Abstract/Details

Molecular aspects of yield and fracture in glassy thermosets and their nano-composites


2006 2006

Other formats: Order a copy

Abstract (summary)

The ability to fundamentally understand how changes in the molecular architecture and reinforcement at the molecular and nano-scale effect the mechanical and thermal behavior of glassy thermosets is of considerable interest. A series of epoxy-based networks with controlled molecular weight between crosslinks and backbone stiffness are utilized to identify characteristics that govern yield behavior. Two parameters, the glass transition temperature, Tg, and cohesive energy density, Ec, are identified to describe changes in network stiffness and strength, respectively. The parameters are incorporated into a model that describes yielding over a range of stress states, strain rates, and temperatures. The same epoxy network is used to explore the effects of backbone stiffness and crosslink density on the strain hardening modulus and fracture. It is found the strain hardening modulus is directly related to the crosslink density of the network similar to a traditional rubber. The backbone stiffness appears to have no effect on several post-yield phenomena. A class of compounds labeled molecular fortifiers are then incorporated into the model epoxy network. Two phosphorus-based compounds, one that is included as a free additive and another that is covalently bound to the network, are shown to improve a range of mechanical, physical, and thermal properties. The covalently bound fortifier increases the crosslink density through specific physical bonding interactions and alters the characteristics of the network. In addition several sulfur and a carbon-based compound are investigated as possible molecular fortifiers. The phhysical interactions in the interphase region are found to be enhanced in nano-clay composites that contain fortifiers. These interactions lead to improved mechanical and thermal characteristics over composites utilizing commercially modified nano-clays.

Indexing (details)


Subject
Polymers;
Materials science
Classification
0495: Polymers
0794: Materials science
Identifier / keyword
Applied sciences; Pure sciences; Fracture; Glassy; Nanocomposites; Thermosets; Yield
Title
Molecular aspects of yield and fracture in glassy thermosets and their nano-composites
Author
Calzia, Kevin J.
Number of pages
152
Publication year
2006
Degree date
2006
School code
0118
Source
DAI-B 67/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542982125
Advisor
Lesser, Alan J.
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3242098
ProQuest document ID
305302867
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305302867
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.