Comparison of pH and conductivity measurement for the determination of thermal stability of PVC pellets and pieces
The thermal stability of PVC was determined under identical conditions according to ISO 182-2 (pH method) and ISO 182-3 (conductivity method).
The stability and induction times obtained with the different indications were compared.
The experiments showed that the evaluated stability times for both methods are equal within the normal result scatter.
In contrast the induction time determined with the pH method is significantly shorter than the one found by conductivity.
The discrepancy can be explained by the difference in the data presentation, logarithmic scaling for the pH and linear for conductivity.
If the pH is converted into H+ concentration the obtained induction times are comparable.
Since ISO 182-2 only specifies the determination of the stability time, there is no restriction to use the 763PVC Thermomat for the determination of the thermal stability of PVC according to the ISO standards.
For a free, full copy of this application article and literature on the Thermomat, please contact Metrohm UK.
