Self-adhesive Tapes

Spiral corrosion due to inadequate overlap has been detected with self-adhesive tapes, and a 25 mm (or preferably half-tape-width) overlap is to be advocated. Within normal limits, the thicker the adhesive the better. 

The self-adhesive tape coatings are thin and the adhesive itself does not necessarily come into contact with the valleys in the cleaned metal surface. Under these circumstances, the transmission of water vapour through the film to the metal may be possible. Moisture-transmission characteristics and other properties of p.v.c. and polyethylene tapes, as given by major manufacturers, are provided in Table 14.6. 

Table 14.6 is only indicative of general properties, and the latest developments of specific manufacturers of self-adhesive tapes may show advances on these. 

The monitoring of temperatures for electronic control systems is now mainly by thermocouples, secured onto the outside of the pipe with self-adhesive tape and the pipe then insulated over. 

Examples are given of the use of extruded PE foam sections in conjunction with other polymeric materials in the production of triangular, semicircular, rectangular and trapezoidal profiles, e.g. beam-like structures in which the rigid support may be of GRP. The foam can be bonded with thermally-fusible adhesives or two-sided self adhesive tape affixed to the foam prior to fabricating. A standard range of the foam prodncts is available, but other types can be tailor-made. 

The gel cassette is assembled according to manufacturer s instructions. Make sure that the glass plates are clean. If necessary, clean the plates with a common washing liquid, rinse thoroughly with water, and dry. Use plain spacers. Sealing of the cassette with self-adhesive tape, molten 1% agarose, or a small amount of polymerization mixture should be done only in exceptional cases. 

Hoinkins et al., (1967) glued the ion exchange particles to a cylinder that rotated in the solution and could be easily removed and reimmersed. Bunzl (1974b) attached peat particles to a polyvinylchloride (PVC) cylinder with self-adhesive tape. The cylinder, which had a small propeller at its lower end, was rotated at 470 rpm in an H solution to saturate the peat. Then the cylinder was dipped in Pb(N03)2 and removed at certain times. Interruption tests showed that FD was rate-limiting for Pb-H exchange on peat. 

Attenuated Total Reflectance This method can be used to identify solid drugs but is only of use where relatively large amounts of compounds are available. The finely-ground sample is spread as a thin layer onto the sticky side of a piece of self-adhesive tape, and the tape is placed against the reflecting surface of the instrument with the sample side in contact. Sufficient sample is required to cover the surface of the tape completely, otherwise the spectrum of the tape will be recorded in addition to that of the sample. The technique is of use when the acid and salt forms need to be differentiated. 

Take a length of natch and with pieces of Crepe self adhesive tape l z l/4" stick the primed ends to the match about 1" apart. Hang up and light one end of the natch standing wall clear. 

Certain surfaces require some form of pretreatment prior to printing. Foil usually requires primer wash, and polyethylenes and polypropylenes need to have the surface oxidised. The corona process is almost invariably used for films and flame treatment for bottles. Whether a surface has received treatment or not can be detected by immersing it in water and observing whether or not the water runs off. An oxidised surface has a lower wetting angle. If the surface is not printed soon after treatment another treatment may be necessary. Inks will not key onto non-oxidised PE and PP and will be removed when a self-adhesive tape test is employed. 

Print adhesion on plastics (and foil) is normally checked using a self-adhesive tape peel test. A few inches of a suitable standard tape is firmly pressed onto the print area then pulled off, slowly at first, then more rapidly. An assessment of print adhesion can be made from the quantity (ideally none) removed. Adhesion can vary according to the type and colour of the ink, the degree of pretreatment, the surface involved and the printing process, etc. In order to test print under likely use conditions, product immersion tests may be necessary 60°C (140°F) is a frequently used condition, for 3 to 6 h. If product-pack may be used with soapy hands, a solution of soap can be employed. A print adhesion test, as above, can then be carried out, on the washed material, after it has been cooled to room temperature. 

Not only fibres can be produced with such technologies. Once the cellulose or its derivative is dissolved, this dope can be shaped into other bodies like hollow fibres for membrane applications (artificial kidney), membrane films, packaging films (e.g. Cellophane), self-adhesive tapes (Sellotape), or sponges. 

