These are formed by the polymerization (a chemical process forming large molecule chains from small ones) of acrylic ester monomers, the basic building block. These adhesives tend to exhibit lower initial tack than rubber adhesives, but have higher cohesive strength, thermal stability, ageing characteristics, UV and solvent resistance.

Adhesion: An intermolecular force of attraction between molecules of different substances.

Cohesion: An intermolecular force of attraction between molecules of the same substance.

With developments in polymer technology it can be dangerous at times to make generalisations about adhesive properties. However, there is a general rule that as one increases the adhesive strength (or initial tack of an adhesive) so one reduces its cohesive strength (internal strength of the adhesive or holding power).

When developing a pressure sensitive tape for a specific application the chemists or production engineers will add various ingredients, such as tackifiers and resins, to modify its performance. For example, pure acrylic adhesives offer very high cohesive strength, which confers on them good stability to temperature, UV, ageing and solvents however, they exhibit poor initial tack.

By modifying the adhesive (modified acrylic) one can improve its initial tack, but this will also affect other attributes of the adhesive. Inevitably it becomes a compromise and the best compromise will depend on the specific intended application for the tape.

Association des Fabricants Europeans de Rubans Auto-Adhesifs (The European Association for the Self Adhesive Industry) is a representative group for the industry.

The type of adhesive employed to make any particular double sided tape will confer on it particular ageing characteristics. The ageing of an adhesive tends to be accelerated by increasing its exposure to air, which causes oxidization, UV light and elevated temperature. As a very general rule one would expect to see an increasing stability through hot melts, rubber, modified acrylics, pure acrylics to foamed acrylics types.

This gradation is closely correlated to the cohesive strength of the adhesive, additionally emulsion/dispersion, which are water based adhesives, exhibit poorer ageing than the solvent based. Aged adhesives, that have hardened, will normally maintain a bond but are less able to withstand shock loads or movement.

Pressure sensitive adhesives are also sensitive to temperature and, as they cool, they lose their initial tack or adhesive strength. It is vital that an adhesive is able to wet-out and form an intimate bond with the underlying substrate when the pressure is applied. Most pressure sensitive adhesives are recommended to be applied between 15° & 25° C for this reason. However, once a bond has been formed, their operating temperature range will be far wider, dependent on their construction and adhesive type.

Some adhesives are specially formulated to be applied at lower temperature, down to 0° C. However, as the temperature reduces, so greater pressure will be required to get the adhesive to adequately wet-out and form a bond.

Relating to an adhesive system where water is used as the method for dissolving and spreading the adhesive on the carrier/release liner.

American Society for Testing Materials is an independent group determining standards for industry.

Australian Wool Testing Authority (Textile Testing) an independent third party testing authority.

This can be confusing since for double sided tapes this will normally mean the release liner and for single sided tapes it is generally referring to the material onto which the adhesive is coated. Consequently care needs to be used if and when using this imprecise term.

This is a discrete number generated by the manufacturer to allow traceability of all raw materials used in the manufacture of a product. Their own internal quality procedures will determine what constitutes a batch and when the batch number has to be changed, however, it allows the manufacturer to identify precisely what components/ingredients were used from various suppliers to create their product. If correctly recorded it is a vital tool for identifying, isolating and quarantining defective stock.

See spool.

This type of adhesive has relatively low cohesive strength but high adhesive strength, it has excellent ageing characteristics and is very resistant to moisture, oxygen, ozone, and weathering. Consequently it tends to get used for gasket and sealing type applications. Butyl rubbers also offer good damping and vibration absorption characteristics.

This is a process for applying a coating of adhesive whereby the adhesive is pressed between two rotating cylinders into a thin layer and then coated onto the carrier. This is the most common way for making cloth tapes and many rubber based adhesive tapes.

When referring to double sided tapes (that are not transfer tapes) this is the medium onto which the adhesive is coated.

Certain applications may state that a Certificate of Conformance is required for the materials being used. A CofC cannot normally be supplied after the goods have been manufactured since it requires special testing at the time of manufacture to ensure that the product conforms to a particular specification. This will normally by some form of third party specification such as a Military Specification (Mil. Spec.). A CofC will relate exclusively to a particular batch number.

A Letter of Compliance, on the other hand, can be tendered by the manufacturer after the date of manufacture and will simply confirm that the product has been manufactured to comply with a particular specification, although no specific batch testing. These documents are normally only requested for critical applications.

Where tapes are being used for bonding clear or translucent materials (e.g. plastics, Perspex, screen printing) or mounting media in windows, clarity can be an important requirement.

If the tape is being used for some form of temporary holding application then it may be desirable for it to clean remove from one or both the surfaces. For a tape to clean remove the adhesive needs to be better bonded to its carrier than it does to the bonding surface and the carrier to have greater structural strength than the bond strength. Temporary bonds require an adhesive to have good cohesive strength but only moderate adhesive strength.

Note: Clean removal from painted surfaces and plasterboard will be dependent on the quality of the keying of the paint or board to their underlying substrate.

This is the mass of adhesive applied to a unit of area. It may also be referred to as Adhesive Mass or Mass Weight and is normally expressed in grams per square metre (gsm)

This is the ease or ability of a tape to conform and make direct contact with the underlying substrate without creasing and folding or air pockets forming.

This is a process used to physically treat the carrier surface to be coated to promote the keying of the adhesive to its carrier. It is most effective when conducted in-line immediately prior to the coating, since its effect will wear off with time. It is particularly relevant in the treatment of low surface energy materials, such as polyethylene, prior to adhesive being coated.

This is a commonly used process within the adhesive tape industry to modify the performance of adhesives. It can be applied to both rubber and acrylic adhesives and involves subjecting the adhesives to either chemical or gamma irradiation treatment. The process aligns the molecules in the adhesive and links them rather than them being mobile and randomly orientated and has the effect of firming the adhesive.

The greater the degree of treatment the lower the tack level but the higher the cohesive or shear performance and also the greater the resistance to temperature, UV light, chemicals and ageing.

Where two dissimilar rigid surfaces are being bonded it is very important to consider this phenomenon. All materials will expand and contract at different rates when subjected to a temperature change. For short lengths the difference will probably be negligible but the longer the length or area of the two surfaces being bonded the greater the forces that will be generated by their different rates of expansion or contraction.

