What Are The Process Parameters That Affect The Bonding Effect Of Hot Melt Glue?

Hot melt glue is widely used as an adhesive in the disposable hygiene products industry. This article briefly describes several process parameters that affect the bonding effect of hot melt pressure sensitive adhesives.

1.hot melt glue and machine open time

The machine's open time is the time it takes for the hot melt adhesive to travel from the glue head to the compounding area, generally measured in seconds. It can affect its temperature and wetting of the second substrate. In theory, it should be as short as possible. However, in practice, the placement position of the rubber head should also be considered, or the limitation of production speed should be considered. Its open time refers to the time it remains tacky after coating. The open time of the machine must be much lower than its open time, otherwise it will be cooled and solidified before compounding and the bonding effect will be poor.

2.hot melt glue and glue temperature

The gluing temperature refers to the temperature of the hot melt adhesive in the glue head, and the temperature affects its wetting to the substrate. In theory, the higher the temperature, the better, but consider its thermal stability, the heat resistance of the substrate, and other considerations such as "bleeding". In some applications, temperatures above 180°C can affect the performance of the adhesive and the sizing process. In general, longer machine open times and spray-on gluing require higher temperature settings due to some heat loss prior to compounding. Add a small amount of glue several times, otherwise the temperature of the glue box will fluctuate greatly.

3.hot melt glue and glue amount

The amount of glue applied affects the cooling rate of the hot melt glue, which affects the wetting of the second substrate. In theory, the less the amount of glue applied, the better, but the final adhesion requirements, opening time, etc. must be considered. Generally speaking, when the machine is open for a longer time, the amount of glue applied should be larger. Usually, the amount of back glue for sanitary napkins or diapers is 25~35g/square meter, the amount of sanitary napkin wing adhesive is 30~40g/square meter, and the amount of structural adhesive is about 3~4g/square meter , 1~2g/square meter of structural adhesive for bottom film compounding, 15~25g/square meter of elastic rubber.

4.hot melt glue and compound pressure

Lamination refers to the bonding of two substrates under pressure. The compound pressure is the pressure given by the machine when the two layers of substrates are compounded and bonded. The compounding pressure will affect the wetting ability of the hot-melt adhesive to the substrate, so that it penetrates into the two substrates respectively, which determines the surface morphology of the bonding area, and it should enter the compounding roller as soon as possible. In theory, the higher the compound pressure, the better, but the bearing capacity of the mechanical properties of the substrate, the wear of the rollers, and the seepage of glue should be considered. 

Hot melt glue is widely used in the disposable hygiene products industry because of its organic solvent-free, fast coating speed, safety and hygiene. Understanding the process parameters that affect the bonding effect of hot melt pressure sensitive adhesives will help people to further understand this material.