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Keywords:

  • coating;
  • contact angle;
  • peel strength;
  • peel test;
  • roughness;
  • surface free energy

ABSTRACT:  Food adhesion is an important attribute that could have both positive and negative ramifications depending on the application. Yet, its quantification remains cumbersome and as a consequence adhesion models are scarce. The effect of surface roughness, free energy, and ozone treatment on adhesion of rough low linear density polyethylene films was investigated. Adhesion was measured by a 180° peel strength test. The plastic films were roughened (surface roughness ratio, r, ranged from 1.00 to 1.15). Exposing the film to ozone treatment (0 to 300 s) modified its surface free energy, γs (32.4 to 37.9 mJ/m2, respectively), and its polar component of the surface free energy, γps (3.0 to 8.3 mJ/m2, respectively). The films were coated with polyurethane capable of forming hydrogen bonds. Adhesion was found to be a function of the apparent contact angle of water, θap[water], surface roughness ratio, and surface free energy. The linear relationship between the apparent contact angle of water, θap[water], and γps was incorporated in building an empirical model that quantifies peel strength as function of r and γps. The model showed good agreement with experimental data, especially for longer ozone exposures and rougher surfaces. The empirical model provides insight into the relationships between surface roughness, surface energy, and adhesion. Quantifying these effects could facilitate reducing biofilm forming on food equipment, antisticking treatments, or easy peel packages, or reducing food residues adhering to the food packages and consequently minimize oxidation, off flavors, and waste.