As new-energy vehicles expand rapidly and vehicle-interior environmental and durability requirements continue to rise, water-based polyurethane dispersions (PUDs) are replacing high-pollution solvent-borne adhesives in the wrapping and bonding of instrument panels, door panels, seats and headliners. The industry still faces prominent pain points: ordinary domestic PUDs may debond at high or low temperatures, lose adhesion after prolonged humid-heat aging, yellow behind light-colored interiors, adhere poorly to certain substrates, provide limited process tolerance or fail odor and VOC targets. Leading competing products may perform strongly in one area but retain obvious weaknesses elsewhere, making it difficult to pass all of an OEM's scenario-specific tests.
RELANET Automotive Material has worked in automotive-interior water-based polyurethane development for more than a decade. Using modified polycarbonate and aliphatic molecular-chain technology developed in its Guangzhou polymer laboratory, the team targets common weaknesses in mainstream products and has created the general-purpose R-5670 and the R-5610 PUD for transparent interior applications. This article uses six performance areas, standardized test data, multidimensional comparisons and visual charts to explain how RELANET's water-based PUD platform addresses industry constraints and provides mainstream automakers and interior suppliers with an integrated bonding route focused on long-term stability, lower cost and lower emissions.
Preface: industry test framework
The manuscript states that the data were generated using commonly applied automotive methods, including GB/T 2792-2014 peel testing, ASTM D412 tensile testing, GB/T 27630 vehicle-interior air-quality evaluation, humid-heat aging at 60°C and 95% RH, and thermal cycling from -40°C to 105°C. Three mainstream benchmark groups were selected:
Competitor A; Competitor B; a benchmark PUD; and imported Competitor C. The competitor identities are anonymized in the source manuscript.
RELANET test sample: R-5670 interior PUD, described as the principal commercial model. All samples were crosslinked for 24 hours at 23°C with the same 100:5 ratio of water-dispersible isocyanate hardener. The chart descriptions below correspond to the figures in the original manuscript.
Advantage 1: high bond strength and leading multi-substrate adhesion to reduce edge lift and debonding
Bond strength is the most fundamental requirement of an interior adhesive. Door-panel folds, instrument-panel curves and repeatedly compressed seat trim all depend on stable 180° peel strength. Conventional PUDs often struggle on PP, TPO and natural leather. After one or two years in service, corners can lift and localized debonding may occur.
Measured comparison data (N/m, 180° peel strength)
Table. Adhesion of four product groups
Figure description: a six-axis radar chart covering ABS, PP, natural leather, foam, PVC and TPO. The blue RELANET outline forms the outer profile, while Competitors A, B and C appear progressively further inward, illustrating the reported multi-substrate coverage.
Interpretation
RELANET uses a polar, polycarbonate-modified molecular structure to increase interaction between the adhesive film and non-polar substrates. The manuscript reports that PP and TPO can be bonded after basic dust removal in the tested constructions, without plasma or primer pretreatment, reducing pretreatment cost by an estimated CNY 0.6-1.2 per part. The stated comparison range on PP is 650-750 N/m for ordinary products, whereas RELANET's peel values across all tested substrates were 20%-35% higher. Production feedback from several new-energy vehicle suppliers reports no opening after 1,000 door-panel fold cycles and no adhesive-layer separation after 300,000 high-frequency seat-compression cycles. These results remain specific to the stated materials and projects.
Advantage 2: broad temperature stability from -40°C to 105°C for severe climates
Vehicle cabins experience a very wide thermal range: temperatures can fall to -30°C or -40°C in northern winters, while a closed cabin exposed to summer sun can exceed 100°C. Conventional PUDs may harden and crack at low temperature or soften and become tacky at high temperature. RELANET adjusts the glass-transition behavior of the adhesive film to create a broad operating-temperature range.
Peel-strength retention across the temperature gradient
- 1. After 24 hours at -40°C, peel-strength retention was reported as 92% for RELANET, 71% for Competitor A, 76% for Competitor B and 83% for imported Competitor C.
- 2. After 24 hours at 105°C, peel-strength retention was reported as 88% for RELANET, 66% for Competitor A, 70% for Competitor B and 79% for Competitor C.
- 3. After 100 thermal cycles between -40°C and 105°C, the RELANET sample showed no delamination and retained 85% of its strength. The three comparison products showed localized edge lift and retained 58%-72%.
Figure 2. Peel-strength retention across the full temperature range
Figure description: temperature appears on the horizontal axis and peel strength on the vertical axis. The blue RELANET curve declines gradually; the curves for Competitors A and B fall sharply at low temperature, while imported Competitor C declines more at high temperature.
Interpretation
The RELANET film has a reported elongation at break of up to 850% at room temperature and retains 500%-800% elongation at 10°C, compared with 300%-500% for the comparison set. This flexibility helps prevent leather tearing during manual wrapping in cold workshops and reduces cracking in severe winter use. During summer heat exposure, the adhesive layer is designed not to flow or bleed oil into the skin. The manuscript cites series-production applications in both cold northeastern and hot Hainan-region vehicle programs as evidence of broad climate coverage.
Advantage 3: 1,000-hour humid-heat and hydrolysis resistance to reduce long-term blistering
Relative humidity in South China and coastal areas can remain above 85% for long periods. Moisture can gradually penetrate the bond line, causing hydrolysis, whitening, swelling and debonding. This is described as a common cause of concentrated interior aging after three to five years in coastal service. Whereas the industry often uses a 500-hour hydrolysis test, the RELANET manuscript reports a 1,000-hour aging program.
Measured aging at 60°C and 95% RH for 1,000 hours
- RELANET R-5670: the film remained clear, without whitening or swelling, and retained 85% of peel strength.