To absorb these tensions the tape needs to be able to "give" and this can be achieved either through a high coat weight of adhesive or a flexible adhesive carrier, such as a foam. Metals tend to have relatively high levels of expansion when compared to glass or stone. One may even get significant differences between dissimilar plastics and synthetic materials. If the force generated by this dissimilar rate is greater than the bond strength then it will weaken the bond leading to failure.

Relating to an adhesive system where water is used as the method for dissolving and spreading the adhesive on the carrier/release liner.

Dwell time is the period taken to achieve maximum bond strength. The bond strength will normally improve over a period of time. Some manufacturer's product specification sheets give figures for the bond strength after a given period. Normally it will take up to 24 hours to form maximum bond strength and after that period or "dwell time" there will be little improvement or change.

As a general rule, the softer the adhesive type and the thicker the coat weight (the thickness of the adhesive) the quicker it will achieve its maximum bond strength. As a very rough guide, if maximum bond strength for any given adhesive is achieved within 24 hours of the tape's application, then a bond strength of between 60 and 80% is achieved within 1 minute and 75 to 90% within 20 minutes.

This test measures the ability of a test sample of the tape to resist a moving force along the plane of the bond with the force applied relatively quickly, as opposed to a static load. The test is conducted using a specified area of tape on a specified surface at a specified temperature. After a dwell period, the two plates are separated at a rate of 300mm per minute and the Force required to break the bond is recorded in Newtons per square centimeter N/cm2.

This test best represents the forces a bond will be subjected to when subjected to a pulling motion.

This test is sometimes called the "T" Block test and measures the ability of the sample to resist a relatively quickly applied load at right-angles to the plane of the adhesive bond. The test conditions and results are recorded as for dynamic shear in N/cm2. This test best represents the forces a bond is subjected to when a tape is used for attaching items to roofs or ceilings.

This is a problem common with transfer tapes whereby the adhesive oozes and then fuses with adjoining layers of tape. The problem is exacerbated where the transfer does not have a glass fibre flock and where the tape is poorly slit (adhesive drag in slitting). The effect of this is that the tape will not unwind easily and will become very hard to apply.

Care is always required when handling rolls of transfer tape to try and reduce this tendency tape should be stored or left on a release liner and not directly on a benchtop.

Normally a rubber-like substance which can easily be deformed by force but will then return to its original shape. Elastomers are one of the key ingredients of most pressure sensitive adhesives.

Relating to an adhesive system where water is used as the method for dissolving and spreading the adhesive on the carrier/release liner.

This normally takes the form of glass fibres that are added to the adhesive batch when making transfer tapes to give the adhesive some dimensionable stability. This makes the transfer easier to tear and convert and limits the adhesive flow.

Federation Internationale des Fabricants et Transformateurs d'Adhesifs (The International Association for Self-Adhesive Labels & Related Products) a representative group for the industry.

This refers to a tape that has a release liner wider than the actual coat width of adhesive. The dry edge may be one or both sides and simply facilitates removal of the release liner when required. e.g. seals on mailing envelopes. See also pattern coating.

These are small circles on the adhesive's surface caused by air being trapped between the adhesive and the next layer of tape or from the evaporation of solvent during curing of the tape. This effect will tend to diminish with ageing and although sometimes unsightly does not signify any defect or lack of coating in the tape. Where clarity is vital then consider a solventless adhesive system.

These high performance tapes are not foams in the true sense but a foamed adhesive with small glass balls to give it internal strength. It has a high density and is non-porous and exhibits very high cohesive and internal strengths. These types of adhesives are very stable and offer superior bond strengths on a wide range of surfaces.

The foamed acrylic core is cured using UV light and is sometimes referred to as solventless adhesive however it may be subsequently coated with a solvent based adhesive to modify or improve its performance.

This is where consecutive layers of tape in a roll become separated, thereby forming a gap. Gapping is unsightly and will affect the consistency of the unwind tension, however, it will not materially affect the performance of the adhesive in the short term. If the roll is left unprotected then it will be more prone to oxidization (drying out).

The majority of tape is applied by hand and so it can be an important feature that it can be easily and cleanly torn by hand. The ease with which a tape can be torn is a function of the release liner and the adhesive's carrier. Whilst certain tapes such as transfers and foams are easily torn they do not usually tear cleanly by hand for different reasons. Where tapes are being used continuously e.g. print finishing shops, curtain & blind trade, sailmakers etc. it is vital that the product exhibits good tear characteristics.

The ability of a tape to retain its cohesive strength under increased temperature, generally speaking, silicon adhesives offer the best thermal resistance and hot melt rubbers the least.

This is the ability of a tape to withstand slippage under shear stress. It is normally measured using a static shear test where a fixed area of tape is used to suspend a fixed weight in the vertical and then the time taken for the bond to fail is measured (as opposed to a dynamic shear test, where the tape is put under an increasing load until the bond fails).

This is an adhesive type that is coated by heating it to a temperature where it flows, on cooling it forms a conventional pressure sensitive adhesive. Hot melts are predominantly rubber based adhesive systems but other types do exist. Inevitably, this type of adhesive system tends to exhibit poor thermal stability but is normally economical and has high initial tack levels.

Impact resistance and vibration absorption may be an important requirement, for example, in the transport industry. Products best designed to cope with these types of forces have adhesives that age well and so retain their tack levels, a high coat weight of adhesive and a carrier that is flexible and conformable.

This term relates to the quick stick characteristics of the adhesive. It is an indicator of how easily a tape will form an initial bond with a surface. Generally the initial tack of the adhesive is a function of the type of adhesive and its coat weight (see also Adhesive Wet Out and Adhesive v Cohesive Strength sections). The nature of the product's initial tack will have implications for other characteristics.

This is a piece of paper or card that is used to separate rolls of tape when they are packed. The interleave needs to have a surface treatment that adhesive will not stick to e.g. silicone or PE (as for the release liners on double sided tapes). The use of interleaves helps prevent edge bleed and makes the tape rolls easier to separate and apply. Also called Slip Sheets.

This is the bulk form that tape is normally stored in when it comes off the coating line, the width is dependent on the size of the base materials and the width of the coating heads. The length is largely determined by the gauge and density of the tape. Jumbos can be converted directly into rolls of tape by a slit rewind process or else logged to shorter lengths and then lathe slit.

This is Du Pont's brand name for their polyamide film that is widely used for high temperature masking and insulating applications. It is invariably coated with a silicon based adhesive to confer high temperature properties on the tape.

