Abstract: A low out-gassing polyurethane is described for use in applications where contaminants must be kept to very low levels, such as during lithography. In particular, the polyurethane is essentially free of silicon-containing species, which present particular contamination problems in the context of electronic device manufacturing. The polyurethane may be utilized as a potting material in filter assemblies, or in other contexts within the environment of electronics manufacturing. Testing of the novel polyurethane formulation shows the off-gassing characteristics to be much lower than commercially available potting materials made from polyethylene.