Metrohm AG

- Model 895 - Professional PVC Thermomat



The 895 Professional PVC Thermomat determines the thermostability of polyvinyl chloride (PVC) and other chlorine-containing polymers by means of the dehydrochlorination test (DHC). This involves exposing the samples to elevated temperatures in the PVC Thermomat and measuring the stability time – the time until gaseous hydrogen chloride is released. The method is compliant with national and international standards, and it is particularly easy to perform, not least thanks to the modern, user-friendly StabNet software.

  • Based on ISO 182 Part 3 standard
  • User-friendly StabNet software for instrument control, results evaluation, and data management
  • Simultaneous analysis of up to eight samples
  • Color display on the instrument provides status overview of all measuring positions
  • Each sample position can be started separately and directly on the instrument


When PVC undergoes thermal decomposition, it releases hydrogen chloride (HCl).

The thermostability is an important quality criterion for PVC and other chlorine-containing polymers. With the PVC Thermomat, you can measure the thermostability of such polymers in all stages of processing, and you can evaluate the effectiveness of added stabilizers.


The PVC Thermomat method is based on the method described in the ISO 182-3* standard, which describes how the tendency of PVC to release hydrochloride at elevated temperatures is to be assessed.

* ISO 182 Part 3: “Plastics – Determination of the tendency of compounds and products based on vinyl chloride homopolymers and copolymers to evolve hydrogen chloride and any other acidic products at elevated temperatures – Part 3: Conductometric method”


StabNet is the control hub for the PVC Thermomat: all instrument functions are controlled via PC with the software. 

However, it also evaluates your results, archives all determinations in its own database, and much, much more.


The PVC Thermomat has eight measuring positions, four in each one of its two independent heating blocks.

Because they are independent, different temperatures can be applied on the heating blocks at the same time. Each single measurement can be started individually – directly on the instrument – once the sample has been put in position.


If you’re dealing with larger sample loads, you can connect up to four PVC Thermomats to a single PC.

This allows you to analyze up to 32 samples at a time, using a single computer.


The PVC Thermomat uses favorably-priced disposable reaction vessels.

This means that there is no need for time-consuming cleaning after each measurement which saves valuable time and costs. The reproducibility of results is also improved because the single-use vessels prevent carryover-effects.


Measurement of the thermostability of PVC and other chlorine-containing polymers with the PVC Thermomat is done by the dehydrochlorination test.

It is based on heating the sample to induce decomposition that results in the release of gaseous HCl.

A continuous stream of nitrogen that passes through the sample transports this HCl from the sample vessel into a vessel containing distilled water whose conductivity is continuously measured.

Conductivity increases in this vessel once HCl emerges. The time at which a 50 µS/cm increase is reached compared to the beginning of the measurement is called the stability time; it is a measure of thermostability.

  • Heating : Two individually heated aluminum heating blocks
  • Max. number of samples : Eight (four in each block)
  • Temperature range : 50 - 220 °C, can be set in steps of 1 °C
  • Temperature correction : -9.9 - +9.9 °C, can be set in steps of 0.1 °C
  • Max. deviation from the set temperature : ±0.3 °C
  • Reproducibility of the set temperature : Typically better than ±0.2 °C
  • Temperature fluctuations : Typically <0.1 °C
  • Temperature differential between the individual measuring positions : Typically <0.3 °C
  • Response temperature of the overheating protection : 260 °C
  • Gas supply : External nitrogen supply
  • Gas flow range : 1 - 25 L/h
  • Conductivity measurement : 0 - 400 µS/cm
  • Interface : USB

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