ISO 15512 Plastics - Determination of Water Content

The ISO 15512 Plastics - Determination of Water Content standard, published by the International Organization for Standardization (ISO), describes methods for determining the water content of plastics in powder, granular, and finished product forms. These methods do not test the water absorption (kinetic and equilibrium) of plastics as measured according to the ISO 62 standard.

Method A is suitable for determining water content as low as 0,1% with an accuracy of 0,1%. Methods B and C are suitable for determining water content as low as 0,01% with an accuracy of 0,01%. Method D is suitable for determining water content as low as 0,01% with an accuracy of 0,01%. Method E is suitable for determining water content as low as 0,001% with an accuracy of 0,001%. The stated accuracies are detection limits depending on the maximum possible sample mass. Water content is expressed as a percentage of water by mass.

Method D is suitable for polyamide (PA), polycarbonate (PC), polypropylene (PP), polyethylene (PE), epoxy resin, polyethylene terephthalate (PET), polyester, polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polylactide (PLA), and polyamidimide (PAI). It is not recommended, especially for samples that may release ammonia. Methods A, B, C, and E are generally suitable for all plastic types and moisture levels.

Water content is an important parameter for processing materials and is expected to remain below the level specified in the relevant material standard.

Six alternative methods are defined in this standard:

• Method A is an extraction method using anhydrous methanol, followed by a Karl Fischer titration of the extracted water. This method can be used for all plastics and is suitable for granules smaller than 4 mm x 4 mm x 3 mm. It can also be used for prepolymer materials in powder form that are insoluble in methanol, for example.
• Method B1 is an evaporation method using a tube oven. The water in the test sample is evaporated and transferred to a titration cell with dry air or nitrogen carrier gas, after which the collected water is subjected to coulometric determination via Karl Fischer titration or a moisture sensor. It can be used for all plastics and is suitable for granules smaller than 4 mm x 4 mm x 3 mm.
• Method B2 is an evaporation method performed using a heated sample flask. The water in the test sample is evaporated and transferred to a titration cell with dry air or nitrogen carrier gas, after which the collected water undergoes Karl Fischer titration. It can be used for all plastics and is suitable for granules smaller than 4 mm x 4 mm x 3 mm.
• Method C is a manometric method. Water content is determined from the pressure increase resulting from the evaporation of water under vacuum. This method is not suitable for plastic samples containing volatile compounds other than water in amounts that significantly contribute to the vapor pressure at room temperature. The presence of large quantities of volatile compounds should be checked periodically, for example by gas chromatography. Such checks are particularly necessary for new types or qualities of materials.
• Method D is a thermocoulometric method using a diphosphorus pentoxide cell for the detection of evaporated water. Water present in the test sample is evaporated and transported to the sensor cell by dry air or nitrogen carrier gas, after which coulometric determination of the collected water is performed. This method is not applicable to plastic samples containing volatile compounds other than water in amounts that significantly contribute to the vapor pressure at room temperature. This is especially relevant for volatile components that can react with the acidic coating of the diphosphorus pentoxide sensor, such as ammonia or any type of amine. The presence of large quantities of volatile compounds should be checked periodically. Such checks are particularly necessary for new types or grades of materials.
• Method E is a calcium hydride-based method. The water content of the sample evaporates due to a combination of vacuum and heating. The evaporated water reacts with calcium hydride to form molecular hydrogen and calcium hydroxide. The hydrogen causes a pressure increase in the vacuum proportional to the amount of water that evaporates. Volatile components that do not react with calcium hydride condense in a cooling trap and do not affect the measurement.

Interlaboratory comparability in determining the water content of plastics is generally low. The main reasons for this are differences in sample packaging, sample processing, and equipment and settings. Samples should be packaged, for example, in special glass containers or sealed bags with a water barrier. Sample processing should preferably be carried out in dry nitrogen or air. To increase repeatability and reproducibility, it is intended that the procedure described in this document be strictly followed.

Temperature settings for the evaporation method are not specified in this standard. For the manometric method, a temperature of 200 degrees is generally used. However, this may be too high for some condensation materials and could lead to water formation, for example, due to the condensation reaction.

Heating temperature should be optimized depending on the material being tested, the equipment used, and practical conditions. If the temperature is too low, the total amount of water in the material being tested will not completely evaporate, while very high temperatures will cause water to form due to effects such as decomposition and condensation reactions.

This standard includes a procedure for optimizing heating temperature to select the correct temperature for water content determination and to improve interlaboratory comparability.

Even small amounts of water in plastic materials can cause significant problems during processes like injection molding or extrusion. Excessive moisture can lead to hydrolysis (chemical degradation), resulting in defects such as bubbles, voids, spreading marks, reduced mechanical strength, dimensional instability, and accelerated deterioration. Moisture control is critical for quality assurance in industries such as automotive, packaging, electronics, and construction.

In short, the ISO 15512 standard ensures consistent and reproducible results between laboratories and manufacturers. It supports compliance with material properties where water content must remain below defined thresholds for safe processing. Adopted as a national standard in many countries, it is widely used for thermoplastics, thermosets, films, and sheets. This standard plays a vital role in maintaining the integrity and performance of plastic products worldwide.

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 in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services to businesses in accordance with the "ISO 15512 Plastics - Determination of Water Content" standard.