Single- and double-sided self-adhesive tapes come in many forms and sizes, using a variety of backing materials such as - cellulose, polyester, foamed polyurethane and PVC. The adhesive is usually based on a tacky, semi-solid acrylic polymer which may be used with a release strip. Some special tapes are heat activated. 

This desalptiou of a spreading drop apphes only when the surface is absolutely smooth. However, most surfaces contain pores and crevices into which the liquid must flow if complete wetting is to be achieved (Figures 4.3 and 4.4). Air ttapped in a pore will oppose the penetration of the liquid. If the air has time to diffuse out of the hole before the adhesive sets, the penetration will be deeper. This is one cause for the increasing adhesion of self-adhesive tapes with time, since the adhesives used remain Uquid. A consolidant or adhesive used in conservation should be given time to penetrate before it hardens. A low-viscosity liquid is obviously more likely to flow readily into the pores. 

Electrostatic theory. When the adhesive and adheiend come into very close contact, they exchange charges, which cause the attraction and adhesion. The discharge can be seen when stripping self-adhesive tape from a substrate. 

Pressure-sensitive adhesive A pressure-sensitive adhesive is a viscoelastic material, which in solvent-free form remains permanently tacky. For example, the adhesive on a self-adhesive tape. 

Eastman Chemical Company presents research study at AFERA (European Association for the Self Adhesive Tape Industry). The study reveals that depending on the specific performance demands of a given HMPSA application, it is now possible to provide substantial substitution of isoprene monomers in an adhesives formulation by using Eastman s Piccotac 7590-N hydrocarbon resin in combination with a blend of SIBS (styrene-isoprene-butad iene-styrene) block copolymer and SBS (styrene-butadiene-styrene) block copolymer. 

Since creep is considered as a key weaknesses of pressure sensitive adhesives, various specific test methods and standards have been developed to evaluate the creep resistance of pressure sensitive adhesives like, for example, in the European Standard EN 1943 ( Self adhesive tapes-Measurement of static shear adhesion ), FINAT (Federation Internationale des Fabricants et Transformateurs d Adhesives et ThermocoUants sur Papier et autres Supports), test method FTM 8 (Resistance to shear from a standard surface), or the Pressure Sensitive Tape Councils test method PSTC 107 (International Standard for Shear Adhesion of Pressure Sensitive Tape) by either monitoring the time- and load-dependent displacement of an adhesive specimen under shear load or simply recording the time to failure. The result of the so called SAFT-test ( Shear Adhesion Failure Temperature ) indicates the temperature at which a sample that has been subjected to an environment with steadily rising temperature under static shear load has failed. 

The second stage of the sample preparation is the elaboration of the striped sample. A mask is prepared from an aluminum sheet, with stripe shaped windows of 1 mm width, separated by a 1 mm spacing. This mask is placed over the sample, using double face self-adhesive tape on the edge (Figure l.b). Special care is taken to flatten the mask on the sample. 

Other uses of PEDOTPSS for antistatic layers are numerous nd mainly described in patent applications. A few examples are highlighted in the following list scratch resistant antistatic hybrid coatings polycarbonate sheets, antistatic latex gloves coated with PEDOTPSS fulfilling the tests for surface resistivity, puncture resistance and charge decay, antistatic textiles, floor coverings, and antistatic self-adhesive tapes. ... 

Thus, if handling strength must be achieved within seconds of assembly, the designer will have to specify either a hot melt or cyanoacrylate adhesive though sometimes double-sided, self-adhesive tape can help in such circumstances. If these possibilities are ruled out on other grounds then an alternative approach to the design problem must be sought. 

Self-adhesive tapes are flexible substrates coated with pressure sensitive adhesives which are wound up in roll form and cut to different widths. 

Besides numerous other authors [46-49], the main contributor to understanding of the very complex peel mechanism in self-adhesive tapes is Kaelble [50, 51]. He has shown that the peel strength is dependent on the moduli of elasticity and the thicknesses of both the adhesive and the support, on the peel angle, and the interaction forces at the adhesive-substrate interface [27]. Peel strength also depends on temperature and peel rate. At a given temperature, the peel strength increases with increasing peel rate. At low peel rates the viscous properties are dominant, polymer mole-... 

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