Key Factors Affecting the Sealing Performance of Aluminum-Plastic Bottle Caps

Release time:

Feb 06,2026

Material Compatibility
Gasket Material: Butyl rubber (pharmaceutical grade), silicone (high-temperature resistant), PE/EVA (food grade). Must be compatible with contents (acids, alkalis, alcohols) to prevent swelling or hardening.
Aluminum Shell Material: 1050/8011 aluminum alloy, wall thickness 0.18–0.22mm, with moderate hardness to ensure secure crimping.
Neck Fit: Neck surface must be smooth and burr-free, with dimensional tolerance ≤±0.1mm. Gap between neck and cap controlled at 0.05–0.1mm.
Design and Processing
Gasket Dimensions: Diameter must cover entire sealing surface of neck, with deviation ≤±0.5mm. Oversized gaskets cause wrinkling; undersized gaskets lead to leakage.
Aluminum Shell Structure: Pull-tab cap opening force (first step 10–30N, second step ≤38N) must balance sealing integrity and ease of use;
Processing Precision: Aluminum shell free of deformation, gasket free of displacement, composite interface shear strength ≥8MPa.
Capping Process
Capping Parameters: Pressure, temperature, and time must match material properties (e.g., PE gasket heat-sealing temperature 180–200°C);
Equipment Precision: Coaxiality between capping machine head and bottle neck ≤0.1mm to prevent uneven sealing due to off-center pressure.
Environmental & Aging Resistance
Sterilization Resistance: Pharmaceutical caps must withstand 30-minute steam sterilization at 121°C with ≤5% increase in leakage rate;
Weather Resistance: No brittleness at low temperatures (-20°C), no relaxation at high temperatures (60°C), and no gasket detachment during long-term storage.