Guayule, a Renewable Resource for Natural Polyisoprene and Resin: Composition, Processes and Applications

April 7, 2021

Amandine Rousset ¹, ⁵, Ali Amor ², ³, Teerasak Punvichai ⁴, Sandrine Perino ⁵, Serge Palu ², Michel Dorget ¹, ³, Daniel Pioch ² and Farid Chemat ⁵

1 GuaTecs, 28 rue Xavier Bichat, 72000 Le Mans, France;
2 UR BioWooEB-Biorefinery Team, CIRAD, 34398 Montpellier, France;
3 CTTM, Centre de Transfert de Technologie, 72000 Le Mans, France;
4 Faculty of Science and Industrial Technology, Prince of Songkla University, Surat Thani, Thailand;
5 Avignon University, INRAE, UMR408, GREEN Extraction Team, 84000 Avignon, France;

Natural Rubber is an essential raw material, it is used in more than 40,000 products and remains irreplaceable for some applications, like plane, truck tyres or medical gloves thanks to the peculiar cis chemical structure of the contained Polyisoprene (PI) and to the presence of other molecules.

Indeed, natural rubber shows better dynamic properties, especially resilience – the ability to undergo big deformations without breaking and to recover its initial form when the constraint is released - as well as very good resistance to abrasion, shock and tearing.

More than 2000 plants produce PI. The best-known plants for their potential commercial interest are part of the families of Euphorbiaceae (Hevea, Bentamia, Manihot), Asteraceae (Parthenium argentatum, Taraxacum kok-saghyz) and Sapotaceae (Gutta percha, Argania spinosa). Among the most promising ones are Kazakh dandelion (Taraxacum kok-saghyz) and guayule (Parthenium argentatum). This article will focus on guayule.

Guayule, also called “yerba de hule” is native to the desert of Chihuaha, located in Mexico (Zacatecas, Coahuila, Chihuahua, San Luis Potosí, Nuevo León and Durango) and southern Texas in the United States. Native plants can live up to 30-40 years or more. It resists to temperature higher than 40°C and can withstand temperatures below -15°C.

Guayule is adapted to hot desert environments and to sites with different soils (shallow, stony, calcareous and friable) and with relatively low concentrations of nutrients, but it grows best in well-drained soils and cannot tolerate waterlogging.

PI and/or resin are found in different sections of the stems, branches, roots, leaves and flowers. On average, there are 8% of PI and 10% of resin in the plant. Natural rubber is contained in thin-walled cells, the parenchyma cells, located in the bark and the pith.

There are two major types of processes for guayule’s PI extraction: processes that extract PI in a coagulated state, the aim being to obtain dry rubber (i.e. for tyres) and processes that extract PI in the emulsion form (i.e. latex for gloves). The main processes to obtain dry rubber are: flotation (aqueous process), sequential extraction (solvent process), simultaneous extraction (solvent process), and more recently supercritical-CO₂ (with co-solvents). To extract PI in the emulsion form, an aqueous process was developed and improved progressively.

Industrial processes to extract rubber and latex from guayule plants

Depending on the used process, products and co-products are different: dry rubber or latex, resin, leaves (if the plant has been defoliated) and bagasse.

Guayule Latex could be used for manufacturing numerous medical supplies. Being non-allergic this latex is suitable feedstock for surgical tools or examination gloves. These last supplies are made by dipping a form inside tanks containing stabilized and formulated latex. Balloons may also be manufactured with this technique.

Tyres and mechanical parts are made with high molecular weight dry rubber, after a vulcanization step; synthetic neoprene can be replaced by dry natural rubber in surf wetsuit.

Proposed applications for products and co-products of guayule processing

Guayule is therefore a promising plant for development to complement current production of natural rubber polyisoprene. Firms can lean on numerous patents and existing processes, on the implication of numerous stakeholders, in particular in Europe, where natural rubber is on the critical material list of the EU, and in full agreement with its new global sustainable strategy. However, efforts have to be made on co-product valorization to be competitive with currently marketed rubber and latex products.

SWOT Analysis of guayule development

Read the full article: https://www.mdpi.com/1420-3049/26/3/664

Guayule plant image source: https://www.britannica.com/plant/guayule#/media/1/248122/106398