Test Assembly for Environmental Cracking of PE Jacket (UL 1072)

The following is a detailed explanation of the test assembly used to evaluate the environmental stress cracking of polyethylene (PE) jackets as per UL 1072 standards. This test ensures the material's reliability and durability under environmental conditions.

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Components of the Test Assembly

1. Test Specimen
- Dimensions:
 

• • Thickness: 0.125 ± 0.005 inches (3.0 ± 0.1 mm)
  • Length: 1.5 ± 0.1 inches (38 ± 2.5 mm)

- The test specimen is a precisely cut section of the PE jacket.
- Ensures uniformity and repeatability across multiple tests.

2. Specimen Holder
- Constructed from hard or half-hard brass for durability and precision.
- Dimensions:
 

• • Width: 3/8 inch (10 mm)
  • Holes: 37/64 inch (15 mm) to securely grip the specimen.
  • Additional features like toothed edges or clamps to stabilize the specimen.

- Purpose:
  - Holds the test specimen in a fixed position.
  - Ensures uniform stress during the test.
  - Allows controlled exposure to the reagent.

3. Reagent Container (Test Tube)
- Made from hard glass to withstand environmental conditions and chemical exposure.
- Dimensions:
 

• • Diameter: 32 mm
  • Height: 200 mm

- Holes: Includes 10 holes of 3/16 inch (5 mm) diameter for ventilation, spaced at 19/32 inch (15 mm).
- Purpose:
  - Holds the chemical reagent.
  - Covers the mounted test specimen with the reagent, ensuring 1/2 inch (13 mm) above the specimen.

4. Cork Closure
- A foil-covered cork is used to seal the test tube.
- Purpose:
  - Minimizes evaporation of the reagent.
  - Maintains consistent testing conditions.

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Test Procedure

Step 1: Specimen Preparation
- Cut the PE jacket into precise dimensions (1.5 inches in length and 0.125 inches thick).
- Ensure the specimens are clean and free from contaminants.
- Mount the specimens securely onto the brass holder.

Step 2: Reagent Placement
- Add the chemical reagent to the glass test tube.
- The reagent level must cover the mounted specimen, ensuring 1/2 inch (13 mm) above the top of the specimen.

Step 3: Test Tube Assembly
- Place the test tube in the holder and seal it with the foil-covered cork to prevent evaporation.
- Ensure the ventilation holes are positioned properly to maintain atmospheric consistency.

Step 4: Testing Duration
- The assembly is subjected to controlled environmental conditions for a specified time, usually 48 hours.
- Parameters like temperature and humidity are maintained as per UL 1072 requirements.

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Objective of the Test
- To evaluate the PE jacket's resistance to environmental stress cracking caused by chemical exposure and mechanical strain.
- The test replicates real-world conditions that cables may face during operation.

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Key Standards
- The procedure adheres to UL 1072, which specifies requirements for PE jacket materials used in cables.
- Results ensure the safety, durability, and compliance of cable materials in diverse environments.

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Conclusion
This test assembly is critical for evaluating the performance and reliability of PE jackets. By identifying vulnerabilities under stress, manufacturers can improve material quality and ensure compliance with industry standards.