This article presents all the information you need to know about adhesive tape. Read further and learn more about:
Adhesive tape is designed with a sticky film that adheres to surfaces to bond or join materials and offer protection. It typically features a backing or carrier made from materials like paper, plastic film, fabric, foam, or foil, all coated with an adhesive layer. Often, a release liner is used to facilitate easy application. These tapes are usually rolled and cut into narrower strips for convenience.
Adhesive tape applications can vary, requiring different methods such as applying light pressure, heat, or moisture. Pressure-sensitive adhesives (PSAs) stick when pressed, while heat-activated tapes need a heat source to bond. Water-activated tapes, which include gummed paper or starch-based options, adhere when dampened. Additionally, some tapes, films, or laminates adhere to surfaces without any adhesive layer.
Adhesive tapes were first introduced in the mid-19th century for medical purposes. In 1845, Dr. Horace Day developed bandages using strips of fabric with rubber-based adhesive, which inspired the creation of Johnson & Johnson’s Band-Aid. The development of adhesive tapes continued, leading to the formulation of the first masking tapes by the 3M Company in 1923. Over time, adhesive tapes have evolved into various types, such as packing tape, painter’s tape, and electrical tape, each tailored for specific uses. Today, adhesive tapes are ubiquitous in offices, homes, shops, and industrial settings, proving to be one of the most versatile and essential tools ever created.
The range of adhesive tapes available today includes specialized types like packing tape, painter’s tape, and electrical tape, each designed for particular applications. These various adhesive tapes are commonly found in diverse environments such as offices, households, retail stores, and industrial facilities, highlighting their significance and utility.
Efficient and readily available, adhesive tapes perform a wide array of functions such as joining, masking, sealing, splicing, bundling, and surface protection. Adhesive tapes gained popularity because their application does not require machinery or special tools. They are lightweight, easy to store, and come in rolls that can be unwound when needed. Unlike traditional mechanical fasteners, such as screws and bolts, adhesive tape eliminates the need to pierce or punch the substrate, creating stress on a surface.
Before adhesive tapes were invented, glues and epoxies were commonly used for securing or sealing surfaces. These adhesives were often messy and inconvenient, drying to a hard, permanent finish that was difficult to remove. Unlike adhesive tapes, glues and epoxies create bonds through chemical reactions, which are not ideal for small, routine tasks.
Adhesive tapes, on the other hand, utilize a sticky resin such as silicone, acrylics, or rubber to achieve adhesion. They rely on physical pressure to create bonds rather than chemical reactions. The adhesive material in the tape has a low-energy surface where molecules are in a state of constant motion. This enables the adhesive to flow into the pores of the surface with minimal pressure, forming a solid physical bond as the molecules integrate into the substrate.
The principle of adhesion involves the ability of different substances to bond surfaces together through molecular attachment, where one type of molecule adheres to another. Additionally, cohesion plays a role in this process, as molecules also stick to each other. Adhesive tape leverages both adhesion and cohesion: the adhesive molecules cling to the surface (substrate) and to themselves. Both of these interactions are crucial for the tape to securely adhere to and stay in place on a surface.
The bonding layer of adhesive tape, as illustrated in the image below, reveals a cross-sectional view of the bond. This layer is composed of three distinct areas: the adhesion zone, the cohesion zone, and the transition layer.
Several mechanisms allow two surfaces to stick together. Adhesion relies on four fundamental principles that facilitate the bonding of tape to a substrate surface.
The principle of adhesion is grounded in absorption theory, which suggests that substances adhere due to interactions between their molecules. This theory is supported by four key mechanisms that facilitate adhesion.
For adhesives to be effective, they must be applied across the surface of the substrate. During the adhesion process, the tape’s adhesive layer attaches to the substrate's surface molecules as if millions of tiny magnets are engaging. Strong bonds are established where the adhesive and substrate interact, creating a robust chemical connection. This process, known as chemisorption, involves the formation of a new chemical entity through the combination of adhesive and substrate.
Adhesion: Adhesion is the ability of an adhesive substance to adhere to another surface using one of the four mechanisms of attraction between the materials. When adhesive molecules come in contact with the substrate, adhesion occurs at the microscopic level through intermolecular forces. This is based on van der Waals forces regarding weak intermolecular forces.
The concept of van der Waal forces is dependent on distance. When molecules are close, their forces are attractive. If the distance is 0.6 nanometers, the force is weak and cannot be seen. When the distance is less than 0.6 nanometers, attraction occurs, a foundational adhesion principle.
Surface energy determines the wettability of the substrate when it makes contact with the adhesive. The wettability of the adhesive allows it to penetrate the surface of the substrate to form a bond using one of the four adhesive mechanisms.
Surface energy is the sum of the intermolecular forces regarding their attraction and repulsion energies and how a liquid exerts force on the surface of a solid. Where the substrate has high surface energy, an adhesive easily flows over it and covers more area. Examples of high-energy substrates are polycarbonate, polyvinyl chloride, and zinc.