This is a coating applied to the carrier or backing prior to the adhesive being applied and causes the adhesive to better key or bond to one side of a carrier/backing than the other. Similarly a release coat can be applied to the opposite surface to prevent the adhesive bonding with it when the tape is in roll form. Corona treatment of the surface can have a similar effect as applying a key coat.

Kraft: A term to describe a sulphate wood pulp paper (tan or brown in colour).

This is a simple splice where the material is simply overlapped so one has a section of double thickness of the product.

Rolls are slit from a log of material to the required width on a rotating mandrel by use of a circular blade which is also rotating. This method of slitting is relatively slow but far more flexible than slit rewind. It is also called Lever Cutting.

This is where the adhesive stretches and strings when put under tension. This generally suggests that the adhesive lacks cohesive (internal) strength and can be symptomatic of problems such as plasticiser migration.

This is where a tape lifts away from a substrate to which it has been applied of its own accord. The reason for this could be one or a mixture of the following possible reasons: insufficient initial pressure applied, ambient conditions unsuitable at time of application, surface not properly cleaned prior to application, product unsuitable for this particular application or tape is not up to specification.

This term refers to the side of the tape to which the release liner is normally attached in a double sided tape, as opposed to open side.

This is the tape in the required length at full width and is created from rewinding the bulk material (jumbo) to the required length on a logging/rewinder machine. Logs can then be slit to the required width to create a roll of tape.

The bond strengths that appear on specification sheets and in these tables relate to results obtained from testing on a smooth stainless steel test panel in laboratory controlled conditions. Stainless steel, like most metals, is receptive to forming a bond with adhesives and these types of surface are termed high energy surfaces. However, there are a variety of materials that are less receptive to forming a bond due to their molecular structure.

These so called Low Energy Surfaces exhibit a weak polarity and so are less able to influence and attract the intermolecular forces present at the surface of the adhesive. Such surfaces require adhesives with a high initial tack, consequently one has to look to the rubber based or modified acrylics or butyl to form a bond with these types of finish.

If these types of tape will not give the performance required then one may have to consider using a chemical primer on the surface to make it more receptive to bonding. Listed below are the surface energies of some common products:

High — Metals untreated paper and board, matt painted surfaces

Medium — Glass, ABS, HIPS (High Impact Styrene), Rigid Vinyl

Low — Polyethylene, Polypropylene, Nylon, Teflon, Silicon & Wax treated surfaces, Thermoplastic Rubbers

This is the direction parallel to the unwind direction of the roll, as opposed to cross direction.

This is a document produced by the manufacturer that details all/any of a product's potential hazards and how they are to be reacted to or treated. They may also be termed a Health & Safety Data Sheet.

This is the tendency of a material to return to its original shape or form after stretching or deformation. It is this property of tapes such as self-amalgamating and plasticized PVC's that make them suitable for electrical insulation applications. The memory in a tape can be utilised to give structural support e.g. grafting in horticulture.

A Mil is 1/1000 of an inch and is an imperial measurement that still is commonly used in US specifications. It is normally used referring either to gauge or coat weight of adhesive. Select the Conversion Chart button on the website to convert this and other imperial measurements to metric.

This is an acrylic adhesive system that has additives such as tackifiers and resins introduced to it to modify or improve its characteristics for a particular application. In this process the chemist is trying to achieve the best compromise between adhesive and cohesive strength for a particular application.

A monomer is the basic building block of hydrocarbon chains and are joined together to form a polymer.

This is the Du Pont brand name for polyester or PET, a strong, clear film used as the backing for both single and double sided tapes.

National Association of Testing Authorities (Australia) an independent third party testing authority.

This is derived from latex rubber trees, as opposed to synthetic rubber, and is a key ingredient of many pressure sensitive adhesives imparting both tack and adhesive properties.

The Newton is defined as, that force which, if applied to a free body having a mass of 1 Kg, would give the body an acceleration of one metre per second per second. I Newton is equal to a force equivalent to 0.102 Kg or 3.6 Ozs under standard gravity.

These are materials, either tissue paper or synthetic, where the fibres are randomly orientated and are bonded to each other either by pressure or some resinous material. They are widely used as carriers for double sided tapes since they give the tape some dimensionable stability and yet are highly conformable and act as very good carriers of an adhesive.

This is where an adhesive residue is left on the uncoated surface of the tape on unwind. It can be caused by a number of issues such as: poor release coat, poor key coat, over age tape or application at high temperature causing the tape to leg and offset.

This is the tendency for the adhesive to flow out at the edge of a roll and is a function of the cohesive strength of the adhesive, the mass of adhesive, the tension in the roll and the temperature it is stored under.

This is the side of tape that does not have the liner on it or is the adhesive side for single sided tapes, as opposed to closed or linered side.

Manufacturer's specifications will normally show an operating temperature range for a tape once a bond has been formed. This should not be confused with the application temperature. Once an adhesive has wetted-out onto the bonding surface and a dwell time of 24 hours has elapsed then the bond strength should maintain its integrity across the published range, albeit with a possible tail-off at the extremes.

This is a natural process that occurs when many chemicals are exposed to air. The effect of oxidization on adhesives is for them to harden and loose their initial tack. Different adhesives will oxidize at different rates and there are additives that can be included within the adhesive to improve their resistance to oxidization.

This is where the coating head applies adhesive in fixed widths to the carrier or release liner. The coat width and the gap between them is altered to produce the required result. Normally the material is then subsequently slit to create fingerlift tape.

This is the force required to peel a strip of tape of a specified width from a specified surface at a specified angle (at right angles to the test plate, 90° or back on itself 180° degrees) and at a specified speed (commonly 300mm per minute). The force required is normally expressed in Newtons per Centimetre: N/cm. This is the test that is most commonly used for comparing different adhesives and gives a useful common reference.

This test best represents the forces a bond will be subjected to when one tries removing the tape or lifting it from the leading edge.

Plasticisers are additives, primarily to PVC, that soften it and give it greater flexibility. Plasticisers, such as Di-Octylphthalate (DOP), are not chemically linked to the vinyl and remain fluid within the material. They are attracted to various materials such as rubber resins and so "migrate" to the surface where they soften the adhesive leading to possible staining and bond failure. Hot melt rubber based adhesives are the most susceptible to migration and pure acrylics the most resistant.

The cross-linking of any adhesive will improve its resistance to plasticiser migration. Where surfaces are suspected of containing plasticisers thorough testing should be conducted.

This is a tough, clear film used as the carrier for both single and double sided tapes, sometimes referred to as Mylar™ which is a Du Pont brand name.

