Experimental and Numerical Investigation Into Metallocene Polymer Melt Flow in Film Blowing Dies

Abstract

A frequent problem in the production of metallocene linear low-density polyethylene (mLLDPE) films is the occur-rence of flow instabilities, e.g. sharkskin, or degradation of material, which limit the production rate and decrease the product quality. If such problems arise, the question is what causes these phenomena and how they can be avoided. With the aim of understanding these problems and providing some guidelines for their suppression, rheological measurements together with modelling of these melt flows are often employed. In the present study, flow behaviour of two commercially available mLLDPEs was determined and used for the process simulation. The paper shows that the capillary-rheology data together with 2D finite element method can be used for the prediction of sharkskin phenomenon as well as degradation of mLLDPE melts in film blowing dies. It also reveals that the degradation of the materials in these dies can be quantified through wall shear stress. Finally, the paper describes how these findings can help optimize the flow channel in the film blowing die to avoid the undesirable flow phenomena.

A Novel Mandrel-Free Blown Film Die with Ultrashort Flow Distance and Uniform Discharge: Theoretical Modeling and Simulation

“…Generally, it is best for polymer molecules to have as low a residence time in the die as possible. This will minimize degradation, and will give an effect to higher strength in the film. ,− In order to further explore the melt residence time in the flow channel, 100 equally spaced streamlines were selected, as shown in Figures a and b. In addition, the residence time distribution is shown in Figure c.…”

Modification of polymers by protein hydrolysate—A way to biodegradable materials

“…The experimental design employed for such a study is shown in Figure 1. The rheological behaviour of the polymer films was used as a tool for measuring the biodegradability in the same way as previously reported in the literature [17][18][19]. Pure and mLLDPE blend films were measured before and after biodegradation for 21 d by using a rotational rheometer (ARES, Rheometrics Scientific, USA).…”