The Tackiness Tester –How does this procedure function?Production of elastomers
Unfortunately during storage unvulcanized compounds, (e.g. "green tires”) change their ability for autohesion (self-adhesion) due to fluctuations of temperature and humidity before the final steps of the production processes can be carried out.
Under such circumstances the tackiness between two unvulcanized components becomes too low due to a reduction of the interaction between the polymer chains at the interface of the two components having to be connected with each other. If the amount of entanglements as well as the mobility of the polymer network between the contact surfaces is reduced, the tackiness will be too low.
This undesired change of the material properties of the unvulcanized compounds means a substantial financial loss even for the tire manufacturers.
Now, our new tack tester is a sufficient solution for the above problem. With the GABOTACK® system the peel strength (“tack” force) and the tackiness energy can be determined. Tack force and tackiness energy corresponds to the required force and the required mechanical energy which must be applied in order to separate two adhesive surfaces with a defined diameter.
Figure 1: GABOTACK® - the principleSegments of the two adhesive components are used as specimens. Dimensions up to 40 mm side length are possible (samples with square, rectangular and round shape). Thereby, a material thickness up to 20 mm (30 mm) can be clamped within the sample holder.
Of course, two samples are required for one measurement. The first sample is inserted and screwed into the lower the second test specimen into the upper sample holder (see Figure 1).
Figure 1: GABOTACK® - the principle
Figure 2: Peeling or “Tack” force in a tackiness testThe experiment is divided in two phases. At a first step an adhesion of both specimens is effected with a defined load and a pre-adjusted contact time (between 1 and 1000 sec). Therefore, the two specimens are pressed together by the servomotor drive. The preload is adjustable in a range between 5 N and 500 N.
If the pressing period is over, in the second step again the samples will be separated from each other (see Figure 2).
Figure 2: Peeling or “Tack” force in a tackiness test
The haul-off speed is selected. The adhesive specifically peel strength is recorded which is needed for the mechanical separation of both specimen. Additionally the tack energy is calculated (see Figure 3).
Figure 3: Result of the adhesion test with the determination of the tack force and the tack energy.
Evaluation of the results
The results of tack force and tack energy show exactly the adhesion properties. High forces and high mechanical energy correlate with high adhesion.
Due to the high resolution of this principle the determination of tack force and tack energy is a powerful method to distinguish even minor differences in the tackiness of similar or even identical materials. Of course, the tackiness test is not restricted to “green tires”. Tackiness tests on prepregs, epoxy resins and other materials are possible, too.