An extruded film that is widely used for single sided tapes, has good moisture stability and stretch characteristics. Can also be foamed to form a carrier for both single and double sided foams.

These are the basis of most films and adhesives and are created by the polymerization of monomers.

The chemical process by which monomers are formed into macromolecules by the application of a catalyst, heat , light or electron radiation.

This is a polyolefin plastic with similar properties to polyethylene but with higher internal strength and thermal stability. Most commonly used for single sided tapes e.g. packaging.

A very tough and flexible polymer with good thermal stability, it can also be foamed to form the basis for single and double sided foam tapes.

The ability or extent to which gases or fluids can permeate and pass through a given material.

This is the term used to define adhesives that are tacky to the touch at ambient temperatures. To form a bond with a surface the application of a force is required to get any adhesive to wet-out and form a bond with the underlying substrate (hence the term pressure sensitive).

The amount of force required will be dependent on a wide range of variables such as: the type of adhesive, the coat weight of adhesive, the ambient temperature, the smoothness and nature of the substrate to which the tape is being applied.

A primer acts as a link between the substrate and the tape by increasing the number and type of adhesive forces at the surface interface. Whilst not normally necessary, the use of primers on surfaces may be required should one need the attributes of a product with high cohesive strength on a low energy surface. The use of primers may represent significant health and safety issues in their use within the workplace.

It is recommended that you seek technical support from your supplier should you find that the product selected does not meet your application requirement or expectations. Tenacious Tapes can assist with primers for a range of surfaces. N.B. Careful surface preparation can often negate the need for primers.

Pressure Sensitive Manufacturers Association (UK) a representative group for the industry.

Pressure Sensitive Tape Council (USA) a representative group for the industry.

This is the percentage of moisture that the air can hold at any given temperature without precipitation forming.

This is a coating applied to the uncoated side of certain single sided tapes to allow the tape to unwind and is the opposite of a key coat which can be applied to the surface that the adhesive is to be applied to. Without this process the tape might not be able to unwind without serious off-setting, if at all.

Release liners are common to all double sided tapes and can be made from a variety of materials. Most commonly they are paper based and are coated with silicon or some other low energy coating that means that the pressure sensitive adhesive will release from them when required. Release liners have a differential release so that when one unwinds the tape the adhesive will consistently stay on one side of the release liner and not offset.

The liner is normally on the outside of the roll to protect the adhesive layer and allow easy application to a surface, however in some instances one may require the adhesive to be on the outside (e.g. for adhesive tape transfer guns, where the release liner is wound back into the dispenser). Although discarded, the release liner can form a very significant part of the overall cost of the tape.

Where double sideds are being laminated to surfaces in wide widths it may be necessary for a liner to be moisture stable, so that it does not absorb moisture and ripple and this will add to the cost. In certain applications, such as splicing, it is vital that the release liner can be stripped quickly and easily without tearing once the tape is in situ.

Whilst the majority of liners are paper based with a variety of release coatings, one can also have filmic release liners such as polyethylene or MOPP, these have the advantage of not breaking so easily and being moisture resistant. Generally, once applied, the heavier the liner the easier it is to lift the edge and expose the second side of adhesive.

A component of many adhesives that will confer tackiness and improved adhesion to the mix, there are both natural and synthetic resins that get used in the manufacture of adhesives.

Different types of product have been historically wound to different lengths and most are intended for hand application. However, certain applications may be automated or semi-automated and therefore require longer length rolls to improve production efficiency. Some of the products are already available in longer rolls, up to 1500 Metre in rolls format and longer in spools or bobbins. Should you have a specific requirement for longer length rolls, discuss this with your Tenacious Tape Distributor.

(Not explicitly defined separately on the page; included here for completeness as a basic specification term.)

(Covered implicitly across several entries; typically high initial tack with more limited UV/heat resistance than acrylics.)

A material that stops burning after the ignition source is removed (used in flammability ratings). (Term listed on source page headings; definition contextualized.)

A single‑sided tape wound without a liner; the backing has a release coating so layers do not block. (Term listed on source page headings; commonly defined.)

Resistance to sliding force parallel to the bond line. (See detailed test definitions for Dynamic Shear and Static Shear Adhesion.)

Temperature at which tape fails in a static shear test under a defined load. (Term occurs on source list; general definition provided.)

Any tape in roll form is still in an intermediate state, since it has not yet been used for its intended application. Since pressure sensitive adhesives will loose tack over a period of time through oxidization, manufacturers will normally specify a recommended shelf life for storage under set conditions. This is the period that the roll of tape can be stored and still remain suitable for its intended application. By their nature, the suggested shelf life by a manufacturer tends to be very conservative.

Silicone backings and coatings offer excellent release and high‑temperature capability. (Listed term; definition summarized from context.)

PSA based on silicone polymers; premium ageing and heat resistance. (Listed term; general definition.)

Single‑sided construction with adhesive on one face only. (Listed term; general definition.)

Converting process that slits a web into narrower widths and rewinds to finished rolls. (Listed term; general definition.)

An adhesive system where the polymer is dissolved in a solvent during coating. (Listed term; general definition.)

Coating without solvent (e.g., 100% solids or hot‑melt); can improve clarity, reduce fisheyes. (Listed term; general definition.)

A document outlining performance, quality and test requirements for a product. (Listed term; general definition.)

A joint connecting two web ends; can be lap or butt style. (Listed term; general definition.)

This is a long length of tape, either single or double sided, that is helically wound backwards and forwards (like a yarn on a bobbin) onto a large core to create a long length of tape for machine applications. Depending on the tape and its width, spools of up to 20,000 Metres can be created using specialist conversion equipment.

This test gives a good measure of the resistance of a tape to slippage or creep when a static load is applied. The test is conducted using a specified area of tape (commonly 25mm x 25mm) on a specified surface, with a specified weight and at a specified temperature. The weight is applied after an appropriate dwell period and the Time is recorded to failure. Where one sees a figure prefixed by ">", it means that the bond did not fail within that given test period of time.

This test best represents the forces a bond will be subjected to when a tape is used for attaching items to walls.

Any surface to which a pressure sensitive tape is applied. Surface Energy is a term used to describe the ease with which any given adhesive will form a bond with that surface and is measured in dynes. See Low Energy Surfaces.

This is a term used to describe the ease with which a pressure sensitive tape wets out and forms a bond with a substrate under minimal application pressure. The term quick stick is also sometimes used to describe this characteristic of the adhesive. Generally the softer an adhesive the better its tack but the poorer its cohesive or internal strength. A tackifier is an ingredient, such as a rosin ester, used in the adhesive batch to improve this particular property.

