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SAE J1639: Classification System for Automotive Polyamide Plastics
SAE J1639-2017 provides a standardized classification and specification system for a limited set of polyamide (nylon) materials used in the automotive industry. Based on ASTM D4066, this recommended practice adds automotive-specific descriptive characteristics and property requirements. It is designed to help engineers and specifiers select and call out polyamide 66, 6, and 66/6 compounds, including unreinforced and reinforced grades, using a simple line call-out designation.
While SAE J1639 is now stabilized and no longer updated, it remains a reference for legacy systems and for understanding the typical property sets required for automotive polyamide applications. For current projects, ASTM D6779 is recommended as it covers a broader range of materials and is actively maintained.
Understanding the Classification System
The standard organizes polyamide materials into three tiers: groups, classes, and grades.
- Groups define the base polymer chemistry: PA66 (01 unreinforced, 11 reinforced/filled), PA6 (02 unreinforced, 12 reinforced/filled), and PA66/6 (18 reinforced/filled).
- Classes specify the modification type, such as injection molding grade, impact modified, glass fiber reinforced, mineral filled, or hydrolysis resistant.
- Grades designate the nominal filler content (e.g., 15%, 35% glass) or a specific formulation.
The following table shows a few standardized grades from the standard:
| PA Group | Description | Filler Content | Designation |
|---|---|---|---|
| PA66 unreinforced | General injection molding | Unreinforced | 0121 |
| PA66 reinforced | Glass fiber reinforced, impact modified, heat stabilized | 15% glass | 1122 |
| PA6 reinforced | Glass fiber reinforced, heat stabilized | 35% glass | 1216 |
| PA66/6 reinforced | Glass fiber reinforced, heat stabilized | 35% glass | 1816 |
All materials covered by this standard are heat stabilized and intended for natural or non-color matched black compounds only.
Specifying Materials with the Line Call-Out
SAE J1639 uses a line call-out system that packs a lot of information into a compact code. The format is:
SAE J1639PAXXXXwhere PA indicates polyamide, and the four-digit number encodes group, class, and grade. The first two digits are the group, the third is the class, and the fourth is the grade. For example:
SAE J1639PA1122: PA66, reinforced group (11), class 2 (glass reinforced, impact modified, heat stabilized), grade 2 (15% glass).
🛠️ Design Insight: The line call-out system provides a concise and unambiguous way to specify material requirements in engineering drawings and procurement documents. Always include the full specification identifier to ensure clarity.
Engineering Considerations and Common Pitfalls
When using SAE J1639, keep these important points in mind:
- Scope limitation: This standard covers only natural and non-color matched black compounds. Color-matched parts must be specified using proprietary OEM standards.
- Stabilized status: SAE J1639 is declared stabilized and is no longer updated. The materials it covers are now included in ASTM D6779, which offers a more extensive and up-to-date listing.
- Recycled materials: The standard permits recycled, reconstituted, and regrind materials as long as they meet all requirements and are identified.
- Test methods: The document references several SAE, ASTM, and ISO test methods for characterizing properties such as flammability, fogging, weathering, tensile strength, and impact resistance.
⚠️ Important: Because SAE J1639 is stabilized, it may not reflect the latest material grades and technologies. For new designs, consider using ASTM D6779 or the appropriate OEM specification. Be sure to verify compliance with current performance requirements.
Frequently Asked Questions
Can SAE J1639 be used for color-matched nylon compounds?
No. The standard explicitly excludes color-matched compounds. Those must be defined by proprietary OEM material standards.
What is the current alternative to SAE J1639 for polyamide specifications?
ASTM D6779 is the recommended replacement. It covers a wider range of materials and is actively maintained, whereas SAE J1639 is stabilized and no longer revised.
How do I create a line call-out for a polyamide material?
Combine SAE J1639 with “PA” and a four-digit code from the tables in the standard. For example, SAE J1639PA1122 specifies a 15% glass reinforced, impact modified, heat stabilized PA66. Refer to Section 5 of the standard for full instructions.
Are recycled materials allowed under this standard?
Yes, as long as they meet all stated requirements and are identified as recycled, reconstituted, or regrind material. The material must not be altered or modified in a way that changes its suitability for processing and use.
