Mechano-chemical conversions in highly oriented polymer systems during mechanical dispersion

Komissarov, S.A.; Baramboim, N.K.

doi:10.1016/0032-3950(69)90387-6

Cited by 7 publications

References 1 publication

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Temperature effect on polymer mechanochemistry

Casale¹

1975

J of Applied Polymer Sci

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SynopsisThe influence of temperature is a fundamental variable for the mechanochemical processes of high polymers. However, it is generally recognized that the effect of temperature in this process is not always direct, as in normal chemical reactions, but is mainly indirect involving change in the properties (principally elastic and viscous), in the physical state of the system, and consequently in the mechanism of rupture. The negative temperature coefficient has been considered a prime criterion of a mechanochemical reaction by many researchers. Recently, it has been suggested that the negative temperature coefficient is really due to the viscous heating durihg polymer deformation and the low thermal conductivity of polymers.The aim of this paper is to reevaluate the role of temperature on mechanically induced reactions of polymers. In light of evidences published in the last 30 years, the dependence of mechanochemical reaction on temperature must involve the overlapping of the following factors: 1) the usual positive dependence of rate on temperature, as predicted by Arrhenius equation; 2) the true experimental temperature, which depends on viscous heating and on thermostatting efficiency; and 3) the breaking tension a t the center of the polymer chain which is inversely dependent on temperature, i.e., greater a t the higher viscosity and the slower relaxation at the lower temperatures, this last factor being dominant in determining the characteristic negative temperature coefficient for polymer mechanochemistry.

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Temperature effect on polymer mechanochemistry

Casale¹

1975

J of Applied Polymer Sci

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Effects of mastication on the distribution of molecular weights and on the mechanical properties of native and commercial dental gutta percha (trans‐polyisoprene)

Arvanitoyannis

Blanshard

Kolokuris

1992

Polymer International

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Mastication of gutta percha (trans‐polyisoprene) resulted in the selective scission of molecules, producing a narrower distribution of lower molecular weights. The mechanical properties of the samples also underwent a significant change due to mastication. The greater the content of incompatible substances (salts and oxides) in commercial gutta percha. the more substantial were these effects. The atmosphere (air, N2, O2) in which the experiments were conducted yielded significantly different results. The decrease in molecular weight was far greater in an O2 atmosphere than under a current of nitrogen or air, owing to the combination of double bonds with O2.

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ESR study of radicals formed during tensile deformation of poly[p‐(2‐hydroxyethoxy) benzoic acid] fibers

Nagamura

Takayanagi

1974

J. Polym. Sci. Polym. Phys. Ed.

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Radical formation during tensile deformation of highly oriented poly[p‐(2‐hydroxyethoxy)benzoic acid] fibers was investigated by electron spin resonance. Stretching of fibers in vacuo and in a stream of nitrogen gas at room temperature generated a large number of radicals which increased rapidly with macroscopic strain, while stretching in air generated only a small number of radicals. The radicals formed in vacuo or in nitrogen decayed rather rapidly after introduction of air. The observed spectrum was apparently a triplet with a line separation of about 7.5 gauss and a small asymmetry. The inspection of the hyperfine structure, line separation, and total width of the spectrum and the comparison between the observed and the calculated spectrum based on a model substance proved that the observed species is a phenoxy type radical generated by rupture of main chains. A small asymmetry of observed spectrum was explained by anisotropy of the g‐tensor. The alkyl end‐radical generated together with one of the phenoxy type could not be detected, perhaps owing to its high reactivity.

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Mechano-chemical conversions in highly oriented polymer systems during mechanical dispersion

Cited by 7 publications

References 1 publication

Temperature effect on polymer mechanochemistry

Temperature effect on polymer mechanochemistry

Effects of mastication on the distribution of molecular weights and on the mechanical properties of native and commercial dental gutta percha (trans‐polyisoprene)

ESR study of radicals formed during tensile deformation of poly[p‐(2‐hydroxyethoxy) benzoic acid] fibers

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