If the substrate has low surface energy, the adhesive builds up as “small beads” covering a minute area. Types of low surface energy substrates include polytetrafluoroethylene (PTFE), rubber, and powder coatings.
Surface contaminants reduce surface energy and prevent the fusion of an adhesive to the substrate. Types of surface contaminants include dust, fingerprints, oil, grease, moisture, and various forms of residue, such as coatings. For the adhesion process to be successful, pretreatment of the surface is necessary, which removes surface contaminants, enhances surface energy, and improves adhesive bonding.
Cohesion: Cohesive force is the bonding of the molecular chains of the tape that are expressed as shear resistance or retention force that occurs after bonding. When tape has good cohesion, it is resistant to high temperatures, with low viscosity and exceptionally strong retention.
Cohesive forces attract the molecules of a liquid by pulling them inward. Surface molecules of the liquid have attractive forces that bind them together, a phenomenon responsible for the property of a liquid referred to as surface tension.
In adhesion, surface tension is the ability of the adhesive to resist deformation on the surface of a solid, reducing its surface area. In the case of adhesive tapes, the molecules of the adhesive have to have strong, cohesive forces to hold and maintain the bond.
Silicone adhesive tape has good adhesion with low surface energy, but it is heat and weather-resistant with good electrical insulation properties and chemical resistance.
Adhesion and cohesion are the properties that engineers consider when designing tape. The two forces work together to form strong, consistent bonds for a high surface energy substrate for low surface tension adhesives. To have good wetting, adhesive forces must be greater than cohesive forces and contact at less than a 90° angle.
Tackiness: The tackiness factor refers to how a pressure-sensitive tape sticks to the substrate when minimal pressure is applied. The adhesive is activated by 14.5 psi to 29 psi pressure. The amount of pressure time varies per the type of adhesive, the nature of the substrate, and the substrate surface's consistency. When an adhesive tape is high in tackiness, less time and pressure are required to ensure a proper bond.
Viscoelastic materials are viscous and elastic. They behave like fluids and elastic solids and have particles that temporarily connect. Their flexibility allows them to slide along each other like fluids. When low pressure is applied to tape, its viscosity decreases, causing the adhesive to flow onto the substrate at a microscopic level. Its elastic properties help it regain its viscosity to form a strong intermolecular force with the substrate.
Rolling Ball and Loop Tack Tests are used as quality control checks to assess the tackiness of adhesive tapes.
Rolling Ball Test: The rolling ball test directly gauges the adhesive behavior of the adhesive tape. A steel ball with a standard weight and diameter is rolled from the top of an inclined track consisting of the sticky side of the tape. The tackiness is measured by the distance traveled by the ball on the sticky tape track; the shorter the distance, the greater the tack.
Surface Energy: Surface energy is the attraction or repulsion between a substrate and another material. When a surface has high surface energy (HSE), molecules easily flow over the surface. With low surface energy (LSE), liquids bead up instead of flow. In the case of adhesives, surface energy influences how an adhesive is capable of wetting out the substrate.
Surfaces with LSE are difficult to bond because the surface resists the adhesive’s wetting out, creating low surface contact and adhesion. With HSE, the adhesive wets out easily, with increased surface contact forming a strong bond.
For adhesive tape to bond with an LSE substrate, the surface must be modified by changing its chemical composition to increase its surface energy. Techniques such as flames, plasma treatments, acid etching, and solvents may be used. In addition, there are specially formulated adhesives capable of bonding with LSE substrates that contain modified acrylics and synthetic adhesives. Rubber adhesives are often used since they are soft and flow well.
Adhesive tapes typically include a carrier, adhesive, and release liner. While not all adhesive tapes require all these components, their presence depends on the specific properties of the tape material and its intended use. The choice of materials for the carrier and adhesive is crucial, particularly when subsequent processes like cutting are involved. Adhesive tapes may feature the following components:
The carrier, also known as the backing material, is a thin, flexible film that holds the adhesive. The choice of carrier material can vary based on the intended use of the adhesive tape and may include the following types:
Plastic Films: Plastic films are a widely used carrier for adhesive tapes. It offers flexibility, high tensile strength, and good weathering resistance. Its color and transparency can be customized, and it can be printed easily. The following polymers used in plastic carriers are:
Polyvinyl Chloride (PVC) Films: PVC adhesive tapes are valued for their chemical, moisture, and flame resistance, high toughness, and high tensile strength. PVC tape is commonly used for household and electrical applications that require the adhesive tape to be durable and to give a semi-permanent bond.
Metal Foil: Metal foil carriers are valued for their resistance to severe temperature extremes, high humidity, and excellent electrical conductivity. Metal foil carriers are usually made of aluminum, copper, or zinc and are used to bond electrical components. It may be reinforced with a plastic or paper film to increase its strength.
