We know that the pur hot melt adhesive bonding object actually penetrates into the object to be bonded and combines with its molecular structure to destroy the surface layer of the object, thereby firmly bonding the two objects. So we can increase the stickiness of pur hot melt adhesive by changing something?
1. Surface treatment
There are some oxide layers (such as rust), chrome-plated layer, phosphating layer and mold release agent on the surface of the material to be adhered. The "weak boundary layer" will directly affect the bonding strength. The oxide layer on the surface is treated first to improve the bonding strength.
2. Improve surface roughness
The roughening process of the surface of the bonded object can also affect the adhesion. If the object is too smooth, the pur hot melt adhesive can penetrate less molecules, thereby reducing the bonding strength. Therefore, we can also increase the bonding strength of the hot melt adhesive by increasing the surface roughness of the bonded object.
3. Adhesive layer thickness
The thicker glue layer is easy to produce bubbles, which will cause defects or early breakage. Therefore, we can make the glue as thin as possible, so as to obtain a higher bonding strength. In addition, the thermal expansion of the thick adhesive layer after being heated makes the thermal stress caused by the bonding surface relatively large. It is difficult to achieve the molecular damage on the surface of the bonding site, and the bonding will not be strong.
When bonding, apply pressure on the bonding surface to make the hot melt adhesive fill the holes on the bonding surface, and even flow into the deep holes and capillaries to reduce bonding defects. Therefore, appropriate pressure during bonding can also promote the surface of the bonded object. The gas escapes, reducing the bonding area of the hole and increasing the bonding firmness.