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The Metrohm 763 Thermomat determines the thermal stability of PVC.

Thermal stability is used to control the quality of PVC and its products, measuring the time taken for HCl to be formed due to thermal decomposition.

When a sample is exposed to elevated temperatures, HCl gas is formed due to the thermal decomposition of the resin.

The time after which the HCl can be detected is the evaluation criterion.

PVC Thermomat uses conductivity to detect HCl.

Pure PVC resin cannot be used for manufacturing; it is always mixed (blended) with additives, improving stability (stabilisers) and plasticity (plasticisers).

Pure PVC has short induction and stability times; the addition of 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.

Evaluated stability times are equal for the pH and conductivity measurement methods for determining the thermal stability of PVC pieces.

However, the pH method’s induction time is significantly shorter than the one found using 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.

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.

Connecting up to four PVC Thermomats to a PC allows the user to increase analysis capacity to 32 samples at up to eight different temperatures.

The Windows-based software makes operating the Thermomat quick and easy.

It controls and manages each individual sample and heating block.

With the 763 PVC Thermomat, the determination of the thermal stability of PVC-type polymers takes place at a sophisticated level.

With the disposable sample-reaction vessels, the cleaning procedure is reduced to a minimum.

Determination of the thermal stability of PVC-chlorinated plastics is a three-step process: PVC decomposes at elevated temperatures and releases gaseous HCl; the gaseous HCl is then moved by a stream of inert nitrogen into the measuring cell filled with distilled water; the thermal stability of the PVC materials is then determined by measuring the conductivity of the aqueous HCI solution.

It features: two heating blocks per Thermomat, which allows eight sample measurements at two different temperatures; wide temperature range (50 to 220C); individual start of each channel; disposable reaction vessels; database archive with sorting, filtering and data export; automatic evaluation with additional computer-supported manual evaluation using the tangent method; and conversion of the results to other temperatures, for example storage temperature.

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