Paper: A paper carrier is suitable for lightweight and decorative applications. It is easily customizable and printed. It can be laminated with other materials to improve their tensile strength, as paper films are naturally brittle. The most common adhesive tapes with paper carriers are masking tapes and paper tapes, which are used to seal boxes and packaging materials, and fragile surgical tapes. Zinc gives the white color to all medical tapes and enables its antimicrobal properties.
Adhesives are the primary element in all adhesive tapes. They are polymeric substances applied to surfaces to bond them together and resist separation. Below are some commonly used types of adhesives:
Rubber Adhesives: These adhesives are inexpensive and intended for low-stress and room-temperature applications. It provides a quick stick to substrates and does not require long cure times. Modifiers are added to rubber adhesives to increase their tackiness. However, heat and UV radiation adversely affect the rubber adhesive's performance.
Rubber adhesives are commonly used in duct tapes, masking tapes, and carton sealing tapes. It may be derived from natural rubber or synthetic rubber.
Synthetic Rubber Adhesives: These are formulated by manufacturers and provide better adhesion and higher shear resistance. Types of synthetic rubber adhesives are:
Acrylic Adhesives: Acrylics are high-performance adhesives based on polymerized acrylic monomers. They overcome the weaknesses of rubber adhesives. Acrylics are resistant to UV radiation, high temperatures, chemical attacks, and oxidation. The bonds made by acrylic adhesives are initially strong from the time of application and become much stronger as it sets. These adhesives offer heavy-duty and long-term bonding solutions.
Acrylic adhesives are available as water-based or solvent-based adhesives:
Silicone Adhesives: They are regarded as the most expensive adhesives used in tapes. Among the adhesive tapes, they can withstand the highest temperatures of up to 475°F (246 ° C). They also have excellent UV radiation and chemical resistance. Silicone adhesive has low initial bond strength, which becomes significantly tougher as the adhesive sets from the time of application.
Silicone adhesives are found in tapes mainly used in the electronics industry, where significant amounts of heat are dissipated in electronic components. These adhesives are also found in splicing tapes and PTFE tapes.
A release liner is essential for double-coated tapes and adhesive transfer tapes. This layer is removed before applying the tape to the substrate. It maintains the adhesive’s stickiness until use and prevents it from adhering to the carrier prematurely.
Adhesive tapes are classified based on the configuration of the carrier, adhesive, and release liner:
Single Coated Tape: Single coated tapes are the most basic configuration of adhesive tapes. The adhesive film is only found on one side of the carrier. The exterior side of the carrier may be coated with a release agent to help unwind the tape, or a release liner may be used. Typical examples of a single coated tape are electrical tapes, duct tapes, masking tapes, etc.
Adhesive Transfer Tape: These are intended for a discrete, seamless bonding of two substrates. The unsupported adhesive film is protected with a release liner, which is peeled off after bonding to the first substrate. The second substrate is then attached to the other side of the adhesive film. The release liner is used on both sides of the adhesive to aid its separation. Unlike double-coated tapes, the temperature resistance of an adhesive transfer tape is limited only by the properties of the adhesive itself.
Double-coated Tape: This type consists of backing material with adhesive film applied on both sides. A release liner is used to separate the adhesive layers.
Double-coated tapes are used to bond substrates with different surface properties that require different bonding requirements. It is highly customizable, and the thickness of the adhesive can be varied on the opposite sides. The thermal resistance of a double-coated tape depends on the properties of its carrier.
Pressure-sensitive adhesive tapes offer several advantages compared to glues, adhesives, and other fastening methods, including:
Uniform adhesive thickness. The adhesive layer on pressure-sensitive adhesive tapes is designed to be uniform in thickness, which gives a precise bond on flat surfaces. Manual application of adhesives tends to be wasteful if in excess, or a weak bonding is produced if insufficient.
Highly versatile. The functions of adhesive tapes are not limited to joining two or more substrates. Adhesive tapes can also serve to:
Convenient to use. No special tools are needed when using adhesive tapes during application. Cutting and sticking it on a surface can be accomplished by hand. Adhesive tapes are also easy to store and do not occupy large spaces.
Pressure-sensitive adhesive tapes may not be suitable under some circumstances. They are not suitable for bonding some joint types and materials that are intended for high-stress applications due to their limited bonding strength. Pressure-sensitive adhesives have weaker adhesive forces produced compared to glues and sealants.
They also underperform at high and low temperatures. Tackiness is dependent on the temperature of the substrate. A poor bond is created when the temperature of the substrate is low. At high temperatures, the viscosity of the adhesives decreases, causing the bond to weaken. Glues and sealants are preferred when objects are exposed to thermal cycling. Pressure-sensitive adhesives are also sensitive to UV radiation and oxidative agents.
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