ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A study is made of the behavior under constant shear stress of several carefully characterized samples of polyisobutylene. The materials used are whole polymers and fractions obtained from these by dractional precipitation. As a first step in the characterization, the intrinsic viscosity of each is determined. It is shown that the samples cover a molecular weight range from 1 × 105 to 1 × 106. To provide a more detailed characterization, sedimentation equilibrium experiments are performed with several of the polyisobutylenes. These experiments yield values of several average molecular weights for each polymer, from which data an approximation to the molecular weight distribution can be made. It is pointed out that the whole polymers of isobutylene are very polydisperse. The viscosity-average molecular weights calculated from these experiments are in good agreement with the results of the intrinsic viscosity measurements. The viscoelastic behavior of some of these polymers is then studied by means of creep and recovery experiments. The melt viscosity is determined in two ways, from flow during creep and from the amount of nonrecoverable deformation after elastic recovery. The elastic recovery of the polyisobutylene samples is analyzed in some detail. A method for the reduction of data taken at several temperatures to a standard temperature, previously used for dynamic-mechanical properties and stress relaxation data, is shown to be applicable to elastic recovery data. Furthermore, the results of creep and recovery experiments can be superimposed in favorable cases. The steady-state elastic compliance is evaluated, and errors in its determination discussed. The results would seem to indicate that this quantity depends, at least in part, upon the degree of polydispersity of the polymer. This dependence appears to mask any direct variation with average molecular weight. Finally, it is shown that an average retardation time is directly proportional to the melt viscosity of the polymer.
Additional Material:
17 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1953.120110307
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