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Hot melt acrylic pressure-sensitive adhesive

Hot melt acrylic pressure sensitive adhesive has high solid content (100%), compared with the traditional solvent, emulsion type acrylic pressure sensitive adhesive, has no organic solvent, green, fast coating rate, low investment cost, beneficial environmental protection, and a high degree of automation advantages; But there are also coating temperature (160 ~ 180 ℃) high, heat aging, poor high-temperature resistance, coating-machine service life reduction, large energy consumption, not easy to control the thickness of the coating, the thin coating is difficult to shortcomings. With the acrylic copolymer, block copolymer, and macromonomer industry productization, crosslinking technology progress, hot melt acrylic pressure sensitive adhesive has been the corresponding development, technical process improvement, has overcome some shortcomings of traditional hot melt pressure sensitive adhesive, such as heat stability, seepage back, transparency, etc.

Hot-melt acrylate pressure-sensitive adhesive has excellent bonding properties, thermal stability, and weather resistance, but has low cohesion without crosslinking agents, resulting in the limited application. At present, the pressure-sensitive products of hot melt acrylate are relatively few, and there are not many related research reports. Most hot melt pressure sensitive adhesives in the market are mainly rubber hot melt pressure sensitive adhesives.

Radiation-curing acrylic pressure-sensitive adhesive

Radiation curing acrylic pressure-sensitive adhesive, including electron ray radiation (EB), and ultraviolet radiation (UV), is one of the solvent-free pressure-sensitive adhesives, radiation curing is the use of electron ray, ultraviolet light irradiation triggered unsaturated monomer polymerization, grafting, crosslinking, and other chemical reactions, the preparation of pressure sensitive adhesive products with practical properties. It has the characteristics of no environmental pollution, fast curing, environmental protection, energy saving, and high efficiency. Compared with the traditional emulsion type acrylic pressure sensitive adhesive, no drying treatment, excellent water resistance, high-speed coating, energy saving, aging resistance, and high-temperature resistance. Compared with solvent-based acrylic pressure-sensitive adhesive, there is no volatile solvent, and volatile composition (VOC) is almost zero; Compared with the hot melt acrylate pressure-sensitive adhesive, the heat resistance is better. At present, UV photocuring technology is widely used in radiation-curing acrylic pressure-sensitive adhesives. UV photocurable pressure-sensitive adhesive has obvious advantages over several types of environmentally friendly pressure-sensitive adhesive. It is the future research and development direction of the environmental protection pressure sensitive adhesive industry, and also the goal of pressure sensitive adhesive industry.

Functional acrylic pressure-sensitive adhesive

In recent years, some functional acrylic pressure-sensitive adhesive products for special purposes are also being developed and widely used. Functional acrylic pressure-sensitive adhesive mainly includes medical acrylic pressure-sensitive adhesive, electronic industry acrylic pressure-sensitive adhesive, flame retardant acrylic pressure-sensitive adhesive, and reputable acrylic pressure-sensitive adhesive.

The types of medical pressure-sensitive adhesives have made rapid development. New medical pressure-sensitive adhesives such as acrylate, silicone rubber, and polyurethane continue to emerge, among which acrylic pressure-sensitive adhesives are more studied and applied, gradually replacing the traditional rubber-type medical pressure-sensitive adhesives. The new acrylate medical pressure sensitive adhesive has good performance, is non-toxic, has no skin irritation, no allergic effect, good air permeability, and good compatibility with various drugs, because it can control drug release in a variety of ways, thus expanding the range of application of pressure sensitive adhesive.
The rapid development of electronic components to miniaturization and miniaturization, as well as the development and progress in the field of polymer chemistry, has led to the reform of bonding technology and promoted the further development and expansion of pressure-sensitive adhesives used in the electronic industry.

