Sonic Modulus Research Articles

Optimization of the pre-tension and separation distance for measurement of the dynamic elastic modulus and macromolecular orientation of a polypropylene monofilament via the sonic velocity method.

Using a fiber orientation degree measurement instrument (i.e., a dynamic modulus tester), 28 groups of averaged sonic pulse travel times in a polypropylene monofilament were measured and recorded under five pre-tensions across eight separation distances. The zero-time (or delay time) T0, sonic velocity C, sonic modulus E, Hermans orientation factor F, and orientation angle θ were calculated via two- and multi-point methods. The good agreement observed between the scatter plots of calculated data and the regression lines shows that the multi-point method provides reliable, accurate determination of the sonic modulus (or the dynamic elastic modulus) and the orientation parameters. Surprisingly, the zero-time for sonic pulse propagation depends significantly on the separation distance in practice, although it does not in theory. For easy and rapid measurement or relative comparisons using the two-point method, the optimal range of pre-tension is 0.1 gf/den-0.2 gf/den, and the optimal separation distances are 200 mm and 400 mm. The two-point method is appropriate for industrial applications, while because of its greater accuracy, the multi-point method is preferred for scientific research.

Dynamic properties of air-jet yarns compared to rotor spinning

In yarn production, the mechanism of twist insertion is a major factor that affects the structure and ultimately the properties and characteristics of the produced yarn. Moreover, the differences within the same spinning technique may have a similar effect where, for instance, the properties of yarns produced using Murata Vortex Spinning (MVS) and Reiter air-jet spinning (J20) will differ, although both technologies are just varieties of the same twist insertion principle of using a stream of air. In this work, the structure and properties of Murata vortex, Reiter, and rotor-spun yarns are compared with more emphasis on their mechanical behavior under dynamic stresses. Unlike the dynamic mechanical analysis of materials that presumes linear viscoelastic behavior and is only valid under small strains, this work suggests a cyclic loading with larger strains as a means of the dynamic evaluation of the yarns. Results show no significant difference between the technologies in terms of their initial modulus and maximum elongation, while a significant difference between the technologies is observed in the maximum loading and, to some extent, the work of rupture. The dynamic sonic modulus is compared to the results of the standard mechanical and the suggested cyclic loading tests, and a high correlation between the values was observed.

Characterization of Polypropylene Staple Yarns by Acoustic Dynamic Modulus

The acoustic or sonic pulse-propagation technique for the measurement of dynamic elastic modulus has the advantage of not being dependent on the sample cross-sectional characteristics. This technique also gives a direct measure of modulus rather than the indirect measure in the form of load versus extension. The sonic tests are relatively simple to apply and are nondestructive. The values of sonic modulus of fibrous structures are dependent on the orientation of components and packing density as well. The main aim of this work is to quantify effect of yarn twist on the sonic modulus of staple yarns from polypropylene fibers. The results are compared with selected models of yarn twist influence on the mechanical properties of staple yarns. The correlation between yarn orientation factor defined by Pan and sonic modulus are shown. The sonic modulus is compared with tensile modulus of yarns.

Determination of intrinsic birefringence values of polycaprolactone filaments

AbstractIntrinsic birefringences of polycaprolactone filaments are determined using the approach suggested by Samuels. First, intrinsic lateral moduli are determined from the values of crystallinity and sonic moduli of unoriented filaments. These values are found to be 3.473 GPa and 0.071 GPa, respectively, for crystalline and amorphous regions. The crystallinity, sonic moduli and crystalline orientation function of drawn and heat set filaments are used to evaluate amorphous orientation functions. Finally, Stein and Norris's equation along with birefringence data is used to obtain intrinsic birefringence values of crystalline and amorphous regions and these values are found to be 0.079 ± 0.002 for crystalline regions and 0.066 ± 0.008 for amorphous regions. Copyright © 2012 Society of Chemical Industry

Comparison of the structure-property relationships for PTT and PET fibers spun at various take-up speeds

A comparison of poly(trimethylene terephthalate)(PTT) and poly(ethlene terephthalate)(PET) fibers spun at various take-up speeds was presented. Fiber characterization included tensile and thermal properties, optical birefringence, density, sonic modulus, boil-off shrinkage, and wide-angle X-ray diffraction. The phenomenon of stress-induced crystallization was inferred from the X-ray diffraction diagrams for fibers spun with take-up speeds over 4000 m/min. The tenacity and elongation of PTT and PET fiber showed typical results, but the initial modulus of PTT fiber was nearly unchanged over the entire take-up speed range (2000–7000 m/min), whereas that of PET, as expected, increased monotonically with increasing take-up speed. This divergent behavior could be explained by the different molecular deformations in the c-axis as determined from X-ray diffraction patterns. The fiber crystallinity, density, and heat of fusion of both polymers increased with take-up speed. The boil-off shrinkage decreased with increasing take-up speed. The optical birefringence of the two fiber types showed a maximum level at a take-up speed of ca. 5000 m/min. The melting temperature behavior of PTT fiber was different from that of PET fibers. It was found that PTT is less sensitive to stress induced changes at high spinning speeds than is PET.

