An Introduction to Industrial Hot Melt Adhesives

Hot melt glues are used in manufacturing across a wide variety of markets and applications:

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• Packaging – corrugated and carton sealing, wrapping, and pallet stabilization
• Furniture & Woodworking – furniture, cabinet and panel assembly
• Automotive – trim and seating assembly
• Additional applications – Carpets, various product assembly, bonding foams, home décor, woodworking, point of purchase displays, filter manufacturing, food and beverage packaging, labeling, construction, and more

Hot melt can be used on various types of materials:

• Corrugated
• Paper
• Wood
• Plastic
• Fabric
• Glass
• Metal

EVA Hot Melt Glues – EVA stands for ethylene vinyl acetate. The most common hot melt adhesive used in packaging and paper converting processes. Extremely versatile with a range of temperature resistance. It sets quickly and is waterproof.

Polyethylene Hot Melt Glues – Low odor and provide excellent thermal stability. It also works well for case, carton, and tray sealing applications.

Polyurethane Hot Melt Glues (PUR) – Cools and forms a bond like a traditional hot melt but provides exceptional heat and cold resistance upon exposure to air moisture. Can’t be re-melted.

Metallocene – A metal-catalyzed polyethylene adhesive. It offers more thermal stability than other hot melts. Light-colored and low odor.

Polyamide Hot Melt Glues – Heat resistant and provides a high-strength bond. It also offers excellent resistance to grease and oils. For use on difficult-to-bond materials.

APAO Hot Melt Glues – Stands for amorphous poly alpha olefins. Soft, tacky and flexible. Often used in product assembly applications.

Removable Low Tack to High Tack Glue – Commonly used on non-porous surfaces to create a removable bond without leaving a messy residue.

Pressure Sensitive Adhesives (PSA) – Also known as self-stick adhesive, it forms a bond when pressure is applied to bond the adhesive with the adherend. No solvent, water, or heat is needed to activate the adhesive.

What temperature does hot melt glue melt at?

Hot glue should not be used on materials where the high temperature could damage the product or material. It should also be used with caution to avoid burns. Carefully selecting the right type of glue gun for your application is essential. Low-temperature guns melt glue at 250 degrees and can be used on more delicate materials. High-temperature hot glue sticks and guns can reach 400 degrees and should only be used on durable, hard materials. Dual-temperature hot melt tool options are also available.

Are there different glues for use on different materials?

Yes, glues are designed to work on certain substrates so it's important to use the correct glue for your application. You will want to use a different glue for general packing applications vs more difficult substrates such as laminated board. We can assist with finding a glue product that will bond the best with your material.

Are there different glues for cold environments vs hot environments?

Yes, some types of hot melt hold up better in extreme environments. Environmental temperature affects the adhesive viscosity and set speed of glue, so make sure to check products' specifications if you will be sealing and storing in these types of environments.

Here are the most commonly used terms when talking about hot melt adhesives:

Adhesive – A substance for bonding, affixing, or holding material together.

Ambient Temperature – The temperature surrounding the object to be glued.

Bond – The attachment of an adhesive to a surface.

Compression Time – The required amount of time to hold the bond while the hot melt cools. This step is key to achieving a good, strong bond

Curing – The chemical process that takes place when a material hardens. Different glues have different curing processes that can be instant to requiring contact with moisture.

Degradation – Damage to the appearance of hot melt due to a change in the chemical structure.

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Glue Backup – This occurs when an operator tries to use a glue gun before it reaches the correct temperature. This causes the glue to be forced back along the barrel of the applicator.

Melt-Back – This happens when a glue gun has been left on for too long without use causing the glue to over-soften and be forced back along the barrel of the applicator.

Open Time – The elapsed time between application and compressing.

Tack – The stickiness of an adhesive to adhere to a material.

Setting Temperature – The optimal temperature for the adhesive to set.

Thermoplastic – A material that is capable of being liquified and re-solidified.

Viscosity – A measure of the ability of a liquid to resist flow. Should be consistent in each batch.

A hot melt adhesive, also known as a hot glue, is the name given to a polymer-based glue which is solid at room temperature and is applied in a molten state.

