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Influence of cross-linking on the segmental dynamics in model polymer networks (2000)

Kramarenko, V. Yu ; Ezquerra, T. A. ; Šics, I. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 113 (2000), S. 447-452

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: In an attempt to study the specific influence of cross-linking on the α relaxation in polymer networks, a series of model heterocyclic polymer networks (HPN) with well-defined cross-link densities and constant concentration of dipolar units were studied. Model HPN systems were prepared by simultaneous trimerization of 1,6-hexamethylene diisocyanate (HMDI) and hexyl isocyanate (HI). These HPN systems were characterized by dielectric relaxation spectroscopy in the 10−1 Hz〈F〈105 Hz frequency range and in the 123 K〈T〈493 K temperature interval. The α relaxation in these systems depends on network density and shifts toward higher temperatures as the cross-link density increases for high HMDI/HI ratios. Discussion of the α-relaxation shape in light of recent models indicates that segmental motions above the glass transition systematically experience a growing hindrance with increasing degree of cross-linking. Description of the temperature dependence of relaxation times according to the strong–fragile scheme clearly shows that fragility increases as polymer network develops. © 2000 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.481809

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Mechanical properties of heterocyclic polymer networks (1993)

Privalko, V. P. ; Kramarenko, V. Yu. ; Maslak, Yu. V. ; [et al.]

Springer

Colloid & polymer science 271 (1993), S. 322-327

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ISSN: 1435-1536

Keywords: Young's modulus ; bulk modulus ; Poisson's ratio ; linear expansivity ; isocyanoureate cycles ; oxazolidone cycles ; network density

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: Abstract Heterocyclic networds prepared by copolymerization of oligomeric epoxy rubber (ER) with different amounts of hexamethylene diisocyanate (HMDI) were characterized by room-temperature static Young's and bulk moduli, as well as by measurements of dynamic Young's modulus and linear thermal expansivity in the temperature interval 293–503 K. It was concluded that the major factor affecting thermoelastic properties of these networks is the relative content of three-arm, six-membered isocyanoureate rings which determine the apparent overall network density, and of two-arm, five-membered oxazolidone rings which act as a sort of “internal diluent”.