ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The PIR raw rubber samples, Ln-PIR and Ti-PIR, were subjected to molecular characterization, which shows that Ln-PIR contains microgel particles, but the least branching in its macromolecular chains; its cis-1,4 content is about 96% and molecular weight distribution is rather broad. The value of α in the Mark-Houwink viscosity equation for molecular weight Mη is determined as 0.70. The abnormal stress-relaxation behavior can be normalized by the introduction of an entanglement reduction factor, e.g., Mη/Mc for maximum relaxation time. This reduction is subsequently verified by evaluating the molecular weight dependence on bulk viscosity with 3.45th power. The starting of a yield process is equivalent to that of a disentanglement process, since both processes have approximately the same activation energy, 8 kJ/mol. For the onset of yield or of entanglement, the critical molecular weight Mc as estimated independently by yield strength method or by relaxation spectrum is equal to (5.4 ± 0.2) × 104. It is confirmed by the reduced yield strength method by calculating Me from the equation Me = 3gNρRT/EeN with gN = 1.22 and then by extrapolation, where EeN is the equilibrium modulus due to entanglement.
Additional Material:
16 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1985.070300133
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