Tensile strength of polymers

FIG. 13.62 Tensile strength of polymers, correlated with modulus. 

About the same time Flory (2) proposed that the tensile strength of polymers is related to the number average molecular weight. Vincent followed with an analysis of polymer mechanical property behavior as a... 

A plot depicting the effect of aging In water on the tensile strength of polymer A Is shown In Fig. 1. The plot Is characterized by an Initial slow decrease In strength with time which accelerates after 10 days. This Increase In the rate of tensile strength loss Is consistent with the autocatalytic nature of the hydrolysis reaction. The reaction generates an acid which In turn catalyzes further hydrolysis of the polyurethane XLL ... 

As shown In Fig. 2, tensile strength of polymer A decreases more rapidly Initially In methanol than In water even though aging In methanol Is conducted at 60 C (20 C lower than In water). The rate of property loss Is observed not to Increase with time. This Is expected since the degradation reaction In methanol (transesterification) Is not autocatalytic. The reduction of tensile elongation In the two media shows a similar behavior. 

Figure 10. Dependence of tensile strength of polymer A on molecular weight. Key aged in methanol at 60°C and a, aged in water at 80°C.

Method of test for tensile strength of polymer-modified mortar ... 

The tensile strength of polymers at first increases strongly, and then weakly with increasing molar mass (Figure 11-23). Below a certain critical molar mass, the tensile strength is practically zero. The transition from sharp to weak molar mass dependence is probably due to entanglements. At very... 

This results in formation of pendant urazole groups. The exact structure of the products, however, has not been fully established. The tensile strength of polymers improves considerably, but it is accompanied by a dramatic loss in molecular weight. Nevertheless, ene reagents like C-nitroso and activated azo compounds are very efficient in adding to rubber. They add in a few minutes at temperatures between 100-140 °C. In the case of the azo compound the addition can be greater than 90%. 

An equation to describe the tensile strength of polymers was introduced by Flory (1945) ... 

Hydrogen bonding makes a major contribution to the intermolecular interactions in PBU and the presence of H-bonds contributes to mechanical properties. As a result of the swelling, the concentration of elastically active chains in a labile network of elastomer is reduced. The theoretical evaluation of change in H-bond concentration in PBU on plasticization by a proton acceptor (DOS) shows that decrease in concentration of H-bonds occurs even with small amounts of plasticizer (< )i = 0.05 - 0.2). The density of a labile network determined by H-bonds decreases sharply and modulus and tensile strength of polymer decrease as well. Figures 10.71 and 10.72 show that the character of influence of a plasticizer on elastomer is similar for two very diiferent strain rates. This allows to carry out evaliration of the physical network density of elastomer under the non-equilibrium conditions of deformation using Eq. [10.33] as previously reported. ... 

Termonia, Y, Meakin, P. and Smith, P. (1985) Theoretical study of the influence of the molecular weight on the maximum tensile strength of polymer libers. Macromolecules, 18 2246-2252. 

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