1. Company introduction: RELANET Automotive Material
As China's automotive industry moves toward electrification, lightweight construction and greener manufacturing, cabin environmental quality, interior durability and production cost reduction have become central requirements for automakers and interior suppliers. As a wrapping and lamination material, the adhesive directly affects cabin air quality, product service life and line efficiency. RELANET Automotive Material has worked for many years in water-based polymeric bonding materials for automotive interiors. The company develops, manufactures and sells water-based polyurethane dispersions (PUDs), matching hardeners and complete application solutions, with an R&D focus on molecular modification for this specialized market.
The company is located in the South China automotive supply region, close to vehicle assembly, interior wrapping and leather-processing clusters. Its facilities include a standardized water-based PUD synthesis workshop, a Class 1,000 clean testing laboratory and a pilot-scale sampling line. Equipment includes rheometers, thermal and humid-aging chambers, VOC emission chambers, universal material-testing machines and differential scanning calorimetry. These resources support internal work from raw-material synthesis and property testing through process simulation and vehicle-level weathering validation. Products are developed around GB/T 27630, automotive-interior adhesive VOC controls and REACH-related requirements, with traceability from raw-material charging to finished-goods release.
For R&D, RELANET has formed a dedicated team of polymer-material, automotive-process and interior-application engineers. Rather than relying on simple blending of general-purpose PUDs, the team follows a customized molecular-chain modification route. It targets five common weaknesses of conventional water-based adhesives: cracking during cold wrapping, debonding after high-temperature exposure, poor compatibility across substrates, excessive residual VOC and a narrow activation window on automated lines. The polyester/polycarbonate-modified PUD system has been iterated into dozens of products for manual wrapping, vacuum forming and fully automated wrapping, serving interior bonding in combustion-engine vehicles, new-energy passenger vehicles, commercial vehicles and recreational vehicles.
RELANET's service model combines product, process and customization. Before a sale, it provides substrate-bonding samples and production-line evaluation. During implementation, technical engineers tune spraying, roller coating and knife coating at the customer's site. Afterward, the team supports high/low-temperature aging, humid-heat cycling and third-party VOC testing. For new vehicle programs, customized samples for low-surface-energy PP, rigid TPO and ultrathin microfiber can be prepared within seven working days, shortening component validation. The manuscript states that products are supplied to dozens of Tier 1 interior companies for instrument panels, door trim, seats, headliners, armrests and luggage-compartment boards. Stable performance, low odor and process versatility support the industry's transition to water-based adhesives.
Looking ahead, RELANET is developing bio-based, lower-carbon PUD and ammonia-free, low-odor modified systems. Its R&D direction-lower-emission bonding, long-term durability and efficient production-is intended to help automotive interiors replace high-VOC solvent-borne adhesive and move toward greener manufacturing.
RELANET PUD applications across the complete vehicle cabin
2. RELANET PUD products for automotive interior bonding
The product system uses a composite molecular structure crosslinked with a water-dispersible isocyanate hardener and uses water as the dispersion medium. It is described as free of benzene, toluene, xylene, formaldehyde and heavy metals. The source manuscript presents two principal models: PUD-RR-5679 for manual wrapping and the high-transmission G/R-5610. Together they address small-scale manual production and large automated OEM lines. Candidate materials include PU leather, PVC, TPO, natural leather, microfiber, PP/ABS plastics, EVA foam, nonwoven fabric and wood-plastic board. Broad material coverage is intended to reduce adhesive changes on mixed-model lines and lower pretreatment cost.
(1) Basic physical and chemical properties
The basic parameters of the two products were measured under standardized laboratory conditions and are shown in the following source figure:
High solids are described as a core advantage. Compared with an ordinary market PUD, solids are stated to be more than five percentage points higher, allowing 20%-30% less adhesive for the same bonded area and reducing cost per interior set. Viscosity is tuned to the process: the manual grade is thick enough to resist sagging, while the line grade flows through a 2.0 mm spray setup during extended operation without blockage. An 8-15 minute open time gives operators freedom to reposition leather on complex surfaces and corners, reducing bubbles, wrinkles and rework.
RELANET PUD finished-product packaging
(2) Mechanical bonding performance
Bond strength and film flexibility directly determine whether an interior component remains bonded and free of edge lift during long-term use. After curing, the two PUD products in the source manuscript exceeded the cited industry baseline in the following tests:
- Elongation at break and tensile toughness
Under ASTM D412, the source reports elongation at break of 600%-1,000% for RJ810 and 750%-1,100% for RJ830 at a 10°C workshop temperature. At 23°C, elongation exceeded 1,200%, with tensile strength of 28-32 MPa.
Conventional water-based PUDs are described as providing 300%-500% elongation at low temperature, increasing the risk of folded-edge cracking and corner lift during winter wrapping. The modified RELANET chain structure gives the film greater conformity, allowing it to deform with the skin during vibration and thermal expansion and contraction.
- 180° peel strength on multiple substrates
Peel force measured after 24 hours of curing:
- Microfiber leather + ABS carrier: ≥1,150 N/m.
- TPO skin + modified PP board: ≥980 N/m.
- Natural leather + EVA foam: ≥1,300 N/m.
- Flexible PVC skin + wood-plastic interior board: ≥1,050 N/m.