Dry‐jet‐wet spun polyurethane fibers. I. Optimization of the spinning parameters

AbstractThis study examined the spinning of polyurethane‐based elastomeric fibers with the dry‐jet‐wet spinning method. The three important spinning variables that were chosen were the coagulation bath ratio (dimethylformamide/water), the bath temperature, and the stretch ratio. A three‐variable factorial design method, proposed by Box and Behnken, was used to optimize these process parameters. The spinning process was further fine‐tuned by the variation of the stretch ratio and the dope solid content. The effect of the dry‐jet length on the fiber properties was also studied. The tenacity and elastic recovery properties of the fibers were found to be optimum at a bath ratio (dimethylformamide/water) of 60 : 40, a bath temperature of 15°C, and a stretch ratio of 2.5. The density and sonic modulus were measured to determine the effect of varying the process variables on structural parameters such as the density and orientation. The surface morphological features, as revealed by scanning electron microscopy, were correlated to the fiber properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Spinning and characterizations of polypropylene/alkylphosphonic acid treated montmorillonite nanocomposite fiber

AbstractFine and well‐dispersed clay was prepared via the in situ conversion of the dodecylamine intercalant inside the clay gallery to dodecylamino dimethylene diphosphonic acid (DDD), using a Mannich reaction, so as to create a repulsive force that delaminated the clay platelets. The clay structure and morphology were characterized by X‐ray diffraction (XRD), Scanning electron microscopy (SEM), and Transmission electron microscopy (TEM) analysis, which revealed changes in the multilayer stacks. XRD analysis showed that the interlayer spacing was largely expanded by the presence of DDD. SEM and TEM images revealed that DDD containing clay (PMMT), but not that without DDD, exhibited transparency, indicating the extremely fine and well‐dispersed clay. Polypropylene/PMMT nanocomposites containing 2, 4, 6, 8, and 10 wt % PMMT were prepared by melt extrusion. The obtained compounds were each spun into a monofilament fiber using a small scale spinning machine and then characterized by XRD, Differential scanning calorimetry (DSC), and Thermogravimetric analysis (TGA), plus the sonic modulus was evaluated. The XRD results revealed an increase in the β crystallinity peak in fibers loaded with 2–10 wt % PMMT, indicating that PMMT particles were capable of acting as a β‐form nucleating agent. However, only minimal changes in the thermal behavior (Tc) were observed due to the tested samples containing insufficient PMMT content. The mechanical properties, in terms of the tensile strength and sonic modulus value (E), of the polypropylene nanocomposite fibers were higher than those of virgin PP fibers, presumably due to the reinforcement effect of the filled PMMT nanoparticles. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Properties of high modulus PEEK yarns for aerospace applications

AbstractA study has been carried out on the influence of extrusion and drawing related process parameters with an object of obtaining high modulus poly ether ether ketone yarns that can be tailor made to meet critical requirements of aerospace applications. The influence of the interaction between rheological properties, spinning process variables, and drawing conditions has been given special attention to engineer a yarn that exhibit excellent structure property relationships. The wide angle X‐ray diffraction results suggest that drawing carried out above glass transition temperature (Tg) influences the structure that include unit cell parameters, density, and mechanical properties. The degree of orientation characterized in terms of sonic velocity measured as high as 3 km/s with sonic modulus of 105 gpd. With progressive increase in draw temperature, crystallinity was found to increase, and useful properties were observed at an optimum draw temperature of 200°C (may be region of maximum crystallization rate) primarily attributed to the maximum crystallization temperature and the heat setting effect. Thermal studies (TGA) indicate that these materials can be used in high temperature applications (up to 250°C) for long time exposure and 500°C for short term exposure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Fine structure and physical properties of poly(butylene terephthalate) sheets prepared by roll drawing

AbstractPBT sheets were extruded from T-die using a single extruder and were winded by a take-up roller controlled at 50°C and with speed at 1.2 m/min. Oriented PBT sheets were prepared with various winding roll speeds at 3.6, 4.8 and 6.0 m/min. Fine structure and physical properties of PBT sheets thus obtained were investigated by measuring the molecular orientation, crystal structure, dynamic visco-elasticity, thermal and mechanical properties, sonic modulus, etc. PBT melts were found to be readily crystallizable in the sheet. In the case of roll drawing, the DRmax of PBT sheet was 5. The PBT sheets prepared from winding speed at 6 m/min showed polymorphism of both α- and β-form crystallites with crystallinity of about 24%. In the tri-directional WAXD patterns, the PBT sheets by the roll drawing method turned out to be oriented in the uniplanar-axial form. For the roll drawn PBT sheets with various winding speeds, large orientation effects were observed in the winding direction together with improved thermal and mechanical properties.

