Transfer Tape

As the name indicates, pressure sensitive tapes need pressure to ensure bonding. The recommended bonding pressure is 14.5 – 29 psi =^ 10 – 20 N/cm². The pressure is needed to ensure that the tape comes in close contact to the surface so that the physical forces between the adhesive and the surface can build up. The tape should be applied at moderate temperatures between 59º F and 95º F. Lower temperatures might lead to insufficient “wetting” (coverage) of the adhesive on the substrate. Extremely high temperatures might cause the tape to stretch when being applied, which could create additional stress in the final application.

Surface Preparation : The surface to which the tape is applied should be clean, dry,and free of oils or grease. To properly clean the surface, a “lintless” cloth should be used. Suitable solvents for use include benzenes, alcohols, esters, and ketones. Ensure that the substrate is able to withstand the solvent prior to application.

Surface Energy/Tension: To ensure the best possible adhesion, it is optimal that the surface onto which the tape is applied has a higher surfaceenergy or polarity than the tape’s adhesive system.

There are some substrates that are generally easier to bond to than others. These are the materials with higher surface tension/energy. It is important to know that coatings on the surfaces or fillers in the substrates might influence the adhesion characteristics. A painted aluminum or plasticized PVC (polyvinyl chloride) might display completely different bonding characteristics as compared to pure, unaltered materials.

To increase the surface tension of substrates with low-surface energy, consider using a primer or adhesion promoter. Corona or flame treatments can also be applied. It is critical that adhesive systems and primers are cooperative in nature. Testing is, of course, always critical to ensure the desired result.

Storage Conditions

Pressure sensitive tapes need to be stored under defined conditions.

Extreme high temperatures can lead to degradation of the adhesive or backing materials. Extreme low temperatures might influence the bonding characteristics.

The recommended storage conditions are:

• 68 - 72° F / 20 - 22° C
• 50% relative humidity
• Rolls store flat in their original packaging, away from direct sources of UV (i.e., lights, sun).

How Pressure Sensitive Tape is Manufactured

Traditional Production Process

The ingredients – adhesive, resin, filler, and other additives are mixed with organic solvents or water.
The solved adhesive is transported to the coating device, after which the adhesive is coated in an even layer onto the backing and dried in the drying channel until all the solvents have evaporated. The result is a long roll of tape. After the coating process, the long rolls are converted into the desired roll sizes.

Hot-Melt Process

In the hot-melt process, the adhesive and other ingredients are processed without solvents. Due to heat in the process, the adhesive remains in a liquid state to be coated.

Four Fundamentals that Affect Tape Holding Power

These tapes are engineered to perform at the highest levels for their given applications. There are, however, additional factors that ultimately determine a tape's true holding power in any circumstance, which include:

In today’s advanced information age, a common search for the term “Pressure-Sensitive Tape” will likely result in a response similar to this: Wikipedia, (the free encyclopedia) – The tape consists of a pressure-sensitive adhesive coated onto a backing material such as paper, plastic film, cloth, or metal foil. Some have a removable release liner which protects the adhesive until the liner is removed.

Some have layers of adhesives, primers, easy release materials, filaments, printing, etc. made for specific functions. Descriptions such as this, however, fail to capture the important role that each of these elements play with regard to today’s advanced pressure-sensitive adhesive tapes. While all tape components are important when determining performance, this article will offer a closer look at the all-important tape backing systems.

In years past, the main function of a tape backing, otherwise known as a “carrier”, was to “carry” the adhesive to its point of use. Today, tape backings are most often highly engineered and essential components of the overall tape solution. Today’s backings are designed to withstand certain forces or to split at an exact defined force; to be optically clear or reflective; to be permeable or to function as a barrier (e.g. for humidity or oxygen); to be very thin (1.5 μm = 0.059 mils) or to be very thick (>3mm or 118 mils); to serve as gap fillers and / or noise dampeners; and to enable the tape to be machine-processed and / or die-cut. These functions are merely a few examples of the variety of functions modern tape backings can fulfill.

Due to the multiplicity of the available types of backings, it is worthwhile to discuss features and benefits of the different types.

