No abstract

Novel fiberglass-reinforced composites were fabricated by the ultraviolet and visible (solar) irradiation of epoxidized vegetable oils in the presence of onium salt cationic photoinitiators. A variety of layup techniques and experimental conditions were explored to optimize composite fabrication. It was demonstrated that composites prepared by wet layup techniques containing up to five plies of glass cloth could be cured by a direct, 25-min exposure to solar irradiation. A series of composite samples were prepared using mixtures of epoxidized vegetable oils and synthetic epoxy resins, and their mechanical properties were evaluated. Based on these measurements, it may be concluded that photochemical routes to the fabrication of composites derived from epoxidized vegetable oils provide a simple, direct, and inexpensive route to the fabrication of composites with many potential low-performance applications.

The synthesis of a series of mono-, di-, and multifunctional monomers bearing the epoxynorbornane group has been carried out. Key to their preparation is the chemoselective epoxidation of 5-vinyl-2-norbornene, which affords the 5-vinyl-exo-2,3-norbornane epoxide in high yields. Monomers were prepared using this substrate and carrying out hydrosilations to make mono-, di-, tri-, and tetrafunctional epoxides. The esterification and etherification of 5-norbornene-2-methanol with succinic acid and 1,4-butanediol gives the corresponding bisnorbornene compounds, which were epoxidized to give diepoxynorbornane monomers containing ester and ether linkages. All monomers were fully characterized by means of IR and 1H and 13C NMR spectroscopy and by elemental analysis.

The reactivity of a novel series of mono-, di-, and multifunctional monomers bearing the epoxynorbornane group in photoinduced cationic polymerization was determined using Fourier transform real-time infrared spectroscopy and differential scanning photocalorimetry. Comparisons were made between the monomers of this investigation containing the epoxynorbornane group with monomers of similar structure bearing epoxycyclohexane groups. Although the cationic polymerizations of the epoxynorborane functional monomers are rapid they, are slower than the aforementioned epoxycyclohexane analogues. This was attributed mainly to steric hindrance effects.

This communication describes recent developments in this laboratory directed towards the design of cationically polymerizable monomers from biorenewable sources. Three classes of ubiquitous biorenewable substrates were explored, namely: lipids, carbohydrates and terpenes. Considered in the synthesis and design were the cost and availability of the substrates, and the practicality and environmental acceptability of the chemical methodology. The polymerizations of the monomers were carried out using photoinitiated cationic polymerization.