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Learn how phenolic resins overcome common challenges with epoxy resins and provide more enhanced solutions for filtration and composite assemblies.  

For certain air, fuel or oil filtration and industrial composite applications, it’s important for assembly manufacturers to use bonding solutions that provide high levels of durability, as the end-use applications can be placed under extreme environmental conditions. Often, manufacturers consider epoxy resins for these situations, but you may not be aware that phenolic resins can provide a better option. Learn how phenolic resins overcome common challenges with epoxy resins and provide more enhanced solutions for filtration and composite assemblies.   

Common Challenges With Epoxy Resins 

Challenge #1: Limited Temperature Range 

Epoxy resins are composed of an epoxide that reacts with a hardener at low temperatures ranging from room temperature to 302°F (150°C) to form a crosslinked solution. This chemical structure provides thermal stability; however, it may not always be high enough for applications that endure extreme temperatures.  

Epoxies also typically have a low maximum service temperature between 248°F to 392°F (120°C to 200°C). They degrade by breaking down or softening if they perform beyond this temperature range, especially if exposed to extensive heat exposure. For filter and composite assemblies, a loss of mechanical strength could lead to decreased load-bearing capacity, increasing the risk of cracking or failure under stress. 

How Phenolic Resins Overcome This Challenge 

Phenolic resins are formulated by reacting phenol with formaldehyde. This creates a highly cross-linked polymer through a condensation reaction and enables phenolic resins to provide high temperature stability. In particular, they cure above 302°F (150°C) and result in the release of water or other by-products to provide rigid, thermal stability. Phenolic resins also offer excellent service temperature stability compared to epoxy resins, withstanding temperatures up to 482°F (250°C) or even higher in some cases. This high thermal stability stems from strong bonds and chemical linking within phenol rings, which help the material resist heat and maintain strength at high temperatures. 

How this benefits filtration and composite assembly applications: 

In filtration applications where high temperature resistance is needed, such as sterilization, phenolic resins can maintain structural integrity due to their high thermal stability. The thermosetting properties in phenolic resins also make them less likely to expand or contract due to temperature when it’s not desired, helping to ensure the filtration system will function properly throughout a range of operating conditions.  

Composites with phenolic resins provide excellent heat resistance and maintain internal strength at high temperatures. This makes phenolic resins more suitable than epoxy for applications where exposure to elevated temperatures is anticipated, especially in large scale electronic or automotive applications. Epoxy resins may degrade or soften at high temperatures, limiting application usage. 

Challenge #2: Limited Flexibility 

While epoxy resins offer rigidity and high strength, they may not provide sufficient flexibility for certain application needs. The crosslinking in epoxy resins as mentioned above tends to create a rigid, inflexible chemical structure during the curing process. Due to strong covalent bonds forming with crosslinking, epoxy resins have restricted movement of molecules, resulting in reduced flexibility within an adhesive formulation. 

In filter and composite assemblies where flexibility is critical in moving the application through different stages without cracking or damage, using epoxy resins may result in degradation or even product failure, leading to additional maintenance, downtime or material usage. This could impact the performance of filter or composite component and the entire end-use product.  

How Phenolic Resins Overcome This Challenge 

Compared to epoxy resins, phenolic resins contain chemical linking that allows them to maintain flexibility even after curing. As previously mentioned, phenolic resins undergo a condensation reaction that helps to provide less crosslinking density compared to epoxy, which contributes to making phenolic resins less rigid and allows for greater flexibility. Phenolic resins also have different coefficients of thermal expansion compared to epoxy, which can help to protect and extend the overall lifespan of the end-use application. 

How this benefits filtration and composite assembly applications: 

Phenolic resins can absorb mechanical stress to maintain structural strength better than epoxy resins, which makes phenolic resins more suitable for filtration assemblies that undergo repeated pressure changes, vibrations, or movements. Flexibility allows phenolic resins to conform to uneven surfaces for better sealing in filtration systems compared to epoxy resins. This helps ensure contaminants do not pass through the filter media. 

This flexibility and ability to absorb stress or vibration without cracking is also crucial for maintaining protection of electronic components inside industrial composites when the application endures mechanical stresses, shocks and vibration during manufacturing and operation. Further, their flexibility enables compatibility with a wide range of materials that may be used with composites such as glass or carbon fibers, allowing for versatility to address specific end-use application requirements. 

Challenge #3: High Costs 

Epoxy resins involve complex chemical processing, as it takes multiple steps to achieve the desired molecular structure. These complexities can lead to increased costs; further, requests for customization may add to the expenses. If stored properly, epoxy resins can offer a shelf life of one to two years, but specific conditions such as controlled temperature and humidity can add to the costs as well.  