This is a double sided tape that consists of a film of adhesive coated directly onto a release liner, so it does not possess a carrier. Transfer tapes can be made from any type of adhesive and may have a glass fibre fill included in the mix to improve their tear characteristics.

Underwriters Laboratories (USA) an independent third party testing authority.

UV has the effect of drying and hardening an adhesive, with possible discolouration, so that it looses its adhesive and cohesive strength. Pure acrylics have the greatest resistance to UV degradation and water based rubber adhesives are probably the most susceptible.

Temperature at which a polymer softens under load. (Listed term on source headings; general definition.)

(Listed term on source headings; property describing combined viscous and elastic behavior that enables stress relaxation and energy dissipation in PSAs.)

This is the ease with which an adhesive flows to uniformly cover a surface and is dependent on the type of adhesive, ambient temperature and smoothness of the surface to which the tape is being applied. When a pressure sensitive tape is applied, firm pressure is required to expel any air pockets trapped underneath. The softer the adhesive the more easily it wets-out and an initial bond is formed.

A good way to view this is to take the tape you intend using and stick it to a piece of glass and observe the pressure required to expel all the air and obtain 100% contact, note that the lighter areas indicate trapped air.

This can be confusing since for double sided tapes this will normally mean the release liner and for single sided tapes it is generally referring to the material onto which the adhesive is coated. Consequently care needs to be used if and when using this imprecise term.

This is a discrete number generated by the manufacturer to allow traceability of all raw materials used in the manufacture of a product. Their own internal quality procedures will determine what constitutes a batch and when the batch number has to be changed, however, it allows the manufacturer to identify precisely what components/ingredients were used from various suppliers to create their product. If correctly recorded it is a vital tool for identifying, isolating and quarantining defective stock.

See spool.

This type of adhesive has relatively low cohesive strength but high adhesive strength, it has excellent ageing characteristics and is very resistant to moisture, oxygen, ozone, and weathering. Consequently it tends to get used for gasket and sealing type applications. Butyl rubbers also offer good damping and vibration absorption characteristics.

This is a process for applying a coating of adhesive whereby the adhesive is pressed between two rotating cylinders into a thin layer and then coated onto the carrier. This is the most common way for making cloth tapes and many rubber based adhesive tapes.

When referring to double sided tapes (that are not transfer tapes) this is the medium onto which the adhesive is coated.

Certain applications may state that a Certificate of Conformance is required for the materials being used. A CofC cannot normally be supplied after the goods have been manufactured since it requires special testing at the time of manufacture to ensure that the product conforms to a particular specification. This will normally by some form of third party specification such as a Military Specification (Mil. Spec.). A CofC will relate exclusively to a particular batch number.

A Letter of Compliance, on the other hand, can be tendered by the manufacturer after the date of manufacture and will simply confirm that the product has been manufactured to comply with a particular specification, although no specific batch testing. These documents are normally only requested for critical applications.

Where tapes are being used for bonding clear or translucent materials (e.g. plastics, Perspex, screen printing) or mounting media in windows, clarity can be an important requirement.

If the tape is being used for some form of temporary holding application then it may be desirable for it to clean remove from one or both the surfaces. For a tape to clean remove the adhesive needs to be better bonded to its carrier than it does to the bonding surface and the carrier to have greater structural strength than the bond strength. Temporary bonds require an adhesive to have good cohesive strength but only moderate adhesive strength.

Note: Clean removal from painted surfaces and plasterboard will be dependent on the quality of the keying of the paint or board to their underlying substrate.

This is the mass of adhesive applied to a unit of area. It may also be referred to as Adhesive Mass or Mass Weight and is normally expressed in grams per square metre (gsm)

This is the ease or ability of a tape to conform and make direct contact with the underlying substrate without creasing and folding or air pockets forming.

This is a process used to physically treat the carrier surface to be coated to promote the keying of the adhesive to its carrier. It is most effective when conducted in-line immediately prior to the coating, since its effect will wear off with time. It is particularly relevant in the treatment of low surface energy materials, such as polyethylene, prior to adhesive being coated.

This is a commonly used process within the adhesive tape industry to modify the performance of adhesives. It can be applied to both rubber and acrylic adhesives and involves subjecting the adhesives to either chemical or gamma irradiation treatment. The process aligns the molecules in the adhesive and links them rather than them being mobile and randomly orientated and has the effect of firming the adhesive.

The greater the degree of treatment the lower the tack level but the higher the cohesive or shear performance and also the greater the resistance to temperature, UV light, chemicals and ageing.

Where two dissimilar rigid surfaces are being bonded it is very important to consider this phenomenon. All materials will expand and contract at different rates when subjected to a temperature change. For short lengths the difference will probably be negligible but the longer the length or area of the two surfaces being bonded the greater the forces that will be generated by their different rates of expansion or contraction.

To absorb these tensions the tape needs to be able to "give" and this can be achieved either through a high coat weight of adhesive or a flexible adhesive carrier, such as a foam. Metals tend to have relatively high levels of expansion when compared to glass or stone. One may even get significant differences between dissimilar plastics and synthetic materials. If the force generated by this dissimilar rate is greater than the bond strength then it will weaken the bond leading to failure.

Relating to an adhesive system where water is used as the method for dissolving and spreading the adhesive on the carrier/release liner.

Dwell time is the period taken to achieve maximum bond strength. The bond strength will normally improve over a period of time. Some manufacturer's product specification sheets give figures for the bond strength after a given period. Normally it will take up to 24 hours to form maximum bond strength and after that period or "dwell time" there will be little improvement or change.

As a general rule, the softer the adhesive type and the thicker the coat weight (the thickness of the adhesive) the quicker it will achieve its maximum bond strength. As a very rough guide, if maximum bond strength for any given adhesive is achieved within 24 hours of the tape's application, then a bond strength of between 60 and 80% is achieved within 1 minute and 75 to 90% within 20 minutes.

This test measures the ability of a test sample of the tape to resist a moving force along the plane of the bond with the force applied relatively quickly, as opposed to a static load. The test is conducted using a specified area of tape on a specified surface at a specified temperature. After a dwell period, the two plates are separated at a rate of 300mm per minute and the Force required to break the bond is recorded in Newtons per square centimeter N/cm2.

This test best represents the forces a bond will be subjected to when subjected to a pulling motion.

