Custom Rubber Extrusions – Microwave

Capillary Rheometry and Microwave Curing in Custom Rubber Extrusions.

Hi all.  Flynn here again with yet another topic of interest for a small few of us.  I hope this finds you in good spirits and I hope to be of service to you in researching custom rubber solutions.  Feel free to contact me at with any questions.

Something that always seems to be interesting is the concept of die swell and that extrusion operation is a tight balancing act of controlling the amount of swell the profile experiences post die.   One tool to predict die swell in rubber extrusions is a capillary rheometer. The Capillary rheometer is the oldest class of instrument designed to test viscosity. In Capillary rheometers, the test sample is caused to flow at a controlled rate through a capillary die. The resulting laminar flow is similar to that of an extrusion die and the typical high shear rates common in extrusions can be achieved. Metrics such as stress, shear rate and viscosity can be calculated using algorithmic derivatives of Poiseulli’s Equation to predict or estimate physical characteristics of the compound such as die swell.

To switch gears here, I will talk just a bit about the cutting edge process of microwave curing for rubber extrusions. Microwave curing systems provide a quick, uniform heating throughout the profile. This is especially useful for thick extrusions and for sponge. The compound does have to be polar to be receptive to microwave curing, which most polymers are not. However it is possible to formulate specifically for microwave receptiveness. Usually, a short microwave section is used immediately after the die to boost the extrudate to curing temperature. This is followed by a hot air tunnel to maintain temperature until the part is cured. Microwave cure systems are very energy efficient and very expensive.

Anyways, thanks for your interest.  As always, let me know if there is anything I can do. We’ve got a great team here at Goodyear and we’re eager to serve. Check out our website!!!



Flynn Sears

Goodyear Rubber



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