CMC Lexicon

Effective adhesive polymer for almost any application. It is processed using aqueous dispersion or solvent systems. Very good resistance to ageing and to UV radiation. Usually good resistance to solvents, therefore ideal for electrical applications (impregnation).

Adhesive effect between a fixed bonding surface and a second phase, which may consist of individual particles, molecules, droplets or powders or of a continuous liquid or solid film. In adhesive technology, adhesion is a measure of the adhesive force on the subsurface.

Also adhesion. Specifies the force require to pull an adhesive tape off a surface. It is usually measured as follows: A 10 mm (N/10 mm) or 25 mm (N/25 mm) wide piece of adhesive tape is stuck to a standard steel (or glass) surface. After a specific period (immediately, 20 minutes, 24 hours), the adhesive tape is pulled off at an angle of 180°. The force required to do so is measured (10 N ~1 kg)

The properties of adhesives change over lengthy storage periods. This does not always mean that they deteriorate. Our adhesives can be stored for at least 6-12 months in appropriate conditions (cool and dry) without compromising their properties. Most adhesive tapes can be used without restriction even after several years of storage.

The carrier is the term used for the material to which the adhesive is applied. Normally this is a film, fabric, fleece or metal foil.

Term used for the bond between materials caused by genuine chemical bonding or inter-molecular forces. Cohesion can be understood as a special case of adhesion, in which parts of the same type stick together. Cohesive forces take effect inside the materials. Cohesion is greater in solids than in liquids; it accounts for the internal strength of adhesives. A measure of cohesion is the shear resistance of an adhesive.

Combination of two or more layers of film-like materials. Usually combines the positive attributes of the laminate partners (e.g. laminate of glass fibre and polyester: tensile strength from glass fibre, dielectric strength from polyester film). The laminate adhesive cannot usually be detached.

Term derived from Latin corrodere (= to gnaw away at) “for the reaction of a metallic material with its environment, which brings about a measurable change in the material and can cause impairment of the function of a metallic component”. Corrosion can also be defined as the change in a material starting from its surface, caused by unintended chemical or electro-chemical attack and having a detrimental effect that reduces quality. But also: destruction of insulation by exposure to voltage. A measure of the destruction caused by the application of a voltage is the CTI value.

Coats of adhesive are applied as solutions or dispersions. The dissolved polymers form cross-links when the solvent evaporates, creating larger molecular groups. The extent of the cross-linking can be used to control the tack and the chemical and thermal resistance. The cross-linking can be strengthened in thermosetting adhesives by subsequent application of heat (above 100 °C at CMC). The adhesive is then more chemically resistant.

(comparative tracking index)

Indication of the resistance of an insulating material to a voltage difference in a damp and dirty environment. Basic measurement set-up: Two electrodes are placed on an insulation material and a salt solution is drizzled between them. The voltage applied generates a flow of current which damages the insulation in different ways depending on the material.

Designates the immediate adhesion force (“tack”) of an adhesive. The immediate adhesion force can be very high, even with inferior adhesives. However, there is no direct connection between the immediate adhesion force and the permanent adhesion.

Indication of the mass of a specific volume, e.g. the mass of one cubic metre. The density of polyester is 1400 kg/m³. 1 m² of film 100 µm thick weighs approx. 0.140 kg.

Collective term for dispersions (lattices) of finely distributed natural and/or synthetic polymers (particle size 0.05 - 5 µm) usually in aqueous, more rarely in non-aqueous dispersion agents. This includes dispersions of polymers such as natural and synthetic rubber, artificial resins and plastics such as polymerisates, polycondensates and polyaddition compounds. A distinction is made between primary dispersions, in which the polymerisation of basic monomers takes place directly in the liquid phase (suspension polymerisation or emulsion polymerisation, e.g. vinyl acetate or acrylics) and secondary dispersions, in which prefabricated polymers are dispersed in a second process stage (polymer dispersions e.g. of polyisobutene, silicone resins). Very little pollution of the environment with solvent during production. However, thermal resistance is not usually high and there is a risk of a corrosive effect when used in electrical technology. Frequent use in the field of mass labelling.

(voltage, dielectric strength, dielectric breakdown)

The voltage at which a current begins to flow through the insulation film. The disruptive discharge voltage marks the absolute maximum voltage to be used and in continuous operation the voltage should be significantly below this.

