B-Tough epoxy functional toughening agents increase impact resistance in adhesives, coatings and composite applications, allowing for the formulation of epoxy systems with enhanced flexibility whilst maintaining hardness.
Overcome epoxy resin limitations!
Epoxy resins are used because of their beneficial properties that include:
- Easy to use
- Strong adhesion
- Chemical resistance
- Heat resistance
- Electrical insulating
These specialised properties make epoxy resins ideal for use in applications such as high-performance structural adhesives, potting of electronics, durable outdoor coatings, heavy-duty protective coatings and strong floor coatings.
However, due to their rigid structure, epoxies can also be prone to cracking under high impact or stress. This makes them less durable in the applications and conditions that they are used in and they have to be reapplied more often.
To meet this need of enhancing the impact resistance and fracture toughness of epoxies, and therefore the durability of the systems, Croda has developed a range of B-Tough toughening agents that can help to extend the lifetime of epoxy formulations in your application. There are two families of B-Tough: the B-Tough A range dedicated to adhesives, and the B-Tough C range for coatings.
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How does B-Tough work?
B-Tough works by reacting with the hardener to form soft rubbery particles in the hard epoxy matrix. These rubbery particles are homogenously spread throughout the system via controlled phase incompatibility and will, as a result, restrict crack growth by absorbing impact and thermal stress.
By increasing the impact strength in this way and maintaining the hardness, toughening is therefore achieved. Furthermore, as B-Tough is chemically reacted into the epoxy, there are no issues with migration or stability.
B-Tough A in adhesive applications
Besides excellent toughening performance, B-Tough A also offers the following benefits to structural adhesives:
- Improved adhesion after humid ageing
- Reduced moisture diffusivity to protect substrates from moisture
- Good thermo-oxidative stability for enhance durability
- Even distribution throughout the adhesive, ensuring a long-term effect
B-Tough A is available in three different polarities to allow it to be matched to the polarity of the epoxy system. This ensures compatibility of the B-Tough with the epoxy so that the reaction can occur, whilst also providing the incompatibility during curing that results in the phase separation needed to provide impact resistance. The three grades to choose from are:
- B-Tough A1 - lowest polarity grade, most suitable for liquid 828 type epoxy resins
- B-Tough A2 - intermediate polarity grade, can be used for both liquid or solid epoxy resins
- B-Tough A3 - highest polarity grade, most suitable for solid 1001 type epoxy resins
You can test multiple grades to find the right one for your epoxy system.
B-Tough C in coatings applications
B-Tough C epoxy functional toughening ingredients allow for the formulation of epoxy systems with enhanced flexibility whilst maintaining hardness. Acting in a similar way as B-Tough A products, these grades are developed to have lower viscosity. They also offer benefits including:
- Excellent impact strength, also at low temperatures
- Excellent impact and crack resistance preventing surface marring for optimal protection
- Liquid product, making it easier to formulate with
B-Tough C is available in two different grades: B-Tough C2r and B-Tough C2x.
B-Tough C2r is a VOC-free grade that allows for the formulation of low to zero VOC coatings based on solid and liquid epoxy resins suitable for indoor and outdoor use. The reactive diluent makes this a 100% active system. B-Tough C2x is more suitable for outdoor applications as the diluent is xylene.
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