Tack performance of pressure-sensitive adhesive tapes under tensile loading

An important property of adhesive tapes is their tack performance, which relates to the adhesive force generated by a small short-term pressure on the tapes. Tack performance declines when an adhesive tape experiences tensile loading, but this influence has not been characterized well, especially for thin adhesive tapes. A testing apparatus is developed to quantitatively evaluate the influence of applied tensile loading on the tack performance of various thicknesses adhesive tapes. The apparatus allows microscopic observation of the adhered area during separation. The separation force of 15 μm and 5 μm thick adhesive tapes exhibit ductile behavior, while that of 1 μm thick adhesive exhibits brittle behavior. These separation behaviors relate to the generation of cavities in the adhesive, whose expansion is affected by adhesive thickness. Microscopic images show that the adhered area becomes smaller with increasing tensile loadings. The unified separation energy is defined and calculated for adhesive tapes, to simultaneously evaluate the tack performance for different adhesive thicknesses and applied tensile loadings. The separation energy decreases with increasing tensile loading, but the separation energy per unit area remains largely constant, regardless of the applied tension. The effect of separation speed on separation behavior is investigated, with a change from ductile to brittle separation observed with increasing separation speed. Separation speed is also reflected in the unified separation energy.