ASTM D6980 (Standard Test Method for Determination of Moisture in Plastics by Loss in Weight) provides a systematic procedure for identifying the moisture content in plastics by measuring weight loss through heating. Moisture content is essential because even low levels can cause defects such as voids, surface defects, hydrolytic degradation, and loss of mechanical properties during molding and extrusion. Laboratories commonly use this process for quality control, material qualification, and the optimization of plastics manufacturing to meet performance and processing requirements.
ASTM D6980 Determination of Moisture in Plastics by Loss in Weight
ASTM D6980 Introduction
ASTM D6980 Scope
- Relevant to most plastics.
- Loss in weight determines moisture.
- Applicable to pellets, powders, and molded plastics. Applied in process control and material qualification.
- Facilitates comparative and regular testing.
Equipment and Sample Preparation
| Specimen Details | Plastic pellets, powder, or molded parts |
| Specimen Preparation | Clean, representative samples free from contamination |
| Specimen Dimensions | Not critical; mass-based measurement |
Technique, Process and Data Collection for Determination of Moisture in Plastics by Loss in Weight
When performing ASTM D6980 testing, technicians weigh all samples and then heat them to a specified temperature to dry them. Following heating, they cool the sample under controlled conditions and reweigh it. They calculate the moisture content by measuring the difference between the initial and final weights. The gathered indirect data provides firsthand information on the materials’ suitability for processing and storage.
Analysis Results and Interpretation for Determination of Moisture in Plastics by Loss in Weight
The ASTM D6980 results express moisture content as a percentage by weight. A higher moisture content indicates the need for further drying before processing, while a lower moisture content indicates that the material is ready for molding or extrusion. Consistent performance across batches contributes to constant manufacturing performance and low defect rates.
ASTM D6980 Use/Applications
- Plastic raw material quality control.
- Checking of drying efficiency.
- Optimization in molding and extrusion.
- Checking of incoming materials.
- Material and research development.
Common Challenges and Troubleshooting
Factors such as incorrect temperature selection, sample contamination, or ambient humidity before testing can cause errors in testing. Technicians enhance accuracy and repeatability by using quick sample processing, sealed containers, fast handling, and proven heating conditions. To resolve discrepancies in moisture readings between tests, they must ensure uniform sample handling, avoid environmental exposure, and strictly control heating temperature and time in accordance with ASTM D6980.
What are the testing procedures and requirements?
In the ASTM D6980 test, the analyst weighs the plastic sample (in grams, g), then heats it to remove moisture, and reweighs to determine mass loss. The analyst places the specimen in a preheated, calibrated oven-analyzer and sometimes grinds it to ensure uniform drying. The oven vaporizes moisture from the sample, and the analysis finishes when the rate of weight loss becomes negligible. For accuracy, technicians use a 0.1 mg analytical balance and frequently validate results using sodium tartrate dihydrate.
| Test Principle | Loss in weight due to moisture removal |
| Heating Method | Oven or moisture analyzer |
| Test Temperature | Material-specific, controlled |
| Sample Mass | As specified by the method |
| Heating Duration | Until a constant weight is achieved |
| Measurement | Initial and final mass |
| Result Expression | Percentage moisture content |
Get Certified ASTM D6980 Testing for Accurate Moisture Analysis
ASTM D6980 certification ensures that labs use internationally accepted methods to state the moisture content in plastics. This certification guarantees consistent outcomes, repeatability, and industry standards, assisting manufacturers as they make process decisions, select materials, and submit regulated applications.
Updated on June 12, 2026
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