Dynamic tensile modulus

Some viscoelasticity results have been reported for bimodal PDMS [120], using a Rheovibron (an instrument for measuring the dynamic tensile moduli of polymers). Also, measurements have been made on permanent set for PDMS networks in compressive cyclic deformations [121]. There appeared to be less permanent set or "creep" in the case of the bimodal elastomers. This is consistent in a general way with some early results for polyurethane elastomers [122], Specifically, cyclic elongation measurements on unimodal and bimodal networks indicated that the bimodal ones survived many more cycles before the occurrence of fatigue failure. The number of cycles to failure was found to be approximately an order of magnitude higher for the bimodal networks, at the same modulus at 10% deformation [5] ... 

Mechanical Properties. To reveal the reinforcing effect of liquid crystalline polymer microfibrils on the mechanical properties of the films both their dynamic torsional moduli and dynamic tensile moduli have been studied as a function of temperature using a Rheometrics Mechanical Spectrometer (RMS 800) and a Rheometrics Solids Analyzer (RSA II), respectively. For comparison purpose the modulus of neat matrix polymers and, in some cases, the modulus of carbon fiber and Kevelar fiber reinforced composites has also been measured. 

Figure 11. Master curves of the dynamic tensile moduli at -40 C for three representative types of primary buffer coatings for optical fibers.

Figure 9.14 Temperature dependence of dynamic tensile moduli at 10 Hz for iPP/EHR57 (75/25) (closed symbols) and sPP/EHR57 (75/25) (open symbols). (From Reference 31 with permission from American Chemical Society.)...

Figure 9.32 Variation of the dynamic tensile moduli with temperature for iPP/EHR crystallized at 403K. The blend ration of iPP/EHR (w/w) is (a) 90/10, (b) 80/20, and (c) 70/30. The open symbols denote iPP/EHR51 and filled symbols denote iPP/EHR33. (From Reference 64 with permission from Society of Rheology Japan.)...

Figure 9.43 Temperature dependence of dynamic tensile moduli for the MD (open symbols) and the TD (closed symboles) (a) iPP, (b) iPP/EHR30, and (c) iPP/EHR53. (From Reference 65 with permission from John Wiley Sons, Inc.)...

The complex dynamic tensile moduli were measured at a frequency of 10 Hz over the temperature ranging from -150°C to 230°C-300°C by using a viscoelastic spectrometer (VES-R, Iwamoto Machine Co. Ltd.). The length of the specimen between the spectrometer jaws was 30mm, and the width was ca. 5 mm. The measurements were desorbed in detail elsewhere (Matsuo et al. 1988,2003). 

The similarity between the thermal behavior of dynamic dichroism signals at 2930 cm" given in Figure 43 and that of dynamic tensile moduli, E and E", described in Section 2.30.3.2.2, is striking. The elastic storage modulus E T) drops precipitously around Tg of the system when the temperature is raised, whereas the viscous loss modulus E"(T) exhibits a... 

Dynamic Mechanical Properties. Figure 15 shows the temperature dispersion of isochronal complex, dynamic tensile modulus functions at a fixed frequency of 10 Hz for the SBS-PS specimen in unstretched and stretched (330% elongation) states. The two temperature dispersions around — 100° and 90°C in the unstretched state can be assigned to the primary glass-transitions of the polybutadiene and polystyrene domains. In the stretched state, however, these loss peaks are broadened and shifted to around — 80° and 80°C, respectively. In addition, new dispersion, as emphasized by a rapid decrease in E (c 0), appears at around 40°C. The shift of the primary dispersion of polybutadiene matrix toward higher temperature can be explained in terms of decrease of the free volume because of internal stress arisen within the matrix. On the other... 

Figure 15. Temperature dispersion of isochronal complex, dynamic tensile modulus function at a fixed frequency of 10 Hz, observed for the SBS-PS specimen at unstrethed and stretched (330% elongation) states...

FIG. 13.87 Diagram of the specific tenacity (specific dynamic tensile modulus (Ea/p), for modern high-performance filaments. The diagonal lines have the indicated ratio, which is the theoretical elongation at break (fractional) high-performance yarns have refractory materials have values between 0.025 and 0.005. (ty = tire yarn). 

A polyester first prepared by Jackson (3) (20 mol% modified p-hydroxybenzoic acid poly(phenyl-1,4-phenylene terephthalate)) was spun at 320°C and fibers were characterized "as-made". The dynamic tensile modulus as a function of DR is seen in Figure 4 and shows that very high values are obtained at even low DR-values. 

