Mechanical modulus

Content of Ot-Olefin. An increase in the a-olefin content of a copolymer results in a decrease of both crystallinity and density, accompanied by a significant reduction of the polymer mechanical modulus (stiffness). Eor example, the modulus values of ethylene—1-butene copolymers with a nonuniform compositional distribution decrease as shown in Table 2 (6). A similar dependence exists for ethylene—1-octene copolymers with uniform branching distribution (7), even though all such materials are, in general, much more elastic (see Table 2). An increase in the a-olefin content in the copolymers also results in a decrease of their tensile strength but a small increase in the elongation at break (8). These two dependencies, however, are not as pronounced as that for the resin modulus. 

Mechanical Modulus Yield and tensile strength Hardness Fracture toughness Fatigue strength Creep strength Damping... 

Thermal analysis techniques are designed to measure the above mentioned transitions both by measurements of heat capacity and mechanical modulus (stiffness). 

Fig.6 Temperature dependence of the mechanical modulus, G and loss tangent, tan 5, at 1 Hz, for poly(cyclohexyl methacrylate) (from [5])...

The 13C NMR crosslink density results were compared with the crosslink density obtained by the mechanical measurements. In the determination of the crosslink density by mechanical methods, the contributions of the topological constraints on the results were neglected and the density was expressed as G/2RT. The 13C and mechanical-crosslink densities were obtained for both sulfur and dicumyl peroxide (DCP)-cured samples to ensure the effect of wasted crosslinks (pendent or intramolecular type sulfurisations), which are expected in the typical sulfur-vulcanisation of NR. In the major range of crosslink densities, the crosslink densities for those two systems are described by the same linear function with a slope of 1.0. Based on these observations, it is shown that the crosslink density of the sulfur-vulcanised NR as determined by 13C is identical with the true crosslink density, and the influence of the wasted or ineffective crosslinks (pendent and cyclic crosslinks) and chain ends is negligible. However, this conclusion seems to be only valid if the effect of topological constraints or entrapped entanglements on the mechanical modulus is negligible which is rarely the case in real systems. 

It was found in both experiments and simulation results that the aspect ratio of the CNTs plays a significant role. Usually it is believed that the chirality of CNTs have minor effects on the mechanical properties of the CNT/polyethylene composite. While the increased orientation ordering leads to an enhancement of the mechanical modulus of the nanocomposite materials, and such... 

Figure 1. Typical Dynamic Mechanical Modulus and Loss Tangent a Function of Temperature.

Figure 1. Typical dynamic mechanical modulus and loss tangent data as a junction of temperature. Key a, glassy region b, transition region and c, rubbery...

Sensor The swellability of superabsorbent polymer gels, their mechanical modulus and rubbery character, and their sensitivity to changes in water content, pH, and ionic strength make them suitable for use in various sensing systems. 

M and G are very similar. More importantly G also shows a second break in the same region where the secondary relaxation occurs (around 0°C). Although this observation of relaxation of mechanical modulus suggest that there is some local reorganization which contributes to modulus, no enthalpy relaxation associated with (5 processes has been reported. (5 processes generally exhibit Arrhenius behaviour over wide ranges of temperature in contrast to a processes which are non-Arrhenius, / -relaxations also follow KWW function. But the relaxation characteristics associated with / processes in electrical and mechanical properties can be different. 

J. K. Kruger, W. Possart, R. Bactavatcha-lou, U. Muller, T. Britz, R. Santuary, P. Alnot (2004). Gradient of the mechanical modulus in glass-epoxy-metal joints as measured by Brillouin microscopy. /. Adhesion, 80, 585—599. 

The mechanical modulus can be measured under different types of load-shear, flexure, and so on. The measured modulus can be expressed as the storage modulus (related to the... 

Dynamic Mechanical Analysis (DMA) is concerned with the measurement of the mechanical properties (mechanical modulus or stiffness and damping) of a specimen as a function of temperature. DMA is a sensitive probe of molecular mobility within materials and is most commonly used to measure the glass transition temperature and other transitions in macromolecules, or to follow changes in mechanical properties brought about by chemical reactions. 

Kim, I. H., and Jeong, Y G. (2010], Polylactide/exfoliated graphite nanocomposites with enhanced thermal stability, mechanical modulus, and electrical conductivity. J. Polym. Sci. Polym. Phys., 8, pp. 850-858. 

A quantitative treatment of the specular reflection spectra obtained from the surface of uniaxially drawn PETP samples was performed. A procedure for correcting for the effect of surface irregularities is presented, and an overall orientation function based on the orientation and content of trans-conformers is calculated. The results are correlated with mechanical modulus and crystallinity values. In addition, an unconventional dichroic ratio parameter based on a combination of two major bands is proposed. Results obtained from the Kramers-Kronig analysis and directly from the reflection spectra are discussed. Both are compared with the overall orientation function obtained before. 21 refs. 

The mechanical characteristics of SPU - tensile strength, o, (the maximum stress calculated on the initial cross-section area) and the relative critieal deformation, 8, (relative deformation at the stress o ) have been evaluated for the strain rate, v = 0.28 s. The mechanical modulus, E , was evaluated from the initial, linear part of the strain diagrams. 

To lower hardness of polyurethane requires plasticizer capable to dissolve hard blocks of polymer. This causes the decrease in the content of a hard microdispersion phase in SPU and, as a result, the decrease in a mechanic modulus and hardness of material. 

Thermal analysis techniques are designed to measure the above mentioned transitions both by measurements of heat capacity and mechanical modulus (stiffness). Refer to Differential Scanning Calorimetry and Thermogravimetric Analysis. (Source Cheremisinoff, N.P. Polymer Characterization Laboratory Techniques and Analysis, Noyes Publishers, New Jersey, 1996). 

TMA consists of a quartz probe which rests on top of a flat sample (a few mm square) in a temperature controlled chamber. When set up in neutral buoyancy then as the temperature is increased the probe rises in direct response to the expansion of the sample yielding thermal expansion coefficient versus temperature scans. Alternatively, with a penetration probe under dead loading a thermal softening profile is obtained (penetration distance versus temperature). Although this is a simple and versatile experiment, it gives only a semi-quantitative indication of mechanical modulus versus temperature. 

Carbon nanotubes (CNT) have attracted great attention due to very high mechanical modulus and strength, ultra-lightweight, and unique optical and electronic characteristics. The first two features make CNT a suitable nano-reinforcement for polymer-based... 

The mechanical modulus can be measured under different types of load shear, flexure, and so on. The measured modulus can be expressed as the storage modulus (related to the stiffness of the material) and the loss modulus (related to the viscous behavior or softness of the material) under the various types of loads. DMA is used to follow the curing of polymers and cross-linking of polymers and to measure glass transition tanperatures. 

In order to investigate the viscoelastic behavior of crosslinked EVA, rheological measurements were made to determine at what temperatures the phase transitions occur and their effect on the dynamic mechanical modulus. The complex dynamic modulus E expression is given by Eq. (6). 

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