Preventing Film Blocking and Optimizing Haze of Metallocene PE Blown Films Through Blending with Rigid Polymers

Abstract

Film blocking typically observed in both mPE and higher modulus mPE/PP blends could be effectively reduced or prevented through the incorporation of only 2 wt.-% of rigid PS or PMMA into the blends. Blocking forces required to separate the two adjacent layers of mPE/[PP/PS] and mPE/[PP/PMMA] films were significantly reduced from 20.9 g for the neat mPE, to 0 g and 10.8 g, respectively. Films containing rigid PS, however, possessed high haze of 32.37 % while a much lower haze of 10.88 % was obtained for films with PMMA. Based on atomic force microscopy (AFM) results, total haze increased systematically with an increase in RMS surface roughness. Nevertheless, there seemed to be a critical surface roughness that could give rise to both low film blocking and low optical haze, as found in the mPE/[PP/PMMA] films. All developed films also had suitable mechanical properties and high oxygen transmission rates, OTR (> 10 000 cm ³/m ² day); these high OTR films are desirable for fresh produce packaging. Current findings also demonstrate that controlling film morphologies of these mPE blends with PS and PMMA through mixing and processing principles appears to be a promising route in determining surface roughness and internal structure that have direct influences on film blocking and clarity or haze.