amorphous phase and the crystalline regions play an important role in determining the tenacity of the fibers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1363–1371, 1997

Wide-angle X-ray diffraction studies of physically and chemically treated silk fibers like bivoltine mulberry silk and tassar silk were carried out to evaluate their crystal size, lattice distortion, and minimum enthalpy, as these determine the properties of silk fibers. The results are also compared with tenacity measurement. (C) 1996 John Wiley & Sons, Inc.

Nineteen varieties of cotton, covering a wide range of fiber properties like maturity, fineness, and strength uniformity ratio were swollen in 5N KOH and NaOH at room temperature (30 ± 1°C). Tensile and fine structural properties of the resultant samples were measured and their relationship with initial fiber properties was examined. A comparative evaluation of fiber properties of KOH swollen fibers with those swollen in NaOH revealed that, irrespective of variety, fibers swollen in the former reagent retain higher tenacity. It was further noted that fine structural parameters like crystallite orientation and amorphous content which influence tensile properties become modified differently while swelling in the two reagents. While changes in crystallite orientation were found to be less drastic during KOH swelling, unlike in NaOH, the reverse was found to be true with crystalline content. These changes in fine structure could more or less explain the variation in tensile properties of fibers swollen in these two reagents. © 1995 John Wiley & Sons, Inc.

High molecular weight poly(ethylene terephthalate) (PET, IV = 3.30 dL/g) was extruded in attempts to prepare high performance fiber using the solution spinning method. Solution preparation, fiber coagulation, and mechanical properties of resultant fibers were examined. An as-spun fiber exhibited high deformability when appropriate coagulation conditions were used. Tenacity and modulus of the resultant drawn fibers achieved 12.9 and 230 gpd, respectively, at draw ratio above 10. © 1995 John Wiley & Sons, Inc.

Jute fiber was grafted by acrylonitrile and methylmethacrylate monomers in raw and bleached condition. It was also noted that optimum grafting takes place after about 4 h of grafting. It was also noted that in bleached jute fiber, the grafting percentage is higher at all stages of grafting but the tenacity value at the highest add-on is practically the same as that of raw fiber with much less add-on. The crystalline orientation of the grafted jute fiber was correlated with the fiber tenacity. The moisture regain (%) of the fiber after grafting showed a decreasing trend with an increase in grafting percentage. No structural change of the fiber occurred due to grafting. © 1995 John Wiley & Sons, Inc.