Effect of Metallocene Polyethylene on Heat Sealing Properties of Low Density Polyethylene Blends

Abstract

Blending of traditional low-density polyethylene (LDPE) with polymers with better sealing properties, such as m-PE and Ethylene vinyl acetate (EVA), is a good alternative to meet the higher speed demands in modern packaging machinery. Even blends with low quantities of m-PE are enough to modify significantly the heat-sealing properties of LDPE. This chapter evaluates the percentage of m-PE (based in octene comonomer) for optimal balance of sealing properties and cost in laminations of BOPP/aluminum foil/PE sealing layer for packaging of diverse products. As a benefit of the enhanced heat-sealing performance, this lamination could meet the modern demands for higher speed in VFFS and HFFS packaging equipment and a better integrity of package. As a result of an extensive study with blends of high pressure low density polyethylene (MFI = 2.0) with metallocene polyethylene (12% octene and MFI = 1, 0) as a sealing layer in laminations with BOPP and aluminum foil, it is found that a blend of around 15% has the best balance of seal properties and cost. DSC studies of glass transition and melting point of the blends are helpful to anticipate total compatibility of both resins and good sealing properties based on the possibility to study interdiffusion of chain segments across the interface.