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Title: Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent

Abstract

Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent strategies have reduced or eliminated such cure stress in thermoset polymers largely by exploiting chemical relaxation processes, wherein temporary cross-links or otherwise transient bonds are incorporated into the polymer network. In this paper, we explore an alternative approach, wherein physical relaxation is enhanced by the incorporation of organometallic sandwich moieties into the backbone of the polymer network. A standard epoxy resin is cured with a diamine derivative of ferrocene and compared to conventional diamine curing agents. The ferrocene-based thermoset is clearly distinguished from the conventional materials by reduced cure stress with increasing cure temperature as well as unique stress relaxation behavior above its glass transition in the fully cured state. The relaxation experiments exhibit features characteristic of a physical relaxation process. Furthermore, the cure stress is observed to vanish precipitously upon deliberate introduction of network defects through an increasing imbalance of epoxy and amine functional groups. Finally, we postulate that these beneficialmore » properties arise from fluxional motion of the cyclopentadienyl ligands on the polymer backbone.« less

Authors:
ORCiD logo [1];  [1];  [1];  [1];  [1];  [1];  [1]; ORCiD logo [1];  [1]
  1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Laboratory Directed Research and Development (LDRD) Program; USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
1372307
Report Number(s):
SAND2017-7074J
Journal ID: ISSN 0024-9297; 655061
Grant/Contract Number:  
NA0003525
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Macromolecules
Additional Journal Information:
Journal Volume: 50; Journal Issue: 13; Journal ID: ISSN 0024-9297
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Jones, Brad H., Wheeler, David R., Black, Hayden T., Stavig, Mark E., Sawyer, Patricia S., Giron, Nicholas H., Celina, Mathias C., Lambert, Timothy N., and Alam, Todd M. Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent. United States: N. p., 2017. Web. doi:10.1021/acs.macromol.7b00501.
Jones, Brad H., Wheeler, David R., Black, Hayden T., Stavig, Mark E., Sawyer, Patricia S., Giron, Nicholas H., Celina, Mathias C., Lambert, Timothy N., & Alam, Todd M. Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent. United States. doi:10.1021/acs.macromol.7b00501.
Jones, Brad H., Wheeler, David R., Black, Hayden T., Stavig, Mark E., Sawyer, Patricia S., Giron, Nicholas H., Celina, Mathias C., Lambert, Timothy N., and Alam, Todd M. Thu . "Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent". United States. doi:10.1021/acs.macromol.7b00501. https://www.osti.gov/servlets/purl/1372307.
@article{osti_1372307,
title = {Stress Relaxation in Epoxy Thermosets via a Ferrocene-Based Amine Curing Agent},
author = {Jones, Brad H. and Wheeler, David R. and Black, Hayden T. and Stavig, Mark E. and Sawyer, Patricia S. and Giron, Nicholas H. and Celina, Mathias C. and Lambert, Timothy N. and Alam, Todd M.},
abstractNote = {Physical stress relaxation in rubbery, thermoset polymers is limited by cross-links, which impede segmental motion and restrict relaxation to network defects, such as chain ends. In parallel, the cure shrinkage associated with thermoset polymerizations leads to the development of internal residual stress that cannot be effectively relaxed. Recent strategies have reduced or eliminated such cure stress in thermoset polymers largely by exploiting chemical relaxation processes, wherein temporary cross-links or otherwise transient bonds are incorporated into the polymer network. In this paper, we explore an alternative approach, wherein physical relaxation is enhanced by the incorporation of organometallic sandwich moieties into the backbone of the polymer network. A standard epoxy resin is cured with a diamine derivative of ferrocene and compared to conventional diamine curing agents. The ferrocene-based thermoset is clearly distinguished from the conventional materials by reduced cure stress with increasing cure temperature as well as unique stress relaxation behavior above its glass transition in the fully cured state. The relaxation experiments exhibit features characteristic of a physical relaxation process. Furthermore, the cure stress is observed to vanish precipitously upon deliberate introduction of network defects through an increasing imbalance of epoxy and amine functional groups. Finally, we postulate that these beneficial properties arise from fluxional motion of the cyclopentadienyl ligands on the polymer backbone.},
doi = {10.1021/acs.macromol.7b00501},
journal = {Macromolecules},
number = 13,
volume = 50,
place = {United States},
year = {Thu Jun 29 00:00:00 EDT 2017},
month = {Thu Jun 29 00:00:00 EDT 2017}
}

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