Premium
Low temperature cure of epoxy thermosets attaining high T g using a uniform microwave field
Author(s) -
Hubbard Robert L.,
Michael Strain S.,
Willemsen Connor,
Tyler David R.
Publication year - 2016
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.44222
Subject(s) - epoxy , thermosetting polymer , curing (chemistry) , materials science , cure rate , glass transition , fourier transform infrared spectroscopy , composite material , microwave , vitrification , polymer chemistry , chemical engineering , polymer , medicine , physics , surgery , quantum mechanics , engineering , andrology
It is demonstrated for the first time that an epoxy thermoset resin can be cured at temperatures well below its T g ∞ . This study compared the use of a uniform variable frequency microwave (VFM) field to standard oven curing at temperatures above and below T g ∞ . Using T g , tan δ, modulus, and FTIR measurements, it is shown that the reaction of BFDGE with MDA to attain a product with T g ∞ of 133 °C is achieved by VFM at temperatures from 100 to 140 °C; in contrast, the thermal cure normally requires 170 °C to attain the same T g ∞ and the same extent of cure. By following the pregel cure reaction with 13 C‐NMR spectroscopy, it was determined that the lower cure temperatures of VFM cure predominately lead to chain extension and smaller amounts of crosslinking compared to the thermal cure. To explain these results, it is suggested that, after gelation, with VFM cure there is higher mobility from dipole rotations that continues the cure to completion without vitrification. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44222.