Carbon-fiber reinforced composites of Vinyl Ester Resin (VER) are largely used in Department of Defense (DoD) weapons platforms. Critical composite structures for ship hulls and transportation vehicles can be made using a low-cost VER that can be processed at ambient temperature using vacuum-assisted resin transfer molding (VARTM). Current precursors for making VER are isolated from petroleum feedstock, which is subjected to fluctuating prices and limitations in supply. In addition, the synthetic route uses epichlorohydrin as one of the precursors, which is a potential carcinogen.

The objective of this SERDP project was to develop a sustainable, environmentally safe VER for military structural composite weapons systems starting with low-cost lignin and glycerin biowaste streams, prepare various formulations and their carbon fiber reinforced composites that can completely or in part replace the current commercial resin manufactured from petroleum feedstock.

The development of bioderived VER was conducted in following steps:

1. Isolation of bioderived phenol from pyrolysate from lignin and its conversion to Bisphenol A (BPA).
2. Synthesis of glycidyl methacrylate (GMA) from glycerin via conversion to glycidol followed by reaction with meth methacrylate.
3. Synthesis of VER via reaction of BPA with GMA, eliminating the use of toxic epichlorohydrin.
4. Developing one-pot synthesis method for VER using glycerin and BPA as reactants.
5. Prepare various formulations of Green Vinyl Ester Resin (GVER) and examine their cure kinetics.
6. Carbon fiber reinforced composites of various formulations using VARTM.
7. Mechanical and flammability testing to determine structural equivalence

BPA from the green phenol from lignin pyrolysis and GMA from biodiesel based glycerin were successfully synthesized. The monodisperse VER was prepared, purified and its various formulations were prepared. The commercial resin with 40 wt. % of styrene have similar viscosity like GVER with 20 wt. % of styrene. Carbon fiber reinforced composites of GVER have similar mechanical and flammability performance compared with commercial resins. In addition, three different syntheses of VER from glycerin and BPA were developed and examined for marine coating.

This program provided a sustainable, environmentally safe source of vinyl ester resin monomer from bio-waste streams of lignin and glycerin. This will enhance the independence of the United States from foreign oil. The proposed synthetic route to produce GVER eliminates the usage of epichlorohydrin. In addition, the GVER has significantly lowered the usage of reactive diluent styrene compare with commercial resins.