1.Hot Melt Adhesive Properties

Hot melt adhesive (HMA) is a 100% solid-content thermoplastic material. It exists as a solid at room temperature, liquefies upon heating, and rapidly solidifies upon cooling. Key components include:

Base resins (e.g., EVA, PO, PUR)

Tackifiers (enhance adhesion)

Plasticizers (adjust flexibility)

Antioxidants (prevent thermal degradation)

Coating Process

HMA is heated to a molten state (120–180°C) in a melting unit, uniformly applied to the substrate via a coating system, and cooled to form an adhesive layer.

2.Hot Melt Adhesive Coating Process Flow

Material Preparation

HMA pellets/blocks are fed into a melting device (e.g., melt tank, screw extruder).

Substrate pretreatment (cleaning, corona treatment to improve adhesion).

Melting & Delivery

HMA is melted in the tank and delivered to the coating head via gear pump or screw.

Precise temperature control prevents carbonization or performance loss.

Coating Methods

Method Application

Roll Coating Continuous uniform coating

Spray Coating Irregular/complex surfaces

Knife Coating High-precision thickness control

Extrusion Coating High-strength bonding applications

Cooling & Curing

Coated substrate is rapidly cooled (curing time: 1–3s) via chill rolls or forced-air systems.

Winding/Slitting

Cured material is wound into rolls or slit into products (e.g., labels, tapes).

3.Core Equipment for HMA Coating

Melting System: Melt tank, heaters, temperature control.

Coating Head: Roll/spray/extrusion modules.

Conveyance System: Belts/rollers (ensure smooth substrate travel).

Cooling System: Chill rolls, blowers, water-cooling units.

Control Unit: PLC/industrial computer (regulates temperature, speed, coating weight).

4.Application Fields

Packaging: Carton sealing, gift box bonding, label backing.

Hygiene Products: Diaper/sanitary napkin structural bonding.

Automotive: Interior trim assembly, acoustic material lamination.

Textiles: Nonwoven fabric lamination, garment interlining.

Electronics: Temporary fixation of flexible circuit boards.

V. Advantages of HMA Coating

Eco-friendly: Solvent-free, VOC-compliant.

High efficiency: Instant curing for high-speed production.

Versatility: Bonds diverse materials (plastics, metals, wood).

Cost-saving: Thin, uniform adhesive layers minimize usage.

VI. Key Process Parameters

Melt Temperature: Affects flowability (EVA: 150–170°C).

Coating Weight: 5–50 g/m² (adjusted via speed/die gap).

Substrate Tension: Prevents wrinkling/misalignment.

Cooling Efficiency: Ensures rapid setting and anti-blocking.

5.Common Issues & Solutions

Issue Solution

Uneven coating Clean clogged dies; optimize temperature/pressure

Adhesive carbonization Reduce melt temp; shorten high-temp exposure

Insufficient adhesion Enhance pretreatment; upgrade HMA grade

Substrate deformation Implement staged cooling