ASTM D6869: Moisture In Plastics Testing Services
Accredited ASTM D6869 moisture in plastics testing from Infinita Lab, performed to the exact standard requirements - accurate, reproducible results with full documentation for compliance, R&D, and quality control programs.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
What Is ASTM D6869 Moisture In Plastics?
ASTM D6869 is the standard test method for determining moisture content in plastic materials using Karl Fischer titration -both the coulometric and volumetric variants. Moisture content in plastics matters more than most engineers initially assume. Many engineering thermoplastics -nylons, polyesters, polycarbonate, ABS, and acrylic among them -are hygroscopic and absorb moisture from the atmosphere during storage and handling. When these materials are processed at elevated temperatures without adequate drying, the absorbed moisture hydrolyzes polymer chains and degrades molecular weight, leading to splay, bubbles, brittleness, and mechanical property loss in the final part. Knowing the actual moisture content, not just estimating it from storage time, is the right way to make the drying decision.
Karl Fischer titration is the gold standard for moisture determination in plastics. It is highly specific to water -it does not respond to other volatiles like residual solvents or monomer -and it is far more accurate at low moisture levels than loss-on-drying (LOD) methods, which cannot distinguish water from other volatiles. Coulometric KF is preferred for low moisture levels (below approximately 1 percent) and is the typical choice for dried engineering resins. Volumetric KF is used for higher moisture levels and wet samples.
The test is performed by dissolving or extracting the moisture from the plastic specimen and introducing it into the Karl Fischer reagent, where water reacts quantitatively with iodine, sulfur dioxide, and a base in the reagent. The amount of water is determined by the electrical charge consumed (coulometric) or the volume of reagent consumed (volumetric) in the reaction. The result is reported as parts per million (ppm) or percent moisture by weight.
Applications and Benefits of ASTM D6869 Moisture In Plastics Testing
Scope
- The ASTM D6869 test method covers the determination of water content in plastic materials, using the chemical reaction between iodine and water that Karl Fischer titration is based on.
- It applies broadly to most plastic resins, compounds, and finished forms, including pellets, powders, flakes, film, and molded parts.
- Two measurement approaches are recognized: a coulometric technique, which generates the Karl Fischer reagent electrochemically and correlates moisture to the electrical charge consumed, and a volumetric technique, which titrates the sample with a standardized reagent and correlates moisture to the volume delivered.
- Sample water can make its way into the titration cell directly, get extracted by dissolution in a suitable solvent, or be released as vapor through controlled heating in an oven or vaporizer unit.
- The method can quantify moisture across a remarkably broad range, from trace levels of a few thousandths of a percent up to materials that are largely water by weight, as long as sample size and technique are matched to the expected concentration.
- Since the reaction is specific to water, it distinguishes actual moisture from other volatile substances a sample might release on heating.
- Plastics containing residual monomer, unreacted catalyst, plasticizer, or other volatile components that can themselves react with the Karl Fischer reagent fall outside the method’s reliable scope and may call for an alternate approach.
- Proper sample handling matters here – protection from ambient humidity during grinding, weighing, and transfer is essential to getting a representative result.
- The standard itself doesn’t set pass/fail moisture limits; acceptable moisture levels are established separately by the material supplier, the molder, or the end-use specification.
- Test conditions, including oven temperature and dwell time when a heated extraction approach is used, are selected based on the specific resin being evaluated.
Applications
- Verifying that hygroscopic engineering resins such as nylon, PET, PBT, polycarbonate, and ABS have been dried sufficiently before molding or extrusion.
- Dryer and desiccant system performance is validated in a production environment, confirming the equipment is actually hitting its intended drying target.
- Incoming raw material lots are screened for moisture as part of routine receiving inspection and vendor qualification.
- It’s also used to confirm compliance with a customer or internal moisture specification before resin or compounded material ships.
- When molding defects like splay, silver streaking, bubbles, or brittleness show up, this test helps investigate whether residual moisture is the root cause.
- Film, sheet, and packaging materials get quality checks here too, since moisture content can affect barrier properties or downstream processing.
- Moisture-sensitive materials used in pharmaceutical, food-contact, or electronic packaging applications are assessed this way, where even trace water levels matter.
