NIST researchers use "frustrated" optical technique to measure formation of nanocoatings.

Additives are frequently mixed into polymeric materials in minute quantities in order to make them processable into the typical products well known to consumers, such as plastic sheets, pipes, and wire insulation. However, the reason behind the effectiveness of these additives had remained mysterious because the existing tools available to measure their behavior in the manufacturing process were rather crude. Now, re-searchers at NIST have utilized the optical phenomena of frustrated total internal reflection to directly visualize the behavior of fluoropolymer additives when added to polyethylene.

Researchers discovered a continuous process in which the fluoropolymer droplets "rain down" on the internal surfaces of the extruder and form a nanocoating. Similar to the fashion in which a fluoropolymer-coated frying pan prevents eggs from sticking, this nanocoating allows the polyethylene to smoothly slide through the processing equipment with lower energy utilization and without defects. Based on the measured thickness of the coating, which ranges from 20 nm to 400 nm, a qualitative model of this process was developed and published in the current issue of the Journal of Rheology. A collaboration between NIST, a private company. The University of Minnesota, and the University of Maryland is currently using this technique to uncover the critical factors influencing the coating efficiency.

For further information, visit www.nist.gov/polymers and search for "frustrated," or read the article in the Journal of Rheology (Vol. 47, No. 6, pp. 1523-1545).

CONTACT: Kalman Migler, [phone]; [e-mail].