Optimization of ethylene acrylic acid and low density polyethylene blend in tie-layer

Ethylene acrylic acid copolymer (EAA) is widely used as tie-layer in multilayer film structures containing aluminum foil. EAA provides adhesion between the foil and rest of the film structure. It can be used alone or as a blend with low density polyethylene (LDPE), ordinarily between 20 and 50%. However, blending EAA and LDPE does not always produce desirable results. From time to time, a clear film becomes hazy as the EAA content is increased. At the same time, the adhesive strength to foil decreases. This study focuses on elucidating the mechanism behind the high haze and poor adhesion associated with EAA/LDPE blends and on determining factors that can optimize blend performance. The results from this study indicate that immiscibility, not viscosity mismatch, is the dominant factor affecting EAA/LDPE blends. In general, EAA with low acid content is more compatible with LDPE than EAA with high acid content. Processing parameters, such as extruder RPM and melt temperature, can also be selectively used to improve the blend haze or layer adhesion.