Understanding Melt Fracture in Polymer Processing with Capillary Rheometers

The Goal: Solving Real-Life Polymer Process Problems

Melt fracture is one of the most challenging phenomena in polymer processing. It leads to surface distortions in extruded products such as pipes, profiles, cables, or films — defects that are unacceptable in most applications. Understanding when and why melt fracture occurs is therefore critical for both material development and process optimization.

In this customer success story, Don Fleming, founder of Fleming Polymer Testing, explains how NETZSCH capillary rheometers have been central to solving real-world polymer processing problems for more than three decades.

Capillary Rheometry Enables Actionable Insights

Using NETZSCH capillary rheometers, Fleming Polymer Testing was able to quantify the critical shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress for different polymer formulations. In a study of metallocene-catalyzed LLDPE blended with Ziegler–Natta grades, the measurements clearly showed that increasing the proportion of Ziegler–Natta material significantly reduced the critical shear StressStress is defined as a level of force applied on a sample with a well-defined cross section. (Stress = force/area). Samples having a circular or rectangular cross section can be compressed or stretched. Elastic materials like rubber can be stretched up to 5 to 10 times their original length.stress at which melt fracture occurs.

This finding provides one of the few practical routes to mitigating melt fracture and demonstrates why capillary rheometry is indispensable for understanding and controlling polymer processing behavior.

NETZSCH Analyzing & Testing's Role in Customer Successes

Get to know the diverse applications of our instruments, from thermal analysis and rheology to fire testing.

Witness firsthand the satisfaction of our customers and understand why NETZSCH Analyzing & Testing remains a trusted, reliable partner for its customers, driving them towards excellence. 

What challenges did these companies face before choosing NETZSCH? What issues were they dealing to address with our solutions? And how have our instruments helped them tackle their specific challenges in research, quality control, development or production? 

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