The source states that the skin itself tore in each peel test, while the adhesive interface remained bonded. The reported strength was comparable to solvent-borne polyurethane adhesive in these constructions. PP and TPO pretreatment requirements must nevertheless be confirmed for the actual resin grade and surface condition.
PUD bonding-performance radar comparison
- Creep resistance and vacuum-forming stability
In vacuum-forming tests at -0.09 to -0.1 MPa, the film continued to stretch without slipping or delaminating. The referenced line achieved saturated initial tack after 40-60 seconds of rapid activation at 120-130°C, within an activation window of 110-140°C. The source reports a 15%-25% increase in line efficiency and an end-of-line bonding defect rate below 0.3%, compared with an industry-average defect rate stated as 2%.
(3) Weathering and durability: vehicle-level environmental simulation
Automotive interiors may experience -40°C winter conditions, 90°C summer exposure, humid rainy seasons and long-term vibration. Adhesive durability affects a component's three-to-eight-year service life. The manuscript reports the following cyclic-aging results:
- High- and low-temperature cycling
After 50 cycles of four hours at -40°C followed by four hours at 90°C, peel-strength retention was ≥88%, without film whitening, embrittlement, shrinkage or debonding. The source states that ordinary market PUDs lost more than 40% of bond strength after 30 cycles and showed extensive corner lift.
- Humid-heat hydrolysis resistance
After 1,000 hours at 60°C and 95% RH, the film showed no hydrolysis or whitening and retained 85% of peel strength. Polycarbonate-modified chains improve hydrolysis resistance for hot, humid and coastal service and are intended to reduce moisture-related blistering and detachment.
- Heat exposure and yellowing resistance
After 500 hours at 85°C, the film showed no reported color change, oil bleed or migration onto the leather surface. The formulation avoids the aromatic structures associated with yellowing, supporting light natural leather and white TPO interiors.
- Resistance to oils and cleaners
After 72-hour contact with hand cream, leather-care product and interior cleaner, the source reports no significant bond-strength loss and no swelling of the adhesive layer, addressing a common after-sales failure caused by interior cleaning.
(4) Environmental and VOC performance for higher cabin standards
As new-energy vehicle manufacturers tighten odor and VOC controls, RELANET addresses environmental performance from the raw-material stage:
- The source describes a solvent-free formulation without formaldehyde, aromatic solvents, DMF or heavy metals and reports VOC release below 8 mg/L, compared with a cited GB/T 27630 limit of 50 mg/L.
- The finished product is reported at odor grade ≤2. Spray and wrapping workshops avoid strong irritating odor, improving the work environment and potentially reducing specialized explosion-proof ventilation requirements, subject to the line assessment.
- After curing, the film is described as releasing no volatile low-molecular components. Acetaldehyde, toluene and xylene results in complete-vehicle testing were below the cited internal automaker limits, supporting passenger EV, ride-hailing and recreational-vehicle cabin programs.
- The water-based system is described as outside hazardous-chemical classification for the stated product, reducing storage, transport and hazardous-waste costs relative to solvent-borne adhesive and lowering safety-management pressure.
Finished appearance of an environmentally oriented interior application
(5) Process compatibility advantages
Reducing total production cost requires a wide, forgiving process window. The manual grade provides an 8-15 minute open time, while the line grade provides 5-10 minutes, giving operators and automation enough time to adjust skins over irregular door panels, curved instrument panels and armrest folds. The source reports 70% less rework, compared with conventional PUD open times of 3-6 minutes that can force a skin to be scrapped after a placement error. One PUD can support knife coating, roller coating, high-pressure spraying and vacuum forming, reducing adhesive inventory and line-change cleaning losses; the stated monthly auxiliary-material reduction is approximately 18% per plant. For low-surface-energy PP and rigid TPO, the manuscript reports bonding after basic dust removal in validated constructions, potentially avoiding primer and plasma equipment and reducing processing cost by CNY 0.5-1.2 per part. Balanced drying-10-25 minutes tack-free at room temperature or 3-8 minutes in an 80°C oven-matches automated conveying without lengthening the tunnel. The dried film remains transparent and flexible, preserving leather texture and appearance.
(6) Main application scenarios
Instrument-panel wrapping: vacuum forming of TPO, microfiber or PVC skin over an ABS carrier, designed to resist blistering and edge lift after heat exposure. Door-panel trim: compatible with manual and automated wrapping, with long-term resistance to cracking at folds. Seats and armrests: bonding natural leather or PU leather to foam under repeated compression and abrasion. Headliners and luggage-compartment boards: laminating nonwoven fabric or textile to PP carriers with humid-heat resistance. Recreational and special-purpose vehicles: combining wood-plastic board, leather and soft trim in enclosed, low-odor cabins. The source summarizes four recurring industry pain points: excessive VOC and safety risk from solvent-borne adhesive; poor cold flexibility and thermal-cycle durability of ordinary water-based PUD; limited substrate coverage and high changeover cost; and narrow process windows that increase rework. RELANET's modified polyester/polycarbonate PUD platform is presented as addressing five system-level values-environmental compliance, high bond strength, weathering durability, broad process compatibility and lower total cost. As water-based PUD continues to replace solvent-borne adhesives, RELANET states that it will develop higher-performance, lower-odor and longer-lasting products and provide practical technical support for combustion-engine and new-energy vehicle interiors.