One way of avoiding melt instability
could be by reducing the shear rates of the process.
Kynar Flex PPA is a new process aid to improve extrusion of LLDPE, mPE, and PP, eliminating or minimizing the effects of melt instability
that can occur during high-shear extrusion.
The technical difficulties include: 1) the melt instability
between the two ingredients; 2) the need to instantly adjust the throughput ratio; and 3) the complex design of the conjugated spinnerette.
* Polymer melt viscosity * Elasticity, die swell, extrudate defects * Mechanism of melt instability
Flow visualization through a glass barrel
However, in spite of extensive study over more than 40 years, there is still no general understanding of the origin of these types of melt instability
. Surface melt fracture (SMF) has been the subject of a number of recent studies (4), while GMF has been investigated rather little recently.