ISSN:
1436-2449
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Summary The dynamic mechanical behaviour of fully cured off-stoichiometric epoxy systems prepared from poly(oxypropylene)diamine (Jeff D-400) or -triamine (Jeff T-403) and diglycidyl ether of Bisphenol A (DGEBA) with initial ratios of reactive amine (NH2) and epoxide (E) groups, r H= (2[NH2])/[E] ranging from 2.4 to 4.3 was investigated in the gelation threshold region. The evolution of the dynamic behaviour of two stoichiometric samples with r H= 1 with reaction time, t r , was also studied. The critical ratios for gelation, r c H, of fully cured samples were determined from extraction experiments (r c H= 2.54 for Jeff D-400/DGEBA and r c H= 4.15 for Jeff T-403/DGEBA systems, respectively). For both stoichiometric critical gel (CG) structures obtained by changing the curing time t r , a power-law rheological behaviour (G′∼ G″∼ωn, G′ and G″ are the storage and loss moduli, respectively, ω is angular frequency and n is a critical exponent) with the loss tangent, tan δ= G″/G′ independent of frequency, was found. On the other hand, both CG off-stoichiometric systems with r c H ratios show a small dependence of tan δ on ω, so that the critical power-law behaviour is not exactly obeyed. More complex CG structure in these samples, formed due to differences in the structure growth process, was suggested to account for violation of the power-law behaviour.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s002890050490
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