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ASKED QUESTION
Frequently Asked Questions
  • Q: What is a PUR hot melt adhesive?
    A:

    A PUR (Polyurethane Reactive) hot melt adhesive is a moisture-curing adhesive that combines thermoplastic processing with thermoset performance.
    After cooling and moisture reaction, it forms a crosslinked structure, providing high strength and long-term durability.

  • Q: How does moisture curing work?
    A:

    After application and cooling, the adhesive reacts with ambient moisture or substrate moisture.
    This chemical reaction gradually increases heat resistance, chemical resistance, and final bond strength.

  • Q: What is the open time of PUR hot melt adhesives?
    A:

    Open time depends on formulation, coating weight, temperature, and ambient conditions.
    PUR systems can be designed for short, medium, or extended open times to match different lamination speeds and processes.

    Open time is typically adjustable through formulation design.

  • Q: Can PUR hot melt adhesives be reactivated?
    A:

    Yes.
    Before full moisture curing, PUR hot melt adhesives can be thermally reactivated to restore tack for secondary bonding operations.
    After full curing, reactivation is no longer possible.

  • Q: What coating processes are compatible with PUR hot melt adhesives?
    A:

    PUR hot melt adhesives are compatible with various industrial coating and lamination processes, including:
        •    Gravure roll coating
        •    Extrusion coating
        •    Slot die coating
        •    Roller and press lamination

    Process compatibility depends on viscosity, temperature window, and coating weight.

  • Q: What substrates can PUR hot melt adhesives bond?
    A:

    PUR hot melt adhesives are suitable for a wide range of substrates, such as:
        •    Textiles and nonwovens
        •    PU, TPU, PE films
        •    PU and PE foams
        •    Synthetic leather and genuine leather
        •    Plastic substrates used in electronics

    Formulation can be optimized for specific substrate combinations.

  • Q: What is green strength and why is it important?
    A:

    Green strength refers to the initial bonding strength immediately after cooling.
    It is critical for maintaining laminate stability during downstream handling before full curing is completed.

  • Q: How long does full curing take?
    A:

    Full moisture curing typically takes 24 to 72 hours, depending on:
        •    Ambient humidity
        •    Coating thickness
        •    Substrate moisture content

    Bond strength continues to increase during this period.

  • Q: What are the typical application temperatures?
    A:

    Application temperatures are formulation-dependent and typically range from 100°C to 140°C.
    Low-temperature systems are available for heat-sensitive substrates.

  • Q: Are PUR hot melt adhesives flexible after curing?
    A:

    Yes.
    PUR adhesives can be formulated to maintain flexibility after curing, making them suitable for textiles, foams, leather, and flexible laminates.