Top 10 Mistakes to Avoid When Using Hot Melt Adhesives | Troubleshooting

Mistakes with hot melt glue are common, and proper measures will provide the most reliable bond without unnecessary issues. The following are the top 10 mistakes to avoid while using hot melt glue and tips on their resolution.

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Hot Melt Adhesive Troubleshooting: Avoiding Common Bonding Issues

1. Using the wrong type of glue:

Hot Melt Glues are available in a variety of formulations tailored for different materials and applications. For example, certain hot melt glues are specifically designed for plain and offset substrates. Using these on coated or laminated paper materials can be a common error, particularly in applications such as paper packaging, bookbinding and graphics, leading to de-bonding and product failures.

2. Applying glue at the wrong temperature:

The flow of hot melt adhesives is essential for their performance and machinability. They are designed to melt (soften) when the temperature exceeds their softening point and to flow properly within a specific temperature range. Incorrect temperature settings are a common mistake in edge-bandingapplications, where the working temperature vastly varies from 120 to 220°C, depending on the type of machines.

3. Not Considering Open and Set Time

Hot melt adhesives have an "open time" where the glue remains workable for a certain period after application. Outside of that period, the bond may be weak or nonexistent. Understand the open and set times of the glue to align with your machine's speed, whether it is automatic or manual operation, to achieve maximum bond strength.

4. Not Considering Summer and Winter time:

During the summer, hot melt adhesives cool down relatively slowly. Conversely, in the winter, they solidify much more quickly, dropping below their softening point. Therefore, it's advised to raise the temperature setting (of the glue pot) by 10°C in winter. Failing to do so may result in weak bonding because the adhesive cools down before being applied to the substrate.

5. Not Considering Temperature Tolerance:

Hot melt adhesives (such as EVA and PO) have temperature constraints. As thermoplastic materials, traditional adhesives will soften above 80°C which can weaken the bond. This poses a problem if finished products are exposed to direct sunlight for extended periods or harsh weather conditions in outdoor applications. Selecting adhesive solutions that offer higher temperature resistance (up to 120°C) is essential.

6. Overfilling of the glue tank:

While it may seem like an excellent idea not to have to refill the hot melt glue tank so often. Overfilling while consuming slowly causes excessive heating, adhesive charring, smoke, odors, and contamination of equipment and nozzles. Fill the tank only up to 75% of its capacity.

7. Wrong pressure settings:

Using hot melt glue systems that depend upon air pressure for application can be prone to several problems if their pressures are set improperly. Too little pressure and the adhesive comes out thin and weak. Too much, and it overflows messy and stringing. Incorrect pressure settings are a common mistake for spray-application, i.e. in mattress and packaging (i.e. carton and case closure) manufacturing.

9. Applying Too Much or Too Little Glue:

Excessive adhesive can lead to a messy, stringy bond-line, impact product finishes, and increase unit costs. Conversely, insufficient adhesive may fail to adequately cover and form a proper bond initially or may de-bond over the product's lifespan.

10. Using the incorrect Glue Applicator:

Correct glue roller and nozzle sizes are essential for effective flow and pattern control. An improperly sized nozzle, whether too small or too large, can compromise bond quality. Pretextures should be applied using appropriately sized rollers and nozzles to ensure optimal glue coverage.

Additionally, ensure that your adhesives are stored in cool and dry locations, avoiding direct sunlight and extreme conditions. Having an excessive inventory and storing it for too long can impair performance. Therefore, it's important to rotate the stock and not keep glue beyond its 24-month shelf life.

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Conclusion:

Above all, hot melt glue has proved to be versatile and practical. Set up for success with the best practices to get the most out of your hot melt adhesive. It is while maintaining operations efficient, clean, and safe. Follow closely to the manufacturer's guidelines for hot melt adhesive troubleshooting. Always perform individual adhesive testing for your specific application and production process before mass production.

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Hot melt adhesive is the most popular option for sealing consumer goods.  A versatile bonding solution for various applications – cartons, cases and trays – hot melt packaging adhesives are used every single day. To maintain a safe work environment while using these adhesives, it is important to maintain hot melt adhesive equipment and provide protection for operators to avoid workplace injuries.

According to the National Safety Council, there are an average of 23,000 on-the-job injuries every day – resulting in 8.5 million injuries annually. Hot melt packaging adhesives are virtually harmless to people until they are heated and melted down to molten form. Contact with the hot melt liquid can result in serious burns. To keep operators safe, it is important to know the basic safety precautions when working with hot melt adhesives.

Application temperatures for hot melt adhesives typically range between 121oC – 204oC (250oF – 400oF). Keeping employees safe from this high heat requires a combination of wearing the appropriate personal protective equipment (PPE) and training. All hot melt adhesives have comprehensive Safety Data Sheets (SDS) available.  These should be the main point of reference for all hot melt packaging adhesive line operators and maintenance personnel.  The SDS documents also recommend PPE for each product, including heat resistant gloves, face shields, safety glasses, as well as heat resistant sleeves.  These will protect employees from contact with molten adhesive or hot equipment while working with hot melt or around the machine.

Some of the common best practices for hot melt adhesive line operators may reinforce training by food and beverage manufacturers.  These include:

• Read and Follow Guidance Documents: Read and follow the adhesive SDS documents and equipment directions before starting application. These guidance documents will outline operating conditions for the adhesive and setup/maintenance of equipment. The documents also contain helpful tips on safety precautions.
• Stay Focused: Accidents can occur when hot melt packaging adhesive operators lose focus. Stay alert and focused when filling the hot melt tanks or checking nozzles on the production line. This will reduce the likelihood of getting burned.
• Wear the Proper Equipment: The appropriate protective gear is advised when working with molten hot melt adhesive. All operators should wear safety glasses or goggles. Leather or other heat-resistant gloves prevent burns.

Low temperature hot melt adhesives are another option to help protect line operators. TECHNOMELT® COOL improves worker safety with reduced burn risks to line operators. The lower operating temperatures also reduce energy consumption and offer sustainability benefits at manufacturing sites. In the s, Henkel pioneered these low application temperature adhesives and continues to develop these preferred general-purpose hot melt adhesives for applications requiring standard heat resistance.

An important part of safety is keeping the equipment well maintained and the production area clear of debris and melted adhesive. Each equipment manufacturer has best practices to keep the machinery working efficiently. If the equipment is used incorrectly or not maintained, the hot melt packaging adhesive can be impacted. If preventive maintenance is not performed regularly on the hot melt equipment, the adhesive can char. This burnt adhesive that clings to the slide of the hot melt tank can impact the efficiency of the equipment causing clogged filters and nozzles.

Understanding how to work with hot melt packaging adhesive is important. Hot melt packaging adhesives, like TECHNOMELT®, have ideal operating conditions. The key to keeping operators safe is being aware and understanding how to achieve application consistency, maintain the equipment, and keep the production line running.

Food and beverage manufacturers rely on the effectiveness of hot melt packaging adhesives to assure a strong seal or bond. Brand owners need to understand the optimum adhesive performance to produce a secure bond. To gain more insights on ways to increase efficiency of hot melt adhesive, register for Henkel’s digital training platform and learn more best practices about improving the operating life of adhesive.

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