Introduction
In recent years, the application of bio-based adhesive technology has increasingly become the focus of attention of the industry. Among them, thermosetting adhesive (TH) has the properties of excellent performance, economy, environment protection and safety, and has become the preferred green adhesive for many industries. TH also has a wide range of applications in woody products, paper products, industrial and engineering processes and even household repairs.
History
Thermosetting adhesive technology originated in the early 20th century, when resins were widely used as binders for wood, paper and metal products. In the early development of TH technology, aldehyde resins were the most commonly used. However, the use of these resins was limited by their relatively low viscosity and poor adhesion.
In the 1950s and 1960s, a variety of crosslinking agents and modifiers, such as melamine and phenolic formaldehyde (PF) resins, began to be used, greatly improving the performance and durability of thermosetting adhesives. Soon after, unsaturated polyesters, etc., became more widely used and many composite products, such as fiber glass and carbon fiber composites, began to be produced with TH adhesive technology.
Types and Characteristics
Thermosetting adhesive (TH) is divided according to the materials used. Common types of TH adhesives include phenol-formaldehyde (PF), urea-formaldehyde (UF), melamine-formaldehyde (MF), alkyd resins, epoxy resins, and unsaturated polyester resins.
Phenol formaldehyde (PF) resin is the most commonly used TH adhesive. This adhesive has a high strength, good adhesion, low water absorption and good electrical properties, making it a good choice for many applications.
Urea formaldehyde (UF) resin is commonly used in medium density fiberboard manufacturing. The adhesive is characterized by its heat and water resistance, good clarity and high shear strength.
Melamine formaldehyde (MF) resin is a thermosetting adhesive characterized by its extreme resistance to water, heat, solvents and aging. It is often used for adhesives that must retain their strength even after long-term exposure to extreme environments and conditions.
Alkyd resins are a class of TH adhesives known for their excellent adhesion, high impact resistance and long-term durability. This type of adhesive is often used in industries where a durable bond is required, such as automobile manufacture.
Epoxy resins are polymer-based TH adhesives and are often used for structural adhesives due to their excellent adhesion and durability. These adhesives are often used to bond metal and other surfaces that need high strength.
Unsaturated polyester resins are used in a variety of applications, including adhesives and coatings. These adhesives have excellent mechanical and chemical properties and are often used in composites and laminates.
Advantages and Disadvantages
Thermosetting adhesives (TH) have many advantages due to their many types and characteristics. The main advantages are their high strength, excellent adhesion, good clarity, low water absorption, good electrical properties, heat and water resistance, and long-term durability.
However, there are also some drawbacks to using TH adhesives. These adhesives tend to be expensive and require a long curing time. In addition, it is difficult to use TH adhesives for delicate substrates, as the force required for adhesion may exceed the strength of the substrate.
Uses
Thermosetting adhesives (TH) are used for a wide range of applications. Common uses of TH adhesives include woody products, paper products, composites, engineering and industrial processes, automobile manufacturing, and even household repairs.
Conclusion
Thermosetting adhesives (TH) are a class of adhesives used for a wide range of applications such as woody products, paper products, composites, engineering, and automotive. They possess the properties of high strength, excellent adhesion, good clarity, low water absorption, good electrical properties, heat and water resistance, and long-term durability. Although they are expensive and require a longer curing time, their various uses and characteristics make them a popular choice for many industries.
