Guayule Rubber: A New Possible World Scenario for the Production of Natural Rubber?

Abstract

Natural rubber is a particularly precious material to the rubber industry; this is indicated, in this paper, by the current world consumption, which must be enthasised as being an increasing demand. The regularity of its chemical structure and its trend to strain-induced crystallisation, makes natural rubber an irreplaceable key material in rubber compounding, not equalled even by the best synthetic cis-1,4-polyisoprene, either from the performance standpoint or also pricewise. The thesis of the author starts from the observation that about 100,000 km²of tropical land is dedicated to the cultivation of hevea rubber. The increasing demand for this product could cause the disruption of other tropical forests to increase natural rubber production. Simultaneously, a trend is already underway to convert the current hevea plantations to more profitable crops such as palm oil. Thus the best answer to avoid further deforestation and to give a correct offer to the increasing demand for natural rubber, is to start the production of guayule rubber. This can be cultivated in semi-desert, abandoned lands, avoiding further deforestation of tropical forests and favouring a partial and gradual reconvertion of the tropical lands currently dedicated to the production of hevea, to the cultivation of more profitable crops, which could be used as a source of food for the increasing world population.

An additional, not negligible item linked to guayule rubber, is the discovery that contrary to hevea, guayule rubber has low protein content, while these proteins are different from those of hevea and do not cause allergy to sensitive individuals. Presently about 6.5% of the U.S. population is thought to be hypersensitive to products made by hevea latex. The use of guayule rubber may overcome this problem especially in rubber goods, used in direct skin contact.

The history of guayule rubber is also reviewed, the aspects concerning its cultivation, equivalence to natural rubber from the chemical standpoint. The proposed processes used to extract guayule from the plant and the possible use of the by-products of the extraction are discussed. Finally typical mechanical properties of guayule are presented together, with the advantages and disadvantages offered by guayule in comparison to hevea.