The application methods and quantities to be considered of EVA hot melt adhesive

The application methods of EVA hot melt adhesive and the variables to be considered: Due to the multi-functionality of a series of markets, the global hot melt adhesive market is growing. Before choosing hot melt adhesive for the process, please carefully review the type of application method and the variables to consider:

EVA hot melt adhesive can be applied in four main ways:

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Channel extrusion: This type of extrusion is used in applications that require a wide bonding area. Generally, this method is suitable for the application requirements of tapes and labels.

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Bead extrusion: Bead extrusion pumps the adhesive through a nozzle and forms a bead-like adhesive dose on the substrate. This type of method is suitable for rigid packaging applications that do not require extensive surface coverage areas for sealing boxes and cartons.

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The spraying method is similar to bead extrusion. The nozzle is used to push out the adhesive. However, it also uses air flow to form vortex-like adhesive patterns on the substrate.

This method is beneficial for temperature-sensitive substrates because air helps cool the adhesive before it reaches the substrate surface. In addition, it can also be used in applications that require large-area bonding but not too much adhesive, such as non-woven fabrics or assembly.

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When the large panels are bonded together, use the roller coating method. The adhesive is measured onto the main substrate through the gap between the rollers. It moves down along the conveyor belt, with the second panel placed on top of the first one and then clamped together. Typically, this adhesive application method is used in truck and RV applications as well as garage door panels.

Application temperature: The temperature at which the adhesive leaves the nozzle

The application temperature of hot melt adhesive should be as high as possible to achieve the required wetting and penetration of the substrate.

Spray applications typically require higher temperatures because heat loss occurs when the adhesive fibers move from the nozzle to the substrate.

Other factors to be considered include:

Thermal stability of adhesive

Substrate heat resistance

Equipment limitations regarding open time/compression time

Additional weight (coating weight) : The amount of adhesive used for bonding

Applications that require a higher coating weight mean that the adhesive will need more time to set up. Solidification is the process by which EVA hot melt colloid loses heat and solidifies. This is because when more adhesive is applied to the substrate, more heat is generated, and the heat must dissipate for the adhesive to solidify.

The amount of adhesive will affect the bonding of the primary and secondary substrates, especially in bead extrusion applications. The more adhesive is applied to the main substrate, the larger the area covered during melting and compression will be. Having more adhesive enables it to remain molten for a longer time and better wet the second layer substrate.

The weight of the coating also determines the surface area of the finished product for bonding.

Compression: To make two substrates physically contact by applying pressure.

Compression mainly affects the adhesion to secondary substrates. Make EVA hot melt adhesive adhesive flow into the primary and secondary substrates. The compression time must be long enough to allow the adhesive sufficient time to develop cohesive strength to overcome substrate memory or stress. Insufficient compression time can lead to incorrect or inadequate bonding.

To promote the maximum wetting and bonding surface area, compression should be carried out as soon as possible after the adhesive is applied.