Biodegradation of natural rubber latex films by highlighting the crosslinked bond

Abstract

Natural rubber latex (NRL) films are used to manufacture single-use items such as condoms, blood transfusion tubes, and gloves. Natural rubber is a biopolymer, but the vulcanization process that imparts resilience and elasticity makes it difficult to degrade, resulting in an amount of waste that takes too long to biodegrade in the environment. This study evaluated the effect of crosslink bonds on the biodegradation of NRL films containing two accelerators, zinc diethyldithiocarbamate (ZDEC) and tetramethylthiuram disulfide (TMTD), in various sulfur-based curing systems. The NRL films were buried for up to 180 days and their physical, chemical, and mechanical properties were examined to determine biodegradability. Microorganism colonies were visible using scanning electron microscopy (SEM), and functional group alterations detected using Fourier transform-infrared spectroscopy (FTIR) indicated chain scission. The sample 0.6/0, followed by 1.2/0, showed a more pronounced Tonset decrease at 60 and 90 days of soil burial. At 180 days, there is no difference among the samples since all of them showed decreases in Tonset and Tmax of about 70 °C and 10 °C, respectively. Tensile strength of all samples decreased over time, but only the 0.6/0 NRL film had a decrease higher than 50% at 30 days. Additionally, lower mono- and disulfide bond concentrations result in greater tensile strength loss. Results indicated that NRL latex films with lower crosslink density and higher polysulfide bond content exhibited significant reductions in mechanical properties, indicating that these factors contribute to biodegradability.