Study of the Viscoelastic Behavior and Molecular Weight Distribution of Polyisobutylene

1954 ◽  
Vol 27 (2) ◽  
pp. 393-414
Author(s):  
Kensal E. Van Holde ◽  
J. W. Williams
Keyword(s):  
Molecular Weight ◽  
Experimental Investigation ◽  
Stress Relaxation ◽  
Mechanical Behavior ◽  
Weight Distribution ◽  
Viscoelastic Behavior ◽  
Elastic Behavior ◽  
High Polymer ◽  
Relaxation Experiments ◽  
Mechanical Studies

Abstract The viscoelastic behavior of linear high polymers has commanded considerable attention in recent years. The very thorough studies by Fox and Flory of the melt viscosity of polystyrene and polyisobutylene, the stress relaxation experiments of Tobolsky and coworkers, and dynamic-mechanical studies by Ferry have contributed greatly to our knowledge of the mechanical behavior of these interesting substances. However, there are many facets of this subject which have not received thorough experimental investigation. In particular, there has been no detailed study of the effect of molecular weight and polydispersity on the elastic behavior of viscoelastic materials. It was felt, therefore, that a study of the viscoelastic behavior of a series of very carefully characterized samples of a representative linear high polymer would contribute substantially to the understanding of this subject. The polymer chosen was polyisobutylene, which displays both flow and elastic behavior at room temperatures.

Study on Nonlinear Viscoelastic Properties of Asphalt Mixture Based on Stress Relaxation Test

2014 ◽  
Vol 563 ◽  
pp. 48-52
Author(s):  
Lei Chen ◽  
Zhi Xin Yu ◽  
Wei Ping Cui ◽  
Li Juan Qin
Keyword(s):  
Stress Relaxation ◽  
Asphalt Mixture ◽  
Viscoelastic Behavior ◽  
Exponential Model ◽  
Relaxation Test ◽  
Asphalt Binders ◽  
Stress Relaxation Test ◽  
Nonlinear Viscoelastic ◽  
Low Temperature Cracking ◽  
Relaxation Experiments

Development of normal stress in the direction perpendicular to the asphalt mixture is an important feature of the nonlinear viscoelastic behavior of asphalt binders. In this paper, this phenomenon was studied with the help of stress-relaxation experiments in torsion.  Results indicate that stress relaxation test by controlling strain could be used to evaluate the stress relaxation ability of asphalt mixture. With the aging degree of asphalt mixtures increased, the low temperature cracking resistance got worse; the higher the temperature is, the faster the stress relaxed; the smaller the initial strain, the worse the stress relaxation ability also. The viscoelasticity of asphalt mixture could be simulated by exponential model fractional and the experiments well supported the modeling results.

Comparison of a Novel Nonlinear Viscoelastic Finite Ramp Time Correction Method to a Heaviside Step Assumption

2011 ◽  
Author(s):  
Kevin L. Troyer ◽  
Christian M. Puttlitz
Keyword(s):  
Stress Relaxation ◽  
Soft Tissues ◽  
Viscoelastic Behavior ◽  
Relaxation Modulus ◽  
Correction Method ◽  
Nonlinear Viscoelastic ◽  
Instantaneous Strain ◽  
Relaxation Experiments ◽  
Time Correction

Connective soft tissues exhibit time-dependent, or viscoelastic, behavior. In order to characterize this behavior, stress relaxation experiments can be performed to determine the tissue’s relaxation modulus. Theoretically, the relaxation modulus describes the stress relaxation behavior of the tissue in response to an instantaneous (step) application of strain. However, a step increase in strain is experimentally impossible and a pure ramp load is intractable due to the inertial limitations of the testing device. Even small deviations from an instantaneous strain application may cause significant errors in the determination of the tissue’s relaxation modulus.

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