Processing Update: On-Site Moisture Analysis Critical

Recent issues of Compounding Lines have addressed various aspects of moisture and its impact on processing. From dehumidifying dryers to drying times, several topics have been covered. Yet, the basic question to be answered remains, "Is the material dry enough for processing?" Checking moisture prior to processing is easy and cost effective — especially compared to absorbing the time and money lost through one rejected lot of molded parts.

Moisture analyzers can be used to check moisture levels of material from the bag, box or hopper. Checking material right out of the shipping container is recommended, as it may be dry enough to process directly. If not, drying the material and subsequent moisture analysis should ensure quality molded parts.

To support this, a nylon compound which measured 0.15% moisture content (better than the recommended 0.2%) from the bag was exhibiting splay as a molded part. After checking the material from the bottom of a machine-mounted drying hopper, the moisture content was 0.38%. The drying hopper was actually drawing moisture into the material just before processing.

When the drying hopper was turned off and material from the bag was processed, the splay problem disappeared.

At RTP Company, the quality assurance lab checks moisture levels of materials prior to shipping. Some moisture analyzers feature a printout option, which could be retained for documentation of the order. This can be a strong selling point, as it ensures testing was conducted and material met acceptable standards.

While all RTP Company materials are checked prior to shipping, moisture analysis is equally important just before processing. Using a moisture analyzer can pay for itself in short order.

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