Environmental stress cracking occurs in polymers due to what conditions?

Environmental stress cracking occurs in polymers due to what conditions?

• A. Solvent or chemical exposure under stress.
• B. Exposure to high humidity only.
• C. Thermal cycling without solvents.
• D. Ultraviolet light exposure with no stress.

Answer: (A)

Environmental stress cracking happens when a polymer is under mechanical stress and is exposed to a chemical environment, typically a solvent. The solvent diffuses into the polymer near the stressed areas, causing swelling and plasticization that lowers the material’s resistance to crack growth. With the stress present, cracks can initiate and propagate more readily than they would in dry conditions. This combination—solvent or chemical exposure plus stress—best describes the phenomenon. The other scenarios miss either the chemical attack or the concurrent stress needed for cracking to occur: humidity alone, thermal cycling without solvents, or ultraviolet exposure without stress don’t produce ESC by themselves.

Environmental stress cracking happens when a polymer is under mechanical stress and is exposed to a chemical environment, typically a solvent. The solvent diffuses into the polymer near the stressed areas, causing swelling and plasticization that lowers the material’s resistance to crack growth. With the stress present, cracks can initiate and propagate more readily than they would in dry conditions. This combination—solvent or chemical exposure plus stress—best describes the phenomenon. The other scenarios miss either the chemical attack or the concurrent stress needed for cracking to occur: humidity alone, thermal cycling without solvents, or ultraviolet exposure without stress don’t produce ESC by themselves.