Measurement of Depolymerization Products in the Polyacetal, Polyamide, and Polymethylmethacrylate Processing Industry

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Abstract
Polyacetal (polyoxymethylene, POM), polyamide 6 (PA 6), and polymethylmethacrylate (PMMA) are thermoplastics processed by all the common methods (injection molding, extrusion, and thermoforming). The air impurity levels were studied at workplaces during processing of these plastics. Because these plastics are known to degrade by depolymerization, the airborne monomers emitted were chosen as indicators for air pollution. Sampling and analysis methods were developed and tested for the field measurements. The results obtained from 11 plants revealed monomer concentrations of 0.06–0.23 mg/m3 of formaldehyde during POM processing; 3 of ε-caprolactam during PA 6 processing; and 0.06–4.6 mg/m3 of methylmethacrylate during PMMA processing. Trace concentrations of formic acid during POM processing and ammonia during PA 6 processing also were found. None of the results exceeded the current threshold limit values. Additionally, the plastic fumes contain small amounts of other substances, e.g., free radicals, aerosols, and additives which also may be harmful to human health.