Selecting an Adhesive for Bonding Rubber Surfaces

AZoM talks to Venkat Nandivada, Manager of Technical Sales at Master Bond Inc. about rubber surfaces and the key considerations in selecting an adhesive for a specific application.

What are some key considerations in selecting an adhesive for bonding rubber surfaces?

Different types of rubbers are used in a number of diverse applications that require a wide range of physical, chemical, thermal, electrical properties to meet specific end user needs. Adhesive systems must satisfy these requirements while providing durable, high strength bonds when adhering natural or synthetic rubbers to itself or to dissimilar substrates such as metals, plastics, ceramics, and glass. Common synthetic rubber surfaces include EPDM, nitrile, neoprene, polysulfide, and SBR. Some rubbers could be silicone based as well. Each of these substrates has unique properties and they may be exposed to different environmental conditions in an application. Therefore, choosing proper surface preparation methods as well as the right adhesive for joining any combination of these materials should be thoroughly evaluated. Each type of adhesive chemistry has its benefits and limitations.

The joint design, surface finish, gap between surfaces, load on the joint, chemical resistance required, impact/vibration exposure, operating temperature/thermal cycling, and aging characteristics of the adhesive are all of prime importance. Additionally, the viscosity, application technique, speed of cure, resilience/toughness, tensile strength, elongation, abrasion resistance, conductivity, color are important in finding the right adhesive.

Why use adhesive bonding of elastomers over mechanical fastening?

Adhesives spread loads uniformly over the joint unlike mechanical fasteners. The stress on the joint is minimal, and many adhesives even offer excellent optical clarity. They are used for weight reduction, have superior resistance to bending stresses, offer excellent sealing, and have the ability to overcome issues associated with joining irregular shapes. They fill gaps, resist cyclic fatigue and are designed to lower costs.

How do you obtain consistent durable bonding solutions for rubbers?

Proper surface preparation techniques may be critical to optimize adhesion with certain types of rubber surfaces. This is contingent on the type of surfaces being used and the application service conditions. Degreasing, abrasion and chemical treatment are commonly employed. In many cases the use of a primer may enhance the performance capability of the bonding agent. The recommended cure schedule needs to be followed after applying the adhesive and positioning parts under even pressure.

What are some examples of Master Bond adhesives used for bonding rubbers?

Single component ethyl cyanoacrylate adhesive MB297 sets up in 20-50 seconds at 75°F and is extremely versatile. It possesses high shear strength properties and has proven effective in multiple rubber bonding applications.

Two component Master bond epoxy adhesive EP21TDC-4 features high peel strength, has an elongation of 100-150% and a Shore A hardness of 75-85. It adheres well to many rubber surfaces, has superior resistance to rigorous thermal cycling, mechanical shock/vibration and withstands 1,000 hours at 85°C/85% RH. Serviceability is from -100°F to +250°F. It is an excellent electrical insulator.

User friendly Master Bond EP21TDC has a convenient 1 to 1 mix ratio weight or volume. It combines dimensional stability, toughness and is ideal for bonding similar/dissimilar rubber surfaces. This compound flows easily and has minimum shrinkage upon cure. It has a Shore D hardness >60.

One part elastomer based Master Bond X5 requires no mixing and cures at room temperature. This durable adhesive formulation provides good strength properties. It has an advantageous low viscosity and has been successfully used in joining rubber substrates to each other. X5 can also be used in bonding different types of rubber surfaces.

High performance silicone elastomer adhesive MasterSil 711 bonds well to silicone rubber and a wide variety of substrates. This single component, moisture curing composition has a rapid tack free time of 2-5 minutes at 75°F, >50% humidity. It has a Shore A hardness of 25-35 and outstanding electrical insulation properties. Elongation is 300-400%. MasterSil 711 has a non-corrosive cure and a translucent color.

Addition cured Master Bond MasterSil 153 has a soft durometer and high temperature resistance up to 400°F. Its self priming feature enhances its bonding capability. Most notable is its ability to bond well to cured silicone rubber. Bonds are highly resistant to water. It has a convenient 1 to 1 mix ratio and a long working life after mixing.

Why has using adhesive for rubber bonding gained popularity?

They have provided design engineers value added solutions, improved efficiency, enhanced technical functionality and a commitment to sustainability. This has enabled manufacturing companies to reduce operating costs and increase productivity while responding to the ever-changing needs of the marketplace. Cutting edge, technologically advanced products have been assembled with the latest manufacturing techniques incorporating easy processing techniques to give companies the highest level of profitability and a competitive edge. Innovative adhesive products have been developed to offer the highest performance in bonding a full range of different elastomeric compounds tailored to meet specific property requirements. In close collaboration with our customers, Master Bond’s team of technical experts has been able to determine new opportunities for rubber compounds containing multiple combinations of various ingredients.

Where are these rubber bonding adhesives used?

The advantageous physical characteristics of different types of rubbers has made them highly desirable for use in the aerospace, electrical, automotive, agricultural, medical, defense, power, oil/gas and other specialty industries. Applications extend from valves, bushings, gears, hoses, tubing catheters, wire and cable insulation to pump linings, electrical connectors, seals, weather stripping, vehicle tires, escalator handrails. Adhesive bonding of critical rubber parts play an essential role in ensuring optimum performance under demanding service conditions.

About Venkat Nandivada

Venkat Nandivada has been the Manager of Technical Support at Master Bond Inc since 2010. He has a Masters in Chemical Engineering from Carnegie Mellon University.  He analyzes application oriented issues and provides product solutions for companies in the aerospace, electronics, medical, optical, OEM and oil/chemical industries.