Adhesives Using Nanofillers Excel in High Performance Applications

In this interview AZoM talks to Rohit Ramnath, Senior Product Engineer from Master Bond, about the high performance applications that require adhesives using nanofillers excel.

Adhesives systems may be formulated to include different types of fillers. What types of nanofillers may be used?

There are several different nanofillers that are used for formulating adhesives. At Master Bond, we have formulations that include graphene and nanosilica particles. Graphene is an allotrope of carbon (a single atomic plane of graphite by itself) whereas nanosilica consists of silicone dioxide nanoparticles.

Why include nanofillers and how do they change an adhesive’s properties?

Nanofillers are added to augment specific performance and processing properties. For example, the addition of graphene may result in improved bulk thermal and electrical conductivity. Certain nanosilica filled epoxy adhesives bring about enhanced dimensional stability and lower shrinkage. It is important to note that not all nano-filled adhesives can be applied in very thin bond lines and factors such as agglomeration and viscosities must be evaluated when selecting an adhesive system.

What are the typical curing profiles for nano-filled adhesives?

Similar to typical polymer systems, nano-filled adhesives come in one and two part systems. Some may cure at room temperature, while others might need the addition of heat for curing. Certain systems require a UV light source with a wavelength range between 320-365 nm, or with UV plus heat (a dual cure) while others require exposure to an LED light.  It is recommended to follow the instructions on the datasheets to achieve optimal curing.

What are the benefits of using nanosilica filled adhesives over conventional epoxies?

As previously mentioned, nanosilica filled adhesive systems are designed to boost particular performance and processing properties, such as lowering coefficient of thermal expansion, and improving abrasion resistance. Since numerous considerations are necessary in selecting the proper compound for a specific use, the degree of improvement provided by nanosilica filled compositions must be carefully evaluated and compared with different conventional types of epoxy filled compositions. Additionally, the size, shape, and concentration of these filled materials will play an essential role in determining key parameters such as viscosity, flow, aging characteristics, strength, shrinkage, hardness, and exotherm of these cured polymers.

What are some of the technical advances that have been made with regard to nanosilica filled adhesives?

A major development in this area has been incorporating agglomerate-free nanosilica particles in UV/visible light curing Master Bond polymers. Utilized for structural bonding, sealing, coating and encapsulation, these unique products require no mixing and cure in thin layers with a UV light source at the right intensity in as little as 10-15 seconds. Two examples are Master Bond UV22 and UV22DC80-1. Both possess superb optical clarity, minimum shrinkage upon cure, contain no solvents or diluents and exhibit high dimensional stability. They also offer good physical strength properties, superior electrical insulation and are capable of withstanding rigorous thermal cycling. These cationic type UV curing systems are serviceable from -80 °F to +350 °F.

What products does Master Bond offer which can cure with not a UV but only an LED ~405 nanometer light source?

Master Bond LED405Med cures tack free without any oxygen inhibition upon exposure to a 405 nm wavelength light source. This lower viscosity, free flowing system is intrinsically safer than UV light polymerization. Among its many benefits is that it meets ISO 10993-5 for cytotoxicity and resists sterilization.

What other chemistries use nanosilica fillers?

Two part epoxy compositions containing nanosilica fillers have made progress in resolving specific application requirements for the assembly of critical components. Master Bond EP30NS is an epoxy which cures rigid with a moderate viscosity with good flow. It not only passes ASTM 595 for NASA low outgassing certification but also offers superb abrasion resistance. It has a high strength profile and is electrically insulative, making it well suited for smaller pottings.

How do you see the future with nanofillers and adhesives?

There are endless possibilities with nanofillers such as graphene, nanosilica, nanoalumina, carbon nanotubes etc. Custom formulations with these added materials may result in improved performance properties and processing requirements. However, choosing the right mix of materials is often a balancing act. There is ongoing research in this area and we expect there to be new developments in the future.

About Rohit Ramnath

Rohit Ramnath is a Senior Product Engineer for Master Bond Inc., a custom formulated adhesives manufacturer. He analyzes application oriented issues and provides product solutions for companies in the aerospace, electronics, medical, optical and oil/chemical industries. He graduated from Carnegie Mellon University with a Masters Degree in Chemical Engineering.