Stress in pharmaceutical glass bottles

Stresses in glass are generally divided into 3 categories, namely thermal, mechanical, and structural.

1. Thermal stress: The stress caused by the temperature difference in glass products is called thermal stress, which is divided into temporary stress and persistent stress according to its existence.

(1) Temporary stress: the thermal stress generated when the glass below the strain point is subjected to uneven temperature changes, it exists with the existence of the temperature gradient, and the stress that disappears with the disappearance of the temperature gradient is called temporary stress.

(2) Persistent stress: the thermal stress generated when the glass undergoes uneven temperature changes below the strain point, it exists with the existence of the temperature gradient, and when the stable gradient of the glass disappears, the remaining thermal stress is called persistent stress.

2. Mechanical stress: refers to the stress caused by external force in the glass bottle, and the mechanical stress disappears immediately when the external force is removed.

3. Structural stress: The stress caused by the uneven chemical composition of the glass due to the uneven structure is called structural stress, which belongs to the persistent stress, and the stress caused by the inherent structure of the glass cannot be eliminated.