ASTM D1693 Environmental Stress-Cracking of Ethylene Plastics

Get Certified ASTM D1693 Testing for Reliable Stress-Cracking Resistance

Resin producers and fabricators want to be sure polyethylene can withstand cracking under real-world stress and chemical exposure. That’s where certified testing comes in—it confirms the material’s resistance to stress cracking before a resin or finished part is put through tough service conditions. By relying on independent laboratory testing, they can eliminate the uncertainty in choosing the right materials and ensuring quality.

The scope of ASTM D1693 includes:

• Material type: Ethylene plastics, including polyethylene homopolymers and copolymers, as defined in ASTM D883.
• Purpose: Screening resins and finished products for susceptibility to environmental stress-cracking.
• Properties evaluated: Proportion of specimens that crack and time to 50% failure (F50) under constant strain.
• Testing Method: Bent, notched specimens immersed in an Igepal surfactant reagent at a controlled temperature (Condition A, B, or C).
• Result: Failure time or cracked proportion reported in hours at the stated temperature and reagent concentration.
• Test Limitations: Results reflect only the stated test conditions and should not be used directly for engineering design.
• Use conditions: Constant-temperature reagent bath, typically 50 °C with aqueous Igepal or 100 °C with full-strength reagent.
• Applications: Pipe, film, wire and cable coating, packaging, and molded polyethylene products.

What are the Uses of ASTM D1693 Testing?

This test method serves a variety of purposes, including resin qualification, quality control, and comparing different materials. Manufacturers often pit new polyethylene formulations against tried-and-true grades, all while keeping the test conditions the same. On the other hand, fabricators rely on these results to predict how well a finished part will hold up against long-term chemical and mechanical stress. Screens polyethylene resins during formulation development.This standard-

• Ensures quality control throughout different production batches. 
• Evaluates the stress-cracking resistance of various competing materials. 
• Aids in diagnosing field failures associated with brittle cracking. 
• Offers a regular inspection process for incoming resin shipments.

Which Materials Can Be Tested Under ASTM D1693?

This method examines polyethylene homopolymers and copolymers, which fall under the category of ethylene plastics. Labs typically assess high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), especially those used in pipe and film applications. Whether molded, extruded, or blow-molded, these products are eligible for testing, along with compression-molded plaques. As a result, various industries, including pipe manufacturing, packaging, and wire and cable production, rely on this method to evaluate the performance of their resins.

Why is ASTM D1693 Important?

This test method is crucial because it uncovers a failure mode that many other mechanical tests overlook. Environmental stress-cracking can lead to a surprising number of brittle failures in polyethylene parts. Even if a component is under stress that’s well within its rated strength, it can still crack when it comes into contact with specific chemicals. That’s why this screening method is so valuable for producers and fabricators; it helps them choose resins that can withstand long-term cracking in real-world conditions.

ASTM D1693 Testing Process and Data Collection Guide

The process begins with a technician slicing specimens from a molded plaque or finished product. A jig then creates a precise notch along one wide side of each strip. Next, the bending clamp folds each specimen into its holder before it dips into the reagent bath. Finally, the lab keeps track of any cracking observations over time and figures out the F50 failure time.

Common Challenges and Troubleshooting

When the notch depth isn’t consistent or if the notching jig is damaged, it can really throw off the stress-cracking results. Plus, factors like reagent concentration or temperature changes during a lengthy test can influence how long it takes for a failure to occur. Any leftover molding stress in the specimen can also speed up cracking, regardless of the bend applied. To tackle these challenges, labs make it a point to regularly inspect their jigs, calibrate their reagent baths, and ensure that specimen conditioning is standardized.

• The laboratory reports the proportion or percentage of specimens showing visible cracking at each specified observation interval and records the corresponding exposure time in hours.
• Analysts determine the F50 value, expressed in hours, from the observed failure data to identify the exposure time associated with 50% specimen failure.
• Engineers compare F50 values and cracking behavior with a reference resin tested under identical conditions to evaluate relative environmental stress-cracking resistance.
• Laboratory technicians document the test conditions, including reagent concentration, bath temperature, specimen condition, and exposure period, alongside the reported failure results.
• Engineers interpret the results as comparative stress-cracking resistance data rather than direct engineering design values and evaluate materials according to the specified test conditions and intended application.

Link to ASTM D1693