Determination of rate constants and activation energies for emission of organic compounds from polyoxymethylene

Emission of organic compounds from two types of polytrioxane (colorless and black-smoke pigmented) has been measured by using a 20-cm3 chamber connected directly to a gas chromatograph. Measurements were performed at 40, 60, and 80 C degrees at a flow rate of 0.45 cm3 min-1. High surface to volume ratio and a relatively large sample loop (3 cm3) enabled detection of signals from organic substances present at low concentrations (~μg cm-3). The results obtained revealed that for the pigmented polytri-oxane the rate of emission of organic compounds and the rate constants for the process were higher than for the colorless form. In contrast, the ac-tivation energy was slightly higher for emission of trioxane from the pig-mented material. For trioxepane emission activation energies were similar. Results show the pigment had no retardant activity on emission of organic compounds from the polymer. The activation energies determined for emis-sion of organic compounds were in the range 15 to 60 kJ mol-1. The rate constants (from 7.6 × 10-10 to 9.2 × 10-8 cm-2 s-1) suggest diffusion or de-sorption are occurring within the polymer matrix.