ISO 22088-3 Plastics resistance test equipment to environmental stress cracking (ESC)
ISO 22088-3:2006 Plastics — Determination of resistance to environmental stress cracking (ESC) Part 3: Bent strip method
ISO 22088-3 specifies a method for the determination of the environmental stress cracking (ESC) resistance of thermoplastics when they are subjected to a fixed flexural strain in the presence of chemical agents.
ESC is indicated by the change of a suitably chosen indicative property of specimens that have been strained for a defined time in the environment. The method of test is suitable for determining the resistance of sheets and of flat test specimens, especially the sensitivity of localized surface regions of specimens, to ESC.
Key principle:
Bend the rectangular plastic sample into a U shape and fix it, so that a constant strain is generated on its surface, and then expose it to a specific chemical reagent environment. The ESC resistance is evaluated by observing the appearance of surface cracks or changes in physical properties of the sample after a specified time. This method is suitable for ranking tests of sheets and rigid plastics (with moderate stress relaxation levels).
Testing Methods and Steps
Sample Preparation
Material: Sheet or flat samples, dimensions according to standard requirements (usually strip-shaped).Requirements: Surface without defects, edges smooth and burr-free, to avoid local stress concentration.
Bending and Fixing
Bend the sample along its length to the predetermined curvature (U-shape) and use clamps to secure both ends. The bending strain level must be calculated and set according to material characteristics, ensuring that the tensile area of the sample surface reaches the target strain value.
Environmental Exposure
Immerse the fixed bent sample in selected chemical reagents (liquid/gas) or contact solids containing migrating substances (such as plasticizer materials). Control environmental temperature (usually 23±2°C) and exposure time (set according to material characteristics, such as 24h, 48h, etc.).
Result Evaluation
Qualitative Assessment: Visually inspect the number, length, and distribution of cracks on the surface of the exposed sample (quantify to an accuracy of ±0.01mm).
Quantitative Assessment: Measure changes in physical properties (such as tensile strength decay rate ≥15MPa or critical value of elongation at break ≥200%), comparing to data from unexposed samples. Record the time of the first appearance of cracks or the degree of performance decay over a specific time as an ESC resistance indicator.
Through these steps, the crack resistance of plastic materials under specific environmental conditions can be effectively measured, thereby assisting in the selection of suitable materials for different application scenarios.
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