Describes the corrosive effect of an adhesive tape on another material. In order to measure the corrosive effect, the adhesive tape is stuck to a brass test foil and tested with the simultaneous effect of direct voltage, heat and humidity – in other words, under difficult conditions. A characteristic value is allocated to the material as a measure of the corrosion of the test material. The positive terminal foil is given values from A (no change), through AN, A/B to B (heavy red discolouration) and the negative terminal foil has values from 1 (no change), through 1.2, 1.4, ... 2, 3 to 4 (significant discolouration). Factors up to 1.4 are deemed to be non-corrosive in electrical technology.

EMC describes the capacity of a device neither to disrupt its electromagnetic environment nor to be disrupted by it. An obvious example is a mobile phone, which is a (disruptive) transmitter itself and a recipient of disruptive signals. Shielded housings are often used to protect electronic assemblies against EMC disruption. These are generally enclosed metallic spaces which can also be made by e.g. copper adhesive tapes/punched parts. The eddy currents induced can be conducted to earth by electrically conductive adhesives, which increases the effectiveness of the EMC shield significantly.

Here: special craft paper with slight creping (elasticity, cushioning). Our flat crepe paper is specially impregnated so that it can be used as a simple insulator in transformer technology. The adhesive is resistant to the impregnating agent.

Adhesive which is melted by heating it up and then applied to the material to be coated via spray heads, for example. Forms a permanent bond when cold. Very good immediate adhesion (sticky), but usually only very low heat and ageing resistance. Hardly used at all in electrical technology.

The capacity to create a barrier to liquids and gases. Usually, water vapour permeability that is as low as possible is expected for the carrier film (polyester approx. 20 g/d × m²). Metal foils are extremely impermeable.

Designates the immediate adhesion force (“tack”) of an adhesive. The immediate adhesion force can be very high, even with inferior adhesives. However, there is no direct connection between the immediate adhesion force and the permanent adhesion.

The capacity of an adhesive tape to create an electrical separation between two electrical conductors. Frequently: separation between primary and secondary winding on a transformer.

Classification of adhesive tapes used in the field of electronics according to their thermal resistance in continuous use.

The individual classes (heat classes) mean:

Class Y a constant temperature range up to 95 °C

Class E a constant temperature range up to 120 °C

Class B a constant temperature range up to 130 °C

Class F a constant temperature range up to 155 °C Class

H a constant temperature range up to 180 °C

The individual insulation classes are allocated to various films. The best known are polyester (B) and Kapton (H).

The heat class describes the capacity of an insulation film to retain at least 50% of its initial dielectric strength after 20,000 hours at the maximum operating temperature. It does not therefore provide any information about the maximum short-term load temperature, which is usually significantly higher (e.g. polyester at about 220 °C/30 min.; Kapton approx. 400 °C/hour). In applications outside the area of electrical technology, other films may be used, as indicated by their heat classes.

The liner is the material used to cover the adhesive. Required in particular if the adhesive would stick too firmly to its own carrier. Silicone-coated paper is usually used. PE and PET films are also available, however. With double-sided adhesive tapes, a double-sided separating layer is always used.

The unit used to designate the thickness of the carrier film or the adhesive in adhesive tapes. One micron = 1 thousandth of a millimetre (0.001 mm). A human hair has a diameter of about 40 µm. The most common insulating polyester film is 23 µm (0.023 mm) thick.

Symbol for Newton. Put simply, 10 N corresponds to a force of 1 kg. The adhesion force and the tensile strength are measured in N/mm, for example.

Largely or completely non-transparent film. In contrast to translucent (allows light to pass through) or transparent.

Temperature range in which adhesive tapes can be used. Defined by the heat class in electrical technology (usually: 130 °C to max. 180 °C). Best combination of tack (immediate adhesion) and adhesion force at room temperature. At very low temperatures, there may be a risk of breaking in acrylic and rubber adhesives with bending load.

Very cheap mass film, mainly used in the packaging industry. Like PE, polypropylene is one of the polyolefins. Good resistance to acids, bases and solvents, good tear strength, low thermal resistance.

Partial discharge is characterised by the fact that only a part of the insulation length is penetrated, not all of it. However, these partial discharges in part of the insulation system lead to ever greater damage over time. After hours, days, weeks, months or years, the insulation system is weakened to such an extent by the continuous partial discharge that a full disruptive discharge occurs. Partial discharges can occur along the surface (tracking paths, sliding discharges) or in solids (treeing). They are usually created on sharp edges (field line concentration) or at damage points (cavities in insulation material).

