Moisture Content ISO 15512

Moisture Content by Karl Fischer ISO 15512

Karl Fischer: An Accurate Method to Determine Water Content

Karl Fischer is a widely used method to accurately determine the water content of samples, including hygroscopic materials like nylon. This method is preferred over the simple weight loss method, which can be less accurate as volatiles other than water can also be lost during the process.

Determining moisture content is important in several applications, as it can impact the properties and performance of the material. For instance, some polymers can degrade when molded wet, leading to reduced properties. Therefore, knowledge of water content can help identify if a material is suitable for a particular application.

The test procedure involves placing a small weighed sample into the Karl Fischer drying oven at a predetermined temperature and for a predetermined period. These values are obtained by testing a similar material and varying temperature and bake time independently to determine the optimal conditions for removal of all water in the sample. If the temperature is too low or retention time is too short, not all the water will be driven off. On the other hand, a high temperature can degrade the polymer and even generate water in some cases.

During the process, the water in the sample is vaporized and carried by dry oxygen-free nitrogen into a reaction vessel with methanol. The methanol traps the water, and then the water content is titrated to an endpoint with a Karl Fischer reagent to determine the amount present.

The size of the specimen for the Karl Fischer method ranges from one to three grams. Once the test is completed, the data obtained includes the water content in percent or parts per million.

In conclusion, the Karl Fischer method is a highly accurate and reliable method to determine water content in samples. It is especially useful for materials that are sensitive to moisture or require dry conditions for processing. With knowledge of water content, better decisions can be made regarding the suitability of materials for specific applications, ensuring their quality and performance.