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Technical Guide · Application

5 Common Mistakes in Polyurethane
Resin Application and How to Avoid Them

Polyurethane resin systems deliver highly reliable insulation when applied correctly. However, common application mistakes can lead to incomplete cure, sticky surfaces, air voids, or premature mechanical failure — all of which compromise long-term performance.

protolin.net · Technical Guide · 3 min read

Wrong Mix Ratio

Components A and B are measured by eye or using the wrong unit — weight instead of volume, or vice versa. Volumetric and gravimetric ratios are not the same.

Result: Excess Component A → soft or sticky surface. Excess Component B → brittle structure or cure failure.

Solution: Always follow the manufacturer’s specified ratio. Use calibrated measuring equipment and verify which unit (volume or weight) applies to your system.

Incomplete or Non-Homogeneous Mixing

Components are poured before mixing is complete. Material adhering to container walls and base remains unmixed and is incorporated into the system.

Result: Sticky, soft, or mechanically weak patches in the cured system.

Solution: Mix until colour change or visual homogeneity is achieved. Scrape container walls and base regularly throughout the mixing process.

Application onto Wet or Contaminated Surfaces

Cable surface or enclosure contains moisture, grease, or dust. No surface preparation is performed before application.

Result: Component B (isocyanate) reacts with moisture → CO₂ gas → foaming, air bubbles, poor adhesion.

Solution: Clean the surface with an appropriate solvent or clean cloth before application. Avoid working in wet or high-humidity conditions.

Application at Low Ambient Temperature

Resin applied in an environment below 10°C. Cure takes much longer or does not complete properly at low temperatures.

Result: Incomplete cure, extended pot life, higher viscosity → increased air entrapment risk.

Solution: Bring the environment and both components to 15–25°C before application. Allow cold-stored materials sufficient time to reach room temperature.

Rapid Pouring and Air Entrapment

Mixed resin is poured quickly and all at once. Air becomes trapped inside the resin mass and cannot escape before the system begins to cure.

Result: Air voids in the cured system → mechanical weak points and moisture ingress pathways.

Solution: Pour slowly from one side of the enclosure. Allow the resin to flow naturally and fill voids under its own weight.

Pre-Application

Application Checklist

Is ambient temperature above 15°C?
Are components at room temperature?
Is the surface clean, dry, and free of grease?
Has the A/B ratio been verified in the correct unit?
Is mixing time consistent with manufacturer instructions?
Will application be completed before pot life expires?

NCpack Advantage

Most of These Mistakes Are Prevented by Design with NCpack

The NCpack dual-component pouch format structurally eliminates the root causes of the most common application errors. The ratio is pre-set at factory conditions; mixing occurs inside the sealed pouch — eliminating moisture contact and measurement error.

Pre-Set Ratio Components A and B are prepared at the correct ratio during production — no measurement error risk.

Sealed Mixing Mixing occurs inside the pouch — moisture contact and CO₂ risk are eliminated.

Clean Application No extra containers, scales or mixing tools required — contamination risk is reduced.

Field Ready Practical pouch format enables fast, reliable application in field conditions.

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5 Common Mistakes in PolyurethaneResin Application and How to Avoid Them