Nanomechanical Study of Model Pressure Sensitive Adhesives by Scanning Probe Microscopy

摘要

The overall objective is to connect the near surface behavior of a model pressure sensitive adhesive with its macroscopic adhesive performance. Work with a new tackifier suggested that for complex commercial tackifiers the mixture of species in the tackifier may benefit miscibility. When miscibility is impaired, aging phenomena become more prominent. Force-distance measurements made at different frequencies can reveal viscoelasticity effects in such adhesives, but the frequency range that can be studied is limited. X-modulation is an excellent technique for probing differences in mechanical properties of adhesive surfaces. For example, changes due to enrichment of the surface by a lower molecular weight species can be detected. However, a characterization protocol combining X-modulation with a force-distance measurement is superior, yielding better reproducibility, higher precision, and more information in one experiment. Using contact mechanics and simplifying assumptions, estimates of modulus at the surface have been made. The new protocol was also demonstrated by characterizing changes in surface behavior with humidity. Humidity effects were most pronounced with the aged model adhesive that we had already shown to have the most strongly adhesive surface of the blends of various tackifier composition. The observed changes with humidity are consistent with the contention that the surface is enriched in tackifier.