There are three main stages to the process of a hot melt adhesive bonding together materials. Firstly, the solid adhesive is heated until it reaches its softening point, at which stage it will turn to liquid. The molten adhesive is then applied and wets the substrate. The period available to make the bond between applying the thermoplastic adhesive and bringing in the secondary material is called the open time. Lastly, cooling time will then occur. This typically varies from just a few seconds to up to 5 minutes, and during which the hot melt will solidify and very quickly build up strength and stability. This fast turn around allows for a quick processing time and rapid assembly.

Main Components of Hot Melt Adhesives:

Polymers: These help to give the adhesive strength and flexibility, as well as heat and impact resistance.

Resins: Control the wetting of the adhesive (how long it remains a liquid whilst in contact with the substrate).

Wax: Primarily controls the open time, and how long the bond takes to form. It also helps thin the adhesive for application. The higher the wax content present within a hot melt, the higher viscosity and greater flexibility the bond will have. High levels of wax also allow for a quicker bond.

Antioxidants: These are used primarily to help preserve the material during its shelf life.

Equipment required for hot melt adhesives:

The equipment which accompanies the hot melt glue is just as important as the adhesive itself, since without the glue gun there is no way of heating the adhesive to the correct application temperature. The glue gun also allows for accurate and precise application onto the substrate. Each gun is specifically made to suit a different need, such as the 3M Hot Melt Low Temperature Applicator LT which maintains a temperature of 129ºC making it an ideal choice for heat sensitive surfaces such as foam and plastics. If a higher temperature is required, the 3M Hot Melt Touch Control Adhesive Applicator TC dispenses up to 196 ºC and is great for more detailed work.

Advantages of Hot Melt Adhesives:

Good for hard to reach areas:  As the adhesive is applied in a purely liquid form, it allows for easy application to more obscure places or surfaces which other glue or adhesive products cannot do as well. Many glue guns and nozzles are manufactured to distribute the glue into these small complex places ensuring the entire chosen surface is reachable and covered which in turn, allows for stronger bonds.

Speed and ease: As the whole process of using hot melt adhesives is quick, this lowers assembly time and allows for optimum productivity with a fast turnaround.

Bonds variety of substrates: Hot melt adhesives are specially formulated for specific tasks. A wide variety of materials can be bonded, such as wood or corrugated cardboard. Heat sensitive materials such as foam or even some plastics and metal can also be bonded using hot melt adhesive when dispensed at a lower temperature. They can also bond both porous and non-porous surfaces.

Neat Application: The bond which forms from a hot melt adhesive is practically invisible which gives an overall pleasing aesthetic. This is particularly useful when used for items such as signs, displays or even furniture.

Long shelf life: Hot melt adhesives have excellent moisture resistance and do not need refrigeration meaning they remain firmly bonded for an extensive period.

Challenges of hot melt adhesives:

As with most adhesive products, alongside the benefits, hot melt adhesives have a few limitations. The temperature at which hot melt adhesives are set at is crucial to the application process.

• Once molten, the adhesive must be hot enough for assembly. If the adhesive is not hot enough at this stage, a weak bond may be formed which is also known as a cold bond.
• However, if the hot melt adhesive is applied in a molten state at too high a temperature, it will remain in a liquid state for too long and result in a soft bond being formed. Any stress or weight on this bond will cause a weakening which could fail immediately.
• Unlike other adhesives, if hot melts bonds are re-heated to their softening point temperature, the previous adhesion caused by the cooling process can be reversed. Although this does make hot melt adhesives more flexible and easier to repeatedly change, it can cause a hindrance should this be applied to a substrate which will undergo or survive in an environment with higher temperatures. However, many hot melts are now being manufactured with higher levels of heat resistance to combat this.

Common Industries:

Packaging Industry

Electronic Industry

Automotive Industry

Bookbinding Industry

Furniture/Woodwork Industry

Retail Industry

Shop our range of Hot Melt Adhesives here. 

Additional links:

At Ellsworth Adhesives, we supply a wide range of hot melt adhesives and glue guns from leading brands Henkel Loctite and 3M. View our complete range of hot melt adhesives here. 

If you are looking for more details, kindly visit Hot Melt Adhesive Wholesale.