The ABC of adhesive tapes
Abrasion resistance is the measurement for the abrasion resistance of adhesive tapes. Differentiations are made between Class A (low) to class E (maximum).
Acrylate adhesives can be dissolved in solvents or watery dispersions. They consist of polymerised acrylic monomers. Synthetic resins are added to increase tack. The special characteristics of acrylic adhesives lie in their high resistance to ageing, temperature and chemicals as well as being largely resistant against UV radiation and oxidation.
Adhesive power is the power required to remove a glued adhesive tape from a surface. Reference values are achieved by way of standardised laboratory tests. For this purpose, a 25 mm wide adhesive tape is glued to a polished steel plate and removed at an angle of 180°. The power required for this is measured in Kilopond (kp) and Newton (N).
All glues age. They are therefore subject to various ageing tests in order to examine the chemical-physical change in their characteristics. These changes may not perforce reduce the usefulness of the adhesive tape. Some adhesives even exhibit greater cohesion levels following ageing. Changes should generally not be apparent during the first six months. We talk about good ageing qualities when no negative effects are measurable also after twelve months. Many adhesive tapes are still perfectly usable also after ten years.
The break-down voltage describes the voltage required to allow electricity to flow through an insulator. It is measured in volt and is very important particularly in case of electro-insulation tapes.
Butyl rubber adhesive
Butyl rubber adhesives consist of a mixture of iso-butyl and natural rubber with enclosed soot particles. A high degree of cross-linking is achieved by way of hot-calendering, which ensures a very good ageing quality. Butyl rubber adhesives are furthermore largely resistant against UV radiation and oxidation.
Calender is a system of above each other or consecutively arranged heavy, usually heated, rollers. They serve to smooth surfaces of various carrier materials and allow the rolling out of adhesives to the desired thickness of the film. For example, calender is used for the production of strapping tape, a film with utmost tensile strength.
Cohesion is the force required to split the adhesive layer. Adhesive tapes leave residues on the previously glued surface in case of low cohesion.
Cold-seal describes the unique characteristic of butyl rubber adhesive to stick to itself as well as almost any other surface immediately and not removable. Good adhesion is possible even in case of slightly soiled and moist surfaces. However, cold-seal is not possible on siliconised surfaces.
Corrosion describes the reaction of a metallic material with its environment, which results in a change and impairment of the function of the material. This process starts with the surface and ultimately leads to the complete destruction of solid materials due to the influence of gases, acids and alkaline solutions.
The cross-linking serves to influence adhesion and cohesion as well as various chemical and thermal characteristics of an adhesive. The cross-linking is based on chemical changes in the cross-linking of molecular chains, which results in the three-dimensional structure of a substance.
The cubic weight is specified in kg/m³ and describes the material weight per cubic metre (see "Density").
The density describes the amount of material with respect to a volume unit (see "Cubic weight"). The specification occurs in the weight of a cubic metre (= cubic weight). In case of adhesive tapes, only the density of foam carriers is important.
Dispersion is the nano-distribution of extremely small solids in water. Acrylic and acrylate adhesive dispersions are particularly important in the adhesive tape sector. The dispersion is stabilised by adding emulsifiers.
The elastic memory describes the characteristic of a flexible material to return to the original dimensions after having been expanded. The elastic memory is particularly important in PP film carriers and sealants.
Adhesive tapes in the electrical industry are classified in various temperature sectors (= Thermal classes) according to their constant heat resistance:
Class Y = Constant heat range to 95 °C
Class E = Constant heat range to 120 °C
Class B = Constant heat range to 130 °C
Class F = Constant heat range to 155 °C
Class H = Constant heat range to 180 °C
Electrolytic corrosion factor
Adhesive tapes may have a corrosive effect on other materials. The electrolytic corrosion factor describes the possible degree of this corrosion. Factor 1 means no corrosion. The greater the corrosion, the smaller is the corrosion factor.
Flat crepe paper
Adhesive tape with a paper carrier is referred to as flat crepe paper. It is generally painted or impregnated one-sided on the surface. Flat crepe paper can be expanded by up to 15% of its original length.
