A PUR Hot Melt Machine
is a specialized industrial device designed to melt, convey, and apply PUR hot melt adhesive- a reactive polyurethane material that cures through two stages: physical initial adhesion and chemical cross-linking triggered by moisture in the air. This dual curing process sets it apart from traditional EVA hot melt machines, which only rely on physical cooling to form bonds. The chemical curing stage (which takes 24–72 hours to reach full strength) creates a bond that is heat-resistant (exceeding 150°C, compared to 80–120°C for EVA), waterproof, and irreversible-making it ideal for applications requiring long-term durability in humid, high-temperature, or high-stress environments.
Sealed Melting System:
The heart of the machine, consisting of a hermetically sealed melting tank or press plate with nitrogen protection (to isolate molten glue from air). The tank is made of high-temperature-resistant alloy or SUS304 stainless steel, with a Teflon coating to prevent glue carbonization and adhesion. The heating element provides uniform heating to 110–130°C (the optimal melting range for PUR adhesive).
Precision Conveying System:
Equipped with a high-precision gear pump (processed for durability under high-viscosity glue) and insulated pipelines to maintain consistent temperature during glue transport. The system features frequency conversion speed regulation to control glue output, ensuring uniform application and reducing waste. A return pipeline recycles excess glue, further minimizing material loss.
Application System:
Includes interchangeable glue guns and nozzles (strip, spiral, fiber) to achieve dot, line, or surface application. A precision filter removes impurities to prevent nozzle clogging, and the system offers adjustable coating width (60mm–550mm) and thickness (0.1mm–2mm) for versatile use.
Working Process: Dual-Stage Curing for Superior Bonds
The working process of a PUR Hot Melt Machine is streamlined but specialized, designed to leverage the unique reactive properties of PUR adhesive:
Adhesive Loading:
PUR adhesive (granular, block, or in drums) is loaded into the sealed melting system-either the press plate (for drum-fed models) or melting tank (for small-batch models).
Melting & Isolation:
The machine heats the adhesive to 110–130°C, melting it into a liquid state. The sealed system and nitrogen protection prevent air from contacting the molten glue, avoiding premature chemical curing.
Precise Conveying:
The gear pump delivers the molten adhesive through insulated pipelines to the glue gun, maintaining consistent temperature and pressure for uniform application.
Application & Initial Bonding:
The glue gun applies the molten adhesive to the substrate, and the adhesive cools rapidly to form a physical initial bond-allowing ample open time (several to tens of seconds) for position adjustment.
Chemical Curing:
The applied adhesive absorbs moisture from the air, triggering a cross-linking chemical reaction that forms an irreversible, high-strength bond. Full curing takes 24–72 hours, resulting in a bond that is heat-resistant, waterproof, and durable.
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