Environmental stress cracking
Under the combined influence of an aggressive fluid and applied stress, thermoplastics may undergo a phenomenon known as environmental stress cracking (ESC). It is responsible for the majority of lifetime shortening of plastic-based products and accounts for about 25% of product failures in service. ESC can be an important issue for many applications and particular risk when the product is used in the medical care. Plastic medical devices often suffer from ESC due to contamination with chemical fluids or drugs combined with mechanical stress during service. This may lead to an increased risk of medicine/blood leakage or air bubble introduction into the therapy system, which is a serious problem for the safety of patients and users. Therefore, the improvement of the environmental stress cracking resistance of polymer based components is an essential part of a product development process. Our research work is focused on investigating if the ESC resistance of polymers in different stress cracking agents and temperatures is affected by the incorporation of nano-scaled fillers.
The assessment of environmental stress cracking with optical crack detection is a new method and efficient approach for determining the ESC resistance of materials and components. In our laboratory, there are three different test set-ups for the ESC investigation as follows:
- Fracture mechanics test method
- Bend strips test method
- Improved method for determining ESC resistance in luer connector