Adhesive crepe tapes with a heavily glued, generally unpainted paper carrier. High-stretch crepe can be expanded by at least 40% of its original length.
Hot-melt adhesives consist of dry, non-adhesive synthetic resins. They only melt at temperatures of 130°C to 180°C and retain a high degree of tack and adhesive force after cooling down. This strong adhesion at normal temperatures is one advantage of the hot-melt adhesives. However, their disadvantage is their great sensitivity to temperatures above 40°C and UV radiation. Hot-melt adhesives furthermore exhibit a low ageing quality and are unstable against emollients. However, the resistance against emollients can be increased by additives.
Depending on the glue, the maximum adhesive force depends on the time after processing. A high initial adhesion exists i.e. in solvent, rubber and silicone glues. Other adhesives, particularly those based on acrylic and butyl rubber, only reach their maximum cohesion values hours or days after adhesion.
Insulation is the partial or complete insulation of an object against electricity as well as external influences such as moisture, heat, cold, sound and dust.
1 Kilopond is the power unit with which a mass of 1 kg affects it suspension point.
A laminate is created by the insoluble amalgamation of different carriers. The combination of the individual characteristics results in a new optimally suited aggregate carrier.
The leak tightness describes the characteristics of a material to counteract external influences. In adhesive tapes the leak tightness is particularly important against chemicals (e.g. alkaline solutions, acids or solvents), moisture and gases.
The liner is positioned between the individual adhesive tape layers and prevents unintentional adhesion of these individual layers. Single or double-sided siliconised paper or films are often used for this purpose. If siliconised materials cannot be applied, embossed foils are generally used whereby the supporting surface is minimal and thus allows the easy detachment of the adhesive tape.
Mµ (µ) is the 12th letter of the Greek alphabet. As a prefix, µ stipulates one millionth, for example 1µm = 1 millionth metre = 1 thousandth millimetre.
1 Newton is the force, which accelerates a mass of 1 kg with one metre per s².
Non-woven fabric consists of natural or synthetic fibres which are only glued or pressed lengthways (e.g. in case of tissues).
Opaque means non-transparent and is important particularly in case of UV-resistant tapes.
The operating temperature stipulates at which temperatures the adhesion is still effective. The tack of an adhesive often increases with increasing temperatures, whereas the adhesive force is reduced. The tack respectively declines in case of falling temperatures. However, the adhesive force only increases in the range of medium temperatures of approx. 20 - 25°C, which is why adhesive tapes which were stored cool often have to be warmed up to room temperature prior to usage (see "Processing temperature").
PA-film, Polyamide film
PA films exhibit a very high heat resistance and are extremely tear proof. They also have a good abrasion resistance, such as in case of adhesive tapes with PA fabric and PA velour, which belong to the highest abrasion class (according to LV 312). Polyamide films are often utilised in the electrical industry.
PE films, Polyethylene films
Polyethylene is a thermoplastic resin. PE films are soft and extremely elastic. They have a high impermeability, however a low tensile strength. Polyethylene is very sensitive to UV radiation and degrades without leaving any residue in daylight. PE films are resistant against solvents. They are utilised e.g. for the production of mildly adhesive protective films, electro insulation tapes and corrosion protection tapes.
PET film, Polyester film
PET stands for Poly-Ethylene-Terephthalate, is a thermoplastic resin and a member of the polyesters. PET film is extremely tear proof and exhibits high abrasion resistance even at a minimal thickness of 0.025 mm. Polyester films are furthermore largely resistant to high temperatures, alkaline solutions, acids, oils as well as numerous solvents and chemicals. PET films are predominately used in the screen print technology and the electrical sector.
PI film, Polyimide film
Polyimide is a high performance resin. PI films are extremely temperature, chemical and radiation resistant. They are stained light brown and have good insulation characteristics, which is the reason they are predominately used in the electro industry.
Polyurethane, PU, PUR
Polyurethane are certain plastics or synthetic resins which are particularly important as PU foam. Depending on the manufacturing, the characteristics may very extremely between constantly elastic soft foam (e.g. kitchen sponges) and hard installation foam. For example, PU foam can be utilised as carrier for mirror foil. Also highly flexible and tear resistant PU films are produced.
