Natural rubber film biodegradation

Authors: McMahan, Colleen; McManus, James; PATTERSON, GABRIEL - Former ARS Employee; Torres, Lennard; Ring, David; Williams, Tina; Wood, Delilah; Orts, William; MARSH, D.THOMAS - Marsh Family Holdings

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2025
Publication Date: N/A
Citation: N/A

Interpretive Summary: The presence of microplastics and tire wear particles (TWPs) in the environment are growing concerns; the use of biobased and biodegradable polymers has been proposed as one solution. Natural rubber is considered both biobased and biodegradable. Rubber degrading microbes, bacteria and fungi, are ubiquitous in the environment, especially in soil. The purpose of this study was to quantify the biodegradability of natural rubber latex films (balloons) by respirometry, mechanical properties, and imaging. Preliminary results indicate balloon films degrade slower than starch or biodegradable polymers but much faster than conventional thermoplastic materials in a composting environment. Since early studies in environmental degradation of TWPs (Cadle and Williams 1980) using roadside soil suggested UV and ozone may be as important as microbial degradation, future studies should take these factors into account.

Technical Abstract: The presence of microplastics and tire wear particles (TWPs) in the environment are growing concerns; the use of biobased and biodegradable polymers has been proposed as one solution. Natural rubber (NR, cis-1,4-polyisoprene from plants) is considered both biobased and biodegradable. Rubber degrading microbes, bacteria and fungi, are ubiquitous in the environment, especially in soil. Specific microbes, e.g. Streptomyces sp. and Xanthomonas sp., and the enzymes responsible for oxidative cleavage of C=C bonds in NR have been identified (Joseph et al. 2002; Shah at al. 2013). When NR is chemically crosslinked, degradation rates may be impacted (Roy et al. 2006; Abraham et al. 2012) but conclusions are complicated by varying methods. The purpose of this study was to quantify the biodegradability of natural rubber latex films (balloons) by respirometry, mechanical properties, and imaging. Film aging conditions were selected, adapting available ASTM standard respirometry methods for thermoplastic materials. White latex balloons were pre-inflated for 24 hours, then placed into a commercial compost/sand mixture as is, die cut into test pieces, or ground into powder. Moisture levels were maintained at ~57% over 70 days. Mineralization (conversion into CO2) by respirometry and mechanical properties were measured, and film images were recorded. Preliminary results indicate balloon films degrade slower than starch or biodegradable polymers but much faster than conventional thermoplastic materials in a composting environment. Sample form had a major influence on % mineralization, as expected, and testing temperature impacted both mineralization and mechanical properties. Since early studies in environmental degradation of TWPs (Cadle and Williams 1980) using roadside soil suggested UV and ozone may be as important as microbial degradation, future studies should take these factors into account.