2011 Volume 60 Issue 3 Pages 275-282
The estimated thermal-oxidation degree and corresponding thermal aging times at practical temperatures with poly(butylene terephthalate) [PBT] mold parts taken from used cars was investigated by applying the time-temperature superposition principle. Methyl 4-methoxybutyrate (MMB), based on the reactive pyrolysis-GC/MS method, was used as an index of the thermal-oxidation degree. This method was applied for pars taken from the engine compartment of the used cars with mileage of 46000 km ; the amount of MMB was 0.0071 wt%. The thermal aging times converted at a thermal history temperature of 84°C by the DSC method and 100°C were 4200 hours and 3500 hours, respectively. Based on the fact that the thermal-oxidation degree can now be represented as a thermal aging time for any assumed temperature, the thermal-oxidation degree can be more accurately evaluated through the relationship between the amount of MMB and t100 than through mileage. The lifetime of parts can also be estimated by adding the mechanical properties. The dependency of the thermal-oxidation rate on the sample thickness and the diffusion controll over the thermal-oxidation rate were mentioned.