This test is sometimes called the "T" Block test and measures the ability of the sample to resist a relatively quickly applied load at right-angles to the plane of the adhesive bond. The test conditions and results are recorded as for dynamic shear in N/cm2. This test best represents the forces a bond is subjected to when a tape is used for attaching items to roofs or ceilings.

This is a problem common with transfer tapes whereby the adhesive oozes and then fuses with adjoining layers of tape. The problem is exacerbated where the transfer does not have a glass fibre flock and where the tape is poorly slit (adhesive drag in slitting). The effect of this is that the tape will not unwind easily and will become very hard to apply.

Care is always required when handling rolls of transfer tape to try and reduce this tendency tape should be stored or left on a release liner and not directly on a benchtop.

Normally a rubber-like substance which can easily be deformed by force but will then return to its original shape. Elastomers are one of the key ingredients of most pressure sensitive adhesives.

Relating to an adhesive system where water is used as the method for dissolving and spreading the adhesive on the carrier/release liner.

This normally takes the form of glass fibres that are added to the adhesive batch when making transfer tapes to give the adhesive some dimensionable stability. This makes the transfer easier to tear and convert and limits the adhesive flow.

Federation Internationale des Fabricants et Transformateurs d'Adhesifs (The International Association for Self-Adhesive Labels & Related Products) a representative group for the industry.

This refers to a tape that has a release liner wider than the actual coat width of adhesive. The dry edge may be one or both sides and simply facilitates removal of the release liner when required. e.g. seals on mailing envelopes. See also pattern coating.

These are small circles on the adhesive's surface caused by air being trapped between the adhesive and the next layer of tape or from the evaporation of solvent during curing of the tape. This effect will tend to diminish with ageing and although sometimes unsightly does not signify any defect or lack of coating in the tape. Where clarity is vital then consider a solventless adhesive system.

These high performance tapes are not foams in the true sense but a foamed adhesive with small glass balls to give it internal strength. It has a high density and is non-porous and exhibits very high cohesive and internal strengths. These types of adhesives are very stable and offer superior bond strengths on a wide range of surfaces.

The foamed acrylic core is cured using UV light and is sometimes referred to as solventless adhesive however it may be subsequently coated with a solvent based adhesive to modify or improve its performance.

This is where consecutive layers of tape in a roll become separated, thereby forming a gap. Gapping is unsightly and will affect the consistency of the unwind tension, however, it will not materially affect the performance of the adhesive in the short term. If the roll is left unprotected then it will be more prone to oxidization (drying out).

The majority of tape is applied by hand and so it can be an important feature that it can be easily and cleanly torn by hand. The ease with which a tape can be torn is a function of the release liner and the adhesive's carrier. Whilst certain tapes such as transfers and foams are easily torn they do not usually tear cleanly by hand for different reasons. Where tapes are being used continuously e.g. print finishing shops, curtain & blind trade, sailmakers etc. it is vital that the product exhibits good tear characteristics.

The ability of a tape to retain its cohesive strength under increased temperature, generally speaking, silicon adhesives offer the best thermal resistance and hot melt rubbers the least.

This is the ability of a tape to withstand slippage under shear stress. It is normally measured using a static shear test where a fixed area of tape is used to suspend a fixed weight in the vertical and then the time taken for the bond to fail is measured (as opposed to a dynamic shear test, where the tape is put under an increasing load until the bond fails).

This is an adhesive type that is coated by heating it to a temperature where it flows, on cooling it forms a conventional pressure sensitive adhesive. Hot melts are predominantly rubber based adhesive systems but other types do exist. Inevitably, this type of adhesive system tends to exhibit poor thermal stability but is normally economical and has high initial tack levels.

Impact resistance and vibration absorption may be an important requirement, for example, in the transport industry. Products best designed to cope with these types of forces have adhesives that age well and so retain their tack levels, a high coat weight of adhesive and a carrier that is flexible and conformable.

This term relates to the quick stick characteristics of the adhesive. It is an indicator of how easily a tape will form an initial bond with a surface. Generally the initial tack of the adhesive is a function of the type of adhesive and its coat weight (see also Adhesive Wet Out and Adhesive v Cohesive Strength sections). The nature of the product's initial tack will have implications for other characteristics.

This is a piece of paper or card that is used to separate rolls of tape when they are packed. The interleave needs to have a surface treatment that adhesive will not stick to e.g. silicone or PE (as for the release liners on double sided tapes). The use of interleaves helps prevent edge bleed and makes the tape rolls easier to separate and apply. Also called Slip Sheets.

This is the bulk form that tape is normally stored in when it comes off the coating line, the width is dependent on the size of the base materials and the width of the coating heads. The length is largely determined by the gauge and density of the tape. Jumbos can be converted directly into rolls of tape by a slit rewind process or else logged to shorter lengths and then lathe slit.

This is Du Pont's brand name for their polyamide film that is widely used for high temperature masking and insulating applications. It is invariably coated with a silicon based adhesive to confer high temperature properties on the tape.

This is a coating applied to the carrier or backing prior to the adhesive being applied and causes the adhesive to better key or bond to one side of a carrier/backing than the other. Similarly a release coat can be applied to the opposite surface to prevent the adhesive bonding with it when the tape is in roll form. Corona treatment of the surface can have a similar effect as applying a key coat.

Kraft: A term to describe a sulphate wood pulp paper (tan or brown in colour).

This is a simple splice where the material is simply overlapped so one has a section of double thickness of the product.

Rolls are slit from a log of material to the required width on a rotating mandrel by use of a circular blade which is also rotating. This method of slitting is relatively slow but far more flexible than slit rewind. It is also called Lever Cutting.

This is where the adhesive stretches and strings when put under tension. This generally suggests that the adhesive lacks cohesive (internal) strength and can be symptomatic of problems such as plasticiser migration.

This is where a tape lifts away from a substrate to which it has been applied of its own accord. The reason for this could be one or a mixture of the following possible reasons: insufficient initial pressure applied, ambient conditions unsuitable at time of application, surface not properly cleaned prior to application, product unsuitable for this particular application or tape is not up to specification.

This term refers to the side of the tape to which the release liner is normally attached in a double sided tape, as opposed to open side.

This is the tape in the required length at full width and is created from rewinding the bulk material (jumbo) to the required length on a logging/rewinder machine. Logs can then be slit to the required width to create a roll of tape.

