ISSN:
1435-1536
Keywords:
Ethylene-propylene copolymers
;
crosslinking
;
irradiation
;
rheo-optical properties
;
crystallinity
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Summary The rheooptical behaviour of radiation crosslinked networks of four commercial ethylene-propylene (E-P) copolymers having different molecular masses and propylene contents from 20 to 35 mol. % was investigated in the main transition and rubbery regions.C p(T) of E-P copolymers prior to irradiation was determined in the range 240–370 K, and the degree of crystallinity was estimated. Crystallinity considerably affected the viscoelastic (mechanical, and particularly optical) behaviour of the networks with a lower propylene content (≈ 20 mol %) in the temperature range 120–338 K. Due to a form contribution of the crystallites to the birefringence, the stress-optical function exhibits a pronounced maximum depending on temperature and time connected with melting of the crystalline phase. In the rubbery region (T 〉 340 K) the dependence of the Mooney-Rivlin constantC 1 on the radiation doseD was the same for all series of networks; the composition of E-P copolymers and especially their molecular masses were reflected in the value of theC 2 parameter and in its dependence onD. Deep in the rubbery region, lightly crosslinked networks exhibited pronounced time dependences of mechanical and optical functions. The high values of extrapolated equilibrium parametersC 1 andC 2 e suggest an important contribution of trapped entanglements to the equilibrium modulus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01525013
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