Paper Backings

Paper backings are mainly used for masking applications. They are easy to tear by hand; allow for good conformability to a variety of surfaces; offer good temperature and solvent resistance; and they are environmentally compatible. Higher degree of “crepe” to the paper allows for easier application of the tape to curves and contours. It is important that the paper be paintable, otherwise the paint would not stick to the backing, and there is the risk that recently painted areas would be unintentionally contaminated. There are more complex paper backings which are used in the paper industry for splicing or end tabbing large paper rolls. In this application, the paper needs to be repulpable (dissolvable without leaving any residues in the newly produced paper).

Filmic Backings

The most used filmic backings are:

• PolyVinylChloride (PVC)
PolyEthylene (PE)
• PolyPropylene (PP)
• PolyEthylene Terephthalate (PET)

Let’s take a closer look at each type:

PVC

Generally speaking, PVC backings typically exude the following characteristics: durability, low flammability, printable, can be embossed, weather resistant albeit temperature sensitive. PVC can be produced in both rigid and soft configurations. Rigid PVC is mainly used as the backing of choice for carton sealing tapes. Soft PVC is most often used as backing for insulating tapes and masking tapes, allowing for the flexibility of applying to curves and contours.

PE, PP

These two backings – PolyEthylene and PolyPropylene - are the environmental friendly alternatives to PVC. PE offers low cost, good flexibility, and due to its softness, a high conformability. PP is a mono-axial-oriented film (MoPP), meaning that it supplies strength in only one direction, as compared to bi-axial-oriented film (BoPP) that offers strength in two directions, along with other various advantages. MoPP shows very high tensile strength (in mid-direction) and low elongation (in mid-direction), but also low tensile strength (in cross-direction). This makes this backing ideal for strapping and bundling applications, as well as for packaging applications that utilize tear strips. BoPP backings offer low-cost, high-tear resistance in mid-direction and cross-direction, extreme flatness, and wellbalanced mechanical properties.

PET

Polyester backings are mostly used as BoPET (bi-axial-oriented polyester). PET is available in a very wide range of thicknesses (1.5μm to 500μm / .059 mils – 19.68 mils). The advantages of polyester include high-temperature resistance and high UV (ultraviolet) stability. It is the preferred backing for die-cutting processes, and therefore, it is one of the most commonly used backings in the PSA (pressure-sensitive adhesive) industry.

Foam Backings

In addition to performing the function of bonding two parts together, PE foam tapes are often used for a variety of reasons:

• to fill gaps / space between the bonding parts
• to compensate for design intolerances; to be conformable to irregular surfaces
• to offer very high bonding strength to compensate for different thermal expansions
to work as a dampening element, as well as a shock absorber

Application examples for foam tapes are endless; specific examples include bonding plastic emblems onto metal substrates (Automotive Industry), or bonding muntin bars on windows, or in many other highend applications. In flexographic printing applications, the foam tape not only holds the printing plate onto printing cylinders / sleeves, but also defines the print quality by its hardness / softness level, as well as altering the possible printing speed by its elasticity and recovery (memory) rate. The faster the foam recovers, the higher the possible printing speed.

Additionally, since some print jobs are very long, the foam performance must maintain its stability throughout thousands of impressions. Closed-cell PE foams have proven to be very suitable for most applications. As PolyEthylene has a low-melting temperature; the application for PE foams is limited to temperatures below 200ºF.

Acrylic Core Backings

For high-temperature applications (above 200ºF), or for applications that require even higher performance than a foam tape can offer, Acrylic Core Backings are the high-end solution. Due to the fact that the backing is made of an acrylic polymer, the backing has outstanding visco-elastic characteristics. In simple terms, the backing is able to dissipate stress, which leads to a much higher performance than “normal” backings. Additionally, the visco-elastic property of the acrylic core backing is capable of compensating for different thermal expansions in a much higher degree than a PE foam tape. Evaluations have shown that, depending on the backing structure, the thermal compensation can achieve three times the thickness of the tape. Combined with the very high bonding strength, acrylic core tapes are the ideal solution for bonding differing substrates such as glass to metal, or metal to plastic. As an added benefit, acrylic backings are very resistant to many environmental elements, such as sunlight, ozone, temperature, and water. These characteristics make acrylic core tapes the ideal choice for long-lasting, high-performance outdoor applications. Application examples include bonding body side moldings to car bodies (automotive); bonding framing of flat screens (electronics); bonding glass panels to metal frames; or joining photovoltaic panels onto back rails (solar panels). These and other appropriate applications demand high-bonding strength, long-term (up to 25 years) outdoor performance, and compensation

In conclusion, when specifying your next adhesive tape application, take the tape backing’s features / characteristics into account. A good backing choice can put you in front of the competition!

