11th INTERNATIONAL SYMPOSIUM ON CONTACT ANGLE, WETTABILITY AND ADHESION
We will deliver the presentation of the following abstract:
Contact Angle Hysteresis of Pressure Sensitive Adhesives due to Adhesion Tension Relaxation
Surface free energy (SFE) is widely adopted in the field of adhesive study. Generally speaking, the greater the SFE is the stronger the adhesiveness is. However, the SFE of the acrylic adhesives, a kind of Pressure Sensitive Adhesives (PSA), can be as low as that of Teflon and silicone rubber while it is known that Teflon and silicone rubber are typical materials with low adhesiveness. Further, PSAs could measure 90-130 degrees of contact angles with water through sessile drop technique, which resembles hydrophobic material surfaces. Obviously it is not appropriate to evaluate the adhesiveness of PSAs only using the SFE analysis and conventional sessile drop contact angle measurements.
Dynamic contact angle experiments by means of Wilhelmy plate method have been used to study contact angle hysteresis of the PSAs. Increases and changes of contact angle hysteresis were found among the PSAs studied. To better explain the phenomena observed, Adhesion Tension Relaxation (ATR) was introduced and employed. The changes of adhesion tension (gLcosq = gS - gSL) along time or the relaxation under advancing status is believed to reflect the reorientation of the PSA segments when they are in contact with water, as a result of molecular rearrangement of multicomponent polymeric systems in order to minimize interfacial tension in response to environmental medium changes.