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Learn about important performance and processing requirements for packaging hard-to-hold substances, and how the right heat seal adhesive coating solution can address them.

Many fast-food restaurants and other to-go establishments are using signature sauces and condiments to differentiate their menus from competitors. Commonly packaged with heat sealable adhesives, these food products are considered “hard-to-hold substances”, because they often contain high-acidity chemicals, oils and vinegar, which can break through package structures if they do not include the necessary performance levels for a tight seal. 

However, packaging these types of popular food products while meeting performance and processing needs can be challenging. Therefore, it’s important for converters to know how the right heat seal adhesive coating solution can address them. 

#1: Combination of Strong Bonds and Excellent Chemical Resistance 

When sealing a sauce or condiment lidding tray, your packaging must offer both strong bonds and excellent chemical resistance. This is because food products that include high acidity, chemical or oil content can react with the packaging materials or produce gases. Without having both sufficient bond strength and chemical resistance levels, this reaction can lead to: 

  • Package corrosion or degradation  
  • Increased pressure inside package 
  • Compromised seal integrity and leaks 

Any of these results may deem the food product unusable or unsafe for the end user. Additionally, you need both strong bonds with excellent chemical resistance; if the chemical resistance is missing, even a strong bond can experience breakage if it is not formulated to prevent high-acidity chemicals from destroying the seal.  

How the Right Heat Seal Adhesive Coating Solution Provides Strong Bonding and Chemical Resistance Needs 

A heat seal adhesive coating designed for dual functionality allows you to combine strong bonding properties with excellent chemical resistance in one coating layer. In particular: 

  • Strong adhesion helps maintain the package integrity around everything else aside from chemical resistance. Heat seal adhesive formulations are also designed with thermal stability, allowing for a tight seal that remains intact throughout various temperatures in production, transportation and storage.  
  • Excellent chemical resistance prevents the heat seal from easily reacting or degrading with sauces or condiments, which helps preserve the quality and freshness of the food product by preventing degradation. In particular, polyester heat seal technology offers versatile resistance for chemicals, gases, moisture and odors.

#2: Easy Peelability 

While it’s necessary to use an adhesive that has strong, chemical-resistant bonding, it’s also crucial for the end user to be capable of easily opening the lidding tray. If the end user struggles to open it, they may be forced to puncture the lidding to use the sauce or condiment inside. Further, they could also risk opening the peel with extra force and getting the inside contents on themselves or their meal, causing an inconvenient mess during their dining experience.   

How the Right Heat Seal Adhesive Coating Solution Provides Easy Peelability  

Through a balance of performance properties, the right heat seal adhesive coating solution is designed to provide strong bonding for processing and storage protection, along with proper peel strength control for end user convenience. In particular, it includes peelable resins or additives that enable easy separation between the lid and tray when desired. This helps the consumer open the condiment package without the risk of inconveniently spilling out the contents. Other additives used to enhance the peelability provide: 

  • Enhanced flexibility: Additives such as plasticizers contribute to providing ease when the seal is peeled open, avoiding damage to the lidding material or tray. Further, the heat seal adhesive coating can be applied to flexible substrates such as polyester films, allowing the material to conform to different tray shapes with a tight, reliable seal.  
  • Coating thickness: If a certain peel strength is required by the brand owner, the coating can be customized to be applied at a coat weight that will achieve the desired peel strength. Furthermore, to reduce raw material inputs, a coating can be optimized to apply the thinnest layer possible while still maintaining the required end performance. 

#3: Compatibility with Common Tray Stocks 

It’s common for fast-food restaurants to require mass-production of signature sauces or condiments to meet their consumer demands. This means you as the converter must be capable of providing high volumes of lidding tray packaging materials to address brand owner needs. This is why it’s crucial to use adhesive technology that offers compatibility with common tray stocks, such as PET trays. While some adhesive technologies may be able to protect against chemicals, oils or vinegars, they may not all be compatible with your tray substrates, which could still result in the food product leaking. 

How the Right Heat Seal Coating Solution Provides Compatibility with Common Tray Stocks 

The right heat seal coating solution accounts for material composition to help ensure the performance characteristics of the adhesive also bond securely with the tray substrate. In order to achieve this, it includes polymers that are compatible with the tray’s polymer structure, allowing for strong adhesion between the seal and tray. Another factor that is taken into account to ensure tray compatibility includes: 

  • Conformability: Similar to providing flexibility features for easy peel, the heat seal adhesive coating formulation includes additives that allow it to contour around specific tray shapes, allowing strong seal protection to any irregularities.  

#4: Easy Processing  

Like any other production, it’s important for your adhesive solution to enable fast processing speeds; however, with the risk of potential setbacks in packaging hard-to-hold substances, it’s important that your adhesive can be applied cleanly on to film. This will help production move along consistently without concerns that application mistakes could create additional downtime.  

How the Right Heat Seal Adhesive Coating Solution Provides Easy Processing 

The right heat seal adhesive coating solution can be applied at low coat weights, allowing for clean application as well as easy peelability to the end user. It also enables:  

  • Improved energy efficiencies: While all can be applied at low coat weights to aid in fast drying, certain adhesive coatings enable even faster drying than others due to their formulation.

How Bostik’s Heat Seal Adhesive Coating Solutions Address Hard-to-Hold Packaging Needs  

As the adhesive solutions segment of Arkema, Bostik offers a large portfolio of flexible packaging adhesive options to meet your specific needs. With a range of both heat seal adhesive coatings and extrudable resins, we offer a heat seal adhesive coating technology specifically designed to help you address performance and processing needs for hard-to-hold substances. Our solution includes: 

  • Dual functionality to help ensure your lidding tray applications have strong bonding with excellent chemical resistance. 
  • Peelable coatings that offer convenience in opening the lid from the tray for the end user. 
  • Compatibility to common tray stocks, allowing for strong adhesion between the seal and tray. 
  • Coater-ready capabilities to help speed up processing times.  

Additionally, when you work with Bostik you’ll receive: 

  • Customized formulations: Our team of experts will test formulations to help ensure your heat seal adhesive coating provides the performance levels you desire. We’ll also help you identify what features are still needed in your solution to help ensure high performance.   
  • Technical support: Our team is here to provide expertise and help you throughout trial processes as well as troubleshooting during production. 

Are you looking for an adhesive solution that can protect against hard-to-hold food products while still enabling convenience to the end user? Contact a Bostik expert to learn how our heat seal adhesive coating solution can provide the performance processing capabilities you need for hard-to-hold substances.  

©2024 Bostik, Inc. All Rights Reserved

All information contained herein is believed to be accurate as of the date of publication, is provided “as-is” and is subject to change without notice. To review our full U.S. Legal Disclaimer, visit:

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