These manufacturing complexities can result in increased production costs for filter and composite assemblies. If large quantities need to be produced, epoxy resin expenses can make it difficult to yield affordable products, putting companies at a disadvantage when trying to make a profit.  

How Phenolic Resins Overcome This Challenge 

Phenolic resins can offer a more cost-effective solution over epoxy resins. The components used to make phenolic resins, phenol and formaldehyde, are relatively cheaper and more readily available than the raw materials used in epoxy resins; phenolic resins also have a more straightforward production process involving condensation reactions that are typically less costly to carry out. With less complexities for raw materials and processing, it’s easier to keep costs down with phenolic resins compared to epoxy resins, which also makes it more cost-effective if customization is required. Phenolic resins do have a shorter shelf life than epoxy resins; however, working with the right supplier can help you find ways to either extend the usage with proper storage procedures or receive the right quantity of supply needed for your assembly to aid in keeping ordering and storage costs down.  

How this benefits filtration and composite assembly applications: 

In filtration applications, phenolic resins provide excellent performance at a lower cost, as their chemical resistance makes them suitable for harsh environments without the need for extensive modifications or protective coatings. Unlike epoxy resins that can entail added costs for these specifications, phenolic resins help reduce material and maintenance costs while still meeting demanding performance requirements in filtration. 

Phenolic resins also help lower costs for composite assemblies. In particular, they are more cost-effective for producing large volumes of composite materials for applications including industrial components, automotive parts or construction panels.

Other Phenolic Resin Advantages Over Epoxy Resins  

Chemical Resistance 

For air, fuel and oil filtration assembly needs, it’s necessary to have a combination of chemical  resistance with flexibility to yield high durability for increased paper penetration. Compared to epoxy resins, phenolic resins provide better chemical resistance. Phenolic resins are highly resistant to a wide range of chemicals including acids, bases and solvents. This makes them especially useful when filtration media may encounter chemical substances. While epoxy resins do offer chemical resistance, they may not offer as sufficient of a resistance level compared to phenolic resins, which could result in degradation. 

Fire Resistance 

Unlike epoxy resins, phenolic resins are inherently fire resistant due to their chemical structure and ability to form a char layer when exposed to flames. This makes them suitable for applications with fire safety concerns such as aerospace, construction and transportation, allowing you to rely on one solution for numerous market assembly needs. 

Additionally, by offering inherent fire resistance, phenolic resins can eliminate the need for additional fire retardant additives in composite assembly, which are often necessary with epoxy resins to achieve similar levels of performance. This can further help reduce material costs. 


Why Bostik’s Arofene™ is the Right Choice for Phenolic Resins 

As the adhesive solutions segment of Arkema, Bostik is dedicated to helping you address niche markets that require higher levels of durability, including filtration and composite assembly.  

Our Arofene™ product line is comprised of both phenolic resins and phenolic adhesives and can be used to: 

  • Provide heat, chemical and water resistance, alongside other specialized properties such as frictional coefficients 
  • Improve strength and heat resistance in adhesives formulations 
  • Protect steel from corrosion and provide an effective bonding surface for metal 

For air, fuel and oil filter assembly, Arofene™ phenolic resins are water-based systems formulated with low phenol and formaldehyde. They offer excellent chemical, heat and water resistance with good paper penetration for increased durability and filtration effectiveness.  

When manufacturing composites, Arofene™ phenolic resins provide one reliable solution to bond layers efficiently through stagable curing processes, helping to ensure you’ll receive the desired performance results even if you’re trying to meet certain specifications. Arofene™ also provides necessary chemical, heat and water resistance to help meet low flame and smoke toxicity standards for applications related to aerospace or industrial electronic engineering.  

Along with high durability, Bostik helps you achieve a cost-effective assembly by offering: 

  • Technical support: We help you customize formulations with our team of experts, testing your desired materials with our solutions. This allows you to save valuable time and resources during trial testing so you can continue regular day-to-day operations.  
  • Troubleshooting: We ensure our solutions run effectively in your assembly to help you reduce overall downtime. If issues arise, our team will visit your facility and recommend solutions to improve operations and help reduce energy usage when possible. 

Are you interested in learning how phenolic resins can help you overcome challenges with epoxy resins? Contact a Bostik expert to learn how Arofene™ solutions can help you achieve cost-effective, high durability levels with your filtration and composite assembly. 

Other Relevant Content: 

Arofene™ Phenolic Resins and Phenolic Adhesives Improving Specialty Applications 

How Can Arofene™ Solutions Benefit Your Application Needs? 

Arofene™ Phenolic Resins and Adhesives 

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