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Title: Structure Within Thin Epoxy Films Revealed by Solvent Swelling: A Neutron Reflectivity Study

Abstract

Structure within thin epoxy films is investigated by neutron reflectivity (NR) as a function of resin/crosslinker composition and cure temperature. Variation in the crosslink density normal to the substrate surface is examined by swelling the films with the good solvent d-nitrobenzene (d-NB). The principle observation is a large excess of d-NB near the air surface. This is not a wetting layer,but rather indicates a lower crosslink density in the new-surface region. This effect is due to preferential segregation of the crosslinker to the air surface, driven by the lower surface energy of the crosslinker relative to the epoxide oligamers. The magnitude of the effect is a function of composition and cure temperature. Exclusion of d-N13from the region immediately adjacent to the substrate surface is also observed, possibly indicating a tightly bound layer of epoxy. Regarding swelling in the bulk of the films, the behavior is non-symmetric with departure from the stoichiometric ratio. The films deficient in curing agent show greater equilibrium swelling and faster swelling kinetics than the films with an excess of curing agent.

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Sandia National Labs., Albuquerque, NM (US); Sandia National Labs., Livermore, CA (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
9495
Report Number(s):
SAND99-2010J
TRN: AH200124%%290
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Journal Article
Journal Name:
Macromolecules
Additional Journal Information:
Other Information: Submitted to Macromolecules; PBD: 3 Aug 1999
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; CURING; EPOXIDES; NEUTRON DIFFRACTION; REFLECTIVITY; SEGREGATION; SOLVENTS; SUBSTRATES; SURFACE ENERGY; SWELLING; CROSS-LINKING

Citation Formats

Yim, H., Kent, M., McNamara, W.F., Ivkov, R., Satija, S., and Majewski, J. Structure Within Thin Epoxy Films Revealed by Solvent Swelling: A Neutron Reflectivity Study. United States: N. p., 1999. Web. doi:10.1021/ma990990c.
Yim, H., Kent, M., McNamara, W.F., Ivkov, R., Satija, S., & Majewski, J. Structure Within Thin Epoxy Films Revealed by Solvent Swelling: A Neutron Reflectivity Study. United States. doi:10.1021/ma990990c.
Yim, H., Kent, M., McNamara, W.F., Ivkov, R., Satija, S., and Majewski, J. Tue . "Structure Within Thin Epoxy Films Revealed by Solvent Swelling: A Neutron Reflectivity Study". United States. doi:10.1021/ma990990c. https://www.osti.gov/servlets/purl/9495.
@article{osti_9495,
title = {Structure Within Thin Epoxy Films Revealed by Solvent Swelling: A Neutron Reflectivity Study},
author = {Yim, H. and Kent, M. and McNamara, W.F. and Ivkov, R. and Satija, S. and Majewski, J.},
abstractNote = {Structure within thin epoxy films is investigated by neutron reflectivity (NR) as a function of resin/crosslinker composition and cure temperature. Variation in the crosslink density normal to the substrate surface is examined by swelling the films with the good solvent d-nitrobenzene (d-NB). The principle observation is a large excess of d-NB near the air surface. This is not a wetting layer,but rather indicates a lower crosslink density in the new-surface region. This effect is due to preferential segregation of the crosslinker to the air surface, driven by the lower surface energy of the crosslinker relative to the epoxide oligamers. The magnitude of the effect is a function of composition and cure temperature. Exclusion of d-N13from the region immediately adjacent to the substrate surface is also observed, possibly indicating a tightly bound layer of epoxy. Regarding swelling in the bulk of the films, the behavior is non-symmetric with departure from the stoichiometric ratio. The films deficient in curing agent show greater equilibrium swelling and faster swelling kinetics than the films with an excess of curing agent.},
doi = {10.1021/ma990990c},
journal = {Macromolecules},
number = ,
volume = ,
place = {United States},
year = {1999},
month = {8}
}