Testing of Polarized Internal Stress

Glass bottle packaging is a common packaging form in pharmaceutical packaging, especially for injectable drugs, such as ampoules, infusion bottles and control molded glass bottles. This is mainly because of the chemical stability of glass containers and their excellent mechanical properties. However, glass bottles are easy to produce internal stress in the production plus over process, the reason for this is: stress refers to the deformation of the glass due to external factors (force, humidity, temperature field changes, etc.), the need to use the glass bottle internal stress detector to detect the internal force that interacts between the various parts of the glass to resist the action of such external factors and try to restore the glass from the position after deformation to the position before the deformation. Therefore, glass bottle manufacturers usually use annealing treatment after the glass bottle is formed, reheat the glass bottle and then cool it to eliminate this residual stress. CD Formulation can perform polarized internal stress test on glass and provide relevant test data to help customers' pharmaceutical packaging meet commercial requirements.

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Analysis of birefringence distribution by polarized light. The distribution and magnitude of refractive index directly reflect the distribution and magnitude of material stress.

Glass bottle polarizing stress meter test method.

The test specimen should be annealed without other tests and must be placed in the laboratory for more than 30 minutes under the temperature conditions in advance, and gloves should be worn during the measurement to avoid direct contact with the test specimen by hand.

1. Test the bottom of the colorless test sample: place the quarter wave plate into the field of view and adjust the zero point of the polarizing stress meter to make it a dark field of view.

2. Put the specimen into the field of view and observe the bottom from the mouth, then a dark cross will appear in the field of view. If the stress of the specimen is small, the dark cross will be blurred. Rotate the detector to separate the dark cross into two arcs moving in opposite directions, and as the dark area moves out, a blue-gray color will appear on the concave side of the arc, and a brown color will appear on the convex side. If the stress value at a selected point is measured, the polarizer is rotated until the blue-gray color is replaced by brown color at that point. Rotate the specimen around the axis to find the Z stress point, rotate the detector until the blue-gray color is replaced by the brown color, record the angle of rotation of the detector at this point, and measure the thickness of the point.

Inspection of the sidewall of the colorless specimen: Place the quarter-wave plate in the field of view and adjust the zero point of the polarizing stress meter to make it a dark field of view. Put the test specimen into the field of view, so that the axis of the test specimen is 45° from the plane of polarization, when the sidewall appears different areas of light and dark. Rotate the polarizer until the dark area on the sidewall meets and just replaces the light area completely. Rotate the specimen around the axis to determine the Z-stress zone. The angle of placement of the detector in the measured Z stress area is recorded, and the original thickness of both walls is measured separately (the sum of the wall thicknesses of both walls is recorded).

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