DIN 53715 Testing of Plastics - Determination of Water Content by Titration Method According to Karl Fischer

The standard “DIN 53715 Testing of plastics - Determination of water content by titration method according to Karl Fischer”, published by the German Institute for Standardization (DIN), describes the method for determining the water (moisture) content in plastics (polymers) and their final products. This method uses the Karl Fischer titration technique, a highly specific and accurate chemical method for measuring trace amounts of water.

Many plastics (such as polyamides, polycarbonates, polyesters, and polypropylene) are sensitive to moisture. Excess water can cause:

• During processing (e.g., injection molding or extrusion), hydrolysis leads to chain disruption and a reduction in mechanical properties.
• Defects in molded parts such as bubbles, spreading, or surface defects.
• Incorrect weight or size measurements during quality control.

Accurate moisture content determination is critical for pre-processing material drying, quality assurance, and compliance with technical data sheets. For materials such as polypropylene (PP), polyamide 66/Nylon 66 (PA66), high-density polyethylene (HDPE), and polymethyl methacrylate/acrylic (PMMA), moisture values ​​are typically reported in technical data sheets according to the DIN 53715 standard.

Karl Fischer titration is a volumetric or coulometric technique based on the Bunsen reaction modified for water:

• The reagent reacts selectively with water.
• The endpoint is determined electrochemically or visually.
• It can measure water volume with high accuracy, from ppm levels to several percentage points.

The DIN 53715 standard method defines sample preparation, titration procedure, reagents, equipment, and calculations for plastics in various forms (granules, powder, finished parts).

Although the DIN 53715 standard has been repealed, the Karl Fischer method continues to be widely used in the plastics industry. This standard has been largely replaced or harmonized with the following international standards:

• ISO 15512 Plastics - Determination of water content (modern equivalent of DIN 53715 standard)
• ISO 760 General Karl Fischer Method
• ASTM D6980 or similar (moisture in plastics)

Many testing laboratories still accept or offer tests according to the DIN 53715 standard for older specifications.

Typical applications are as follows:

• Raw material incoming inspection (resins, compounds)
• Quality control of hygroscopic engineering plastics (e.g., nylon/PA)
• Verification of drying processes (dryers, dehumidifiers)
• Failure analysis of molded parts (moisture-related defects)
• Material data sheet verification

In short, the DIN 53715 standard describes a method for determining the water content in plastics using the highly sensitive Karl Fischer titration technique. Moisture content is a critical parameter in polymer materials, as even small amounts of water can significantly affect processing behavior and final product performance.

The purposes of this standard are to:

• To provide an accurate and repeatable method for measuring trace amounts of water in plastics.
• To support quality control during material production and processing.
• To prevent defects such as bubbles, voids, and deterioration caused by moisture.
• Ensuring consistency in materials used in sensitive applications such as electronic and automotive components.

The DIN 53715 standard is based on Karl Fischer titration, a chemical method specifically designed to measure water content. This method works as follows: The water in the sample reacts with iodine, sulfur dioxide, and a base in a suitable solvent (usually methanol). The reaction is stoichiometric, meaning the amount of iodine consumed is directly proportional to the amount of water present.

Two common approaches are used with this method:

• Volumetric Karl Fischer titration: Suitable for high moisture content (typically at least 0,1%).
• Coulometric Karl Fischer titration: Ideal for very low moisture levels (ppm range)

The procedure described in the DIN 53715 standard typically follows these steps:

• Sample preparation: Plastic samples are finely divided (granules, powders, or small pieces). Moisture gain or loss is avoided during processing.
• Water extraction: Water is extracted from the plastic as follows:
  • Direct dissolution (if the polymer is soluble)
  • Thermal extraction (oven method), where water is evaporated and transferred to a titration cell.
• Titration: The extracted water is reacted in Karl Fischer reagent. The endpoint is determined as follows:
  • Visually (rare nowadays)
  • Electrochemically (modern automated systems)
• Calculation: Water content is calculated as a percentage or parts per million (ppm).

The DIN 53715 standard is commonly used for moisture determination in the following areas:

• Thermoplastics (e.g., polyamide, PET, polycarbonate)
• Engineering plastics used in automotive and electronics.
• Raw polymer granules before processing
• Finished plastic parts requiring strict moisture control.

Moisture can have serious effects on plastics:

• Hydrolysis (reduces molecular weight) during processing
• Surface defects (bubbles, streaks, silvering)
• Reduced mechanical strength
• Deterioration of electrical properties

Using the DIN 53715 standard, manufacturers provide the following:

• Optimal processing conditions (e.g., proper drying)
• Improved product quality and durability.
• Reduced production waste and rejected products.

The main advantages of the Karl Fischer method are as follows:

• High accuracy and precision (down to ppm levels)
• Selective towards water (minimum interference)
• Suitable for a wide range of plastic materials.
• Compatible with automated laboratory systems.

The DIN 53715 standard is compatible with similar international standards, including:

• ISO 15512 Determination of water content in plastics.
• ASTM D6869 Coulometric Karl Fischer method for plastics

These standards share the same basic principle, but may differ slightly in procedure and reporting.

In conclusion, the DIN 53715 standard provides a standardized Karl Fischer titration procedure for reliable moisture measurement in plastics. Although no longer active, its principles remain fundamental in polymer processing and quality control. In current work, laboratories often refer to the ISO 15512 standard, and many older material specifications still refer to this standard.

For many years, our organization, with its competent and experienced staff, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services in accordance with the DIN 53715 standard.