Keep an eye on the mixture, humidity, and temperature.
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.
Hardens too slowly or too quickly: 3 test steps
Pot life, nozzle life and strength build-up are different quantities.
1 · Mixture
Do the components, mixing ratio and mixing nozzle match the product data sheet?
Uneven application or unsuitable nozzles will leave unmixed areas. A general mixing ratio does not apply to all products.
Check the correct resin/hardener combination and prescribed ratio.
Check the cartridge piston, the discharge of both components, and the recommended mixing nozzle; pre-run the nozzle according to the manufacturer's instructions.
For dosing systems, check the actual quantities of both components. Document any streaks or unmixed areas.
2 · Temperature
Does the actual processing temperature correspond to the specifications for the product?
Cold temperatures slow down many curing reactions. A thin layer of adhesive may cure more slowly than a larger, mixed quantity.
Measure the temperature of the material, component, and workplace.
Adhere to the specified waiting and curing times. Use heat only within the product-specific curing plan.
Consider pot life and time in the mixing nozzle separately from the time until load-bearing capacity.
3 · Segregation
Are the components homogeneous before discharge?
PT products may be prone to separation.
Turn the cartridge over or homogenize it according to the product instructions.
Check streaks and discharge; in warm conditions, consider a suitable slower type.
Does it become thick or gelled? 2 test steps
Moisture can promote the premature aging of polyurethanes.
1 · Storage
Has the material been stored within its shelf life and according to the data sheet?
Aging, humidity, separation of components or unsuitable temperatures can alter processing and hardening.
Record batch number, expiry date and inventory history.
Check for segregation, thickening, and contamination. Do not correct conspicuous material with unauthorized additives.
If the material quality is unclear, check a fresh, correctly stored batch for comparison.
2 · Moisture protection
Does moisture stay away from the stored material?
Open containers and humid environments can promote gel formation.
Check closure, storage and handling.
Do not introduce air during permissible homogenization.
Lumps in the material: 2 test steps
Pay particular attention to the separation of the components at the outlet.
1. Clean outlet
Is cross-contamination avoided during nozzle changes?
Resin and hardener residues can react locally.
Keep outlets clean and separate, and change the mixing nozzle correctly.
Document any conspicuous batch and processing.
2 · Storage
Has the material been stored within its shelf life and according to the data sheet?
Aging, humidity, separation of components or unsuitable temperatures can alter processing and hardening.
Record batch number, expiry date and inventory history.
Check for segregation, thickening, and contamination. Do not correct conspicuous material with unauthorized additives.
If the material quality is unclear, check a fresh, correctly stored batch for comparison.
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-polyurethanes.md. Always compare product-specific values and procedures with the corresponding technical data sheet.
