Three factors that affect the bonding effect of hot melt adhesives

A, hot melt adhesive

(a) Viscosity: influences fluidity, permeability, coating properties, glue temperature, drawing, etc.

(b) Softening point: affects the temperature, heat resistance, curing speed, etc. of the glue.

(c) Opening hours: Impact on permeability and adhesive strength.

(d) Curing speed: affects adhesive strength and production efficiency.

(e) Affinity: Affects adhesive strength.

(f) Other factors: cohesion, hot tack, temperature resistance, flexibility, etc.

B, substrate

(a) Polarity: The polar phase attracts, and the adhesiveness between the adhesive and the substrate is similar.

(b) Density: The porous substrate is easy to infiltrate, requiring a short pressurization time and high pressure; the dense substrate is reversed.

(c) Surface tension: Insufficient surface tension can affect wetting and bonding. Corona treatment, sanding, and punching help increase adhesion.

(d) Ink: The polarity of the ink, the density and the adhesiveness of the backing paper all affect the adhesion of the hot melt adhesive.

(e) Surface temperature: If the surface temperature of the hot melt adhesive substrate is too low, it will affect the infiltration, open time, and penetration of the adhesive; excessively prolonged curing time.

(f) Moisture, surface treatment agents and contamination severely affect bond strength.

C, Equipment and Process

(a) Speed: High-speed production lines tend to reduce the requirements for open time, but increase the speed requirements for curing.

(b) Temperature of glue: Increasing the temperature of the glue will prolong the opening time, slow down the curing speed, and enhance the permeability.

(c) Pressure: Adequate pressure aids penetration, infiltration, and curing of hot melt adhesives.

(d) Holding time: It should be designed so that the holding time of the equipment is longer than the curing time of the hot melt or at least sufficient hot tack is formed.

(e) Use of glue: Increasing the amount of glue can improve the penetration and penetration of glue, extend the opening time, and slow down the curing speed.

(f) Hot melt adhesive dispensing mode: With the same amount of glue, the large surface area of ​​the dispensing model has a short open time and a fast curing speed.