Advantages of Adhesive Bonding over Alternative Assembly Techniques

Master Bond offers unique polymer adhesives to meet specific performance and processing requirements. These versatile compounds can be cured at ambient temperatures, elevated temperatures and upon exposure to UV light. Our line of products consists of epoxies, silicones, polyurethanes, polysulfides and cyanoacrylates.

Specific grades offer:

• Improved Durability
• Abrasion Resistance
• High Physical Strength Properties
• Gap-Filling
• Fast Cures
• Low Stress
• Easy Application
• NASA Low Outgassing Approval
• Superior Electrical Insulation Properties
• Thermal and Electrical Conductivity
• Withstands Exposure to a Wide Range of Chemicals and Water
• High Bond Strength to Similar and Dissimilar Substrates
• Resistance to Vibration, Impact, Shock and Thermal Cycling
• Comply with UL94V-0 Flame Retardant Specification

Master Bond polymer adhesives are successfully employed in industries ranging from aerospace, optical and electronics to oil/chemical processing, medical and automotive. Our products are designed to speed productivity, reduce waste, save energy and enhance performance. We can recommend a formulation tailor-made to meet your needs.

Some of Our Most Popular Polymer Adhesive Systems

Master Bond's popular polymer adhesive systems are given below.

Advantages of Adhesive Bonding Over Alternative Assembly Techniques

The advantages of adhesive bonding over alternative assembly techniques are outlined in the following list:

• Improved stress distribution; stresses are evenly distributed over the entire bonding area thereby minimizing high localized stress concentrations.
• Outstanding fatigue resistance of adhesively bonded joints especially to cyclic loading.
• Superior resistance to mechanical shock and vibration even upon prolonged exposure to hostile environmental conditions.
• Ability to bond dissimilar as well as similar materials including metals, plastics, elastomers, glass, ceramics and wood.
• Outstanding humidity and corrosion resistance at both ambient and elevated temperature conditions.
• Superior thermal resistance.
• Availability of adhesive formulations for a wide range of service conditions from as high as 600°F to cryogenic environments.
• Adhesively bonded surfaces feature smooth contours free from gaps and external projections unlike rivets and other mechanical fasteners.
• Less critical tolerances acceptable for high-performance bonding compared to mechanical fastening methods.
• Substantial weight and significant cost savings without decrease of pertinent bonding strength parameters.
• Unexcelled dimensional stability and long-term durability.
• Techniques are available for disassembly of adhesively bonded assemblies without deleteriously affecting the individual components.

Joint Design Considerations

With structural adhesives, joint design is as important as adhesive selection. Joint design requires selection of the correct style, proper surface preparation, and use of careful applications and assembly procedures. Joint design should minimize stress concentrations by ensuring that the load is distributed over the entire bonded area. Some stresses, such as peel, cleavage, and shear stresses, should be minimized. Most structural adhesives withstand tensile stress well, so joints should maximize this type of stress and minimize others.

Adhesive Joint Types

Joint style should serve to improve bond strength. Some joints used in structural applications include butt, scarf, lap, and offset lap. Butt joints are used when stress forces are concentrated along the bond line and when forces perpendicular to the bond are minimal. Scarf joints allow a large adhesive contact area, but parts joined in this way must maintain a close fit.

Adhesive Joints for Bonding Thin Cross-Sections

Lap and offset lap joints are recommended for bonding thin cross-sectional, rigid parts. In lap joints, the bonded parts are slightly offset; thus, peel and cleavage forces develop when the joints are under load. These forces can be minimized by using the offset lap joint.

Surface Preparation to Ensure Adhesive Joint Integrity

Surface preparation is critical. Surfaces are often contaminated with oil, grease, dirt, moisture, or other contaminants, so they must be cleaned before adhesive is applied. Certain forms of oxidation, such as the loose rust formed on iron, can contaminate adhesive. However, some metals, such as aluminum and copper, form oxide layers that cling tenaciously to the substrate and form a satisfactory surface for adhesives. Glass and some other substrates require special surface treatments to maintain good bonds.

Failure to follow recommendations for adhesive application and processing is a major cause of bond failure. Often, cure temperatures are raised and cure times shortened to get a faster cure. Yet, adjusting cure rates and temperatures may result in weak bonds.

Epoxy Adhesives – Leading The Way

Much progress has been made in the last few years in improving performance characteristics of epoxy adhesives. These advances relate to improving toughness and peel strength, increasing their high-temperature service capabilities and upgrading their resistance to water and other chemicals, including fuels and lubricants, at elevated temperatures. Also, for one-component pastes and films, shelf life without the need for low-temperature (40°F) storage has been substantially extended and cure schedules shortened while bonding properties are retained and sometimes advanced. Much of this development work was stimulated by the needs of aerospace industries for lighter weight, more fuel-efficient aerospace components.

Improved Peel Strength and Heat Resistance

The gains achieved in upgrading peel strength and heat resistant characteristics of epoxy adhesives are particularly impressive. Epoxy adhesives have traditionally exhibited high-tensile shear strengths but have shown low peel strength, a marked disadvantage for many bonding operations. This deficiency is being overcome by more sophisticated chemistry and formulation technology including modification with liquid elastomers. Furthermore, epoxy-based adhesives with greatly improved peel strength retain the desirably high tensile shear strengths typical of these materials.

Improved Thermal Stability

Equally significant are the improvements in thermal stability for one and two component epoxy-based adhesives. Today's advanced epoxy adhesive systems perform quite satisfactorily at temperatures at and above 500°F. The key to this remarkable development has been the production of new heat-resistant epoxy resins based on novel chemical structures. These advanced epoxy resins can be cured over a wide temperature range with specially designed curing agents and give impressive bond strengths.

Customized Packaging to Customer Specifications

Master Bond offers a wide array of packaging options to speed productivity, minimize waste and save energy including:

• Quantities from grams to gallons
• Cans, bottles and jars
• Cartridges for manual and pneumatic guns
• Premixed and frozen syringes for two part systems
• Bipaks for field service kit

This information has been sourced, reviewed and adapted from materials provided by Master Bond Inc.

For more information on this source, please visit Master Bond Inc.