Why doesn’t hot melt glue stick?
Hot melt adhesive is a widely used adhesive in the industrial production process, but it is inevitable that it will not stick during the application process. So what are the reasons that affect the viscosity of hot melt adhesives? Mainly divided into the following three categories:
1. Hot melt adhesive itself
1. Viscosity: affects fluidity, permeability, spray performance, glue temperature, wire drawing, glue output, etc.
2. Softening point: It affects the temperature, heat resistance and curing speed of the glue.
3. Open time: Affects operational suitability, permeability and bond strength.
4. Curing speed: affects the production speed and bonding strength.
5. Affinity: affects the bonding strength.
6. Cohesion: affects transfer resistance, peel strength or shear chord.
7. Hot adhesive force: affects the bonding effect.
8. Temperature resistance, etc.: It affects the temperature that the final bonding system can withstand.
9.Compliant with green environmental protection standards
2. Substrate
1. Polarity: The polarities attract each other, and the adhesive with similar polarity to the substrate has a better bonding effect.
2. Density: loose substrates are easy to penetrate, requiring short pressurization time and high pressure
3. Surface tension: Insufficient surface tension will affect wetting and bonding. Corona treatment and sanding help to improve adhesion.
4. Surface temperature: If the surface temperature of the substrate is too low, it will affect the infiltration, opening time and penetration of the glue; if it is too high, the curing time will be prolonged.
5. Moisture, surface treatment agents (such as talc) and pollution: seriously affect the bonding strength.
6. Adsorption and transfer performance: It seriously affects the aging and adhesion of hot melt adhesives.
3. Equipment and technology
1. Speed: High-speed production lines often reduce the requirements for open time, but increase the requirements for curing speed.
2. Glue temperature: Raising the glue temperature will prolong the opening time and reduce the curing speed.
3. Open distance: open distance/production line speed = open time of the equipment, which should be shorter than the open time of hot melt adhesive.
4. Pressure: Sufficient pressure helps the penetration, wetting and curing of the hot melt adhesive.
5. Pressure holding time: The pressure holding time of the equipment should be designed to be longer than the curing time of the hot melt adhesive.
6. The amount of glue used: increasing the amount of glue used can replace the infiltration and penetration of the glue, prolong the opening time, slow down the curing speed, and the curing speed is fast.
