Tackifier Interfacial Segregation in Pressure Sensitive Adhesives

摘要

The aim is to precisely characterize the tackifier distribution in model pressure sensitive adhesives and correlate variations in this distribution with the adhesives properties. Work focused on investigating the mechanical properties of the model adhesives near the surface, following the aging of a phase separated model adhesive, and synthesizing and isolating a new model tackifier which is closer in structure to common commercial tackifiers derived from wood rosin. Probing of the surface mechanical properties was done on two scales. Force-distance measurements done with a spherical indenter probed the behavior averaged over lateral areas on the order of millimeters and to depths of order microns. Force-distance measurements done with an atomic force microscope were able to resolve differences in the behavior of various domains in a phase segregated model adhesive and to limit the depth with which the mechanical properties were probed to less than one aim. In the phase segregated model adhesive a viscoelastic behavior was seen in the tackifier enriched domains, an intermediate behavior in the domain interfaces, and a viscous response in the matrix. The tackifier enriched phase appears to contribute primarily to the surface adhesion. AFM images and force-distance curves were collected for model adhesives of various compositions and after aging for 3.5, 7, 10, and 12 months.