Proteins and amino acids as biobased polymer modifiers

Authors: McMahan, Colleen; Hathwaik, Upul; Torres, Lennard; Lhamo, Dhondup; Orts, William

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/29/2017
Publication Date: 9/20/2017
Citation: Mcmahan, C.M., Hathwaik, U.I., Torres, L.F., Lhamo, D., Orts, W.J. 2017. Proteins and amino acids as biobased polymer modifiers. [abstract].

Interpretive Summary:

Technical Abstract: Natural rubber (NR) is a critical agricultural material vital to industry, medicine, and defense, yet global supply is largely limited to latex from Hevea brasiliensis cultivated in tropical regions. Guayule (Parthenium argentatum), a woody desert shrub indigenous to the U.S. and Mexico, is under development as a renewed agricultural crop in semi-arid farmlands1,2. Both plants produce high molecular weight cis1,4-polyisoprene by biosynthesis. Guayule natural rubber (GNR) may be used in place of Hevea NR, or petroleum-based rubber, but substitution must take into consideration differences in physical and chemical properties. In natural rubbers those differences are attributed to non-rubber constituents, mainly proteins and lipids, depending on the plant species and post-harvest processing. NR from Hevea typically contains high levels of proteins that contribute to allergenicity but also to the outstanding material strength which renders Hevea NR uniquely suited for the most demanding rubber applications (e.g. aircraft tires). In contrast, guayule natural rubber is low in proteins, thus deprived of some attributes of Hevea. Our laboratory explored the feasibility of post-harvest modification of guayule latex with proteins and amino acids, either from commercial sources or extracted from Hevea latex. We were not able to duplicate the material strength of Hevea with modified guayule, even when Hevea proteins were used. However, our results demonstrated other formulated polymer properties (melt viscosity, thermal and oxidative stability, vulcanization rate) could be dramatically improved using these bio-based additives3,4. In some cases, incumbent polymer additives have known environmental and health concerns. Our studies confirm that commercial proteins and amino acids from natural sources may be considered as a new class of biobased rubber compounding chemicals, expanding options to produce environmentally-friendly polymer formulations.