ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
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:
Linear 1,2-polybutadiene is cross-linked near its glass transition temperature by γ-irradiation while strained in simple extension with a stretch ratio λo. After release, the sample retracts to a state of ease (λs). From λo, λs, and stress-strain measurements in extension from the state of ease, the concentrations of network strands terminated by trapped entanglements (vN) and by cross-links (vx) can be calculated. For vx/vN ≡ R′o 〉 1, retraction to the state of ease is rapid. For R0o ≃ 0.3 or less, retraction is slow and extends over many logarithmic decades of time scale. When an eased sample is stretched to λo where the cross-links do not contribute to stress, the subsequent stress relaxation of the entanglement network toward equilibrium is also very slow if R′o is small. The slow timedependent processes are attributed to a high proportion of untrapped entanglements on dangling branched structures. The concentration of trapped entanglement strands, vN, can also be calculated from the equilibrium stress at λo. The fraction of trapped entanglements agrees rather well with the predictions of the theory of Langley.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760190408
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