Outdoor Clear Polyurethane Doming Resin for Stickers and Panels｜EU-118S-5S / HU-118S-5S

Fong Yong Chemical Co., Ltd. is one of the leading manufacturers and suppliers of outdoor clear polyurethane doming resin for stickers and panels｜eu-118s-5s / hu-118s-5s in Taiwan. With abundant experience, we warmly welcome you to buy high quality customized products at competitive price from our factory. If you have any enquiry about quotation, please feel free to email us.

 

EU-118S-5S/HU-118S-5S is a two-component, flexible clear polyurethane resin developed for doming and protective coating on stickers, labels, and outdoor panels where UV resistance and long-term outdoor durability are the primary selection criteria - including automobile panels, outdoor decorative stickers, and curved exterior surfaces. Designed for outdoor service applications where polyurethane chemistry is the material selection basis, the system delivers Shore A 75–85 hardness, a crystal-clear high-gloss surface, good waterproof and oil resistance, weather and impact resistance, and good adhesion to many metals, coated surfaces, and engineering plastics - with controlled heat cure.

 

Key Takeaways

• UV and weathering resistance are key design targets of this formulation, developed for outdoor service - formulated for the UV and weathering service conditions of automobile and outdoor panel applications, where outdoor durability is a baseline requirement, not an optional specification.
• Shore A 75–85 - firm, glossy dome profile suitable for flat and curved outdoor surfaces, with good impact resistance and weather resistance for automotive and exterior panel applications.
• Moisture sensitive: application environment must be below 50% relative humidity - heat cure should begin promptly after dispensing. Allowing the material to gel at room temperature before oven cure increases bubble risk and is not recommended.
• Mix ratio 1:1 by weight; pot life 60 minutes (60g, 25°C) - cure is normally performed under controlled heat to support process consistency and optical quality. Lower-temperature cure conditions may be feasible with extended cure time and should be verified under actual production conditions. Vacuum degassing is recommended to eliminate surface bubbles; suggested duration 3–5 minutes depending on vacuum pump specification.

 

Why Outdoor Doming and Panel Coating Requires PU Chemistry, Not Modified Epoxy

The material selection for outdoor doming begins with the base polymer, not with UV additives. Many clear epoxy systems experience progressive yellowing, surface gloss loss, and adhesion reduction under long-term UV and outdoor weathering exposure. UV stabilizers in an epoxy system can delay this degradation, but the degradation pathway remains. Polyurethane resins are a distinct polymer class developed for protective coatings where outdoor weathering resistance is the primary design requirement - which is why the TDS identifies automobile panels and outdoor panels as the primary application context for EU-118S-5S/HU-118S-5S. Selecting EU-118S-5S/HU-118S-5S is a chemistry-level selection decision: polyurethane for outdoor service, not epoxy modified for outdoor tolerance. The formulation is developed for the UV and weathering service conditions of application categories where outdoor durability is a baseline requirement - not an added feature.

 

Outdoor-rated PU chemistry also carries process requirements that are inseparable from its performance. EU-118S-5S/HU-118S-5S is moisture-sensitive: polyurethane chemistry reacts with ambient moisture during cure, and water vapor in the application environment will affect dome formation. The  application must be performed in a dehumidified environment below 50% relative humidity. Heat cure should begin promptly after dispensing to reduce variability associated with ambient exposure during early cure stages. These process requirements are introduced to maintain transparent clarity and reduce variability during outdoor service - they are the operational tradeoff for outdoor-rated PU chemistry, not arbitrary constraints.

Figure 1. Required cure sequence for EU-118S-5S/HU-118S-5S: mix → vacuum degas → dispense → oven immediately. Allowing room-temperature gelation before heat cure causes bubbles in the cured dome.

 

Outdoor dome failure does not typically present as sudden delamination. The more common pattern is progressive surface degradation - initial loss of gloss uniformity, followed by micro-cracking or edge instability under cumulative UV and thermal cycling - which often appears after the product has already reached the end user. Material selection based on initial dome clarity alone, without accounting for the service environment over the product's service life, is where outdoor dome failures originate.

