Improving Layer Adhesion of Co-Extruded Polymer Sheets by Inducing Interfacial Flow Instabilities

Area of Science:

• Polymer Science and Engineering
• Materials Science
• Rheology

Background:

• Co-extrusion is vital for creating polymer multilayer products with tailored properties.
• Layer adhesion in these products is critical for overall performance, influenced by polymer compatibility and processing conditions.
• While temperature and residence time effects are known, the impact of shear load on adhesion layer formation is less understood.

Purpose of the Study:

• To investigate the influence of varying shear loads on layer adhesion during co-extrusion.
• To explore the formation of adhesion layers under different processing conditions in a polypropylene system.
• To analyze the role of interfacial flow instabilities in enhancing layer adhesion.

Main Methods:

• Co-extrusion of a two-layer polymer sheet using polypropylene and a polypropylene talc compound.
• Variation of processing conditions, including flow rates and die geometry, to induce different shear loads.
• Analysis of the interfacial structure using confocal Raman microscopy.

Main Results:

• Specific processing conditions triggered interfacial flow instabilities, leading to the formation of micro-layers at the interface.
• These micro-layers significantly increased the layer adhesion between the polymer sheets.
• The study identified a correlation between controlled shear loads and enhanced adhesion layer formation.

Conclusions:

• Controlled interfacial flow instabilities offer a novel method for enhancing layer adhesion in co-extruded polymer products.
• Understanding and manipulating shear load effects can unlock new potentials for multilayer material design.
• This research provides insights into optimizing co-extrusion processes for improved material performance.