The bond strengths that appear on specification sheets and in these tables relate to results obtained from testing on a smooth stainless steel test panel in laboratory controlled conditions. Stainless steel, like most metals, is receptive to forming a bond with adhesives and these types of surface are termed high energy surfaces. However, there are a variety of materials that are less receptive to forming a bond due to their molecular structure.

These so called Low Energy Surfaces exhibit a weak polarity and so are less able to influence and attract the intermolecular forces present at the surface of the adhesive. Such surfaces require adhesives with a high initial tack, consequently one has to look to the rubber based or modified acrylics or butyl to form a bond with these types of finish.

If these types of tape will not give the performance required then one may have to consider using a chemical primer on the surface to make it more receptive to bonding. Listed below are the surface energies of some common products:

High — Metals untreated paper and board, matt painted surfaces

Medium — Glass, ABS, HIPS (High Impact Styrene), Rigid Vinyl

Low — Polyethylene, Polypropylene, Nylon, Teflon, Silicon & Wax treated surfaces, Thermoplastic Rubbers

This is the direction parallel to the unwind direction of the roll, as opposed to cross direction.

This is a document produced by the manufacturer that details all/any of a product's potential hazards and how they are to be reacted to or treated. They may also be termed a Health & Safety Data Sheet.

This is the tendency of a material to return to its original shape or form after stretching or deformation. It is this property of tapes such as self-amalgamating and plasticized PVC's that make them suitable for electrical insulation applications. The memory in a tape can be utilised to give structural support e.g. grafting in horticulture.

A Mil is 1/1000 of an inch and is an imperial measurement that still is commonly used in US specifications. It is normally used referring either to gauge or coat weight of adhesive. Select the Conversion Chart button on the website to convert this and other imperial measurements to metric.

This is an acrylic adhesive system that has additives such as tackifiers and resins introduced to it to modify or improve its characteristics for a particular application. In this process the chemist is trying to achieve the best compromise between adhesive and cohesive strength for a particular application.

A monomer is the basic building block of hydrocarbon chains and are joined together to form a polymer.

This is the Du Pont brand name for polyester or PET, a strong, clear film used as the backing for both single and double sided tapes.

National Association of Testing Authorities (Australia) an independent third party testing authority.

This is derived from latex rubber trees, as opposed to synthetic rubber, and is a key ingredient of many pressure sensitive adhesives imparting both tack and adhesive properties.

The Newton is defined as, that force which, if applied to a free body having a mass of 1 Kg, would give the body an acceleration of one metre per second per second. I Newton is equal to a force equivalent to 0.102 Kg or 3.6 Ozs under standard gravity.

These are materials, either tissue paper or synthetic, where the fibres are randomly orientated and are bonded to each other either by pressure or some resinous material. They are widely used as carriers for double sided tapes since they give the tape some dimensionable stability and yet are highly conformable and act as very good carriers of an adhesive.

This is where an adhesive residue is left on the uncoated surface of the tape on unwind. It can be caused by a number of issues such as: poor release coat, poor key coat, over age tape or application at high temperature causing the tape to leg and offset.

This is the tendency for the adhesive to flow out at the edge of a roll and is a function of the cohesive strength of the adhesive, the mass of adhesive, the tension in the roll and the temperature it is stored under.

This is the side of tape that does not have the liner on it or is the adhesive side for single sided tapes, as opposed to closed or linered side.

Manufacturer's specifications will normally show an operating temperature range for a tape once a bond has been formed. This should not be confused with the application temperature. Once an adhesive has wetted-out onto the bonding surface and a dwell time of 24 hours has elapsed then the bond strength should maintain its integrity across the published range, albeit with a possible tail-off at the extremes.

This is a natural process that occurs when many chemicals are exposed to air. The effect of oxidization on adhesives is for them to harden and loose their initial tack. Different adhesives will oxidize at different rates and there are additives that can be included within the adhesive to improve their resistance to oxidization.

This is where the coating head applies adhesive in fixed widths to the carrier or release liner. The coat width and the gap between them is altered to produce the required result. Normally the material is then subsequently slit to create fingerlift tape.

This is the force required to peel a strip of tape of a specified width from a specified surface at a specified angle (at right angles to the test plate, 90° or back on itself 180° degrees) and at a specified speed (commonly 300mm per minute). The force required is normally expressed in Newtons per Centimetre: N/cm. This is the test that is most commonly used for comparing different adhesives and gives a useful common reference.

This test best represents the forces a bond will be subjected to when one tries removing the tape or lifting it from the leading edge.

Plasticisers are additives, primarily to PVC, that soften it and give it greater flexibility. Plasticisers, such as Di-Octylphthalate (DOP), are not chemically linked to the vinyl and remain fluid within the material. They are attracted to various materials such as rubber resins and so "migrate" to the surface where they soften the adhesive leading to possible staining and bond failure. Hot melt rubber based adhesives are the most susceptible to migration and pure acrylics the most resistant.

The cross-linking of any adhesive will improve its resistance to plasticiser migration. Where surfaces are suspected of containing plasticisers thorough testing should be conducted.

This is a tough, clear film used as the carrier for both single and double sided tapes, sometimes referred to as Mylar™ which is a Du Pont brand name.

An extruded film that is widely used for single sided tapes, has good moisture stability and stretch characteristics. Can also be foamed to form a carrier for both single and double sided foams.

These are the basis of most films and adhesives and are created by the polymerization of monomers.

The chemical process by which monomers are formed into macromolecules by the application of a catalyst, heat , light or electron radiation.

This is a polyolefin plastic with similar properties to polyethylene but with higher internal strength and thermal stability. Most commonly used for single sided tapes e.g. packaging.

A very tough and flexible polymer with good thermal stability, it can also be foamed to form the basis for single and double sided foam tapes.

The ability or extent to which gases or fluids can permeate and pass through a given material.

This is the term used to define adhesives that are tacky to the touch at ambient temperatures. To form a bond with a surface the application of a force is required to get any adhesive to wet-out and form a bond with the underlying substrate (hence the term pressure sensitive).

The amount of force required will be dependent on a wide range of variables such as: the type of adhesive, the coat weight of adhesive, the ambient temperature, the smoothness and nature of the substrate to which the tape is being applied.

A primer acts as a link between the substrate and the tape by increasing the number and type of adhesive forces at the surface interface. Whilst not normally necessary, the use of primers on surfaces may be required should one need the attributes of a product with high cohesive strength on a low energy surface. The use of primers may represent significant health and safety issues in their use within the workplace.

