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Effects of frequency, molecular weight and thermal oxidation on the dynamic mechanical response of poly (ethylene oxide)
Author(s) -
Bigger S. W.,
Scheirs J.,
Delatycki O.,
Billingham N. C.
Publication year - 1991
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/pi.4990260310
Subject(s) - materials science , dynamic mechanical analysis , crystallinity , glass transition , oxide , polymer , ethylene oxide , amorphous solid , polymer chemistry , thermal oxidation , quenching (fluorescence) , thermal analysis , analytical chemistry (journal) , chemical engineering , composite material , thermal , thermodynamics , chemistry , organic chemistry , copolymer , fluorescence , physics , quantum mechanics , engineering , metallurgy
The technique of dynamic mechanical thermal analysis (DMTA), operated in the dual cantilever mode, was used to characterize the effects of frequency, crystallinity, molecular weight (MW) and the extent of thermal oxidation on the dynamic mechanical response of poly(ethylene oxide) (PEO). The glass transition temperature ( T g ) of PEO (MW = 9 × 10 5 Dalton) was found to be −44°C. For PEO (MW = 1 × 10 5 Dalton) the T g is −39°C and this value increases by 2–9°C for every decade increase in the measuring frequency. Two minor, second‐order transitions of PEO are also discernible at −33 and 32°C. An inverse dependence of T g on molecular weight was found in the molecular weight range studied and this is contrary to the Fox‐Flory theory. It was also found that a partially crystalline sample is obtained despite very rapid quenching of PEO from the melt into liquid nitrogen. Thermal oxidation of PEO before processing leads to an increase in the amplitude of the loss tangent peak. This reflects the effect of oxidation products in restricting polymer crystallization and the subsequent increase in the amorphous fraction of the polymer. The position of the T g peak in PEO remains reasonably fixed with progressive ageing and this was attributed to crosslinking having occurred in addition to chain scission during thermal oxidation.