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Understanding Latex Foam Rubber Specifications: SAE J17-2009 and ASTM D 1055
Latex foam rubbers are widely used in automotive applications for cushioning, seating, and sealing due to their open-cell structure. The standard SAE J17-2009, Latex Foam Rubbers, provided specifications for these materials but was officially cancelled in October 2009 and superseded by ASTM D 1055. Despite its cancellation, the standard’s definitions, grade designations, and testing methods remain a valuable reference for engineers and specifiers. This article summarizes the key aspects of SAE J17 and explains how to use it in conjunction with the current ASTM standard.
⚠️ Important Note: SAE J17-2009 has been cancelled and is no longer maintained. Users should refer to the current ASTM D 1055 specification for new designs and procurement. However, understanding J17 can help interpret legacy requirements and the transition between standards.
Grade Designations and Physical Properties
SAE J17 defined two main categories of latex foam rubber based on structure: cored (RC) and uncored (RU). Cored materials have internal voids designed for specific load-deflection characteristics, while uncored materials are solid throughout. The grade number indicates firmness, with lower numbers for softer grades and higher numbers for firmer grades. For example, RC10 is a soft cored foam, while RC70 is very firm.
The standard specified basic physical requirements including indentation force at 25% deflection, compression set, and aged air oven change. The following table shows selected grades from SAE J17 Table 1.
| Grade | Indentation Force (N) at 25% Deflection | Compression Set (Constant Deflection) Max % |
|---|---|---|
| RC10 | 44 ± 13 | 10 |
| RC20 | 89 ± 18 | 10 |
| RC30 | 133 ± 27 | 10 |
| RU20 | 89 ± 22 | 10 |
| RU35 | 156 ± 44 | 10 |
| RU55 | 245 ± 44 | 10 |
🛠️ The indentation test is performed on a 325 cm² specimen with 25% deflection; the compression set is measured after 22 hours at 70°C and 50% deflection. All grades also required an air oven aged change of no more than ±20% from original load.
Suffix Letters for Additional Test Requirements
Beyond the basic requirements, SAE J17 allowed the use of suffix letters to specify additional tests. These suffixes indicate that the latex foam must meet extra performance criteria, agreed upon between purchaser and supplier. For example:
- F1/F2 – Low temperature flexibility at –40°C or –55°C
- H – Flexing resistance (dynamic fatigue)
- P – Staining test
- E – Oil resistance
- R – Resilience
A typical designation might be RC20 F1H, indicating a soft cored foam with low-temperature and flexing resistance requirements.
🔍 Engineering Design Insight: When specifying latex foam, always consider the end-use environment. Suffix letters allow precise tailoring: choose F for cold climates, H for dynamic cushions, or P where staining could be a cosmetic issue. Work with suppliers to ensure test methods and acceptable values are clearly defined, as the standard does not specify pass/fail limits for all suffixes.
Frequently Asked Questions
- What is the difference between cored (RC) and uncored (RU) latex foam?
Cored foam contains internal air pockets or channels that reduce weight and modify compression characteristics; uncored foam is solid throughout and typically used where higher load capacity or a smooth surface is needed. The indentation force ranges differ between the two types. - What does the grade number mean?
The grade number approximates the indentation force in pounds (lbf) at 25% deflection on a standard 50 in² specimen. Lower numbers are softer, higher numbers are firmer. Always refer to the tolerance range, as the actual force can vary. - Which tests are required for all grades?
Basic tests include indentation, compression set (constant deflection), and air oven aging. Additional suffix tests (e.g., flexing, low temperature) are only required if specified in the grade designation. - Why was SAE J17 cancelled, and what should I use now?
SAE J17 was a mirror of ASTM D 1055, and the SAE committee lacked expertise in latex foam. ASTM D 1055 (now under D20.22) is the current, maintained specification for flexible cellular materials—latex foam. Always specify ASTM D 1055 for new products.
By understanding the structure of SAE J17, engineers can more effectively navigate legacy documentation and ensure accurate material selection.