 

For applications with defined UV aging specifications - such as ASTM G154 or ISO 4892 - performance validation under the actual exposure profile and substrate conditions is recommended as part of the qualification process. Share your test protocol requirements at the inquiry stage.

 

Applications

Doming on Outdoor and Vehicle-Applied Stickers

EU-118S-5S/HU-118S-5S is developed for doming on stickers and labels intended for outdoor service - including product identification labels, promotional stickers, and branded applications on vehicles, outdoor equipment, and exterior surfaces. UV resistance and weather resistance maintain dome clarity and adhesion under UV exposure, temperature cycling, and moisture exposure in outdoor service. Substrate surfaces must be dry and free of moisture, dust, and non-porous materials before application; hygroscopic inks and inks containing glycerin are not compatible with this system. For vehicle-applied stickers, pre-baking the substrate before application is specified in the TDS to remove surface moisture. Specific substrate adhesion and service condition compatibility should be confirmed before production use.

Figure 2. Process boundary for EU-118S-5S/HU-118S-5S application: relative humidity must be below 50% RH. PU chemistry is moisture-reactive - humidity above this threshold increases risk of CO2-generated bubbles in the cured dome.

 

Protective Clear Coating on Automotive and Outdoor Panels

The TDS identifies automobile panels and outdoor panels as the primary application context for EU-118S-5S/HU-118S-5S. The system forms a crystal-clear, high-gloss protective layer with good adhesion to many metals, coated surfaces, and engineering plastics under validated application conditions - suitable for flat and curved panel surfaces. Its impact resistance and weather resistance support performance in automotive and exterior panel service environments. Application requires a dehumidified environment with relative humidity below 50%, and heat cure should begin promptly after the dispensing process is finished.

 

Curved Surface Doming for Exterior Decorative Applications

For domed overlays on curved exterior surfaces - including outdoor signage, equipment badges, and curved decorative panels - EU-118S-5S/HU-118S-5S accommodates minor surface curvature while maintaining dome continuity in outdoor service conditions. Its flexibility supports adhesion to curved substrates without dome delamination under thermal cycling. Specific substrate adhesion and service condition compatibility should be confirmed before production use.

 

Selection Notes

Use these notes to determine whether EU-118S-5S/HU-118S-5S is appropriate for evaluation for your application.

• Outdoor sticker doming or panel coating with UV exposure - EU-118S-5S/HU-118S-5S may be evaluated. PU chemistry is selected for outdoor service conditions.
• Indoor soft flexible dome on stickers or labels - E-1155/H-1155 is developed for soft flexible indoor doming (Shore A 45–55) and should be evaluated separately. EU-118S-5S/HU-118S-5S is developed for outdoor service.
• UV-resistant dome that must remain soft (Shore A 45–55) - a UV-resistant soft clear doming system should be evaluated separately. EU-118S-5S/HU-118S-5S cures to Shore A 75–85.
• Anti-yellowing indoor clear coating on leather, wood, bamboo, or mixed-material decorative objects - E-1188TT/H-1188TT is developed for natural material coating with Shore A 75 flexibility and indoor anti-yellowing performance and should be evaluated for these applications. EU-118S-5S/HU-118S-5S is positioned for outdoor service.
• Processes that cannot support controlled heat cure - EU-118S-5S/HU-118S-5S requires heat cure for stable dome formation. Production environments with oven capability at any controlled temperature may discuss adjusted cure schedules at the inquiry stage.
• High-humidity production environment (above 50% RH) - EU-118S-5S/HU-118S-5S is moisture sensitive; a dehumidified application environment is required.

Figure 3. Application boundary guide for EU-118S-5S/HU-118S-5S: primary use (outdoor doming and panel coating with UV exposure) and situations requiring evaluation of a different system (indoor soft dome, RT cure, high humidity environment, anti-yellowing indoor coating).

 

Frequently Asked Questions

Q: Why should EU-118S-5S/HU-118S-5S be heat-cured promptly after dispensing?

