NIST measurements identify mechanisms that limit polymer processing. (News Briefs).

NIST has developed visualization tools that allow processors to improve the way polymers are manufactured. Polymer processors have long battled against a manufacturing defect known as "sharkskin," which causes the surface of the extruded polymer to become rough. The defect limits the speed at which polymeric materials are extruded; the speed limitation adversely affects manufacturing costs. Studied since the Second World War, the precise nature of the instability remains widely debated. Central to the debate is the precise flow pattern of the polymer as it flows through and exits an extrusion tube.

Utilizing a transparent extrusion tube and a custom-built high-speed microscope, researchers at NIST have been have been able to map out the flow in the necessary detail to settle the question of the flow behavior at the exit. This work will be published in the March edition of the Journal of Rheology. Armed with this knowledge, manufacturers will be able to understand questions relevant for the next generation of materials, for example how to reduce the prevalence of sharkskin while maintaining the physical properties and appearance of the final material.

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