PP film, Polypropylene film
Polypropylene is a so-called thermoplastic; a resin which can be shaped at a certain temperature range. PP films are predominately used as packaging ribbons. They are resistant against alkaline solutions, acids and solvents; however, they are extremely UV sensitive.
Primers improve the adhesive force on difficult substrates. They are applied as a pre-coating prior to the adhesive coat.
The processing temperature describes the optimal temperature at which the adhesion should occur. This optimum is usually within room temperature between 10°C and 30°C.
PVC film, Polyvinyl chloride film
PVC is a thermoplastic resin which can be shaped by adding emollients and stabilisers. PVC films often serve as carriers for adhesive tapes. Due to their high resistance against UV radiation, PVC tapes are predominately used for exterior application. As they furthermore possess flame inhibiting characteristics and exhibit good break-down values, they are often utilised as electro insulation tapes. As hard PVC films they are extremely tear resistant and printable, which is why they are often used in the packaging sector.
Rolling ball tack
The rolling ball tack is used to determine the tack. For this purpose, a steel ball is rolled on the adhesive side on an inclined plane. The tackier the adhesive, the shorter is the travelled path of the ball.
Differentiation is made between natural and synthetic rubber adhesives. They are made tacky with the aid of resins and emollients and processed from a solution or as hot-melt adhesive. Rubber-solvent adhesives exhibit high initial adhesion; however, they have the disadvantages of bad temperature and ageing qualities as well as a lack of resistance against UV radiation.
The shelf life describes the time between manufacturing of an adhesive or adhesive tape up to the moment until the material can be processed at certain storage conditions (e.g. temperature, moisture).
Silicon compounds are non-metallic and dissolved in solvents or dispersions. In this state they are applied to papers or foils and subsequently cross-linked. Siliconised surfaces are smooth enough to prevent any conventional adhesive to stick to them. Special silicone adhesives are necessary. Siliconised paper is particularly important in the sector double-sided adhesive tapes.
Silicon rubber adhesive
Silicon rubber adhesives are the only adhesives which adhere to siliconised surfaces. They consist of synthesised polymers and have rubber-like characteristics (elastomer). Silicon rubber adhesives are extremely temperature resistant against cold as well as heat.
Splice means as much as adhesive or repair spot. The specification is particularly common in the film, paper and cardboard industry in the splicing of paper and film webs.
The tack is a measurement for the ease of flow of an adhesive and describes the adhesive force at minimum pressure. A material that feels tacky generally has no internal strength, meaning no cohesion. However, a very tacky material is usually required for uneven, rough and dusty surfaces. The tack can be measured by way of rolling ball tack.
Telescoping describes the lateral funnel-shaped displacement of an adhesive beyond the roll core. This deformation is often created by the internal pressure of the adhesive tape, which may be the result of unsuitable storage and transport conditions as well as a too tight coiling. This does not generally influence the adhesive characteristics.
The tensile strength stipulates the power force necessary for an adhesive tape to tear. The value is related to the width of the tape and is thus stipulated in Newton per cm (N/cm). To determine the tensile strength, a tensile test machine is applied in which both ends of an adhesive tape are clamped and pulled in opposite directions.
In case of thermo-setting adhesives the hardness and the adhesive force of an adhesive increase with the impact of heat. Such materials are usually applied in electrical engineering for the manufacturing of capacitors.
The power required to unwind an adhesive tape from the roller. The measurement unit for unwind force is called N (Newton)
UV (ultraviolet) radiation
UV rays are a part of sunlight and are the trigger for numerous chemical reactions. In extreme cases, the molecular adhesive structure can be destroyed within a few minutes, which is why UV sensitive adhesives have to be stored dark under any circumstances. Hot-melt and rubber-solvent adhesives are particularly susceptible. However, butyl rubber and acrylic adhesives are extremely resistant against UV radiation. In case of the latter, UV radiation can even be specifically applied to increase the chemical stability by cross-linking.