Macromolecules under tension

The Basic Model for the Behaviour of Carbon Black in Rubbers Single Macromolecules Under Tension... 

It has been demonstrated 54) that the dependency of viscosity upon elongation velocity varies significantly in its character with alteration of the lateral (transverse) mobility of macromolecules. In case there is no lateral mobility of macromolecules, the longitudinal viscosity strictly decreases under tension (see Fig. 11) which corresponds to prognostications proceeding from the Doi-Edvards theory. In case there is a lateral mobility of macromolecules, an insignificant maximum or monotonous increase in longitudinal viscosity of the medium with increase in extension velocity is observed. 

If a force is applied to wood within the proportionality limits, the wood will bend and if the force is released, the wood returns to its original form with an elastic recovery. In contrast, if the wood is dried under stress, a substantial superposition of stresses occurs in conjunction with the drying and shrinking process. Since the ordering of macromolecules or larger structural elements under tension is different from those under compression, as the water molecules are removed, new hydrogen bonds can form between different subunits of the structure to support the distorted structure in its new form. 

Brown, D. and Clarke, J. H. R. (1991) Molecular dynamics simulation of an amorphous polymer under tension 1. Phenomenology, Macromolecules, 24, 2075-2082. 

In the processing of plastic masses the destruction is traditionally considered as a negative factor deteriorating physical and mechanical properties of products and manufacturers try to avoid it in every possible way. Mechanical destruction of molten polymers takes place, primarily, under the action of shear strains effectuating the tension of macromolecules 65-661 in this case, molecules with a high molecular mass... 

Figure 9.13 Number averaged diameter of droplets d of polypropylene (M = 60,000) in polystyrene (M = 200,000) as a function of wt% polypropylene mixed in three different mixers at a nominal shear rate of around 65 sec and T — 200°C. The viscosities of the the PP and PS under these conditions are 840 and 950 Pa-s, respectively. The interfacial tension F is 5.0 dyn/cm. The error bars represent the distribution of droplet sizes, and they encompass one standard deviation in each direction from the mean. The deviation from the Taylor limit at low concentrations is attributed to non-Newtonian effects, while the increase in droplet size at higher concentrations is attributed to droplet coalescence. Note that similar droplet sizes are obtained in all three different mixers. (Reprinted with permission from Sundararaj and Macosko, Macromolecules 28 2647. Copyright 1995, American Chemical Society.)...

The linking macromolecules, having more or less strength conformations, traverse the inter-crystalline domains. Under the deformation conditions, these ones gradually adopt stretched conformations, are tensioned, and suffer the homolytical splitting. Therefore, under the creep fatigue conditions, the fracture process is directly influenced not by the applied stress but the induced deformation. An important effect is played by the increase of solicitation rate, due to the fact that the stress duration becomes comparable with the relaxation time. The overtensioned macromolecules are not able... 

We next show the process of solvent evaporating from the surface covered by adsorbed macromolecules. There are two forces attached to macromolecule the force of attraction to the solid surface and the force of the surface tension between the solution and air. Under the action of these forces, the deformation of macromolecule takes place and it becomes flatter. 

Ma X, Sauer JA, Hara M. Poly(methyl methacrylate) ionomers. 2. Deformation modes under simple tension. Macromolecules 1995 28(16) 5526-5534. 

Hara M, Jar P. Deformation and fracture of ionomers under simple tension. 1. Sulfonated polystyrene film from THE solution. Macromolecules 1988 21 3187. 

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