Impact Analysis of Friction Coefficient Variations on Quality
1. PA//PE Composite Film - Difference in Peel Strength
Some flexible packaging companies observe poor peel strength after composite PA//PE. Upon peeling, a white "frost"-like substance is visible on the PE film, removable by hand. Placing the composite film back into a curing room or an 80℃ oven for a period results in a significant increase in peel strength. However, leaving the composite film at room temperature for two days gradually reduces peel strength. This is attributed to the migration of slip agents to the PE film's surface, forming a thin, dense layer that hinders adhesive bonding between PA and PE. This phenomenon underscores the importance of not storing PE films with high slip agents for extended periods.
2. Effect of Slip Agent Interlayer Transfer on Composite Bond Strength
The internal surface of PA film is bonded to the PE film's composite surface through adhesive action. The external surface of the PA film tightly adheres to the PE film's heat-sealing surface under winding tension. Migration of slip agents to the heat-sealing layer's surface may cause a decrease in peel strength, a reduction in effective slip agents on the PE film's heat-sealing surface, leading to increased friction coefficient. Moreover, slip agent migration to the PA film's surface alters the friction coefficient on the external surface while reducing slip agents on the PE film's heat-sealing surface.
3. Impact of Friction Coefficient on BOPA Film in Solvent-Free Lamination
The friction coefficient of solvent-free adhesives varies significantly based on their types and components. When opting for solvent-free lamination, selecting an appropriate adhesive is crucial depending on the specific friction coefficient requirements.
An increase in adhesive amount not only raises the friction coefficient but may also lead to adverse effects. Post-composite, the friction coefficient increases by approximately 0.1~0.2 due to adhesive absorption of slip agents and wear during production. Therefore, controlling adhesive amount is vital, as every additional gram per square meter raises the friction coefficient by about 0.025.
Inadequate adhesive amounts may cause uneven coating, white spots, and reduced strength, especially in white ink areas, leading to problems like white spots and bubbles.
The type and composition of solvent-free adhesives influence the friction coefficient differently as the curing temperature rises. For instance, variations in the main components, such as polyester or polyether, result in different friction coefficients at higher curing temperatures. The friction coefficient increases with temperature due to faster adsorption reactions between the adhesive and slip agents, rendering some slip agents ineffective. Extending the curing time also leads to a higher friction coefficient. Solvent-free lamination typically recommends a curing temperature not exceeding 40℃.
In summary, the friction coefficient of raw materials like PE and CPP directly impacts the composite film's friction coefficient. Controlling it at the source is essential to ensure the final product has the desired friction coefficient. In solvent-free lamination, products with BOPA//PE, BOPET//CPP combinations are recommended for quality assurance after lamination.