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Drying and Moisture Analysis Testing of Materials

Significance and Purpose

Drying and Moisture Analysis Testing is essential for plastics and moisture-sensitive materials to ensure optimal performance, processing stability, and product quality. Plastics can absorb moisture from the environment, which can significantly impact mechanical, thermal, and processing properties such as strength, viscosity, dimensional stability, and appearance.

The primary goals of moisture analysis include:

  • Ensuring Material Performance: Moisture can cause hydrolytic degradation in polymers, reducing mechanical strength and durability.
  • Optimizing Processing Conditions: Many polymers require specific moisture levels before injection molding, extrusion, or thermoforming.
  • Quality Control: Inconsistent moisture levels can lead to defects, surface imperfections, and variable product performance.
  • Compliance with Specifications: Industries such as automotive, aerospace, and electronics require precise moisture control to meet performance standards.

Relevant ASTM, ISO, and DatapointLabs (DPL) Standards

Drying for Moisture-Sensitive Materials

  • DPL D-017: Drying of Moisture-Sensitive Materials.

Moisture Analysis

  • DPL D-017: Moisture Content Analysis using an Aboni Moisture Analyzer.

Water Absorption Testing

  • ASTM D570: Standard Test Method for Water Absorption of Plastics.
  • ISO 62: Plastics — Determination of Water Absorption.

DatapointLabs Tests for Drying and Moisture Analysis

Tests in the DatapointLabs test catalog that reference drying and moisture analysis are as follows:

Drying and Moisture Analysis Specific to Plastics

Test ID Test Description Standards
D-017 Drying for Moisture Sensitive Materials DPL D-017*
D-018 Moisture Analysis DPL D-017*
D-019 Water Absorption ASTM D570, ISO 62

* Internal DatapointLabs Standard

Principle of Operation

Moisture content and water absorption are measured through distinct methods depending on the material and application:

  1. Drying for Moisture-Sensitive Materials (DPL D-017):
    • Moisture-sensitive polymers are dried in a vacuum oven or fluid bed dryer at a specified temperature and time.
    • Moisture content is monitored at regular intervals using an Aboni moisture analyzer until the target level is reached.
  2. Moisture Analysis (DPL D-017):
    • A sample is analyzed in the Aboni moisture analyzer, which measures moisture content through a calcium hydride technique.
  3. Water Absorption (ASTM D570, ISO 62):
    • A specimen is dried, weighed, immersed in water, and reweighed after a specified time to determine water absorption.

Typical Procedure

Drying for Moisture-Sensitive Materials (DPL D-017)

  1. Sample Preparation:
    • Pelletized samples are prepared and weighed.
  2. Drying Process:
    • Place samples in a vacuum oven or fluid bed dryer.
    • Set the temperature and drying time as specified by the customer or material manufacturer.
  3. Moisture Monitoring:
    • Remove small samples at regular intervals.
    • Analyze moisture content using the Aboni moisture analyzer.
  4. Drying Completion:
    • Continue drying until the target moisture level is achieved.

Moisture Analysis (DPL D-017)

  1. Sample Preparation:
    • Weigh the sample before testing.
  2. Moisture Analysis:
    • Place the sample in the Aboni moisture analyzer.
    • Heat is applied at selected temperature.
  3. Moisture Content Determination:
    • Moisture content is inferentially determined via detection and measurement of hydrogen gas generated via calcium hydride reagent reaction with water vapor in reactor chamber.
  4. Data Recording:
    • Record moisture content for process optimization and quality control.

Water Absorption (ASTM D570, ISO 62)

  1. Sample Preparation:
    • Prepare standardized specimens (e.g., 50×50×3 mm for ASTM D570).
    • Dry the specimens to a constant weight.
  2. Weighing & Immersion:
    • Record the initial mass (mi).
    • Immerse specimens in distilled water at a specified temperature for a predefined time.
  3. Final Measurement:
    • Remove the samples, wipe dry, and weigh immediately to obtain the final mass (mf).
  4. Water Absorption Calculation:
    Water Absorption  ( % ) = m f − m i m i ⋅ 100

Specimen Types

Specimens used by DatapointLabs in drying and moisture analysis testing are as follows:

Specimen Type DatapointLabs Test IDs
Pellets [Details] D-017
Specimens, Any Type [Details] D-018
Discs (50mm Diam.) [Details] D-019

Characterization Measurements

Drying for Moisture-Sensitive Materials (DPL D-017)

  • Moisture Content (%): Percentage of moisture removed from the sample over time.
  • Drying Time: Time required to reach the target moisture level.

Moisture Analysis (DPL D-017)

  • Moisture Content (%): Moisture level in the sample before processing or testing.

Water Absorption (ASTM D570, ISO 62)

  • Initial Mass: Mass before water immersion.
  • Final Mass: Mass after water immersion.
  • Water Absorption (%): Increase in mass due to absorbed water.

Typical Data Reported (see test descriptions for exact details)

  • Moisture Content (%): Pre- and post-drying measurements.
  • Drying Time: Time required to reach the desired moisture level.
  • Water Absorption (%): Mass increase due to water uptake.
  • Temperature and Humidity Conditions: Environmental factors affecting moisture behavior.
  • Material Type & Processing History: For correlation with mechanical and thermal performance.

Suitable Material Types

  • Moisture-Sensitive Polymers: Nylon (PA), PET, PBT, PC, PLA.
  • Thermoplastics: ABS, PP, PE, PS.
  • Thermosets: Epoxy resins and composites.
  • Elastomers: TPU, TPE, natural rubber.
  • Foams: Open- and closed-cell structures.

Suitable Applications

  • Automotive: Ensuring moisture control in polyamide-based components (e.g., intake manifolds).
  • Aerospace: Moisture-resistant composite materials for structural components.
  • Electronics: Reducing moisture-induced electrical failures (e.g., PCBs).
  • Medical Devices: Maintaining dimensional stability in hygroscopic materials.
  • Packaging: Evaluating barrier performance against moisture ingress.
  • Additive Manufacturing: Drying 3D printing materials to ensure consistent extrusion and mechanical properties.

Conclusion

Drying and moisture analysis testing is a critical material evaluation process to ensure consistent, high-quality material performance in moisture-sensitive applications. By applying DPL D-017, ASTM D570, and ISO 62 standards, engineers and manufacturers can accurately assess moisture content, drying efficiency, and water absorption behavior. Maintaining optimal moisture levels is essential for improving product reliability, optimizing manufacturing processes, and meeting industry specifications.

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