The foam gasket in the bottle cap is a critical component of the bottle cap sealing system, and its role is far more than just simple filling. It achieves multiple functions through material properties and structural design. Here are its core functions and detailed explanations:
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### **1. Core Function
#### **（1）Sealing to Prevent Leakage
- **Liquid Sealing**: The foam gasket fills the tiny gaps between the bottle mouth and the lid, preventing the leakage of liquids (such as water, beverages, oils).
- **Gas-tightness Maintenance**: For carbonated beverages, beer, and other gases-containing liquids, the gasket maintains its elastic deformation to prevent the escape of carbon dioxide, maintaining the internal pressure of the bottle, and avoiding the "leakage" of the beverage to change its taste.
- **Protection against external contamination**: Prevent dust, bacteria, or air from entering the bottle (e.g., for medicine bottles requiring sterile sealing).
#### **(2) Buffering and Damping
- **Transport Protection**: During transportation or when falling, the gasket absorbs the impact energy, reducing the risk of damage to the cap and bottle mouth due to hard contact (especially for glass bottles).
- **Protection against opening and closing**: When repeatedly opening and closing the bottle cap, the gasket's elasticity can reduce the wear on the thread, extending the service life of the bottle cap.
#### **(3) Adaptive Compensation**
- **Tolerance Compensation**: The manufacturing tolerances of the bottle mouth or lid may cause size deviations, and the foam gasket compensates for the gap by compressing and deforming, ensuring the reliability of the seal.
- **Temperature Change Adaptation**: In environments with temperature changes (such as refrigeration or high-temperature transportation), the difference in material expansion coefficients may affect the sealing, and the elasticity of the foam gasket can be dynamically adjusted to form deformation.
