Bond Composites with Flexible Epoxy

Laurie Gibbons
Bonding Composites, Material Specific Adhesives
March 3, 2016

Two-part epoxies are normally rigid materials and generally have excellent compressive, tensile, and shear strength. They have limited performance in terms of peel strength and flexibility.  Rubber toughened epoxies tend to fare a little bit better, offering the user better impact and vibration resistance, combined with the ability to absorb stress caused by differential expansion and contraction of dissimilar substrate materials.

Permabond has developed new modified epoxy technology which combines typical epoxy curing characteristics with the flexibility of an RTV-type silicone – and the strength performance is not too shabby either!

Modified Epoxies

These products bond a wide variety of plastics, metals, and in particular composite materials. Carbon fiber (or Carbon fiber depending on which side of the “pond” you’re from!) is the 21st-century whizzy substrate of choice for all things high performance e.g., sports equipment, prosthetics, race cars, performance bikes etc.Since carbon fiber absorbs impact, vibration, and all sorts of stress and strain without shattering, it is important to reflect these properties in the adhesive. These flexible products also bond GRP, FRP, laminate, and other composite materials.

Permabond’s flexible epoxies are 2-part systems that cure at room temperature when you mix the resin and hardener. They are available in convenient cartridge packaging for use with static mixer nozzles or in bulk packaging for use on automatic dispensing equipment.   Typical hardness is 55-85 on the Shore A scale (20-30 Shore D).  Shear strength on carbon fiber is 6-8 MPa (600-1200 psi), and shear strength is 140-160 N/25mm (31-36 PIW).

MT382 modified flexible epoxy is a low viscosity and self-levels. So it can be easily spread or used for potting and encapsulation. These properties make it very attractive to electronics manufacturers for potting sensitive electronics. Its flexibility helps prevent stress on sensitive electronic components as it allows expansion and contraction without cracking. Pot life is 20-50 minutes, with handling strength achieved in just under two hours.

MT3821 modified flexible epoxy is a higher viscosity version with good gap fill capability. Pot life is 10-20 minutes with handling time in 60-90 minutes.

Both are color matched to match carbon fiber for an aesthetically pleasing finished appearance. These materials offer excellent resistance to thermal shock and

For further information, please contact Permabond.

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