Environmental protection, flame retardant, and environmentally friendly pressure-sensitive adhesive are more and more favored by the market. Bi Shuguang [40] et al. compared various methods of preparing flame retardant acrylate pressure sensitive adhesive on the basis of analyzing the adhesion characteristics and structural characteristics of acrylate pressure sensitive adhesive. Adding flame retardant groups to develop bulk flame retardant acrylate pressure sensitive adhesive will attract more and more people’s attention, and the composite technology of flame retardant is also one of the important ways to achieve high flame retardant. The synergistic effect of organic flame retardants and inorganic flame retardants will open up broad prospects for the flame retardation of synthetic materials, and the new environment-friendly acrylic pressure-sensitive adhesive with flame retardation function will be more widely used.

Repulpable acrylic pressure-sensitive adhesive is mainly used in the paper industry, which will not pollute equipment in the process of waste paper recycling and meet the requirements of environmental protection and sustainable development.

Classification of acrylic pressure sensitive tape

• Packing tape acrylic + hot melt adhesive
• Label tape acrylic + hot melt adhesive
• PVC tape (telegraph insulation tape) rubber class
• Protective tape acrylic + rubber
• Double-sided tape acrylic + hot melt adhesive
• Hot melt tape Hot melt adhesive
• Paper tape acrylic + rubber
• Medical tape acrylic + rubber
• Special tape acrylic class + rubber class + silicone class
• Anticorrosive tape rubber
• Other adhesive tapes acrylic + hot melt adhesive + rubber class

Hot melt pressure sensitive adhesive

Hot melt pressure sensitive adhesive is developed in recent years, it is mainly used in women’s sanitary napkins, the elderly and children’s diapers, double-sided tape, and trademarks, and its composition is mainly SIS and SBS elastomer and viscosifying resin. In recent years, with the development of the garment manufacturing industry, the demand for hot-melt adhesive powder used for clothing hot-melt interlining has increased year by year. In 1998, the demand of about 12,000 tons is not included in our statistics. The main role is polyethylene accounting for about 50%, polyamide for about 22%, and the rest is polyester and EVA hot-melt adhesive powder.

Acrylic pressure sensitive adhesive

The reaction medium of the acrylate pressure-sensitive tape is an organic solvent or water, and the glass transition temperature of the tape film is between minus 60 degrees Celsius and minus 30 degrees Celsius, which is adjusted by the branched chain of the acrylate copolymer.
Under normal conditions, the longer the side chain, the lower the glass transition temperature of the acrylate, and the more flexible the polymer chain, and the shorter the side chain, the higher the glass transition temperature of the acrylate, and the better the rigidity of the polymer chain.

Compared with other types of pressure-sensitive tapes, the single-component of acrylate pressure-sensitive tapes is very simple, which solves the problem of low molecular weight migration on the surface of the film. The adhesion mechanism of acrylate pressure sensitive tape is the same as that of pressure sensitive tape.

Adhesion can be explained by citing two theories:

• The first one is mechanical interlocking. When the adhesive material is cured, it has a certain fluidity, so the pits or gaps on the surface of the adherend that cannot be seen by the naked eye will complement the pressure-sensitive tape. When the adhesive material is cured, the adhesive The bonded substances and adhesives achieve the bonding of different substances through mechanical interlocking. In this regard, the adhesive performance of acrylate pressure-sensitive tape is actually formed after the two substances are infiltrated and interlocked.
• The second is the adsorption theory. The essence of bonding is the mutual contact between the bonded substance and the molecular level of the bonding material, which leads to the interaction between different atoms, so as to realize the connection between the two objects. Another way of saying this is the bonding material. One way of saying is that there will be van der Waals force between the bonding material and the substance to be bonded, and the electrostatic interaction will cause the two to connect.

Do you know about pressure-sensitive adhesives? Pressure-sensitive adhesive is an adhesive kind featuring a special formulation. It binds together two surfaces upon applying pressure and does not need water, solvent, or heat activation. The advantage of pressure-sensitive adhesive is it is waterproof and odorless.

