Abstract/Details

Selected studies on the thermal and mechanical responses of amorphous glassy polymers at different length scales


1999 1999

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Abstract (summary)

This thesis describes investigations into the mechanical and thermal characteristics of amorphous polymeric materials by structural changes on the molecular and the microscopic scale. On the molecular scale, the structure of a cross-linked polymeric material is controlled by changes in the molecular weight between cross-links, cross-link functionality, and chain stiffness. With control of the network structure, an expansive range of mechanical and thermal characteristics is possible. These properties range from intrinsic properties, such as the glass transition temperature, to performance properties, such as impact behavior. Relationships between the network structure and measured properties are established by the use of a variety of theories from rubber elasticity to free volume. Relationships are also established between the various measured properties through solid and fracture mechanics.

The introduction of soft rubbery particles on the microscopic scale into a glassy polymeric matrix is commonly employed to create a tougher material. Despite the prevalent use, the mechanisms and sequence of mechanisms of toughening are poorly understood. The mechanisms and sequence of mechanisms are elucidated in this investigation through the use of unique mechanical tests and materials with favorable properties. The unique mechanical tests in this investigation include tensile dilatometry and a multi-axial stress state test. The multi-axial stress state test, which allows independent control of the dilational and deviatoric stresses of a material between uniaxial compression and equal biaxial tension, consists of a uniaxially loaded and pressurized thin walled hollow cylinder. The materials include liquid rubber modified epoxies, voided epoxies, and core-shell rubber modified polyvinylchloride. The voided epoxy material separates the matrix contributions from those of the rubbery phase, while the core-shell rubber modified polyvinylchloride provides optical verification of rubber particle cavitation. By combined use of these materials and the unique mechanical tests, the mechanics of rubber toughening are evaluated.

Indexing (details)


Subject
Plastics;
Polymers;
Materials science
Classification
0795: Plastics
0495: Polymers
0794: Materials science
Identifier / keyword
Applied sciences, Pure sciences, Amorphous polymers, Glassy polymers, Network structure, Toughening
Title
Selected studies on the thermal and mechanical responses of amorphous glassy polymers at different length scales
Author
Crawford, Emmett Dudley
Number of pages
168
Publication year
1999
Degree date
1999
School code
0118
Source
DAI-B 60/05, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780599328785, 0599328789
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
9932304
ProQuest document ID
304515128
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304515128
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