Guayule coproduct utilization: Synthesis, characterization, derivation, and formulation of value-added products
Guayule, Parthenium argentatum Gray, grows in semi-arid regions such as southwest Texas and northern Mexico. As a result of economic restraints, guayule has never realized full commercialization. Specifically, guayule has been commercially exploited only during times of conflict when economic imbalances and material superiority outweighs cost. Today's interest in guayule is not one of conflict, but one of desire to improve the environment, by using natural, renewable resources, and to improve the rural economy. For guayule to recognize its potential, value-added products must be formulated from its coproduct fractions as the value and quantity of natural rubber it supplies is not sufficient to offset cultivation and processing costs. Guayule yields five major fractions of potential use: high molecular weight rubber, low molecular weight rubber, organic soluble resin, water soluble resin, and bagasse. To add value to the low molecular weight rubber, epoxidized, acrylated epoxidized, maleinized, and chlorinated maleinized low molecular weight guayule rubber have been synthesized. The materials possess utility as crosslinking agents in powder coatings, ultraviolet cured coatings, or waterborne coatings, all environmentally friendly technologies. The compounds have been characterized by standard techniques such as Fourier transform infrared spectroscopy, nuclear magnetic resonance, differential scanning calorimetry, and elemental analysis. Formulations of coatings based on the compounds have yielded aesthetically pleasing, environmentally friendly compositions with improved properties compared to control formulations. Guayule also produces organic soluble resin, an agent with known antifouling and antitermitic activity. To determine the origin of the activity, the resin was separated via column chromatography after which compounds were purified via recrystallization techniques. Five compounds thus obtained have been analyzed for activity and the active fraction(s) have been identified. Additionally, selected guayule compounds have been saponified to yield Partheniol, a sesquiterpene alcohol of substantial biological activity.