Pressure-sensitive adhesive combines viscosity with elasticity. Viscosity refers to the thick state, that is semi-fluid and sticky in consistency. It is the same as honey. Elasticity is stiff and solid, like rubber. It adheres well on a surface, consisting of adhesive substances in the raw materials.

The pressure-sensitive adhesives are not actual solids. It means with the increase in temperature, the bond, and the strength decrease. This adhesive type is permanently sticky and strong at room temperature.

What is the difference in pressure-sensitive adhesives?

The pressure-sensitive adhesive does not need much pressure, while other types require solvent, water, or heat to work as the adhesive. Engineers find pressure-sensitive adhesives useful due to the properties of load-bearing. It means the bond is strong to bear the required weight.

Pressure-sensitive adhesive tapes are known as PSA. They are self-stick adhesive, self-adhesive, featuring viscoelasticity. It is a polymer with this feature, viscoelasticity and which means the material is solid and liquid. The tape stays sticky on peeling and protects the adhesive. The demand for PSA is growing as this tape is simple to use, and is a cost-effective fastening solution.

The adhesive system repeatedly is useful for reuse. The strength of the adhesive stays the same with each cycle of adhesion, and reversing adhesion is a fast process, relatively.

Pressure-sensitive adhesive (PSA) tape characteristics

PSA tape features three qualities, such as:

• Cohesion- It is the adhesive strength or the stickiness strength.
• Adhesion– It is the adhesive strength, where the sticky material or the surface tape sticks to the substrate.
• Tack– It is the adhesive time taking to any surface or substrate. Any the sticks with little pressure, while a less tacky tape requires harder pressure to stay in sticking.

A tape is a pressure-sensitive adhesive when it bonds with pressure. Any tape involving heat or a solvent is not a pressure-sensitive adhesive tape.

Benefits of using Pressure-Sensitive tape

Pressure-sensitive tape is an efficient and quick tape. It is gaining popularity for various reasons:

• The material of PSA tapes is light and thin, making working easy with them.
• Fast to bond, so requires no other element to activate, but for pressure. It bonds dissimilar materials, so no worries about the compatibility of materials.
• The PSA tapes reduce the noise of vibrations. The tapes absorb noise and do not rattle like any traditional fastener.
• PSA reduces refinishing a surface need and eliminates visible mechanical fasteners. There is no fastener or screw, but there is a smooth finish.
• PSA tapes fill gaps, creating uniform thickness and creating aesthetically pleasing products.

What Adhesive types are used for PSA tapes?

Rubber: The rubber-based adhesives are synthetic or natural rubbers. They are formulated with oils, resins, and anti-oxidants. It is a cost-effective PSA, offering quick sticking ability, but not an appropriate choice for high-heat applications.

The rubber-based PSA are easily removable and suitable as a permanent bonding option. They are designed to optimize PSA applications, and they are popular for their reliability, quality, and efficiency. They are ideal for manufacturing industries or organizations dealing with:

• Packing list envelopes, Food labels, Specialty labels, Tire and Fabric labels, Permanent General purpose labels, and Resealable and Removable labels.

Acrylic: Acrylic-based adhesives are pressure-sensitive adhesives featuring acrylic polymers. They feature long-term aging and have resistance to environmental factors and solvents. These adhesives develop a stronger bond and manage higher temperatures.

The acrylic PSAs are versatile and offer better UV stability, provide lower operating temperatures, and improve clarity. The applications withstand temperature and moisture changes in the application. These adhesives provide advanced bonding as they are coater-ready. They are ideal for industries dealing with:

• Pharmaceutical labels, Clear labels, Foam tape, Resaleable, and Removable labels, General purpose permanent labels, and Mounting tape.

