Loop tack test

The methods to evaluate PSAs include the rolling ball test (ASTM D3121, PSTC-6, BS EN 1721), loop tack test (ASTM D6195, FINAT Test Method 9, BS EN 1719), and quick stick test (PSTC-S). ... 

Figure 5 Quick-stick tack testing (a) compressive effect of 90° peel (b) loop tack testing.

Test Procedures and Conversion Tables, V, Loop Tack Test, Publication 6512, Gelva, Monsanto, p. 20. 

A more universal test is the probe test, in which the end of a cylinder of standard diameter is brought lightly into contact with the film for a very short time and the force required to separate it from the surface is measured. Similar in principle is the loop tack test, in which a loop of coated film is lowered onto a steel plate, making contact under its own weight, and the force required to withdraw the plate is then measured. All of these tests are markedly affected by the cleanliness of the ball, probe, or plate. Figure 4 illustrates the loop tack test. 

Another fundamental mechanics solution that has many applications in bonded joints is that of a beam on an elastic foundation. Emil Winkler first reported this analysis in 1867 [49]. The method has been widely applied to a variety of problems, perhaps most obviously that of trains passing over rails supported by the earth, and has been included in most texts on advanced mechanics of materials [16]. Since many bonded Joints have beam-like adherends supported by a more flexible adhesive layer, this model of a beam on an elastic foundation is also of great importance for a variety of joints ranging from the lap shear specimen to fracture specimens, from peel specimens to the loop tack test. 

This FINAT method differs from the PSTC (PSTC-5) quick-stick method, in which peeling is carried out at an angle of 90° without formation of a loop [55]. The Tag and Label Manufacturers Institute (TLMI, Iowa City, lA 319-337-8247) specifies a loop tack test and within their manual, includes a host of useful TAPPI and ASTM methods for testing paper and plastic film substrates used in pressure sensitive labels, respectively. 

A loop tack (Fig. 2c) test consists of allowing a tear-shaped loop of conditioned tape to drape into contact with a test surface of specified area (usually 25.4 x 25.4 mm), with the force of contact limited to the weight of the tape itself (ASTM Ref. D-6195). The ends of the loop are held in a tensile tester. After a momentary contact time the tester is engaged and the tape is removed at a specified speed. The maximum in the removal force is ordinarily observed just at the point where the two peel fronts Join. The value is reported in a force per area of tape width, or lb in. -. While this tack test has some popularity, it is perhaps more of a very short dwell time peel test, and it has variables more associated with that test, especially backing effects, since heavier backings lead to higher tack values. 

Fig. 2. Tack tests and results, (a) Probe tack, (b) Probe tack vs. temperature for a natural rubber PSA. (c) Loop tack, (d) Rolling ball.

In practice, block copolymer based PSA are often formulated from base polymer blends of triblock and diblock copolymers in various proportions. Setting aside cost considerations, the reasons for using a certain blend or even a pure triblock copolymer are typically based on performance in standardized PSA tests such as loop tack, peel, or shear tests. Yet, the effects of adding diblocks to a triblock copolymer on the details of the mechanisms of debonding are not known. 

Tack is the measurement of the quick grab or stickiness of an adhesive. Tack is a surface phenomenon that is not always indicative of an adhesive s performance. There are several methods of measuring tack. One test is called the quick stickIt is a measure of the force required to remove a tape at a 90 angle from a surface to which it has been applied under no other pressure than the weight of the tape itself. Another version of this test is called loop tack, in which the pressure sensitive tape is applied in a loop form using only the pressure of the... 

Illustrations of several test methods used to characterize tack of pressure-sensitive adhesives (PSAs) (a) flat probe tack, (b) loop tack, and (c) rolling ball tack... 

Primary tack measurement techniques include probe tack tests, loop tack, quick stick, and rolling ball techniques. These techniques are illustrated schematically in Fig. 22.12. 

Fixed bows must be tested for color fastness to water. Bows must be securely attached with the bar tack at the center. However, there are maximum length restrictions to consider for the loop and tail lengths of bows when used on children s clothing. 

Another ASTM standard method, rolling ball tack (12), involves placing a piece of tape, adhesive side up, at the base of an inclined surface. A steel ball is allowed to roll down the incline from a fixed height, and the distance that the ball travels across the adhesive surface of the tape is taken as a tack value. Longer distances of travel indicate that the tape is less tacky. Other tests involving drums, rollers, or loops of tape have also been used, but are not as common. 

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