Mechanical Properties. Dynamic mechanical properties were determined both in torsion and tension. For torsional modulus measurements, a rectangular sample with dimensions of 45 by 12.5 mm was cut from the extruded sheet. Then the sample was mounted on the Rheometrics Mechanical Spectrometer (RMS 800) using the solid fixtures. The frequency of oscillation was 10 rad/sec and the strain was 0.1% for most samples. The auto tension mode was used to keep a small amount of tension on the sample during heating. In the temperature sweep experiments the temperature was raised at a rate of 5°C to 8°C per minute until the modulus of a given sample dropped remarkably. The elastic component of the torsional modulus, G, of the samples was measured as a function of temperature. For the dynamic tensile modulus measurements a Rheometrics Solid Analyzer (RSA II) was used. The frequency used was 10 Hz and the strain was 0.5 % for all tests. 

Figure 11 compares the low-temperature modulus characteristics of representative fiber-coating (buffer) materials of the three types described earlier. The figure depicts the dynamic tensile modulus as a function of frequency at -40 °C. The data were obtained on films of the materials by using a Rheometrics rotational dynamic spectrometer operated over the frequency range from 10 to 10 rad/s. Curves obtained at different temperatures were shifted both horizontally and vertically in accord with established linear... 

A number of polymer films and fibers have been examined as a function of temperature. Dynamic measurements were made at 11 Hz, l C/min heating rate in nitrogen atmosphere. Data point of dynamic tensile modulus and tan 6 were obtained at 1°C increments. This is essentially a continuous monitoring of the changes in storage modulus, loss modulus, and tan 6 and length of sample. 

The effects of high humidity on the dynamic mechanical properties and thermal transitions of a commercial nylon-epoxy adhesive have been reported by Butt and Cotter." Exposure of the cured adhesive to 43°C and 97% RH for times ranging from 142 h to 2,040 h resulted in a substantial decrease (as much as 82%) in the complex dynamic tensile modulus. Some of the results of these authors are shown in Table I. The thermal transitions... 

Table I. Effect of Exposure to High Humidity on the Complex Dynamic Tensile Modulus (E ) of a Cured Nylon-Epoxy Adhesive"...

As an alternative, one can employ as well the complex dynamic tensile modulus E (u)j defined as... 

As will be noted no molecular anisotropies and no effects due to size and size distribution of the particles of the discrete phase are recognized. Through E = 2(1 + p)G Eq. (2.5) can be used to predict also the complex tensile modulus. A good example for the applicability of Eq. (2.5) is furnished by the experimental data obtained by Dickie et al. [75]. For the dynamic tensile modulus of a physical mixture (polymer blend) of 75% by weight polymethylmethacrylate (PMMA, continuous phase) and 25% butylacrylate (PBA, discrete phase) within experimental error correspondence of calculated and measured data was obtained (Fig. 2.13,... 

Fig. 2.13. Complex dynamic tensile modulus of blends (solid line) and graft copolymers (circles) respectively of polymethyl-methacrylate (75% by weight) and polybutylacrylate (25% by weight) at 110 Hz (after [75, 761).

Nylon-6. Nylon-6—clay nanometer composites using montmorillonite clay intercalated with 12-aminolauric acid have been produced (37,38). When mixed with S-caprolactam and polymerized at 100°C for 30 min, a nylon clay—hybrid (NCH) was produced. Transmission electron microscopy (tern) and x-ray diffraction of the NCH confirm both the intercalation and molecular level of mixing between the two phases. The benefits of such materials over ordinary nylon-6 or nonmolecularly mixed, clay-reinforced nylon-6 include increased heat distortion temperature, elastic modulus, tensile strength, and dynamic elastic modulus throughout the —150 to 250°C temperature range. 

Dynamic properties are more relevant than the more usual quasi-static stress-strain tests for any application where the dynamic response is important. For example, the dynamic modulus at low strain may not undergo the same proportionate change as the quasi-static tensile modulus. Dynamic properties are not measured as frequently as they should be simply because of high apparatus costs. However, the introduction of dynamic thermomechanical analysis (DMTA) has greatly widened the availability of dynamic property measurement. 

Aside from this, the literature on the subject has largely been concerned with dynamic mechanical properties where experiments have been performed to gather data consisting of loss tangent (tan d) and storage tensile modulus (E). Rather than being... 

Dynamic-Mechanical Measurement. This is a very sensitive tool and has been used intensively by Nielsen (17) and by Takayanagi (18). When the damping curves from a torsion pendulum test are obtained for the parent components and for the polyblend and die results are compared, a compatible polyblend will show a damping maximum between those of the parent polymers whereas the incompatible polyblend gives two damping maxima at temperatures corresponding to those of the parent components. Dynamic mechanical measurement can also give information on the moduli of the parent polymer and the polyblend. It can be shear modulus or tensile modulus. If the modulus-temperature curve of a polyblend locates between those of the two parent polymers, the polyblend is compatible. If the modulus-temperature curve shows multiple transitions, the polyblend is incompatible. 

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

The theory is not limited in its application to the transient properties of amorphous polymers it can be used to make molecular interpretation and prediction of the dynamic viscoelastic properties of crosslinked polymers [24] as well. According to the Fourier-Laplace transformation, the complex tensile modulus can be separated into the real and imaginary parts... 

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