Visible light alone does not prove sufficient UV performance.
Product and application
Select the system so that only relevant test steps appear. If no system is specified, the test will remain general.
01
What are you observing?
02
Identify the cause
03
For reference
All test steps in this guide can be used even without the guided process.
Terms briefly explained
Hand strength
The parts should be handled carefully. The connection is not yet fully load-bearing.
Complete curing
The curing conditions and times prescribed for the product were adhered to.
Adhesive gap
Distance between the two joining surfaces, not the length of the adhesive seam.
Pot life and nozzle life
Test the processability of a mixed quantity and the processability in the mixing nozzle separately.
Does not fully harden; 4 test steps
Check the light source, light transmission, and the actual joint.
1 · UV measurement protocol
Are the light source and exposure documented at the actual gluing point?
Visible light alone does not prove sufficient irradiation. The measurement must be appropriate for the light source.
Document wavelength (nm), irradiance (mW/cm²), exposure time (s), distance and, if applicable, dose (J/cm²).
Use a suitable measuring device. Compare target values with the product data sheet and the system specifications; take shadows and light transmission into account.
2 · Luminous flux
Does the light source at the component deliver the required power and wavelength?
Aging light sources may provide insufficient effective radiation despite emitting visible light.
Check output power and lifespan; replace bulbs if necessary.
Adjust the distance and exposure time according to the product specifications.
3 · Light path
Does the appropriate radiation reach the adhesive through the component?
UV-stabilized plastics, coatings, and shaded areas can block the radiation.
Test a comparative sample between suitable glass panes. If it hardens there, examine the light transmission of the actual component.
Check for a suitable wavelength or a suitable dual-cure system. The source cites UV630/UV640 as examples for certain plastics.
4 · Layer & Movement
Is the layer thickness within the permissible range and does the joint remain closed?
UV curing has a limited depth. Movement can create air pockets and crack-like structures.
Check layer thickness, shadows, and fixation. Layer-by-layer application is only permitted according to product instructions.
Assess sticky excess separately from the joint: oxygen can inhibit surface hardening.
Air bubbles 2 test steps
Transport, shaking, and unfavorable application can trap air.
1 · Handling
Is the container processed without unnecessary shaking?
Air bubbles rise only slowly in viscous products.
Allow the material to rest; check suitable vibration or vacuum degassing.
2 · Order
Can air escape to the outside when the parts are assembled?
A closed ring of adhesive at the edge can trap air in the middle.
With suitable geometry, dispense centrally and slowly place the second part on top.
Clean the wet surfaces that have been pulled apart again and reapply. Check for a suitable lower viscosity.
Whitening under stress: 2 test steps
Highly stressed UV compounds can turn visibly white.
1 · Load
Is the bond only subjected to stress within its operating conditions after sufficient curing?
Premature stress, peeling forces, media, or differing thermal expansion can weaken a connection that initially appears to be good.
Compare the waiting time before loading with the product data sheet.
Capture joint geometry, temperature, chemicals and humidity in real-world use.
For peeling loads or different materials, test tougher or more flexible systems with the application engineer.
2 · Optical requirement
Was the optical stability tested under real-world stress?
The source mentions UV6160 as a possible alternative for optical clarity.
Document the stress and fracture pattern.
Test suitable type with application engineering; test transparency in the actual setup.
Adhesive is leaking from the joint. 3 test steps.
Viscosity and reaction rate must match the geometry.
1 · Order & Fixing
Is sufficient adhesive applied to the correct area and is the joint held still during the curing process?
Gaps in the order, incorrect contact points, and movements during curing can explain local failures.
Check the dosage and actual wetting of the contact surface.
Maintain fixation until the required strength is achieved; pay attention to air gaps and torn structures.
Document the error rate and distribution. Individual failures may indicate fluctuating process conditions.
2 · Remaining in the joint
Will enough material remain in the contact zone until it hardens?
Leaking material can leave insufficient wetting.
Check for a higher viscosity or faster hardening rate.
Check dosage and installation position.
3 · Load
Is the bond only subjected to stress within its operating conditions after sufficient curing?
Premature stress, peeling forces, media, or differing thermal expansion can weaken a connection that initially appears to be good.
Compare the waiting time before loading with the product data sheet.
Capture joint geometry, temperature, chemicals and humidity in real-world use.
For peeling loads or different materials, test tougher or more flexible systems with the application engineer.
Insufficient strength: 3 test steps
First, define the fracture pattern and then examine the surface, application, and load.
1 · Surface
Are the actual materials clean, dry, and properly prepared?
Oil, release agents, varnishes, and weak oxide layers can impair adhesion. Changing suppliers can also alter the surface.
Determine the material and alloy or plastic mixture. Ask the supplier about any changes to release agents, plasticizers, and coatings.
Adjust the cleaning process to the material and allow the cleaning agent to evaporate completely. Check the blasting media for cleanliness and condition.
Apply adhesive promptly after pretreatment and avoid further contact or oxidation. If necessary, test wettability using suitable testing methods.
2 · Order & Fixing
Is sufficient adhesive applied to the correct area and is the joint held still during the curing process?
Gaps in the order, incorrect contact points, and movements during curing can explain local failures.
Check the dosage and actual wetting of the contact surface.
Maintain fixation until the required strength is achieved; pay attention to air gaps and torn structures.
Document the error rate and distribution. Individual failures may indicate fluctuating process conditions.
3 · Load
Is the bond only subjected to stress within its operating conditions after sufficient curing?
Premature stress, peeling forces, media, or differing thermal expansion can weaken a connection that initially appears to be good.
Compare the waiting time before loading with the product data sheet.
Capture joint geometry, temperature, chemicals and humidity in real-world use.
For peeling loads or different materials, test tougher or more flexible systems with the application engineer.
German version prepared according to the archived Permabond guide troubleshooting-uv-curables.md. Always compare product-specific values and procedures with the corresponding technical data sheet.
