BLOCKING OF LLDPE FILMS – EFFECT OF

ABSTRACT: The mechanism of LLDPE blown film blocking has been investigated. Film specimens exhibiting different levels of blocking force are fabricated using resins with various molecular characteristics. The film surface morphology and the chemical composition are studied. Atomic force microscopy observations clearly linked blocking with the formation of a soft layer at the films ’ interface. This layer is made of amorphous PE chains, which migrated to the film surface during conditioning at 60C. No evidence of co-crystallization at the interface is observed. The chemical nature of the soft layer has been derived from its mechanical properties. A predictive model for film blocking is proposed based on a single molecular parameter. KEY WORDS: LLDPE, polyethylene films, matallocene, Ziegler–Natta, self-adhesion, short-chain branching, blocking force, hexane extractables