Industrial hot melt glue can be used in all kinds of product assembly, such as small joint assembly, large surface lamination, assembly and shooting accessory. Product assembly involving hot melt application may include household appliances, mattresses, HVAC and many others. Hot melt adhesive (HMA), also known as hot glue, is a form of thermoplastic adhesive commonly sold as solid cylindrical sticks of various diameters designed to be applied with a hot glue gun. The gun uses a continuous duty heating element to melt the plastic glue, which the user pushes through the gun with a mechanical firing mechanism on the gun or with direct finger pressure.
The glue squeezed out of the heated nozzle is initially hot enough to burn and even the skin of the blisters. The glue is sticky when hot and solidifies in a few seconds to a minute. Hot melt adhesives can also be applied by dipping or spraying, and are popular with hobbyists and craftsmen both for fixing and an economical alternative to resin casting. Hot melt adhesives are generally 100% solids formulations based on thermoplastic polymers.
They are solid at room temperature and are activated by heating them above their softening point, where they are liquid and can therefore be processed. After application, they retain the ability to wet the substrate until they solidify. When they solidify, they return to a physical state that has structural integrity and can function as an adhesive. The adhesive is applied by extrusion, lamination or spraying and bonding is carried out immediately after application or after reheating the solidified layer.
The variety of polymers of this class is very wide and includes both natural and synthetic polymers. The high viscosity of the melt makes them particularly suitable for porous and permeable substrates that would otherwise be more difficult to bond with a solvent system. A feature of hot melts is that, when cooled, they quickly increase their internal strength, which allows quick assembly and subsequent processing. Because they are based on thermoplastic polymers, hot melts can be repeatedly heated to melt and cooled to solidify.
This property limits the temperature resistance of hot melt joints and they also have a tendency to deform when subjected to continuous stresses or high temperatures. On the plus side, these adhesives can be used to create bonded joints that are thermally removable and can also be reattached. Hot melt adhesives can be used to bond a wide variety of substrates, from cardboard, metal, glass, leather and wood to ceramics, plastic, rubber, fabric and foam. The high viscosity of a hot melt makes it suitable for use on both porous and non-porous substrates that would otherwise be more difficult to bond with, for example, a solvent-based adhesive.
The same properties that make hot melt popular for woodworking also make it ideal for construction and construction projects. Carpets and bonded floors are typical applications for hot melt glue. The use of hot melt prevents surfaces from bending or bending after drying, and improves the aesthetics of new floors by removing staples and nails. The glue also dries quickly, making it easy to apply materials to vertical surfaces.
Hot melt adhesives are used to bond fusible interlinings, in seam and hem sealing, fabric lamination and a variety of other textile applications. The melting point of hot melt adhesives must be above the minimum temperature that the application will see in service. This could provide a problem in that many textile substrates are heat sensitive, and conventional hot melt adhesives must be applied at high temperatures. To avoid this problem, formulators have developed hot melts with a lower application temperature, sometimes referred to as “hot melts”.
The most popular adhesive in this category is the thermoplastic polyurethane and polyurethane reactive adhesives described below. Hot melt adhesives are ideal for situations where simplified processing, optimized manufacturing and end-product protection are required. The applications of hot melt adhesives are incredibly diverse. The adhesive is used in the manufacture of hygiene products, furniture and packaging, as well as for medical, electronic and automotive applications.
Hot melt slot coating is often used when working with pressure-sensitive adhesives on thin substrates. Polyamide based hot melt adhesives offer excellent resistance to heat, oil, grease, plasticizers and solvents. Hot melt spray adhesives are dispensed by manipulating a continuous bead of adhesive in a pattern with compressed air. While most of us probably knew hot glue during crafts, it is one of the most widely used adhesives in industrial manufacturing.
They are best suited for applications where rapid fusion is needed to keep the manufacturing process running at a high rate. Hot melts are also used in the printing industry for joining book spines, in the textile industry for joining appliques and in the shoemaking industry for joining, for example, shoe soles. In the transport section, hot glue is used for mounting moldings, joining small joints and bonding laminate surfaces and other miscellaneous components. Simply put, hot melts offer long-term cost savings and a variety of uses and applications to meet the high production demand that no other type of adhesive can match.
In hot melt slot coating, a layer of hot melt adhesive is applied to the substrate before it is cooled and solidified. Theoretically, any thermoplastic can be a hot melt adhesive, but the ten or more preferred materials are typically solids up to 79.4°C or more, then melt sharply to give a low viscosity fluid that is easily applied and capable of wetting the substrate to be bonded, followed by a rapid setting to the cool down. As factory footprints shrink in size and line speeds increase to keep up with equipment growth and advances, hot melt adhesives continue to adapt. From binding book spines to packaging sealing and tape manufacturing, hot melt adhesives have a wide range of uses.