SES N 3238 Rubber Hardness Requirements

Developed by Suzuki Motor Corporation as part of its standards for rubber and elastomer materials, the “SES N 3238 Rubber Hardness Requirements” standard is a technical standard that defines the hardness values of elastomer parts used in the automotive industry. This standard explains how to determine and control hardness, a critical quality criterion, especially for sealing elements (such as gaskets, seals, and gaskets).

The primary purpose of the SES N 3238 standard is as follows:

To define the hardness range (Shore A / IRHD) of rubber materials.
Determining the appropriate hardness levels for different applications.
To provide repeatable measurement methods in production and quality control processes.

Hardness indicates the rubber's resistance to deformation and directly affects performance. Rubber hardness is generally measured using the following methods:

Shore A / Shore D durometer
IRHD (International Rubber Hardness Rating)

These tests are based on measuring the depth of indentation by applying a specific force to the surface of the material.

In the automotive industry, the use of rubber hardness requirements is not just about measuring hardness; it's about designing, selecting, verifying, and controlling rubber parts to ensure they perform correctly throughout the vehicle's lifespan.

In the automotive industry, the required stiffness range is determined during the design phase, depending on the function. For example,

Door seals / airtight strips:
Typically, it should be 50-70 Shore A.
Flexibility and leak-proof properties are required.
Engine gaskets:
Typically, it should be 70-90 Shore A.
Compressive strength and thermal stability are required.
Anti-vibration coupling elements:
Typically, it should be 40-60 Shore A.
Damping capability is required.

At this stage, the SES N 3238 standard is used for the following:

Determining target hardness values.
Defining the acceptable tolerance (e.g., plus/minus 3 Shore A)

When supplying rubber parts, original equipment manufacturers include the SES N 3238 standard in technical drawings. This ensures the following:

All suppliers produce consistent material behavior.
There will be no variation between parties or suppliers.

Rubber parts are tested before mass production. The basic tests include:

Initial hardness measurement (Shore A / IRHD)
After hardening:
Heat aging (e.g., 70-150 degrees)
Oil or fuel exposure
Ozone/UV exposure

The goal is to ensure that the hardness does not change drastically over time.

During production quality control at production facilities,

Each batch is checked using a durometer.
Measurements are compared with SES N 3238 limits.
If it is off-specification, the batch is rejected or a root cause analysis is performed (mixing, curing, etc.).

The correct hardness value has a direct impact during assembly and performance:

Sealing performance:
Too soft: It will cause leaks.
Very hard: Indicates poor contact.
Vibration and noise (NVH):
Softer rubber: Provides better cushioning.
Harder rubber: Means more hardness.
Durability:
Suitable hardness: Means a longer service life.

Failure to meet the SES N 3238 standard hardness requirements will result in door seal failure or poor sealing issues.

The SES N 3238 standard generally includes the following parameters:

Hardness ranges: For example,
Soft rubber: 30-50 Shore A
Medium hardness: 50-70 Shore A
Hardness: 70-90 Shore A

These ranges may vary depending on the type of rubber.

Tolerances: Limits such as plus/minus 3 Shore A or plus/minus 5 IRHD.
Measurement conditions:
Temperature (usually 23 degrees)
Sample thickness
Test duration (e.g., 3-second press duration)
Post-aging hardness: The standard also checks for changes in hardness after the following conditions:
Heat aging
Oil/chemical contact
UV and ozone effect

The SES N 3238 standard applies directly to the following parts:

Door and window seals
Engine gaskets
hoses
Vibration dampers

The SES N 3238 standard is often used in conjunction with the following standards:

ISO 48 Rubber, vulcanized or thermoplastic - Hardness determination (hardness between 10 IRHD and 100 IRHD)
ISO 7619 Rubber, vulcanized or thermoplastic - Determination of indentation hardness.
ASTM D2240 Standard test method for rubber properties - Durometer hardness
ASTM D471 Standard test method for rubber properties - Effect of liquids

These standards support the hardness measurement methodology.

The SES N 3238 standard is essential in the automotive industry because rubber hardness directly controls a part's performance, lifespan, and interaction with other components. Without a clear standard, even small differences in hardness can lead to serious functional and quality problems. This standard is considered important for the following reasons:

Ensures functional performance: Rubber parts are designed for very specific tasks. Seals must compress properly to prevent leaks, assembly elements must absorb vibration, and hoses must withstand pressure without collapsing. Hardness determines all this behavior. This standard defines the correct hardness range, ensuring parts function as intended.
It guarantees consistency among suppliers: Automotive manufacturing involves multiple suppliers worldwide. Without a hardness standard, one supplier could produce 55 Shore A, while another could produce 70 Shore A. Even if both seem correct, the performance will differ. This standard ensures the same hardness range, the same measurement method, and the same acceptance criteria.
Quality control in mass production: Rubber properties can vary due to differences in mixing ratios, curing conditions, or raw materials. This standard ensures clear tolerances and standardized testing conditions.
Ensures long-term durability: Rubber hardness can change over time due to heat, oil and fuel exposure, UV rays, and ozone. If hardness is not controlled, seals will harden, leaks will begin, the rubber will soften, and deformation will occur.
It improves comfort and reduces noise, vibration, and stiffness. Stiffness directly affects vibration damping and noise insulation. This standard ensures optimum ride comfort and quietness.

In conclusion, the SES N 3238 standard stipulates that automotive rubber parts...

To be produced with the correct hardness.
Ensuring its performance
Ensuring standardization among suppliers.

It is a critical engineering standard aimed at ensuring hardness, which is a key parameter in a complete verification process.

For many years, our organization, with its competent and experienced team, has been understanding the needs of its clients, providing the advanced testing services they require, and assisting them in the establishment, implementation, and improvement of management systems. Within this framework, we also provide testing services compliant with the SES N 3238 standard.