Designing greener plasticizers: Effects of alkyl chain length and branching on the biodegradation of maleate based plasticizers. (September 2015)

• Record Type: Journal Article
• Authors: Erythropel, Hanno C.; Brown, Tobin; Maric, Milan; Nicell, Jim A.; Cooper, David G.; Leask, Richard L.
• Is Part Of: Chemosphere. Volume 134(2015)
• Page Start: 106
• Page End: 112
• Publication Date: 2015-09
• Subjects: Green plasticizer -- DEHP -- Phthalate -- Maleate -- Biodegradation -- Bacterial growth inhibition; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2015.04.014
• Languages: English
• ISSNs: 0045-6535

Abstract

Highlights: Development of green plasticizers to replace phthalates. Evaluation of unbranched maleate plasticizers. Ethyl side branches are an important factor for biodegradation rate. No influence of ethyl side branches on Tg reduction efficiency. Abstract: The ubiquitous presence of the plasticizer di (2-ethylhexyl) phthalate (DEHP) in the environment is of concern due to negative biological effects associated with it and its metabolites. In particular, the metabolite mono (2-ethylhexyl) phthalate (MEHP) is a potential endocrine disruptor. Earlier work had identified the diester di (2-ethylhexyl) maleate (DEHM) as a potential greener candidate plasticizer to replace DEHP, yet its biodegradation rate was reported to be slow. In this study, we modified the side chains of maleate diesters to be linear (i.e., unbranched) alkyl chains that varied in length from ethyl to n-octyl. The plasticization efficiency of these compounds blended into PVC at 29 wt.% increased with the overall length of the molecule, but all compounds performed as well as or better than comparable samples with DEHP. Tests conducted with the equally long DEHM and dihexyl maleate (DHM) showed that branching has no effect on glass transition temperature ( Tg ) reduction efficiency. Biodegradation experiments with the common soil bacterium Rhodococcus rhodocrous in the presence of the plasticizer showed acceptable hydrolysis rates of maleates with unbranched side chains, while the branched DEHM showed almost no degradation. The addition of hexadecane as auxiliary carbon source improved hydrolysis rates. Temporary buildup of the respective monoester of the compounds were observed, but only in the case of the longest molecule, dioctyl maleate (DOM), did this buildup lead to growth inhibition of the bacteria. Maleates with linear side chains, if designed and tested properly, show promise as potential candidate plasticizers as replacements for DEHP.