The Metrohm 763 Thermomat is an instrument for determining the thermal stability of PVC.
Thermal stability is an approved method for the quality control of PVC and its products.
When a sample is exposed to elevated temperatures, HCl gas is formed due to the thermal decomposition of the resin and the time after which the HCl can be detected is the evaluation criterion.
The detection of HCl is either by pH or conductivity; the 763 PVC Thermomat uses conductivity for this detection.
Pure PVC resin cannot be used for manufacturing; it is always mixed (blended) with additives improving stability (stabilisers) and plasticity (plasticisers).
Pure PVC shows very short induction and stability times, and adding additives significantly increases these times.
Applications for the PVC Thermomat include determination of PVC stability times (raw PVC and PVC products), and examination of PVC additives (stabilisers and plasticisers).
The Thermomat enables compliance to the following international standards: Din 53381 part 1, Din VDE 0472 part 614, and ISO 182-3 parts 1, 2, 3 and 4.
In a comparison of pH and conductivity measurement, 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 763 PVC Thermomat for the determination of the thermal stability of PVC according to the ISO standards.
The 763 PVC Thermomat, a fully PC-controlled instrument for the determination of the thermal stability of PVC plastics, features data storage and archiving into a database as well as automatic evaluation of the curves.
Two heating blocks allow the user to analyse eight samples at one or two different temperatures.
Analysis capacity can be increased to 32 samples at up to eight different temperatures by connecting up to four PVC Thermomats to a PC.
The Windows-based software makes operating the Thermomat quick and easy.
With the 763 PVC Thermomat, the determination of the thermal stability of PVC-type polymers takes place at a high level.
With the disposable sample reaction vessels, the cleaning procedure is reduced to a minimum.
