Biodegradation studies of polyether polyurethane in a landfill site

Abstract

Polyether polyurethane rigid foams have always been considered as inert materials due to their extreme stability. Urethanes and polyethers, which are the main constituents of the polymer structure, are well known for theirstability and resistance to hydrolysis.t 32 These groups give to the foam its high hydrophobic property. This research work presents an evaluation of polyether polyurethane biodegradation based on a field study made at Baxenden Chemicals Limited, Accrington, England. The study of the landfill site of up to 100m 2 and 30m depth, has offered us the unique opportunity to investigate the fate of polyether polyurethane over a 30 years period.
A Gas Chromatography-Mass Spectrometry (GC-MS) analysis of leachate water samples collected in a water reservoir at Baxenden (September 2000), revealed the presence of phenolic, polyether and chlorophosphate compounds that could be the direct results of potyether polyurethane degradation. However, it is important to mention the apparent absence of carcinogenic aromatic amines in the teachate water, which are thought to be potential chemical or biological breakdown products of polyether polyurethane.° 2 These if they have been formed, appear to have been metabotised, which would be a positive aspect for the environment.
An Attenuated Total Reflectance-Fourier Transform Infra Red (ATR-FTIR) analysis (November 2000) of polyether polyurethane foam pieces disposed in the waste disposal tip at Baxenden for up to 30 years, revealed a decrease of 37.95% to 65.64% in the ratio urethane/ether content for foam pieces collected from 10.45 to 18.00m depth within the tip (when using C=O stretch vibrations at 1698cm" to characterise the urethane group and C-O stretch vibrations at 1107cm" to characterise the ether group). In addition, the physical properties of the buried foams appeared to have changed over the years: the foams were able to absorb water and Environmental Scanning Electron Microscopy (ESEM) photomicrographs taken of the foams have shown a complete disruption of the polymer structure (July 1999).
A susceptibility study (July 2000), using microorganisms isolated from the buried foams collected from within the tip (May 1999), has shown that these microorganisms were able to survive after 6 weeks in a mineral salts medium containing polyether polyurethane as the sole source of carbon.
The results of the different analysis have provided evidence that polyether polyurethane may be degradable and possibly susceptible to microbial attack. The degradation process seems to be initiated via the hydrolysis of the urethane bonds. However, the process appears extremely slow and can take decades to achieve. This research provides new information in the field of polyurethane research and could be an important environmental issue.