Halogen Moisture Analyzer Temperature Settings by Sample Type
By Lim Xu, Export Manager
Halogen moisture analyzer temperature depends on the sample. See the oven temperatures standard methods use and how to find and confirm your own setting.
The right halogen moisture analyzer temperature is one that drives the water out of your sample without melting, burning or decomposing it. Published oven methods give a first trial point for each sample type. The setting you keep should come from a temperature study on your own material, checked against a reference method.
Why does the drying temperature change the result?
A halogen analyzer reports the mass the sample loses while it heats. That loss is not specific to water. A 2014 NPL review of loss on drying methods notes that solvents, oils and other volatiles can be counted in the weight loss. Bound water can also come off with the free water if the drying temperature is too high.
The same review notes that the water left in a material after drying depends on the drying temperature. Set the temperature too low and water stays behind. Set it too high and other losses get counted as moisture.
ASTM D6980, the loss in weight method for moisture in plastics, makes the same point. It warns that volatiles other than moisture can give a biased high result, and it asks you to stay below any melting or decomposition temperature of the material.
The set temperature is also not the sample temperature. D6980 notes that the optimum test temperature for a plastic can sit above its melting point, because of the distance between the temperature sensor and the sample pan.
What temperatures do standard oven methods use by sample type?
Reference oven methods fix a drying temperature for each material. The table lists some of them, taken from the NPL survey of moisture standards and from ISO 287 for paper. These are oven settings. Use them as the reference you check against and as a first trial point, not as a setting to copy.
| Sample type | Reference oven method | Oven drying temperature |
|---|---|---|
| Paper and board | ISO 287 | 105 ± 2 °C |
| Cellulose acetate | ISO 585 | 105 ± 2 °C |
| Toughened polystyrene | BS 3241 | 80 ± 2 °C |
| Roasted ground coffee | ISO 11294 | 103 °C |
| Soaps | ISO 672 | 103 ± 2 °C |
| Plaster and gypsum | SR 4474-2 | 40 ± 4 °C |
Two plastics in the table are dried 25 °C apart, so even one material family has no single setting.
Not sure where to start with your sample? Tell us your test requirements. We source similar samples, run the test and send you the video. No need to ship samples.
How do you find the right temperature for a new sample?
D6980 sets out a temperature study for plastics. You can apply the same logic to other samples, as long as you confirm the result against their own reference method.
- Set up several drying programs that are identical except for temperature, each one 5 °C higher than the last.
- Run the lowest temperature first. D6980 links the programs into one consecutive test.
- Stop before any temperature where the sample could give off harmful fumes.
- Plot the result against temperature.
Keep the sample mass and the way you spread it on the pan the same in every run, so temperature is the only thing that changes.
Then read the curve in three parts. In the lowest steps, most of the moisture comes off. Next comes a range where the result is very low and constant, and D6980 says to choose the test temperature inside that range. If the result starts to rise again above it, the sample is likely producing water through decomposition or solid phase polymerization.
How do you confirm the setting before you rely on it?
Check the chosen temperature against a reference method on the same material. NPL notes that faster methods can be checked against direct techniques by applying both to the same batch or sample and comparing the results.
Where water content is what you need, the NPL review says loss on drying results should be compared with a water specific technique such as Karl Fischer titration. D6980 also says a Karl Fischer apparatus is useful when you work out the optimal test conditions for a material.
Our guide to the drying oven vs halogen moisture analyzer suggests running a set of temperature profiles for each resin type and comparing them with oven or Karl Fischer data. The goal is a validated setting for each material, not one setting for the whole lab.
Setting the temperature on the KHT-HMA-01
Our KHT-HMA-01 sets the drying temperature from 40 to 160 °C in 1 °C steps. That range covers the nominal oven temperatures in the table above and leaves room for a study in 5 °C steps. A method that calls for more than 160 °C is outside its range. The halogen moisture analyzer page lists the full specification.
Frequently asked questions
What if my material has no published drying temperature?
Find it by experiment. D6980 says that test conditions for a plastic not listed in its annex tables have to be determined experimentally or with help from the analyzer manufacturer. The temperature study above is that experiment.
Does sample preparation matter as much as temperature?
It can matter more. The NPL review lists sample preparation and handling, sample size, humidity and drying time among the factors behind loss on drying uncertainty, and it says preparation and handling may be the largest of them. D6980 asks for a representative specimen and for hygroscopic plastics to be stored in airtight containers.
What should I record with each result?
D6980 asks for the sample identity, including material type, source, form and previous history, plus the test date, each specimen size and each moisture result. Add the drying temperature and program, so the result can be repeated.
Get a test video for your samples
Tell us your test requirements, such as the material, the size and the test you need. We source similar samples here, run the test on the instrument you are looking at and send you the video. No need to ship samples.
Questions about a model or a test? Email Amy Zhao, Export Manager, at [email protected].