Abbreviation for polyethylene. Polyethylene is one of the polyolefins and has a high tensile strength even in small thicknesses. As LD (low-density) PE, the film is soft and moulds around surfaces well. Frequently used as a convenient surface protection film. Low UV and thermal resistance.

Film that is extremely resistant to high temperatures, bases, acids, oils and numerous solvents and also has very good tensile strength. The most widely used insulation film in the electrical sector and a popular adhesive tape. Cheap but has excellent physical-chemical properties. Standard thicknesses: 23 µm, 36 µm, 50 µm, 100 µm, 150 µm, 190 µm and 250 µm.

Plastic film with high thermal resistance. Generally known as Kapton (trade name of Du Pont). Poyimide film can be used up to about 350 °C and provides excellent mechanical and electrical properties. The brown-lucent film is relatively expensive and is frequently used in the electrical industry as high-performance insulation.

If there is insufficient adhesion (e.g. on EPDM, PP or PE), significantly better adhesion forces can be achieved by using primers. Primers must usually be applied very thinly and form an almost invisible film on the surface to be glued.

PU ist die Abkürzung für Polyurethan. Für doppelseitige Klebebänder im Einsatz und für Schall- und Abriebschutz. In der Elektroindustrie kaum Einsatz.

PVC stands for polyvinyl chloride. Film that is extremely resistant to UV. Used as soft PVC film in the field of insulation. Low thermal resistance and can cause damage to the subsurface as a result of plasticiser migration.

Determination of the tack of an adhesive. A steel ball runs down an inclined surface into the adhesive coating. The distance required for the ball to come to a stop is measured. The ball tack test is measured in cm. The test is controversial because of the inexact results, however.

Adhesives made of natural or synthetic rubber. These adhesives generally have a high adhesion strength and very good shear resistance.

The shear resistance describes the internal strength of an adhesive in particular. A distinction is made between static shear resistance and dynamic shear resistance. The measurement methods differ as follows. With static shear resistance, a piece of adhesive tape measuring 25 mm x 25 mm is stuck to an almost vertical steel plate and a specific mass is applied to pull it downwards (0.5 kg, 1 kg, 2 kg). The time it takes for the adhesion to shear off is given in hours. In the case of dynamic shear resistance, the adhesion described above is tested with a tensile testing machine and the force (in Newtons) required for the adhesive to shear off is determined. Shear-resistant adhesives are ideal for bonding flat materials that are under tensile stresses.

Polysiloxane adhesives have outstanding heat and cold resistance properties. The adhesives can usually be used above 300 °C and below -50 °C. They have good adhesion to silicone papers / silicone profiles. Used on other surfaces (e.g. metal surfaces), can be removed without leaving a residue even after heat exposure.

Treatment of surfaces to make them resistant to adhesive, e.g. papers or films. The surfaces are very smooth and can only be glued with polysiloxane adhesive. These adhesives cannot therefore be lined with siliconised paper, and fluorosiliconised films are used instead.

A mend or glued spot. In the paper and film industry, it is the term used for a point at which two lengths of material are glued together. Silicone papers, in particular, can only be spliced with polysiloxane adhesive tapes.

Modern adhesives can be stored for a long period, i.e. their properties do not change with correct storage. Storage in a dry, dark room at approximately 18-22 °C is ideal. Adhesive tapes can then often be stored for years.

Error pattern in adhesive tapes. As a result of over-tight winding, the layers of adhesive tape move in a funnel shape to one side. The tape therefore telescopes out of its original roll width. This error pattern can also come about if materials that can absorb water (e.g. Nomex) are stored in conditions that are too damp.

Force required to tear e.g. a 25 mm-wide strip of film (adhesive is not relevant to the test). The test involves clamping a strip of film in a tensile testing machine and pulling it apart at a defined speed. The result is given in N/mm.

Adhesive tapes with thermosetting adhesive coatings can be used at room temperature as normal. When heat is applied (over 100 °C at CMC), the resistance to solvents (impregnating agents in the transformer industry) is enhanced.

High-energy electromagnetic radiation with a wavelength below visible light (l = 400 - 10 nm). UV rays are present in daylight and destroy many rubber adhesives. This process depends on the intensity of the radiation. Adhesive tapes must therefore be stored in dark conditions. Acrylic adhesive tapes are largely resistant to UV rays. The application therefore determines which adhesives are used.