Bend Test Procedure

To simulate real-world conditions, test specimens are clamped onto strain jigs designed to apply specific levels of mechanical stress. We offer two strain levels for 3 mm and 4 mm thick materials. Once secured, cotton wool saturated with disinfectant or another test chemical is placed in direct contact with the specimen to maintain continuous exposure. The cotton is re-saturated at the start and end of each day to ensure consistent chemical contact throughout the exposure period.

The picture below shows a cotton pad soaked with disinfectant placed on the material while it is held in a bent position.

Evaluation

The specimens are monitored daily for visible signs of damage such as cracking or crazing. After the exposure period, a detailed examination is conducted under low magnification with illumination to detect any minor degradation that may not be visible to the naked eye.

Tensile Testing for Invisible Damage

For specimens that do not show visible damage, further evaluation is conducted via tensile testing using tensometer to detect potential invisible weakening of the material. It is important to note that this test requires dumbbell-shaped specimens, which must be provided by the customer.

Following ISO 22088-3 (ESC Index), a sample is considered to have invisible damage if:

• Mean break or yield stress is <80% of an unstrained, unexposed control sample.
• Mean break or yield strain is <50% of an unstrained, unexposed control sample.

The video below demonstrates how materials break when subjected to pressure using a tensometer, highlighting potential weaknesses not visible to the naked eye.