Hot Melt Adhesives
The term “adhesives and equipment” is typically used to refer to hot melt adhesives and their various dispensary tools. Hot melt adhesives are essential components in many manufacturing industries. They are commonly used in applications including packaging, product assembly, cable assembly, automotive interiors, woodworking, and insulating glass.
The hot melting process consists of heating a thermoplastic polymer and applying it as an adhesive to parts and components in liquid form. When the plastic cools, it becomes solid again to form a tight, secure bond. Depending on the bonding agent and the tools used, hot melts can produce bond strengths similar to welding.
Types of Adhesives and Equipment Parts
Regardless of the application, choosing the appropriate adhesive and equipment can help reduce costly downtime and lost production due to adhesive failure. Plus, by ensuring the selected nozzles, hoses, and modules are suitable for the specific application, you can increase process speed, minimize waste, and reduce bonding defects.
The typical hot melt equipment consists of three primary parts: the hose, the module, and the nozzle.
Hot Melt Hoses – These are tube-like structures responsible for delivering the molten adhesive to the nozzle. These flexible, reinforced hoses must be specifically designed to work with the chosen module and nozzle. Incorrect hose selection can compromise part reliability, leading to issues such as breaking and clogging.
Hot Melt Modules – The module is the heart of the hot melt adhesive system. It is a valve that dispenses the molten adhesive. The amount administered by the module is further controlled by a nozzle. As with all the other parts, the selected module should be compatible with the rest of the system, including the hose and nozzle. The module must also dispense the intended adhesive type and be suitable for the particular mode of glue application.
Hot Melt Nozzles – The nozzle has the most significant impact on the quality, consistency, throughput, and performance of the adhesive application. When you’re selecting the right nozzle to match the application, you must consider several factors, such as the glue pattern, number of orifices, orifice diameter, nozzle angle, and style of gun.
Besides the equipment parts, it’s essential to use the correct type of adhesive to ensure optimum bond performance. The hot melt process can be performed with various types of thermoplastics, each with properties that can be used for different applications. Some of the most common types of adhesives include:
- EVA (Ethylene Vinyl Acetate) – This thermoplastic polymer is economical and effective at temperatures between -22oF (-30oC) to 175oF (80oC). EVA is the most common type of hot melt and is commonly used in packaging and product assemblies.
- PA (Polyamide) – PA is costlier than EVA but offers a higher level of heat resistance. Service temperatures range from -76oF(-60oC) to 266oF (130oC), making this polymer widely used in the woodworking, automotive, and electrical industry.
- PP (Polypropylene) – Polypropylene is a versatile thermoplastic polymer commonly used in adhesive spray formulations. It is lightweight, relatively durable, and resistant to chemical degradation. Polypropylene is effective in temperature ranges between -22oF (-30oC) and 230oF (110oC). Due to its wide range of properties, PP is used in applications from consumer packaging to bonding in the medical industry.
- PUR (Polyurethane) – PUR melts are nontoxic, fast-curing, and temperature- and weather-resistant. This adhesive absorbs small amounts of moisture to undergo a chemical reaction that causes it to solidify and form a strong bond. PUR adheres to glass, plastics, metals, and timber, making it ideal for furniture, footwear, boat construction, and various other assemblies.
Efficient Production with the Right Adhesive
Although the hot melt process may seem simple on the surface, there are several adhesive- and equipment-related factors to carefully consider for optimal performance of the bonding application. Once you understand your needs, you’ll find an option that provides an effective solution.
Resources: