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Five Steps to choosing the best adhesive for your application

With the vast array of adhesives and adhesive types available, the process of elimination is the best method to quickly narrow in on the appropriate product.

Step 1--Are there any certifications or qualifications the adhesive must meet?
Step 2--Select the correct technology for the application.
Step 3--What are the application specific requirements?
Step 4--What are the process requirements?
Step 5--TEST

Step 1
Are there any certifications or qualifications the adhesive must meet?
These include MilSpecs, Commercial Aircraft Specification (Boeing, Airbus, etc), Military Specifications (Lockheed Martin, Raytheon, Honeywell etc) Commercial Standards, NSF, or many others.

Step 2
Select the correct technology for the application.
Contact AdhesiveWhen an adhesive is a contact this means it adheres to itself, taking along what ever it is attached to. To use a contact adhesive you simply apply even coats of the adhesive to each material you wish to adhere, allow it to dry, and stick them together. Contact adhesives are ideal when it is awkward to clamp, or when you have large surface area. Some Glue can be used as contact adhesives or as straight application

Water Base Adhesive is a mixture in a liquid state that adheres or bonds items together. Adhesives may come from either natural or synthetic sources. The types of materials that can be bonded are vast but they are especially useful for bonding thin materials. Adhesives cure (harden) by evaporating the water from the surfaces. Polyvinyl Acetate, PVA, Neoprene or Latex is the common adhesive bonding materials,


Hot Melts
Hot melts generally aren’t very strong but work well as an instant adhesive for fast production on components that won’t have much pressure placed on them.

Pressure Sensitive Adhesives Pressure sensitive adhesives are durable in various environments and excellent for labeling and on adhesive tapes but really aren’t much of an option for industrial adhesives purposes.



Polyurethanes--Polyurethanes are known for their high resistance to low temperatures and are excellent for bonding GRP, or glass fiber reinforced plastics. Polyurethanes are impact resistant and cure quickly with the help of special tools.

Epoxies--Available in one and two part, they offer structural strength on metals but do not excel on plastics. Single part epoxies require ovens to cure them and two part epoxy may require a good bit of time to cure.

Toughened Acrylics--Toughened acrylics come in one and two part systems and work well on a wide variety of surfaces. Toughened acrylics are quite versatile, working with minimal surface preparation.

Silicones--Silicone adhesive products aren’t incredibly strong, but are quite flexible and resistant to high temperatures. Two-part silicone products tend to work more effectively than the one part products. These are a popular choice for shower and bathtub repairs.

Anaerobics--Anaerobics are adhesives which cure when in contact with metal without contact with air. Anaerobics would include thread locker adhesives, used to lock bolts into nuts.


Cyanoacrylates--Cyanoacrylate adhesives cure through reaction with moisture. A cyanoacrylate adhesive works best with rubber or as a plastics adhesive on small components. They bond most substrates well but have poor durability on glass.

Phenolic--Phenolic require heat and pressure for the curing process but have peen proven to be excellent in bonding metals, or bonding metals to wood.

Polyimides--Polyimides are based on synthetic organic chains. These are available in liquid and film form but tend to be more expensive and tricky to handle efficiently. Polyimides are generally excellent with regards to durability under extreme temperatures.

Plastisols
Plastisols require heat in order to cure and generally produce strong, durable joints.


Step 3
what are the application specific requirements?
Surfaces & Substrate
Joint Design, Gap & Strength
Temperature & Environmental Resistance

Surfaces & Substrates

Adhesion to Substrates

 

Cyanoacrylate

2-Part

Acrylic

SurfaceActivated Acrylic

1-Part Epoxies

2-Part Epoxies

UVlight Cured

Metals

Very good

Excellent

Excellent

Excellent

Excellent

Good

Plastics

Excellent

Good

Good

N/A

Fair

Very Good

Glass

Poor

Good

Excellent

Excellent

Excellent

Excellent

Rubber

Very Good

Poor

Poor

Fair

Poor

Poor

Wood

Good

Good

Good

Very Good

Very Good

Poor

Properties

Shear Strength

High

High

High

Very high

High

High

Peel Strength

Low

Medium

Medium

Medium

Medium

Medium

Flexibility

Low

High

High

Low

Medium

Medium

Hardness

Rigid

Semi-Rigid

Semi-Rigid

Rigid

Semi-Rigid

Simi-Rigid

Tensile Strength

High

High

High

High

High

High

Some substrates may require surface treatment.

 

Temperature

Temperature Resistance

 

CA

(Cyanoacrylate)

2-Part

Acrylic

SurfaceActivated Acrylic

1-Part Epoxies

2-Part Epoxies

UVlight cured

Typical

-65°F

-65°F

-65°F

-40°F

-40°F

-65°F

 

+ 180°F

+ 250°F

+ 250°F

+ 300°F

+ 180°F

+ 250°F

 

-54°C

-54°C

-54°C

-40°C

-40°C

-54°C

 

+ 82°C

+ 120°C

+ 120°C

+ 150°C

+ 82°C

+ 120°C

Highest rated product

482 °F

250°C

250 °F

120°C

390 °F

200°C

355 °F

180°C

250 °F

120°C

300 °F

150°C

 

Environmental

Solvent Resistance

 

CA

(Cyanoacrylate)

2-Part

Acrylic

SurfaceActivated Acrylic

1-Part Epoxies

2-Part Epoxies

UVlight cured

Polar Solvents (e.g. Water, Ethylene Glycol, IPA, Acetone)

Poor 1

Good

Good

Very Good

Very Good

Good

Non-Polar Solvents

(e.g. Motor oil Toluene, Gasoline)

Good

Very Good

Very Good

Very Good

Very Good

Good

 

Step 4
what are the process requirements?
How fast does the adhesive need to be dispensed and cured? Is rapid fixturing required? Will UV light pass through one of the substrates? Are the components temperatures sensitive? What viscosity is required to fill the gap in the joint? Is that gap too large for optimum strength?

Review these requirements against adhesive selector guides or individual data sheets.

Step 5
Test! When combining the large number of variables which can affect the bond, the only sure way to know is to test the adhesives in actual conditions.