How To Strengthen The Bonding Strength Of Hot Melt Adhesive?
Published on Jan. 15, 2019
In the use of hot melt adhesives, glue is often non-sticky because the user does not have a deep understanding of the Hot Melt Adhesive, which causes various troubles in the production process.
The following is a detailed introduction to several methods on how to strengthen the bonding strength of hot melt adhesives.
1, improve surface roughness
When the Hot Melt Packaging Adhesive wets the surface of the adherend material well (contact angle θ<90°), the roughening of the surface is beneficial to increase the degree of wettability of the hot melt adhesive liquid to the surface, and increase the density of contact points between the hot melt adhesive and the adherend material. , which is beneficial to improve the bonding strength.
2, surface treatment
Due to the "weak boundary layer" formed by the oxide layer, the chrome plating layer, the phosphating layer, the release agent, etc., the surface treatment of the adherend will affect the bonding strength, the surface treatment of aluminum and aluminum alloy, and the aluminum surface is desired. The alumina crystal is formed, and the surface of the naturally oxidized aluminum is very irregular, and the relatively loose alumina layer is not favorable for bonding.
Bonded joints are often infiltrated into some other low molecules by the action of the ambient atmosphere. For example, the joint penetrates into the adhesive layer in a humid environment or underwater; the polymer adhesive layer is in an organic solvent, and the solvent molecules penetrate. In the polymer, the penetration of the low molecular weight first deforms the adhesive layer, and then enters the interface between the adhesive layer and the adherend, so that the strength of the adhesive layer is lowered, thereby causing the damage of the adhesive.
When bonding, pressure is applied to the bonding surface, so that the hot melt adhesive more easily fills the pits on the surface of the adherend, and even flows into the deep holes and the capillary to reduce the bonding defects.