Fine structure and physical properties of poly(buthylene terephthalate) sheets prepared by roller drawing method

Poly(butylene terephthalate) sheets were prepared by roller-drawing method with various draw ratio. The drawing temperature is 100 °C and draw ratios were varied 2, 2.5, 3, 3.5 and 4. The effect of draw ratio on the crystal structure, the molecular orientation, dynamic viscoelastic properties, sonic modulus and tensile properties of the roller-drawn PBT sheets were investigated. In WAXD results, with increasing of the draw ratio, (010) and (100) planes of preferred orientation have the strongest intensity on the equator. In the meridional scans, it was confirmed that α and β crystal co-existed in the roller drawn PBT sheets with various draw ratio. Uniaxially roller-drawn PBT sheets clearly increased orientation along the stretched direction at high draw ratio. And the four-methylene groups of PBT orient along the surface of the sheet. The mechanical properties of PBT sheets were improved by orientation-induced crystallization during roller drawing process at 100 °C.

Structure, Property, and Relaxation Behavior of Mulberry (Bombyx Mori) and Tasar (Antheraea Mylitta) Silk

ABSTRACT Mechanical properties of fully degummed filaments of mulberry and tasar silk have been investigated and correlated with structure and morphology. The tensile behavior of mulberry silk filament was different from tasar, which demonstrated characteristic yield point, lower modulus, and breaking extension twice as high as that of mulberry. Stress relaxation and inverse relaxation/stress recovery were observed for both varieties of silk. The magnitude of inverse relaxation increases with the increase in peak tension and reduction in retraction also observed with the decrease in peak tension. Tensile properties and relaxation behavior were correlated with density, birefriengence, orientation index, and sonic modulus.

Comparison of Field Testing with Laboratory Testing of the Durability of Stone

Abstract Samples of three granites (Texas Pink, Mount Airy White, Academy Black), one marble (Carrara) and Indiana Limestone have been exposed to 11 years of natural weathering on the roof of a building in the Chicago area. Twice a year, the samples are visually reviewed. In addition, the changes in physical properties have been monitored using non-destructive test procedures for determination of the dynamic (sonic) modulus of elasticity. The sonic modulus measurements were recorded using procedures as outlined in ASTM C 215, “Standard Test Method for Fundamental Transverse, Longitudinal, and Torsional Frequencies of Concrete Specimens.” The sonic modulus measurements were compared to measurements of similar stone samples that were exposed to laboratory accelerated weathering testing. The exposed and protected surfaces have recently been examined petrographically, and the changes due to the natural weathering recorded. Based on this additional testing and evaluation, conclusions can be drawn which further indicate the use of accelerated weathering. Testing can effectively evaluate the long-term changes in the mechanical and physical properties of dimension stone when exposed to natural weathering.

STUDY OF PROPERTY & STRUCTURAL VARIANTS OF MULBERRY AND TASAR SILK FILAMENTS

Abstract The tensile behaviour of fully degummed filaments of two commercial varieties of silk produced in India, namely mulberry (Bombyx mori) and tasar (Antheraea mylitta), has been investigated in dry and wet state. The tensile properties were correlated with the structures and morphologies of these two varieties of silk. The tenacity and elongation at break of these silks were not significantly different in dry and wet state; however, a slight reduction in initial modulus was noticed in wet state. The stress-strain behaviour of mulberry silk filament was different from that of tasar in that it demonstrated a characteristic yield point, lower modulus and elongation at break twice as high as that of mulberry. The characteristic stress-strain behaviour of theses two varieties of silk was correlated with density, birefringence, orientation index, sonic modulus and amino-acid composition. Poor orientation and less order in tasar are related to the higher percent of bulky groups present in fibroin.

High modulus/tenacity filaments from blends of different molecular weights of polypropylene

AbstractPolypropylene (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

Imparting disperse and cationic dyeability to polypropylene through melt blending

The present paper deals with improvement in disperse dyeability as well as imparting of cationic dyeablility to difficultly dyeable polypropylene by a melt blending technique. Isotactic polypropylene (PP) was blended with fibre grade polybutylene terephthalate (PBT), cationic dyeable polyethylene terephthalate (CDPET) and polystyrene (PS), individually. The resulting binary blends were spun and drawn into fibres at draw ratio 2, 2.5, and 3. The compatibility of blends, structural changes of fibres in terms of X-ray crystallinity, relative crystallinity, sonic modulus, birefringence and thermal stability were examined. The blended fibres were found to be disperse dyeable by the conventional method of high temperature and high pressure dyeing. And this dyeability increased with increase in the level of substitution. PP/CDPET blend also exhibited dyeablility with cationic dyes in addition to that with disperse dyes. The optimum level of blending was predicted keeping in view of tenacity and thermal stability of melt blend fibres. The wash fastness properties of the dyed fibres were found to be of high rate.

