What Is a Hot Melt Adhesive?
Hot melt adhesives, commonly known as hot glue, are used in a method called hot melt. This process involves melting the resin by heating it and causing it to adhere as it cools and solidifies. These adhesives are safe as they do not contain solvents, making them popular in DIY projects.
Hot melt adhesives are available in various forms, such as pillow, stick, block, and container types, wrapped in non-adhesive release paper. They are melted using a heating device called an applicator.
Uses of Hot Melt Adhesives
Hot melt adhesives are widely used due to their safety and versatility. They are used in “hot glue” guns in discount stores for DIY projects, for sealing cardboard boxes in packaging, and even in food-related applications due to their safety. Additionally, their easy peelability makes them ideal for attaching labels in logistics.
Principle of Hot Melt Adhesives
To use, hot melt adhesives are heated to about 120°C, becoming liquid. They spread between bonding surfaces, form a resin film, and then cool and solidify, creating physical adsorption at the molecular level. This process does not alter the physical properties of the resins and does not affect the adherend, making them suitable for bonding a variety of materials like polypropylene, polystyrene, wood, glass, iron, stainless steel, and aluminum.
Features of Hot Melt Adhesives
Hot melt adhesives are environmentally friendly, as they do not use solvents and bond quickly. They adhere through a “heating-melting-cooling-solidifying” cycle, which is faster than the chemical reaction of general adhesives.
Types of Hot Melt Adhesives
Common types of hot melt adhesives include olefin-based and rubber-based adhesives. Olefin-based adhesives are effective for materials hard to bond with general adhesives, while rubber-based adhesives are used when liquid adhesives penetrate the adherend.
Other Information on Hot Melt Adhesives
Advantages and Disadvantages of Hot Melt Adhesives
Hot melt adhesives have several advantages, such as quick bonding, applicability to various materials, high safety, reusability, easy storage, and automation compatibility. However, they have limited heat resistance, lower adhesive strength compared to curable adhesives, and are not suitable for heat-sensitive materials. Their adhesion also varies with temperature and requires a special applicator.