Title page for ETD etd-12062001-080749


Type of Document Dissertation
Author Starr, Brian Craig
URN etd-12062001-080749
Title Inter-Relationships Between Chemistry, Network Structure and Properties of Chain Growth Dimethacrylate Thermosets
Degree PhD
Department Chemistry
Advisory Committee
Advisor Name Title
Riffle, Judy S. Committee Chair
Lesko, John J. Committee Member
McGrath, James E. Committee Member
Shultz, Allan R. Committee Member
Wightman, James P. Committee Member
Keywords
  • fracture toughness
  • aliphatic vinyl ester
  • dimethacrylate
  • water absorption
  • accelerated UV aging
Date of Defense 2001-10-23
Availability unrestricted
Abstract
Inter-relationships between Chemistry, Network Structure and Properties

of Chain Growth Dimethacrylate Thermosets

Brian Craig Starr

Advisor: Dr. Riffle

Dept. of Chemistry, Virginia Tech

Blacksburg, VA 24061

Abstract

Dimethacrylate oligomers diluted with styrene reactive diluents (so-called vinyl ester resins) are becoming increasingly important for composites in applications such as transportation vehicles, printed wiring boards and civil infrastructure. This research has focused on the generation and comparative analysis of glassy dimethacrylate networks as a function of oligomer structure, the type of reactive diluent, composition and curing conditions. A novel cycloaliphatic dimethacrylate was synthesized and its networks were compared to oligomeric structures containing dimethacrylates derived from epoxy terminated oligomers (from bisphenol-A and epichlorohydrin). Both types of dimethacrylates co-cured with methyl methacrylate exhibited increases in Mc and fracture toughness as the concentration of methyl methacrylate was increased. By contrast, networks prepared with a styrene diluent displayed reduced toughness with increasing styrene and Mc.

Due to the need for long-term composite environmental durability, the effects of moisture and exposure to sunlight are important. Thus, these materials were exposed to ultraviolet light on a rotating drum for 225 days and the exposure was carefully monitored. Initial results from this study suggest that both the networks comprising the aromatic dimethacrylate/styrene structures as well as the cycloaliphatic analogues cured with methyl methacrylate undergo reductions in rubbery moduli upon aging under these conditions. X-Ray photoelectron spectroscopy shows higher levels of oxidation on the bisphenol-A vinyl ester networks cured with styrene, especially those containing dimethylaniline and cobalt naphthenate as accelerators. Scanning electron microscopy indicates a smooth surface for the cycloaliphatic networks cured with methyl methacrylate and a pitted surface for the aromatic networks cured with styrene. Water absorption is also higher for the cycloaliphatic vinyl ester; however, curing with a longer alkyl chain methacrylate (butyl methacrylate) decreases the water absorption to levels comparable to those cured with styrene.

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