The graphics industry also relies on the emulsion-acrylic PSAs for their clean removability, high clarity, and cohesion, making them ideal for various purposes including:

• Corporate and architectural graphics
• Exhibition graphics
• Removable protective film
• Advertising graphics

Precisely, the emulsion-acrylic PSAs are useful in medical product manufacturing. They are skin safe and suitable for:

• Bandages, Wound dressings, and Medical tape

Another vital market using emulsion-acrylic PSAs is food contact. They are 100% safe as food-based applications. It is tested and tried to receive food range approval. These adhesives offer good adhesion and reliability, being consumer safe.

Silicone: The silicone polymer’s formulation and the adhesive bonds with silicon substrates. These adhesives of silicone are expensive and have a low initial tack. Yet, they withstand higher temperatures in comparison to acrylic and rubber adhesive.

Solvent acrylic PSAs assure the product’s resistance to weathering, moisture, UV, and a few chemicals, besides operating temperature. Manufacturers opt for solvent-based PSA for production, owing to its durability and strength that manages under challenging conditions. It is resistant to chemical and weather exposure, and UV, and is suitable as PSAs for a variety of applications:

• Automotive tape
• Exhibition graphics
• Pharmaceutical labels
• Over-laminating films
• Durable labels
• Ostomy care
• Vehicle graphics
• Conspicuity tape
• Resealable and Removable labels
• Surgical drapes
• Would dressings

These PSAs withstand chemical contact and extreme temperatures that fulfill the need for supporting applications. Manufacturers require adhesive to various substrates to safeguard customers in extreme conditions. The pressure-sensitive adhesives are useful for pipe marking appliances to drum labels and work under extreme conditions perfectly as strong bonds.

UV-curable PSAs offer the freedom to get more options and grab the consumer’s attention. These PSAs optimize productivity for thicker tapes. PSAs are offering superior clarity and offer no-look labels featuring 100% coating benefits as solids technology. As per silicone material, the material lasts ranging from 6 to 12 months. It features a release liner or comes with a self-wound.

Composition of thermoplastic elastomer pressure sensitive adhesive:

A thermoplastic elastomer is a new type of synthetic rubber developed after 1963. It has the stay solubility and hot workability of thermoplastic plastics. It has the elasticity of vulcanized rubber at room temperature without chemical crosslinking. Therefore, it is also called the third-generation rubber. A typical thermoplastic elastomer is an A-B-A block copolymer, which is made of styrene (St), diolefin (D), and styrene (St) terpolymer, referred to as SDS.

Specific varieties of SBS and SIS, its unique structure makes it can be in some organic solvents without plasticizing, at the same time at high temperatures, and have low melting viscosity. Pressure sensitive adhesives with different properties were prepared by adding components with different compatibility with polystyrene (PS), polybutadiene (PB), and polyisoprene (PI). Due to unsaturated bonds in PB and PI segments, it can also be modified by grafting copolymerization. Thermoplastic elastomer pressure sensitive adhesives are mainly solvents. Thermoplastic elastomer pressure sensitive adhesives are composed of SBS, SIS, viscosifying resin, softener, antioxidant, colorant, and so on. Only when the allocation of each group is appropriate, can the pressure sensitive adhesives with excellent performance be prepared.

Definition of pressure sensitive adhesive

There are more than ten interpretations of the meaning of pressure sensitive adhesive and pressure sensitive adhesive products, the most common definition is as follows:

Definition

• 1: Using finger energy pressure can make the adhesive immediately adhere to any adhesion object’s smooth surface. At the same time, if the damage is the adhesive surface, the adhesive does not pollute the surface of the adhesive, this type of adhesive is called pressure sensitive adhesive. Its bonding process is very sensitive to pressure, so it is called pressure sensitive. Pressure sensitive adhesives are  generally not directly used to bond the adhesive. Pressure sensitive adhesives are made of various materials (tape and adhesive labels).
• 2: (pressure sensitive adhesives) Academic definition: pressure sensitive adhesive is a viscoelastic body with viscous properties of liquid and elastic properties of solid; This kind of viscoelastic body has the influence factors and properties of both the contact process and the failure process of bonding.