A: The TDS specifies that allowing the applied object to gel at room temperature and then post-curing at high temperature causes bubbles. Polyurethane chemistry is moisture-reactive during cure: if gelation begins under ambient conditions before heat cure, uneven cure progression and moisture-related CO2 generation result in bubble formation within the dome. Heat cure should begin promptly after dispensing - before meaningful gelation occurs under ambient conditions - to eliminate this mechanism. Controlled heat cure also supports optical consistency across production batches.

 

Q: What is the humidity limit for applying EU-118S-5S/HU-118S-5S, and why does it matter?

A: Application must be performed in an environment with relative humidity below 50%. EU-118S-5S/HU-118S-5S is a polyurethane system, and PU chemistry is moisture-reactive during cure. Moisture in the application environment reacts with the uncured material, generating CO2 which forms bubbles in the cured dome. The 50% RH limit is the process boundary for bubble-free dome formation. In practice, this means doming operations should be conducted in a climate-controlled or dehumidified room, not in an open production area where ambient humidity is uncontrolled.

 

Q: What substrates is EU-118S-5S/HU-118S-5S compatible with?

A: TDS indicates good adhesion to many metals, coated surfaces, and engineering plastics - reflecting the automobile and outdoor panel substrate categories for which the product was developed. Substrate surfaces must be dry, clean, and non-porous before application. Hygroscopic inks and inks containing glycerin are not compatible. Specific substrate adhesion under production conditions, including any surface coatings or treatments on the substrate, should be confirmed by application testing before production use.

 

Q: Can EU-118S-5S/HU-118S-5S be used for indoor doming applications?

A: EU-118S-5S/HU-118S-5S is developed and positioned for outdoor service. Its process requirements - dehumidified environment, prompt heat cure, vacuum degassing - reflect the demands of outdoor-rated PU chemistry. For indoor doming on stickers and labels where UV resistance and outdoor weathering are not required, a soft clear doming epoxy resin is the appropriate starting point and does not carry the same process constraints.

 

Q: Before Requesting a Sample

A: To reduce unnecessary qualification cycles, prepare three items before inquiry: (1) intended service environment - indoor or outdoor; (2) current cure process capability - oven temperature range available; (3) substrate category - label, metal panel, or plastic. This allows us to determine whether EU-118S-5S/HU-118S-5S enters sample evaluation directly or whether an adjusted cure schedule should be discussed first.

Existing production lines do not need to match the reference cure profile exactly before evaluation. Initial discussion is intended to determine whether process adjustment is feasible within the current manufacturing environment.

 

If you are evaluating outdoor doming materials, 🔗share your substrate type, current cure process, and outdoor exposure condition. This helps determine whether EU-118S-5S/HU-118S-5S should enter sample evaluation directly or whether another system may reduce qualification time.

Sample evaluation is recommended before production release.

 

Evaluation discussions may include cure schedule adjustment, substrate compatibility review, and preliminary process recommendations based on the provided application conditions.

 

Technical Documentation

🔗 TDS Download - EU-118S-5S / HU-118S-5S Technical Data Sheet

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Property	EU-118S-5S (Part A)	HU-118S-5S (Part B)
Appearance	Clear Liquid	Clear Liquid
Viscosity (cps, 25°C)	300–500	900–1,500
Specific Density (25°C)	1.04	1.07
Mix Ratio (wt/wt)	1 : 1
Pot Life (60g, 25°C)	60 minutes
Curing Condition	80°C × 120 minutes (ˊ60°C~70°C are available for extened curing time)
Hardness (Shore A, 25°C)	75–85

All values from TDS (Rev. 2018/06/28). Curing conditions will depend on temperature, size, and thickness of material. EU-118S-5S/HU-118S-5S is moisture-sensitive: application must be performed in a dehumidified environment below 50% relative humidity. Heat cure should begin promptly after dispensing - room-temperature gelation followed by elevated-temperature post-cure will cause bubbles. Lower-temperature cure conditions may be feasible with extended cure time and should be verified under actual production conditions. Verify performance under your specific application conditions before production use.