What is PUR Reactive Hot Melt?
PUR (Polyurethane Reactive) hot melt adhesive is an advanced bonding technology that combines the best features of traditional hot melt adhesives and structural polyurethane adhesives. Like conventional hot melts, PUR is applied in molten form and sets quickly through cooling. However, unlike standard hot melts, PUR continues to cure through a moisture-crosslinking reaction, creating an irreversible chemical bond that offers superior strength, heat resistance, and chemical resistance.
How PUR Curing Works
The PUR curing process occurs in two stages:
- Stage 1 - Initial Set (seconds to minutes): The molten adhesive cools and solidifies, providing initial handling strength. This is similar to conventional hot melt behavior.
- Stage 2 - Moisture Cure (hours to days): The reactive isocyanate groups in the PUR polymer react with moisture from the air and the substrates, creating crosslinked polyurethane bonds. This process continues for 24-72 hours, gradually increasing bond strength, heat resistance, and chemical resistance.
Key Advantages of PUR
- Highest Bond Strength: PUR achieves bond strengths of 10-25 MPa, significantly higher than standard EVA hot melts (3-8 MPa).
- Excellent Heat Resistance: Once fully cured, PUR bonds can withstand temperatures up to 150°C without softening.
- Chemical Resistance: Crosslinked PUR is resistant to solvents, fuels, cleaning agents, and environmental exposure.
- Flexibility: PUR maintains flexibility even after curing, absorbing impact and vibration without cracking.
- Low-Temperature Application: PUR can be applied at 120-140°C, lower than many standard hot melts, making it suitable for heat-sensitive substrates.
- Gap Filling: PUR formulations can fill gaps up to 3mm, accommodating imperfect joints.
Applications
PUR reactive hot melt is used in demanding applications across multiple industries:
- Automotive: Structural bonding of interior trim, headliners, door panels, and composite components.
- Electronics: Bonding of displays, touch panels, battery packs, and housing components in consumer electronics.
- Furniture: Edge banding of high-end kitchen and bathroom furniture, particularly where heat and moisture resistance are required.
- Construction: Structural bonding of panels, flooring, and decorative elements.
- Textile: Lamination of technical textiles, footwear components, and protective clothing.
Considerations When Using PUR
While PUR offers exceptional performance, there are some important considerations:
- PUR requires moisture to cure—both substrates must allow moisture access to the bond line
- Once cured, PUR bonds cannot be reheated and repositioned (unlike standard hot melts)
- PUR applicators must be kept clean and sealed when not in use to prevent moisture contamination
- Open containers have a limited pot life (typically 8-24 hours) and should be used promptly
- Storage must be in sealed, moisture-proof packaging
Our PUR Products
Jiajian offers PUR reactive hot melt adhesive in both cartridge and bulk formats. Our PUR Reactive Hot Melt Adhesive is designed for demanding structural bonding applications. Request a free sample to test in your application.