It is recommended that you seek technical support from your supplier should you find that the product selected does not meet your application requirement or expectations. Tenacious Tapes can assist with primers for a range of surfaces. N.B. Careful surface preparation can often negate the need for primers.

Pressure Sensitive Manufacturers Association (UK) a representative group for the industry.

Pressure Sensitive Tape Council (USA) a representative group for the industry.

This is the percentage of moisture that the air can hold at any given temperature without precipitation forming.

This is a coating applied to the uncoated side of certain single sided tapes to allow the tape to unwind and is the opposite of a key coat which can be applied to the surface that the adhesive is to be applied to. Without this process the tape might not be able to unwind without serious off-setting, if at all.

Release liners are common to all double sided tapes and can be made from a variety of materials. Most commonly they are paper based and are coated with silicon or some other low energy coating that means that the pressure sensitive adhesive will release from them when required. Release liners have a differential release so that when one unwinds the tape the adhesive will consistently stay on one side of the release liner and not offset.

The liner is normally on the outside of the roll to protect the adhesive layer and allow easy application to a surface, however in some instances one may require the adhesive to be on the outside (e.g. for adhesive tape transfer guns, where the release liner is wound back into the dispenser). Although discarded, the release liner can form a very significant part of the overall cost of the tape.

Where double sideds are being laminated to surfaces in wide widths it may be necessary for a liner to be moisture stable, so that it does not absorb moisture and ripple and this will add to the cost. In certain applications, such as splicing, it is vital that the release liner can be stripped quickly and easily without tearing once the tape is in situ.

Whilst the majority of liners are paper based with a variety of release coatings, one can also have filmic release liners such as polyethylene or MOPP, these have the advantage of not breaking so easily and being moisture resistant. Generally, once applied, the heavier the liner the easier it is to lift the edge and expose the second side of adhesive.

A component of many adhesives that will confer tackiness and improved adhesion to the mix, there are both natural and synthetic resins that get used in the manufacture of adhesives.

Different types of product have been historically wound to different lengths and most are intended for hand application. However, certain applications may be automated or semi-automated and therefore require longer length rolls to improve production efficiency. Some of the products are already available in longer rolls, up to 1500 Metre in rolls format and longer in spools or bobbins. Should you have a specific requirement for longer length rolls, discuss this with your Tenacious Tape Distributor.

(Not explicitly defined separately on the page; included here for completeness as a basic specification term.)

(Covered implicitly across several entries; typically high initial tack with more limited UV/heat resistance than acrylics.)

A material that stops burning after the ignition source is removed (used in flammability ratings). (Term listed on source page headings; definition contextualized.)

A single‑sided tape wound without a liner; the backing has a release coating so layers do not block. (Term listed on source page headings; commonly defined.)

Resistance to sliding force parallel to the bond line. (See detailed test definitions for Dynamic Shear and Static Shear Adhesion.)

Temperature at which tape fails in a static shear test under a defined load. (Term occurs on source list; general definition provided.)

Any tape in roll form is still in an intermediate state, since it has not yet been used for its intended application. Since pressure sensitive adhesives will loose tack over a period of time through oxidization, manufacturers will normally specify a recommended shelf life for storage under set conditions. This is the period that the roll of tape can be stored and still remain suitable for its intended application. By their nature, the suggested shelf life by a manufacturer tends to be very conservative.

Silicone backings and coatings offer excellent release and high‑temperature capability. (Listed term; definition summarized from context.)

PSA based on silicone polymers; premium ageing and heat resistance. (Listed term; general definition.)

Single‑sided construction with adhesive on one face only. (Listed term; general definition.)

Converting process that slits a web into narrower widths and rewinds to finished rolls. (Listed term; general definition.)

An adhesive system where the polymer is dissolved in a solvent during coating. (Listed term; general definition.)

Coating without solvent (e.g., 100% solids or hot‑melt); can improve clarity, reduce fisheyes. (Listed term; general definition.)

A document outlining performance, quality and test requirements for a product. (Listed term; general definition.)

A joint connecting two web ends; can be lap or butt style. (Listed term; general definition.)

This is a long length of tape, either single or double sided, that is helically wound backwards and forwards (like a yarn on a bobbin) onto a large core to create a long length of tape for machine applications. Depending on the tape and its width, spools of up to 20,000 Metres can be created using specialist conversion equipment.

This test gives a good measure of the resistance of a tape to slippage or creep when a static load is applied. The test is conducted using a specified area of tape (commonly 25mm x 25mm) on a specified surface, with a specified weight and at a specified temperature. The weight is applied after an appropriate dwell period and the Time is recorded to failure. Where one sees a figure prefixed by ">", it means that the bond did not fail within that given test period of time.

This test best represents the forces a bond will be subjected to when a tape is used for attaching items to walls.

Any surface to which a pressure sensitive tape is applied. Surface Energy is a term used to describe the ease with which any given adhesive will form a bond with that surface and is measured in dynes. See Low Energy Surfaces.

This is a term used to describe the ease with which a pressure sensitive tape wets out and forms a bond with a substrate under minimal application pressure. The term quick stick is also sometimes used to describe this characteristic of the adhesive. Generally the softer an adhesive the better its tack but the poorer its cohesive or internal strength. A tackifier is an ingredient, such as a rosin ester, used in the adhesive batch to improve this particular property.

This is a double sided tape that consists of a film of adhesive coated directly onto a release liner, so it does not possess a carrier. Transfer tapes can be made from any type of adhesive and may have a glass fibre fill included in the mix to improve their tear characteristics.

Underwriters Laboratories (USA) an independent third party testing authority.

UV has the effect of drying and hardening an adhesive, with possible discolouration, so that it looses its adhesive and cohesive strength. Pure acrylics have the greatest resistance to UV degradation and water based rubber adhesives are probably the most susceptible.

Temperature at which a polymer softens under load. (Listed term on source headings; general definition.)

(Listed term on source headings; property describing combined viscous and elastic behavior that enables stress relaxation and energy dissipation in PSAs.)

This is the ease with which an adhesive flows to uniformly cover a surface and is dependent on the type of adhesive, ambient temperature and smoothness of the surface to which the tape is being applied. When a pressure sensitive tape is applied, firm pressure is required to expel any air pockets trapped underneath. The softer the adhesive the more easily it wets-out and an initial bond is formed.

A good way to view this is to take the tape you intend using and stick it to a piece of glass and observe the pressure required to expel all the air and obtain 100% contact, note that the lighter areas indicate trapped air.