Mechanical properties of BPDA–ODA polyimide fibers

An aromatic polyimide was synthesized via a one-step polycondensation reaction between biphenyltetracarboxylic dianhydride (BPDA) and 4,4′-oxydianiline (ODA) in p-chlorophenol. The polyimide (BPDA–ODA) solution dopes were spun into fibers by means of dry-jet wet spinning. The as-spun fibers were drawn and treated in heating tubes for improving the mechanical properties. The thermal treatment on the fibers resulted in a relatively high tensile strength and modulus. Thermal mechanical analysis (TMA) was employed to study the linear coefficient of thermal expansion (CTE). Thermal gravimetry analysis (TGA) spectra showed that the BPDA–ODA fibers possessed an excellent property of thermo-oxidative degradation resistance. The sonic modulus E s of the polyimide fibers was measured.

Studies on Indian silk. II. Structure–property correlations

AbstractThis second in a series of articles deals with studies on the structure and physical properties of five varieties of Indian silk: two mulberry (bivoltine and crossbreed) and three nonmulberry (tasar, muga, and eri). A detailed analysis of the microstructural parameters and mechanical properties was reported. Significant differences between and within the varieties with respect to microstructural parameters (crystallinity, density, birefringence, dichroic ratio, sonic modulus, etc.), as well as the effect of microstructural parameters on mechanical properties, were discussed. Some of the observations made on the inverse stress relaxation behavior of the different silk varieties were also reported. The extent of variation of these morphological parameters was found to correlate well with the mechanical properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1098–1115, 2004

Structure and Properties of Biodegradable Polymers: Rolling Effect in Poly (butylene succinate) Sheets

Sheets made from poly (butylene succinate) (PBS) were prepared by extrusion. They have been studied under uniaxial drawing as a function of the draw condition. Changes in molecular orientation and crystallinity were investigated using the criteria of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, sonic modulus, X-ray diffraction, density, birefringence and measurements of % Haze. Rolling improved the thermo-mechanical and dynamic properties of extruded sheets as a result of changes in molecular orientation and crystallinity.

Thermal behavior of drawn acrylic fibers

AbstractThe effect of stretching on the thermal behavior of acrylic fibers was investigated with differential scanning calorimetry (DSC), thermogravimetric analysis, and Fourier transform infrared spectroscopy (FTIR). In air atmosphere, the peak temperature of the dynamic DSC thermogram was significantly lowered from 289 to 273 °C when the gel fibers (undrawn) were drawn to a draw ratio of 11.2. However, the initiation temperature was unchanged at 202 °C. The shoulder in the region of 310–380 °C was gradually converted to a sharp peak during the drawing process. However, the dynamic DSC in nitrogen atmosphere did not change in all cases. In air atmosphere the total heat liberated, ΔH, for gel fiber was 851 J g−1. However, upon drawing to 11.2, ΔH increased to 1580 J g−1 showing an increase in the total chemical changes. An intimate relationship of chemical changes during the heating process was observed with FTIR of heated samples at various temperatures. The initiation of a DSC exotherm in air begins with nitrile cyclization, and subsequently dehydrogenation was initiated between 220 and 260 °C. An increase in the X‐ray orientation factor and sonic modulus gave a correlation between the stretching draw ratio and crystalline/overall molecular orientation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2949–2958, 2003

Effect of coagulation conditions on properties of poly(acrylonitrile-carboxylic acid) fibers

Acrylic fibers are among the most useful synthetic fibers for textile applications, and special acrylic fiber (SAF) has industrial applications. The physical and mechanical properties of fiber are affected by several parameters; one such parameter is coagulation conditions: bath temperature, bath composition, and drawing. Acrylonitrile–carboxylic acid copolymers, that is, acrylic methacrylic and itaconic acid, were converted into fibers using the dry-jet wet spinning technique. The coagulation bath temperature was varied from 5°C to 35°C, and the properties of the fibers so obtained were investigated. The effect of the final drawing ratios (6.5 and 8.5) on such physical and mechanical properties as tenacity, sonic modulus, initial modulus, density, crystallinity index, and X-ray orientation were also investigated. In addition, thermogravimetric analysis and scanning electron microscopy were used to determine the thermomechanical properties and fracture morphology of the fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1825–1837, 2003