Processing guayule for latex and bulk rubber

The production of latex or bulk rubber from guayule has been pursued at various times since guayule rubber ceased being an article of commerce more than 60 years ago. Hypo-allergenic guayule latex has been prepared in 25-50-kg laboratory batches. Dilute latex was first washed from ground shrub and then concentrated by a combination of multi-stage centrifugation and creaming steps. This material was used to fabricate prototype medical products. A total of 8.8 t of dry guayule rubber was produced by simultaneous extraction of rubber and resin with a mixed organic solvent, followed by fractionation of the polymer stream. This material was tested in aircraft and light truck tires. At present, those seeking to process guayule must be prepared to meet several challenges: increasing the bulk viscosity of the rubber polymer, reducing the level of entrained resin and assuring oxidative and thermal stability. From this standpoint, latex process development remains in its early stages, whereas processing guayule for bulk rubber has been more thoroughly and successfully evaluated.