5 Steps to choosing the best adhesive for your situation

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 Standards, NSF or WRAS (for potable water contact), DVGW for water or gas, or perhaps biocompatibility for a medical device.

Step 2
Select the correct technology for the application.
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.
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.
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.
Polyurethanes
Polyurethanes are known for their high resistance to low temperatures and are excellent for bonding GRP, or glass fibre reinforced plastics. Polyurethanes are impact resistant and cure quickly with the help of special tools.
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.
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.
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.
Plastisols
Plastisols require heat in order to cure and generally produce strong, durable joints.
Polyvinyl Acetate, or PVA
PVAs are considered an excellent solution for porous materials, including wood and paper. You can find plenty of polyvinyl acetate in packing and shipping companies.
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.

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 temperature 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.

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