Moisture measurement in plastics.

Moisture affects the workability, usability and quality of many plastics. That is why information about and control of the moisture content is of significant importance. But if you want to measure moisture in plastics, that will take some searching. The specifications for moisture in plastics are often very low (<250ppm). The most commonly used analyser for determining moisture (or dry matter content) when using an oven is the halogen dry matter meter. A method that works according to the 'loss on drying' principle. However, the halogen balance is too insensitive to measure the low moisture content in plastics. The Karl Fischer method is sensitive enough, but there are many conditions attached to it. Both methods are very time consuming.

A method that is used in-line in many processes is near infrared spectrometry. Although this method is fast and can be applied in-line, it is not sensitive enough to the low moisture specifications of plastics. (In-line) NIR is a nice application for identification of different types of plastics, for example.

Fast and accurate moisture measurement in plastics

TEWS' patented microwave technology allows you to measure moisture in plastics up to 100 ppm. The unique sensor measures the moisture both at the surface and in the core of the product. Because changes in colour, density and mass have no influence on the measurement, the result is reliable and accurate.

TEWS Elektronik offers lightweight portable instruments, laboratory analyzers and an in-line (bypass) solution that are able to measure very low moisture contents (from about 250 ppm) in plastics.

Moisture measurement in plastics with microwave technology

Below we take a closer look at the results, benefits and implementation of TEWS moisture and density meters. We have opted for various production lines for the manufacture of PVC (products).

Do you have questions about moisture measurement for other applications? Please contact our Product Manager Kees van der Sar.

The inspection of PP granules (density) and PVC powder (moisture) in the laboratory

Compared to conventional halogen dryers, the analyzers from TEWS offer significant time savings when measuring moisture and density. Preparing and measuring samples with a halogen dryer takes about 6 to 7 minutes. With the TEWS analyzer this time is reduced to approximately 1 minute.

In addition, the reaction time of the dryer speeds up, you avoid scrap or rework and the operator can guarantee product quality faster and more accurately, resulting in a faster time to market.

In-line measurement of the plastic PVC during the drying process

PVC has a moisture range between 0.1% and 0.3% after the drying process. In the drying process, the moisture and density measurement can be installed with a bypass solution. The bypass sensor allows simultaneous moisture and density measurement every 30 seconds. This measurement has a standard deviation of 0.017% and a high reproducibility (correlation: 0.9987). The in-line moisture and density measurements from TEWS help you on your way to automating your internal processes (Industry 4.0) and fully control your drying process of plastic online, which saves energy and costs.

Conclusion measuring moisture in plastics

Whether we are talking about (plastic) powders, granules, flakes or plates, the high-quality moisture and density meters from TEWS help companies to achieve their goals in a simple way. They can even be used for plastics with a moisture content of 100 ppm. Chemical companies are thus able to quickly and very accurately determine the moisture content and density of their plastic products. Without any sample preparation, the entire production process is optimized, leading to significant cost savings and excellent quality control.

Contact about a moisture measurement in plastic

Would you like more information about a moisture measurement in plastics specifically aimed at your application or are you interested in a test?

Contact Inventech for more information

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Moisture and density measurement of plastics in laboratory and proces