Practice A: Immersion Test
Practice A is all about immersing test specimens in a chemical reagent to simulate exposure in real-world applications (like a plastic container for a chemical, or a pipe for a chemical). It is further broken down into two procedures:
Procedure I: Immersion for Short-Term Effects
Objective: To evaluate the effect of a chemical reagent on the plastic material after a relatively short period of time. This is useful for applications where the material might see occasional or brief contact with the chemical, such as spills or splashes.
Methodology: Test specimens are fully immersed in the specified chemical reagent.
Evaluation: After a specified exposure time (e.g., 7 days, 14 days), the specimens are removed from the reagent and are typically evaluated for:
Changes in weight: Did the material absorb the chemical (weight gain) or lose material (weight loss)?
Changes in dimensions: Did the material swell or shrink?
Visual changes: Did it show signs of discoloration, cracking, crazing, blistering, or surface attack?
Changes in mechanical properties: While the standard doesn’t require it for a simple “pass/fail,” it does include provisions for measuring properties like tensile strength, elongation, or hardness before and after the test to get quantitative data on degradation.
Procedure II: Immersion for Long-Term Effects
Objective: To evaluate the effect of a chemical reagent on the plastic material after a prolonged period of time. This is for applications where the plastic will be in constant or long-term contact with the chemical, such as in transfer lines, containers, or chemical processing equipment.
Methodology: Identical to Procedure I, test specimens are fully immersed in the specified chemical reagent.
Evaluation: The key difference is the duration of exposure. Procedure II involves much longer immersion periods, which can be defined by the end-use requirements (e.g., 30 days, 60 days, 90 days, or even longer).
Purpose: This procedure is used to predict the long-term durability and chemical compatibility of the plastic material, revealing slow-acting degradation mechanisms that might not be apparent in a shorter test.
