Suzhou Oushida Hot Melt Machinery Equipment Co., Ltd.

Why does PUR hot melt adhesive have drawing and bubbles?

Company Profile

Suzhou Oushida Hot Melt Adhesive Machinery Equipment Co., Ltd. is a high-tech enterprise specializing in the research and development, production, sales and technical consulting of hot melt adhesive intelligent spraying equipment.

PUR hot melt adhesive (Polyurethane Reactive) is a new type of one-component, solvent-free hot melt structural adhesive. It cures in the air through moisture. After being fully cured, it has excellent bonding strength and impact resistance. It also has excellent bonding strength, temperature resistance, chemical corrosion resistance and aging resistance. In recent years, it has become the best choice for bonding in the electronic industry such as mobile phones, electrical appliance assembly, and automotive parts assembly. Why does PUR hot melt adhesive have the phenomenon of drawing when in use?

1. Cohesive strength of PUR hot melt adhesive

The influence of the cohesive strength of PUR hot melt adhesive and wire drawing is: the greater the cohesive strength, the obvious wire drawing phenomenon; on the contrary, the cohesive strength is low, and the wire drawing phenomenon will not appear.

2. Curing time of PUR hot melt adhesive

The curing time of PUR hot melt adhesive is an important factor affecting the wire drawing phenomenon. Generally speaking, the probability of wire drawing of PUR hot melt adhesive with a short curing time is low, because the filaments formed when the hot melt adhesive is sprayed out of the gun cannot be continuously stretched due to rapid curing, and are prone to breakage. Sometimes, no wires can be seen.

3. Rheology of molten PUR hot melt adhesive

The rheology of molten colloid plays a decisive role in wire drawing, which is related to the design of hot melt adhesive formula, the selection of materials in the formula and the compatibility.

4. Influence of PUR hot melt adhesive machine temperature

If the temperature of the PUR hot melt adhesive machine is too low, the viscosity of the PUR hot melt adhesive itself will increase, resulting in wire drawing.

For PUR reactive hot melt adhesive, bonding should be completed within the open time after application to ensure the best effect after bonding. However, bubbles will appear during the bonding process. What is the reason?

1. The problem of the glue tank temperature being too high. This phenomenon may occur if the temperature is too high and the hot melt adhesive has poor heat resistance;

2. The problem of the hot melt adhesive itself. The hot melt adhesive is not completely melted and mixed during the production process. The air in the rubber will be released during the user's heating process, or the hot melt adhesive is not vacuumed or not completely vacuumed during the production process;

3. If there are bubbles when the glue comes out of the nozzle, you can consider whether the temperature of the hot melt glue machine is too high or whether there is residual glue that has not been completely discharged. You can try to discharge the glue for a few minutes to see if the glue is smooth and free of bubbles;

4. If there are no bubbles when the glue comes out of the nozzle, but there are bubbles after the reaction, one possibility is that there is tension after bonding, the external force is not strong enough, or the pressure is not good. Another possibility is that the pressure is not positioned in time after bonding, so that it bounces off during the initial bonding, resulting in bubbles at the edge or both ends.

Application sharing

Washing machine cover assembly

Floor glue

Integrated board composite

Overview of Oushida hot melt adhesive intelligent spraying equipment: