ASTM D1693: Evaluating Environmental Stress Cracking in Plastics

The standard test method ASTM D1693 evaluates Environmental Stress Cracking Resistance (ESCR) of Ethylene plastics, by chemical immersion of pre-stressed specimens at elevated temperatures. High local multiaxial stresses are created as described in this test method by the controlled introduction of a defect. Environmental stress-cracking has been seen to happen most frequently in these circumstances.The resulting ESCR value indicates Slow Crack Growth susceptibility of Polyethylene resins. Read more about ASTM D 1693 below.

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ASTM D1693: Evaluating Environmental Stress Cracking in Plastics

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Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

ASTM D1693 describes a standard method of test for determining the resistance to environmental stress cracking (ESCR) of ethylene plastics. This type of cracking arises from a combination of mechanical stress and exposure to specific chemicals, and it often results in premature, and sometimes catastrophic, failure of the plastic part.

The ASTM D 1693 technique approximates ESCR by immersing unstressed or prestressed plastic specimens in high-temperature chemical environments. A controlled defect is introduced to generate localized multiaxial stresses, one of the conditions under which stress cracking most frequently occurs. The resulting ESCR values provide a measure of a material’s susceptibility to slow crack growth and long-term failure.

Scope, Applications, and Benefits

Scope

ASTM D1693 outlines procedures for assessing the resistance of ethylene plastics to environmental stress cracking under chemically aggressive conditions.
It evaluates:

Susceptibility of polyethylene to slow crack growth
Crack initiation and propagation behavior
Resistance to combined chemical and mechanical stress
Material durability under simulated service conditions

The method applies primarily to polyethylene and related ethylene-based plastics commonly used in industrial and consumer products.

Applications

Automotive plastic components (e.g., lighting and housings)
Packaging containers and closures
Pipes, tanks, and chemical storage products
Consumer goods exposed to detergents and chemicals
Quality control of polyethylene resins
Material selection for chemically demanding environments

Benefits

Identifies materials prone to environmental stress cracking
Supports the selection of ESC-resistant polymers
Helps prevent premature and catastrophic product failures
Improves material reliability and service life
Enables standardized comparison of polyethylene resins
Enhances quality assurance and product safety

Test Process

Specimen Preparation

Plastic specimens are molded or cut and formed into loops or U-shaped samples to introduce controlled stress concentrations.

Chemical Immersion

Specimens are immersed in a specified chemical agent at elevated temperature to simulate aggressive service environments.

Exposure & Monitoring

Samples are maintained under exposure for a defined period (often several hundred hours) and monitored for crack initiation and growth.

Crack Evaluation

The number, size, and location of cracks are recorded to assess environmental stress cracking resistance.

Technical Specifications

Parameter	Details
Applicable Materials	Ethylene plastics, primarily polyethylene
Specimen Geometry	Loop or U-shaped specimens
Stress Introduction	Controlled bending to create localized multiaxial stress
Exposure Medium	Chemical agent relevant to the intended service
Measured Outputs	Time to crack, crack density, crack severity

Instrumentation Used for Testing

Temperature-controlled chemical bath
Chemical immersion containers
Specimen holders or jigs for looped samples
Timers and monitoring systems
Optical magnification tools for crack inspection
Data recording and reporting tools

Results and Deliverables

Environmental stress cracking resistance ranking
Crack initiation time and failure behavior
Crack location, size, and distribution data
Comparative performance of polyethylene resins
Data supporting material qualification and selection
Quality control documentation for ESC resistance

Frequently Asked Questions

ASTM D1693 is the standard test method for ethylene plastics' environmental stress cracking resistance. The resistance is estimated by immersing unstressed and prestressed specimens into chemicals at increased temperatures.

It is a process that occurs in plastic materials when they are subjected to stress and certain chemicals. Stress is produced by mechanical forces on the material, such as tension or compression, or it can be induced by the environment, such as temperature changes or UV radiation.

Prevention of ESC can be achieved by abiding the following steps: By ensuring the selection of ESC-resistant materials, By Designing products to avoid stress concentrations and By optimizing processing techniques to minimize internal stresses.

The specimens are exposed to a particular chemical agent according to their anticipated use. The duration of the testing is variable but usually runs into a few hundred hours. During this time, the specimens are continually monitored for any cracking tendencies.