Development of a probe tack method for determining the surface tack of thin-walled rubber films

Surface tack plays a key role in the technical application of rubber products as it affects their tribological, haptic and packaging properties. For medical gloves, a variety of surface modification techniques and coatings are applied in industry to adjust and reduce the surface tack. However, the testing of tack often relies on empirical bricking block tests that do not allow a quantification of this surface related property. Herein, a pull-off test setup was developed to reliably quantify the surface tack of thin-walled latex films. As test material, sulphur vulcanised carboxylated nitrile butadiene rubber (XNBR) films and natural rubber (NR) gloves were utilised, having been prepared by a classic coagulation dipping process. By utilising a high-speed servo-hydraulic equipment, the adhesion between two XNBR films was measured as a function of the compression load/force, contact time and separation speed. During the experiment, the required maximum vertical force was recorded with a high-frequency sensor. In addition, the consumed energy to separate two rubber films in-contact was calculated yielding the work of adhesion per unit area (G) of the samples. An increase of the compression time from 30 to 90 s enhances G by 17% while a 670 higher stress at maximum force is obtained by rising the compression force from 10 to 100 N. The results clearly show that the method gives reliable results and paves the way towards a quantitative benchmarking of the surface tack of thin-walled rubber articles.