How to Determine the Moisture Content of TPU Material with a Halogen Moisture Analyzer
How to determine the moisture content in TPU (thermoplastic polyurethane) with a halogen moisture analyzer? This is a question of great concern to TPU (thermoplastic polyurethane) suppliers and their customers. This article provides a moisture determination solution for typical TPU (thermoplastic polyurethane) samples. You will learn how to use a halogen moisture analyzer to determine the moisture content of TPU samples, as well as the operating procedures and specifications of the VM-E01 rapid halogen moisture analyzer.
VM-E01 Halogen Moisture Analyzer（0.1mg/0.0001g）
Plastic part suppliers and their customers care about quality and fast production. Proper moisture in raw material ensures trouble-free compounding and molding, smooth surfaces, and ideal mechanical properties. The VicoMeter VM-E01 rapid halogen moisture analyzer is ideal for simple, accurate moisture measurement on the production floor.
Measuring moisture in plastics with a halogen moisture analyzer is a recognized ASTM method: D6980-12, "Standard Test Method for Determination of Moisture in Plastics by Loss in Weight".
VicoMeter is an expert in moisture testing, providing fast, targeted industry solutions. This article presents a moisture measurement solution for typical TPU (thermoplastic polyurethane) samples: how to measure TPU moisture content with a halogen moisture analyzer, plus the operating procedure and best practices for the VM-E01 rapid halogen moisture analyzer.
Before learning how to measure TPU (thermoplastic polyurethane) moisture with the VM-E01 halogen moisture analyzer and its operating procedures, you may also want to know the following:
Can a halogen moisture analyzer replace the oven method? Yes — seeCan Rapid Halogen Moisture Analyzers Replace the Oven Method?as discussed in that article.
How to choose a fast, accurate model? See"Rapid Halogen Moisture Analyzer Selection Guide"as discussed in that article.
Where to learn more about halogen moisture analyzers? See"Basic Knowledge of Rapid Halogen Moisture Analyzers"、"Explanation of Halogen Moisture Analyzer Technical Specifications"、《Halogen Moisture Analyzer》and other articles.
Other questions about measuring plastics? See the FAQ in"FAQ: Measuring Plastics with a Halogen Moisture Analyzer"as discussed in that article.
WKT-A9 Karl Fischer Trace Moisture Analyzer Coulometric
In this test, the VicoMeter WKT-A9 Karl Fischer moisture analyzer was used to determine the reference moisture value of TPU (thermoplastic polyurethane). Paired with the WKT-V2 Karl Fischer oven, the sample is transferred into the oven chamber and the released moisture is carried by dry nitrogen into the electrolytic cell for measurement.
If you have no reference method for plastics samples on the VM-E01, VicoMeter recommends these settings from experimental experience:
Heating mode: Standard
Shutoff mode: Automatic (1 mg/140 s)
Sample size: 30 g
Resolution: High (0.1 mg/0.0001 g)
Warm-up: standby, 100°C; at standby temperature, preheat the empty pan for 1 minute, then tare.
Figure 1: Same Sample Heated at Different Temperatures
(Click image to enlarge)
Choose a drying temperature matching the Karl Fischer reference value. Melting or marked color change means the temperature is too high. Some samples inevitably discolor when heated (polyamide unavoidably turns brown).
Figure 1 compares samples after two heating runs. Left: correct temperature — no melting or discoloration. Right: the sample browned, so the temperature was too high.
Measure samples promptly. Otherwise, fill the container completely (use a smaller one if needed) and seal it to minimize air and prevent moisture uptake during storage.
Place the VM-E01 rapid halogen moisture analyzer in a suitable location, switch it on and warm up for 30 min, level it (bubble centered), and perform weighing and temperature calibration. You can then start the TPU (thermoplastic polyurethane) moisture measurement procedure (installation, operating environment, warm-up and calibration are covered inPreparation Before Formal Measurement with a Halogen Moisture Analyzeras discussed in that article; click the link to learn more.).
1. Place the empty sample pan on the tripod at the center of the instrument, preheat for 1 minute at a standby temperature of 115˚C, then press the tare key to zero.
2. Using a spatula, quickly and evenly spread about 30 g of TPU (thermoplastic polyurethane) sample on the sample pan and wait for the reading to stabilize.
3. Once the reading is stable, press the start key. After a few minutes, the TPU (thermoplastic polyurethane) moisture result is displayed on the screen.
VM-E01 Halogen Moisture Analyzer（0.1mg/0.0001g）
Heating mode: Standard
Heating temperature: 115℃
Shutoff mode: Automatic (1 mg/140 s)
Sample size: 30 g
Resolution: High (0.1 mg/0.0001 g)
Warm-up: standby, 100°C; at standby temperature, preheat the empty pan for 1 minute, then tare.
Sample description: TPU, beige, hydrolysis-resistant, antimicrobial, plasticizer-free
Typical Maximum Allowable Moisture Content [%]: 0.1
Hygroscopicity (23°C/50% rH) [%]: Not provided
Chart Notes
Recommendation: measure 6 TPU (thermoplastic polyurethane) samples, each with a different moisture content (dry, moist).
Green line:Moisture content (average) measured with the WKT-A9 Karl Fischer moisture analyzer and WKT-V2 Karl Fischer oven.
Blue line:Moisture content (average) measured with the VM-E01 rapid halogen moisture analyzer.
Red line:Typical maximum allowable moisture for pellet processing; refer to the supplier's material-specific values.
| Sample Information | Moisture content of the TPU sample before drying | Moisture content of the TPU sample after drying | ||
| Test Method | Halogen Moisture Analyzer | Karl Fischer Moisture Analyzers | Halogen Moisture Analyzer | Karl Fischer Moisture Analyzers |
| Moisture %MC | 0.492 | 0.491 | 0.051 | 0.050 |
| Std Dev Δ | 0.003 | 0.003 | 0.001 | 0.003 |
| Test Time [min] | 19 | 30 | 10 | 30 |
Sample-Specific Test Notes
Maximum allowable moisture for pellet processing must always follow supplier specifications. Values here are typical only and may not suit your material or process.
These drying parameters were obtained on common plastics and do not cover all grades or colors; optimizing them may be needed for best results on a specific material.
Yes. Measuring moisture in plastics with a halogen moisture analyzer is a recognized ASTM method: D6980-12, "Standard Test Method for Determination of Moisture in Plastics by Loss in Weight".
Yes — seeCan Rapid Halogen Moisture Analyzers Replace the Oven Method?).
Yes — reinforced plastics contain glass or other materials that do not affect moisture measurement.
Adjust drying temperature for heat absorption — e.g., black resin about 10°C lower than white.
Take care: loss on drying counts volatilized plasticizer as moisture. Heat at a lower temperature where possible to prevent plasticizer loss.
Not directly. As a rule of thumb, the VM-E01 drying temperature is about 30°C lower than the oven's.
It is a good reference, but should be adapted to the other suppliers' polymer compounds.
Thermoplastic polyurethane elastomer, also called thermoplastic polyurethane rubber (TPU), is an (AB)n-type block linear polymer in which A is a high-molecular-weight (1000–6000) polyester or polyether, B is a diol with 2–12 linear carbon atoms, and the AB segments are linked by a diisocyanate. TPU is cross-linked through intermolecular hydrogen bonds or light cross-linking between macromolecular chains; both cross-link structures are reversible as temperature rises or falls. In the molten or solution state the intermolecular forces weaken; after cooling or solvent evaporation, strong intermolecular forces reconnect and restore the original solid properties. A typical TPU is spandex.
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