Elasticity and Strength

This is similar to the variation in the skin hardening and softening as discussed in Sect. 24.3. For instance, the Y value of ZnO nanobelts of 50-140 nm thick and 

The elastic modulus of single polymer nanofibers increases exponentially as the diameter of the polymer nanofibers decreases to a few tens of nanometers (Fig. 26.2b) [71] being opposite to the measured trend of polymers using the indentation method. The unusual behavior of nanobeams corresponded to the microstructure and confinement [68]. 

The defect-free nanotubes are ideal cases of cylindrical nanocavities with defect-free shells that are much stronger than the bulk materials unless excessive defects are presented in the unreconstructed walls [12], Defects in the walls of nanotubes serve as centers initiating the failure in particular for the plastic 

---

Mechanical Properties. Mechanical properties (4,6,55) are important for a number of steps in coal preparation from mining through handling, cmshing, and grinding. The properties include elasticity and strength as measured by standard laboratory tests and empirical tests for grindabiUty and friabihty, and indirect measurements based on particle size distributions. 

With most homopolymers and copolymers the apparent viscosity is less dependent on temperature and shear stress (up to 10 dyn/cm ) than that of the polyolefins, thus simplifying die design. On the other hand the melt has a low elasticity and strength and this requires that extruded sections be... 

Cox, H.L., The elasticity and strength of paper and other fibrous materials, liritish Journal of Applied Physics, 1952, 3, 52. 

Other properties such as solubility, viscosity (above Tg and T ), modulus of elasticity, and strength are highly dependent on the polymer architecture, or pattern of the interconnections between units. In other words, these properties vary to a marked degree with changes in the molecular weight and in the degree of cross-linking. 

Powers, J. M., Farah, J. W. Craig, R. G. (1976). Modulus of elasticity and strength properties of dental cements. Journal of the American Dental Association, 92, 588-91. 

Many of the polymers formed from conjugated dienes are elastic and are used to manufacture synthetic rubbers. The raw polymers usually are tacky and of little direct use, except as adhesives and cements. They are transformed into materials with greater elasticity and strength by vulcanization, in which the polymer is heated with sulfur and various other substances called accelerators, with the result that the polymer chains become cross-linked to one another by carbon-sulfur and carbon-carbon bonds. Some of the cross-linking appears to occur by addition to the double bonds, but the amount of sulfur added generally is insufficient to saturate the polymer. With large proportions of sulfur, hard rubberis formed such as is used in storage-battery cases. 

Most of the commonly used degradable polymer scaffolds are mechanically strong, but for certain applications such as engineering muscles and tendons, which require considerable elasticity, these polymers are not optimal. Novel biodegradable polyesters have been developed with superior elasticity and strength that resemble vulcanized rubber and are hence termed as biorubber. Scaffolds made with these mechanically functional materials may be useful especially in engineering elastic tissue such as muscular-skeletal tissues and blood vessels. 

Friede (43) published a series of equations for calculating the depth of the corroded zone for concrete specimens exposed to carbonic acid attack as a function of the physical and mechanical properties of corroded and noncorroded specimens, i.e. density, volume, mass, modulus of elasticity and strength. The equations, however, do not take into consideration such factors as the composition of the concrete or the degree of attack to which it is subjected. In addition, the wide variation in test results, obtained from laboratory tests performed to verify the theoretically derived equations, limit their applicability. 

M. Kornfeld, Elasticity and Strength of Liquids, Verlag Technik, Berlin, 1952. 

Cox H.L. 1952. The elasticity and strength of paper and other fibrous materials. Br. Appl. Phys. 3 72. Crolet, J.M., Aoubiza B., and Meunier A. 1993. Compact bone numerical simulation of mechanical characteristics. /. Biomech. 26 677. 

How could you work out, if you wanted to, what kind of architectural style was typical of some period in history It turns out that you do not really have to study the aesthetic views of that epoch. All you need is just some knowledge of the mechanical properties, the elasticity and strength, of the building materials used at that time. 

Kraton polymers blended with polypropylene can provide films with elasticity and strength, puncture resistance, low permanent set to prevent finger marks and indentation due to handling, high oxygen permeability, moisture-barrier properties, and clingJ ]... 

G. Sines, Elasticity and Strength, Allyn and Bacon, Boston (1969). 

The effect of the particle adhesion on the elasticity and strength of gels has been described (Chapter 11). From such measurements, values of the woik of adhesion have been calculated. ... 

---