Chemical Resistance of Elastomers According to ASTM D471 – Analysis of Rubber Properties

Chemical resistance of elastomers is the ability of rubber materials to maintain stability when in contact with chemical substances over a long period of time without deterioration of their properties. Chemically resistant materials retain their functional properties and remain insensitive to the destructive effects of chemicals. If elastomers are not sufficiently resistant to the action of various liquids, they may begin to swell, harden, soften, or their mechanical properties (tensile strength, elongation) may deteriorate, which directly results in a reduction of their service life.

What is the ASTM D471 standard?

ASTM D471 is a globally recognized standard test method used to determine the effect of various liquids, such as fuels, oils, and other chemical substances, on the properties of rubber. The physical properties of materials are of key importance in many industries where rubber products are exposed to harsh environmental conditions. Contact with chemicals may be continuous or intermittent and may occur at both low and high temperatures.

Testing rubber materials makes it possible to understand how the concentration of a chemical substance and operating temperature determine the industries and applications in which a given elastomer can be used. Chemical resistance tests indicate which range of chemicals a rubber product can be exposed to in order to maintain durability and functionality throughout its expected service life.

Purpose and significance of the ASTM D471 standard

The ASTM D471 test method examines the reaction of elastomers to direct contact with specific working liquids over an extended period of time. Rubber samples are used for this purpose. Various rubber testing methods make it possible to determine how rubber material behaves in different chemical environments. ASTM D471 rubber property testing standardizes the assessment of chemical resistance of rubber materials, allowing any user (designer, manufacturer, customer) to verify and compare the resistance of different elastomers based on the same criteria.

Main objectives of rubber testing according to ASTM D471:

• assessment of rubber material compatibility – chemical resistance tests are used to determine whether a given elastomer compound is able to withstand the action of a specific working liquid over a long period of time;

• predicted service life – evaluates how chemical factors affect changes in material properties, such as swelling, hardness, or tensile strength after immersion in a liquid;

• ensuring operational safety and reliability – rubber material testing minimizes the risk of failures, leaks, or installation damage. Rubber property testing confirms that a given elastomer will provide stable, long-term, and safe performance in environments exposed to large amounts of chemical substances.

ASTM D471 test method – benefits of rubber property testing

Avoidance of failures and unplanned downtime

ASTM D471, as a method for testing rubber material properties, allows assessment of how the physical and mechanical parameters of elastomers change when exposed to a specific liquid for a defined period of time. Understanding how different chemicals affect materials significantly reduces the risk of unwanted leaks, premature component damage, system failures, and associated costs.

Increased product and process safety

Rubber testing according to ASTM D471 plays an important role in increasing the safety level of rubber products, especially in applications where they come into contact with aggressive chemicals. Proper and careful selection of materials for specific applications is particularly important in areas where product safety is critical. This is especially relevant in the medical, pharmaceutical, and food industries.

Extended component service life

The ASTM D471 test method allows evaluation of changes in volume, hardness, and mechanical properties of rubber (cracking, swelling, loss of elasticity) after contact with chemical substances, making it possible to select rubber materials with the highest operational resistance and limit premature aging, which has a positive impact on component durability and operating costs.

Method for testing chemical resistance of elastomers according to ASTM D471

The stages of chemical resistance testing of elastomers according to ASTM D471 consist of several steps:

• Preparation of rubber samples – rubber samples are prepared according to the standard dimensions specified in ASTM D471. They have defined dimensions, markings, mass, and hardness. Before testing, samples are cleaned and weighed.

• Selection of a specific chemical substance – the choice of a specific liquid depends on the purpose and application of the rubber product. Various liquids are used, such as fuels, oils, lubricants, hydraulic fluids, etc.

• Testing (immersion) – prepared samples are immersed in the test liquid under controlled conditions, including a defined time and temperature.

• Measurement – after exposure, physical properties (mass, volume, hardness) and mechanical properties (tensile strength and elongation) are analyzed in comparison to the initial condition.

• Evaluation and reporting of test results – all changes are documented and assessed, with attention paid to any significant changes related to rubber specifications and properties.

How does rubber react to chemicals?

The ASTM D471 test method is a fundamental tool for assessing the impact of chemical liquids on rubber properties, such as changes in mass, volume, hardness, or mechanical properties. Chemical compatibility is one of the key parameters in selecting elastomers for industrial applications. Elastomer reactions to chemicals can be divided into several categories:

• diffusion and swelling – penetration of foreign substances into the polymer structure of rubber leads to volumetric swelling, resulting in an increase in volume and mass, a decrease in hardness, and reduced mechanical strength;

• plasticizer extraction – plasticizers are additives introduced into rubber during production to soften the elastomer, improve flexibility, and reduce hardness. Extraction occurs when the chemical medium (e.g. solvent, detergent, hot water) migrates from inside the rubber into the surrounding liquid, leading to increased hardness, reduced elasticity, brittleness, and cracking;

• chemical reactions – direct chemical reactions may occur between the medium and the elastomer, destabilizing chemical bonds and often leading to permanent and irreversible changes in rubber properties, such as significant increases or decreases in hardness, loss of tensile strength, or reduced service life;

• physical changes – long-term contact of rubber with chemical substances often leads to physical property changes resulting from disturbances in the polymer structure, including reduced tensile strength, loss of elasticity and resilience, and decreased fatigue resistance under prolonged chemical exposure.

It should be noted that the ASTM D471 rubber testing method is not limited to observing swelling or mass changes. A crucial element of chemical resistance assessment is the comparison of mechanical properties before and after exposure.

How do elastomers behave under CIP/SIP conditions?

Evaluation of elastomer chemical resistance to CIP (Clean in Place) and SIP (Sterilize in Place) processes is widely used in the food, dairy, pharmaceutical, and biotechnology industries.

In these processes, elastomers are exposed to cleaning and sterilizing agents, including detergents and oxidizing agents, hot alkaline and acidic solutions, high-temperature steam, and cyclic temperature changes. Under such conditions, rubber swelling is commonly observed, often accompanied by an increase in mass or a change in hardness, which may lead to leaks. A gradual loss of chemical resistance is also observed during repeated cycles.

Therefore, in CIP/SIP applications, long-term resistance to cyclic chemical and thermal exposure and proper elastomer selection (e.g. EPDM, FKM) for the specific process are of key importance.

How to effectively protect rubber products against chemical exposure?

To effectively protect rubber products from degradation caused by chemical exposure, it is essential to select the appropriate elastomer for a specific application. Each type of rubber exhibits different resistance to oils, fuels, acids, alkalis, or steam. Analysis of the operating environment helps reduce the risk of diffusion and swelling, loss of elasticity and resilience, and material degradation. Chemical resistance tests conducted in accordance with ASTM D471 allow evaluation of changes in mass, volume, hardness, and mechanical properties. It is worth comparing materials and selecting solutions with the highest chemical resistance and operational stability.

At the rubber compound design stage, the curing system and the selection of fillers and plasticizers are equally important, as they can improve chemical resistance. Monitoring rubber behavior during operation also allows early detection of degradation symptoms and prevention of failures.

In summary, effective protection of rubber products against chemical exposure is based on proper material selection, ASTM D471 rubber testing, quality control, and supervision of operating conditions.

Rubber products according to ASTM D471 available at the Power Rubber store

At the Power Rubber store, we offer rubber products whose chemical resistance has been assessed in accordance with the requirements of the ASTM D471 standard. We will be happy to assist in selecting the appropriate material for a specific application, including conditions requiring high chemical resistance.

Please contact us by phone: +48 22 292 40 24 or +48 505 16 03 03, by email (Power@PowerRubber.com), or via our contact form.