Peel tests pressure-sensitive tapes

The Tape Peel test, described by ASTM standard D2141, measures the amount of force required to peel a pressure sensitive tape from a polyolefin surface. The ability to obtain an acceptable bond between the polymer surface and the coating or adhesive depends on the level of treatment, i.e., the dyne level. The force required to peel a pressure sensitive tape is directly related to the degree of adhesion. 

Peel Adhesion of Pressure-Sensitive Tape at 180°, D3330, American Society for Testing and Materials, Philadelphia. 

Typically, pressure-sensitive tapes are applied in region B. The effective pulling rate of the standard peel test at 180° is 2.5x10 m/s, which is in the middle of region B (indicated by an arrow in Fig. 12). At very low temperature, region C may be reached. For application under freezer conditions, special tapes with lower Tg are available. 

Peel adhesion is the force required to remove a pressure sensitive tape or label from a test surface at a specified angle and rate of peel. This gives a measure of the ultimate strength obtained by the adhesive and the dwell time before peeling must be specified. In this test, the adhesive tape or label is applied to the test surface with a specified force. 

Due to the high practical relevance of adhesion forces in industrial and everyday applications, a broad spectrum of experimental methods to measure adhesion forces has been established and there are, for example, standardized procedures such as peel tests for adhesive tapes or tack tests for pressure-sensitive adhesives. We will focus here on some representative examples of experimental work targeted toward a fundamental understanding of contact mechanics and adhesion phenomena. 

In practice the methods of test used most frequently are those that measure adhesion. Wechsberg and Webber17 noted that some pressure-sensitive adhesive tapes adhered more strongly to treated rather than untreated film when tape was pressed in the same manner on samples of film and peeled off under controlled conditions with a tensometer, the force required to separate the tape... 

ABSTRACT Dif sion of acetone at the interface of a bonded pressure sensitive adhesive tape was measured using single frequency capachance measurements (SFCM) and a novel interdigitated electrode sensor design. The relative concentration of acetone at the bondline as a function of distance from the edge of the specimen and exposure time was correlated to adhesion loss measured by the 90° peel test. 

The test methods presently used to evaluate the adhesion of pressure-sensitive adhesives to release liners are modified adhesion tests, such as the 180° or 90° peel test, with the liner adhered to a test panel, or a T-peel test, where the sample is freely suspended while the tape is peeled at a controlled rate from the release liner. The values obtained by the latter method are alfected considerably by the stiffness of the liner, which alters the angle of peel. 

Standard tests used to characterize the adhesion properties of tapes are for the assessment of shear strength (see Shear tests) (the ability of a tape joint to resist a load applied in the shear mode), peel strength (see Peel tests) (the resistance of a tape joint to peeling under specified conditions) and Tack (the ability of a pressure-sensitive adhesive to form a bond immediately on contact with another material). There are many standard test specifications laid down by different authorities to assess these properties and many differences in detail between them (e.g. see Appendix). No attempt will be made to describe them comprehensively, but the principles of the tests will be discussed separately. 

Knife incisions were made for cross cut adhesion test through the coating system down to the substrate at three different places. Pressure sensitive adhesive tape was firmly pressed over the inscribed area. Coating removal along the scribed lines was examined and no peeling or removal of paints was found. 

Figure 13. Standard test methods for peel and shear adhesion of pressure-sensitive adhesive tapes...

Scotch-Tape" Test A method of evaluating the adhesion of a lacquer, paint, or printed label to a plastic substrate. Pressure-sensitive adhesive tape is applied to an area of the painted plastic article, which may first be cross-hatched with scored lines. Adhesion is considered to be adequate if no paint adheres to the tape when it is peeled off. 

Most adhesive tapes are composed of a flexible backing (paper, plastic, cloth, metal foil, etc.) to which a pressure-sensitive adhesive has been applied to one side (both sides for double-sided tapes). Pressure-sensitive adhesives typically consist of a rubbery material with a modifying tactifier that may be applied to the tape by a solvent system, hot melt, or by other means. One would expect such materials to be sensitive to the mode of stress (tensile versus shear) in the region where debonding occurs. Furthermore, since tacky rubbers of the type used in pressure-sensitive adhesive are viscoelastic, one would anticipate material properties to be time- and rate-dependent. Are these expectations consistent with the observations from your simple peel test ... 

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