Benefits
- Specific to water -does not respond to other volatiles, residual solvents, or processing aids unlike LOD methods
- Accurate at low moisture levels -detects moisture down to 10 ppm where LOD methods are impractical
- Both coulometric (low moisture) and volumetric (higher moisture) covered under one standard
- Results in ppm or percent weight directly comparable to resin supplier specifications and dryer recommendations
- Fast analysis -typical test time 5 to 15 minutes per sample depending on method
- Applicable to all major hygroscopic engineering thermoplastics and specialty resins
- Results directly drive processing decisions -no more guessing on drying time
Our ASTM D6869 Testing Procedure
Sample Preparation
Plastic samples -pellets, granules, ground material, or cut film sections -are weighed to the nearest 0.1 mg.
1Moisture Extraction
For coulometric KF analysis of solid plastics, the oven extraction method is used
2Karl Fischer Titration
In coulometric KF, the water entering the titration cell reacts with iodine generated electrochemically at the anode.
3Calculation and Reporting
Moisture content is calculated from the mass of water determined and the initial sample mass.
4ASTM D6869 Test Parameters and Requirements
| Parameter | Details |
|---|---|
| Standard | ASTM D6869-17 |
| ASTM Committee | D20 – Plastics |
| Methods Covered | Coulometric Karl Fischer (low moisture), Volumetric Karl Fischer (higher moisture) |
| Sample Types | Pellets, powders, film, molded parts, ground or dissolved plastic material |
| Extraction Methods | Oven extraction with dry gas sweep, solvent dissolution, direct injection |
| Typical Detection Range | Coulometric: 10 ppm to 10,000 ppm; Volumetric: 0.01% to several percent |
- Coulometric Karl Fischer Titrator – Generates iodine electrochemically within the cell and measures moisture from the charge consumed; well-suited to trace-level moisture determinations.
- Volumetric Karl Fischer Titrator – Delivers a standardized Karl Fischer reagent to the sample and measures moisture from the volume of titrant consumed, typically the go-to for higher moisture concentrations.
- Karl Fischer Oven or Vaporizer Unit – Heats the sample externally so moisture releases as vapor, which then carries into the titration cell without exposing the resin directly to the reagent.
- Analytical Balance – Supplies the precise sample mass needed to convert titration data into an accurate moisture percentage or ppm value.
- Drying Oven – Used when thermal pre-treatment or comparative drying studies support the moisture evaluation.
- Desiccator and Moisture-Controlled Sample Handling Equipment – Keeps samples from picking up ambient humidity between preparation and testing.
Equipment and Instrumentation Used for ASTM D6869 Testing
What You Receive: Test Report, Data, and Certification
- A formal test report referencing ASTM D6869, identifying whether the coulometric or volumetric mode was used.
- Moisture content values are expressed as a percentage or in parts per million, with replicate data included where applicable.
- Sample identification, condition, and preparation details tie the result back to the specific lot or part tested.
- When requested, interpretive commentary relates the measured moisture level to typical drying targets for the resin family involved.
- Reports are available in digital and hard-copy formats suitable for supplier qualification files, audits, or internal quality records.
- Turnaround options range from standard to expedited service, depending on how urgent the project is.
ASTM D6869 Moisture In Plastics FAQs
ASTM D6869 determines the precise moisture content in plastics using Karl Fischer titration methods. It is used to quantify both surface and absorbed water that can affect processing and performance.
Even small amounts of moisture can cause defects like voids, hydrolysis, or reduced mechanical strength during molding or extrusion. Measuring moisture helps ensure consistent material quality and process stability.
Coulometric KF is used for very low moisture levels (trace analysis), while volumetric KF is suitable for higher moisture content. The selection depends on expected water concentration in the plastic sample.
The method is widely used for engineering plastics, resins, polyethylene, polycarbonate, nylon, and other hygroscopic polymers where moisture sensitivity impacts performance.
Why Choose Infinita Lab for Moisture In Plastics Testing
When your Moisture In Plastics results have to hold up - for compliance, a customer audit, or an engineering decision - ASTM D6869 accuracy and an unbiased third-party report matter more than price. Infinita Lab routes your ASTM D6869 moisture in plastics testing to ISO/IEC 17025-accredited U.S. partner labs with hands-on method experience, so you get defensible data, transparent reporting, and turnaround times built around your project deadline - not ours.
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