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The effect of curing of unsaturated polyester resin on the dynamic relaxation time
Author(s) -
Alperstein D.,
Narkis M.,
Siegmann A.,
Binder B.
Publication year - 1995
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760350904
Subject(s) - curing (chemistry) , materials science , activation energy , dielectric , composite material , relaxation (psychology) , polyester , dynamic relaxation , stress relaxation , chemistry , creep , psychology , social psychology , geometry , mathematics , optoelectronics
The effect of hot curing of unsaturated polyester resin on the dynamic relaxation time was studied using dielectric measurements along with two dynamic mechanical measurement methods. It was found that the dynamic response during cure was a material frequency dependent property and did not depend on the measurement method. All relaxation times, measured during cure, by all three measurement methods used, converged to a single equation: τ( t ) av = at b where t = curing time, a, b =constants. The increase of the relaxation time during cure followed the same trend as a friction factor, which was found to increase with conversion. The crosslinking density was found to increase slowly with conversion, while the relaxation time increased exponentially. These two different modes of behavior during cure explain the high resolution of dynamic measurements as a cure monitoring tool, which can easily detect small curing changes. This behavior of the relaxation time was explained by the sharp rise of activation energy due to a parallel decrease of free volume at high conversion.