- Competitor A PUD: localized film whitening and 62% retained strength.
- Competitor B PUD: slight hydrolysis and 68% retained strength.
- Competitor C PUD: slight whitening and 75% retained strength.
The manuscript cites ≥65% retention as a commonly applied higher-level industry requirement.
Figure 3. Strength retention after 1,000 hours of humid-heat aging
Interpretation
RELANET uses a hydrolysis-resistant polycarbonate backbone in place of conventional polyester segments that are more susceptible to hydrolysis, making it harder for water molecules to disrupt the polyurethane chain. Production feedback cited from retrofit suppliers in the Pearl River Delta and coastal Fujian reports that wrapped interiors remained flat and secure after five years, without moisture-related blistering or detachment. The manuscript describes a service-life improvement of more than 40% over the comparison products and a corresponding reduction in after-sales maintenance cost.
Advantage 4: chemical resistance plus UV and yellowing resistance for lasting light-colored interiors
White, cream and light-grey interiors are increasingly common in new-energy vehicles. Aromatic PUDs can yellow under ultraviolet exposure. Neutral cleaners, hand cream and leather-care products can also contact the adhesive layer and cause swelling or debonding, creating two long-standing design concerns.
Two dedicated test groups
- 1. Chemical-resistance test: 72-hour exposure to a neutral interior cleaner and silicone-oil care fluid.
RELANET: no swelling and less than 6% strength loss; Competitor A: 21% loss; Competitor B: 17% loss; imported Competitor C: 11% loss.
- 2. Yellowing-resistance test: 500 hours at 85°C plus 300 hours of ultraviolet aging.
RELANET: color difference ΔE <1.2, with no yellowing visible to the unaided eye.
Competitors A and B: ΔE >3.8, with obvious yellowing; imported Competitor C: ΔE ≈2.1, with slight yellowing.
Figure 4. Color-block comparison after yellowing exposure
Interpretation
RELANET's PUD range uses a fully aliphatic synthesis route without the readily oxidized aromatic-ring structures associated with yellowing. Light-colored natural leather, TPO and microfiber are therefore intended to retain color without staining during long-term use. Routine cleaning is not intended to corrode the bond line. The film is also designed to resist silicone oil and plasticizer migration, helping prevent long-term softening and debonding behind flexible PVC skins.
Advantage 5: production-friendly processing, wider tolerance and lower manufacturing cost
Even an adhesive with strong laboratory performance cannot succeed if it is incompatible with the production line. RELANET separately optimizes materials for manual and automated wrapping to address narrow activation windows, unsuitable open times, high drying energy and excessive scrap. The following figures compare process parameters.
Table. Process-data comparison
Figure 5. Activation-temperature and open-time operating window
Figure description: the RELANET operating region is wider than the comparison regions, indicating greater process tolerance.
Interpretation
- 1. Manual wrapping: an 8-15 minute open time allows slow skin adjustment over curved surfaces and irregular corners. After adoption in a South China winter workshop, the reported scrap rate among newly trained operators fell by 60%.
- 2. Automated production: activation from 65°C was reported to reduce oven energy by 20%. Thin leather and light-colored skins are less likely to shrink at this temperature, and a 3-8 minute drying time can align with the line cycle.
- 3. Material efficiency: lower coat weight reduces material use by 10%-20% per square metre in the stated comparison, lowering procurement cost at scale. The dried film is transparent and does not obscure the leather grain, supporting interior appearance.
Advantage 6: low-VOC environmental design for healthier cabins
Against the background of carbon-reduction goals, automakers are tightening controls on cabin odor, formaldehyde and VOCs. The manuscript references GB/T 27630-2020 for the domestic market and EU ELV and REACH requirements for overseas programs. RELANET controls restricted substances from the raw-material stage. The following figures present the reported environmental test data.
Table. VOC comparison
Figure 6. Bar chart comparing VOC release
Figure description: the national-standard limit is marked in red, and the reported RELANET value is below both the limit and the comparison products.
Interpretation
The RELANET process is described as solvent-free synthesis without added formaldehyde, conventional plasticizers or harmful additives. The finished adhesive has a mild odor, while spray workshops avoid the strong odor associated with solvent-borne materials and may reduce the need for specialized exhaust treatment, subject to the complete line assessment. The manuscript cites cabin applications for NIO, BYD and Li Auto and states that the system is intended to support EU ELV and REACH export programs. Because the water-based adhesive is non-flammable and non-explosive under the stated classification, storage and production safety can be improved relative to solvent-borne adhesives and fire-protection conversion cost may be reduced.
Conclusion: the combined value of RELANET PUD and a new benchmark for domestic interior adhesives
The six performance areas build progressively from basic adhesion through weathering, durability, appearance, production implementation and occupant health: strong adhesion addresses after-sales debonding; a wide temperature range covers varied climates; hydrolysis resistance extends interior life; yellowing resistance supports light-colored designs; a production-friendly window reduces manufacturing cost; and lower VOC supports automaker environmental targets.
Compared with Competitors A and B and imported Competitor C, the RELANET concept is not to maximize one property at the expense of another, but to balance the system through molecular modification. The Guangzhou R&D center continues to refine formulations and can develop tailored PUDs for special cases such as PP/glass-fiber composites, ultrathin leather and enclosed recreational-vehicle interiors. Support covers adhesive selection, process tuning and aging tests.
RELANET Automotive Material will continue to focus on water-based polyurethane for automotive interiors, supporting the transition to water-based processes through material technology, stable products and rapid localized technical service. The goal is to work with automakers and interior suppliers to advance domestically developed automotive bonding materials.