Experiments of Classic PP Extrusion

As a classic thermoplastic, the polypropylene (PP) material presents a well known behaviour during the extrusion process. Its behaviour can be easily controlled during extrusion. In this context, the numerical simulation allows to quickly identify the key zones of the process.

The PP behaviour in twin screw extrusion has been studied in many publications*.
In the one we focus* in this post, PP is processed by a standard screw profile, as presented hereafter. It holds one main melting zone and two short additional mixing areas.

Screw profile

Twin Screw profile

The given screw profile has been modelled into the Ludovic® software with different screw elements (screw elements – for the conveying parts, kneading blocks and reverse screw for the melting and mixing parts). The simulation consists in the computation of the material flow inside the screw channel, in order to predict the mechanical behaviour of the PP.
In this way, the pressure and temperature increase zones are readable on the results display.

Temperature & pressure analysis

Display of the temperature and pressure curves along the screw profile

Interest of the numerial approach
The numerical approach allows a quick quantification of the main key areas of the process : how much degrees does the temperature increase with a 45° kneading block? How much the pressure increase with a reverse screw elements with a narrow pitch?
All those questions can be answered by numerical simulation tools such as Ludovic®

*based on “Experimental and theoretical study of twin screw extrusion of polypropylene” by O.S. Carneiro, J.A. Covas, B. Vergnes (Journal of Applied Polymer Science, Vol. 78 – 1419-1430), 2000.

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