The Direct Influence of Thickness on the Heat Sealing Process
Thermal Conductivity Efficiency
Too Thin (< 30μm): Heat rapidly penetrates the aluminum foil, which may cause the hot melt adhesive to cure prematurely, resulting in false seals or edge warping.
Too Thick (> 60μm): The thermal resistance increases. Higher temperatures or longer time are required to reach the activation temperature of the hot melt adhesive (usually 120-180°C). This leads to increased energy consumption and is likely to cause deformation of the bottle mouth.
Ideal State: For every 10μm increase in thickness, the heat sealing time needs to be extended by 0.2-0.5 seconds or the temperature needs to be increased by 5-10°C (for example, a 40μm aluminum foil can achieve an effective seal at 160°C for 1.2 seconds).
Sealing Uniformity
Thin aluminum foil (such as 25μm) is prone to local non-fusion due to pressure fluctuations on high-speed production lines. Thick aluminum foil (such as 50μm) has a higher tolerance for pressure uniformity, but it requires higher pressure (usually 0.3-0.6MPa).
Interface Bonding Strength
For a 30μm aluminum foil: The penetration depth of the adhesive layer is approximately 8-12μm, which is suitable for low-viscosity hot melt adhesives.
For a 50μm aluminum foil: A higher-viscosity adhesive is required, and the penetration depth needs to reach 15-20μm to avoid delamination.
Thickness affects the flow and penetration of the hot melt adhesive:
