Influence of Stress on Peel Strength of Acid Copolymers to Foil

Abstract

As an acid copolymer is converted in the extrusion coating process, it undergoes considerable stress and orientation. This stress arises from shear forces in the extruder and die, from extensional forces as the melt curtain is drawn down and from shrinkage forces during crystallization. It is hypothesized that these stresses may influence peel strength by impacting tensile properties and residual stress at the foil-polymer interface. Relationships are developed between stress and common processing parameters such as air gap, die gap, melt temperature and line speed. An experiment is described where processing parameters were changed in a systematic way to alter the stress imposed on the polymer. Data is presented which strongly supports the hypothesis, and provides an understanding as to the role and impact of various processing parameters.