When considering the components that affect the performance of pressure-sensitive adhesive (PSA) tapes, it is vital to glean an understanding of the adhesive systems that are most often incorporated in the tape production process. In this article, we will explore varying types of adhesive systems and the unique characteristics of each.

When considering the components that affect the performance of pressure-sensitive adhesive (PSA) tapes, it is vital to glean an understanding of the adhesive systems that are most often incorporated in the tape production process. In this article, we will explore varying types of adhesive systems and the unique characteristics of each.

These characteristics allow for a wide-application window for NR adhesives. The type of rubber used, the compounded resins, and other ingredients determine the performance of the NR adhesive. As a general rule, natural rubber PSAs offer the following advantages:

• High initial tack or “grab”
• Excellent peel adhesion on non-polar and polar surfaces
• Short dwell time to final adhesion level
• Clean removal after application (e.g. masking tapes)

NR adhesives have some disadvantages, which are important to know when determining whether or not the product is suitable for the specific application:

• Poor cohesion at higher temperatures (T>70°C)
• Poor aging resistance
• Low environmental resistance (needs stabilizers) to protect against UV, ozone, etc.
• Poor chemical and solvent resistance

For many non-permanent, especially indoor applications, NR adhesives are an excellent choice.

Synthetic Rubber Adhesives

There are several synonyms for synthetic rubber(SR) adhe-sives, such as SBS, SIS, or SEBS. The SR polymer for adhesives shows a very unique molecular structure. There are two hard-end segments (Styrene) and a softer, rubbery middle segment (Butadiene), so the structure is: Styrene – Butadiene – Styrene = SBS.

The styrene-end segment determines the cohesiveness (internal strength) of the adhesive; the rubbery middle segment determines the adhesiveness. By itself, SR does not harbor any adhesive properties. To create a PSA, tackifier resins need to be added. In contradiction to natural rubber polymers, the SR polymer has a short length and a low molecular weight.

The advantages of SR adhesives are:

• High initial tack or “grab” (like natural rubber)
• High initial tack or “grab” (like natural rubber)
• Excellent peel adhesion on polar and non-polar surfaces
• Transparent coatings possible (in contrast to natural rubber)
• Low cost (due to high speed compounding + coating process); this point is often the reason why SR adhesives are very often called hot-melt adhesives.

The disadvantages of SR adhesives are:

• Low resistance to elevated temperatures
• Poor aging resistance, but better than natural rubber
• Low environmental resistance (needs stabilizers) to protect against UV, ozone, etc.
Moderate solvent resistance

Acrylic Adhesives

Acrylic adhesives are industrially produced by polymerization, otherwise known as a customized formulation. Adhesive properties of acrylic can be adjusted and controlled by manipulating the selection of monomers used in the formulation, as well as the polymerization process. In contradiction to NR and SR adhesives, acrylic adhesives are tacky by nature. Acrylic adhesives have long polymer chains that are cross-linked. This cross-linking feature catapults acrylic adhesives into a much higher performance category than both natural rubber and synthetic rubber adhesives.

The advantages of acrylic PSAs are:

• High transparency
• High-aging resistance (do not yellow)
• High-temperature resistance
• High resistance to UV, ozone, and moisture
• High resistance to solvents and plasticizers
• Very good peel adhesion on polar surfaces

Disadvantages are:

• Low immediate peel adhesion
• Longer dwell time
• Lower adhesion on non-polar substrates

To create acrylic PSAs with increased immediate peel adhesion or reduced dwell time, tackifier resins are often added to the acrylic polymer. The addition of resins, however, will change the cohesiveness of the acrylic adhesive. Due to the fact that the acrylic adhesive is cross-linked and shows excellent resistance to aging and temperature, acrylics are the best adhesive solution for long-term, outdoor applications.

Aside from the three major types of adhesives used in tape production, there are a few lesser used and lesser known types of adhesives on the market, such as:

• Silicone adhesive (high-temperature resistance, chemically inert)
• Butyl adhesives (corrosion protection, roof sealing)
• Butyl adhesives (corrosion protection, roof sealing)