Figure 1.

Polymer-polymer adhesion testing between glass- and gel-phase films. (A) Liquid pectin solutions (3% w/w) were cured in a low-humidity environment; the progressive evaporation of water created the gel phase and glass phase films used in these studies. (B,C) The films in the gel phase (38–41% w/w W_c) were soft and flexible. The glass phase films (10–13% w/w W_c) were hard and brittle. (D) Polymer-polymer adhesion experiments were performed with a custom fixture composed of a flat-ended cylindrical probe and parallel fixture surface for a preset development time. The cylindrical probe compressed the two polymers followed by the separation of the probe from the surface by an applied tensile load. (E) The fixture ensured that the radius of contact was defined as the radius of the probe (a) and the thickness of the contacted polymers was h. The pre- and post-experimental geometries were nearly equivalent for large values of a/h with minimal edge effects. (F) The data from a standard adhesion test reflected the compression force applied by the probe (i), the development time (ii) and the strength of the polymer-polymer adhesion during probe separation (iii).