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Latex-Dipped Goods and Coatings for Automotive Applications
Standard Overview and Classification
SAE J19 (cancelled August 2005) provides a common specification for dipped goods and coatings manufactured from compounded latex for automotive applications such as boots, coated clips, sponge parts, and fabrics. The standard defines two types of compounds:
- Type LR (Non-Oil Resistant): Made from natural rubber, synthetic rubber, or rubberlike materials for services where petroleum-base fluid resistance is not required.
- Type LS (Oil Resistant): Made from synthetic rubber or rubberlike materials for services requiring resistance to petroleum-base fluids. Only Class LSC remains active under this standard.
Each type has specific grades with prescribed physical property requirements. For example:
| Property | LR 420 | LSC 515 |
|---|---|---|
| Durometer Hardness | 45 ± 5 | 55 ± 5 |
| Min Tensile Strength | 14.0 MPa (2000 psi) | 10.5 MPa (1500 psi) |
| Min Ultimate Elongation | 500% | 400% |
| Heat Aged (70 h at 70 °C LR / 100 °C LSC) | ΔHardness ±5, Tensile min 10.5 MPa, Elongation min 400% | ΔHardness +10, Tensile min 8.5 MPa, Elongation min 300% |
| Oil Immersion (22 h at 100 °C, Oil No. 2) | – | Volume change max 80% |
Test Methods and Practical Considerations
All physical property tests are performed on standard laboratory dipped films prepared using production procedures but with a controlled thickness of 0.63 to 0.75 mm (0.025 to 0.030 in). Test methods follow ASTM standards (D412, D471, D573, D925, D2137, D2240), with the exposure periods and temperatures given in the tables taking precedence. Suffix letters (e.g., E2, F1, G, K1) may be added to a grade designation to specify additional requirements such as oil resistance, low-temperature brittleness, or adhesion. If no test value is provided in the table, the purchaser and supplier must agree on the required value and test method.
🛠️ Engineering Design Insight: Results from standard test films may not duplicate those from finished parts due to differences in geometry and processing. To avoid confusion, the purchaser and supplier should agree on acceptable deviations, ideally by comparing results from test films and actual parts.
⚠️ Cancellation Notice: SAE J19 was cancelled in August 2005 due to lack of industry interest and maintenance expertise. For new designs, consider active alternative specifications such as SAE J200 or ASTM D2000 which cover similar material properties with broader scope.
Frequently Asked Questions
How do I choose between Type LR and LS?
Select Type LR for applications where resistance to petroleum-base fluids is not a concern. Choose Type LS (Class LSC) when oil resistance is required, for example when parts may contact engine or transmission oils.
What do suffix letters mean?
Suffix letters add extra performance requirements beyond the basic table. For instance, E2 requires oil resistance measured by volume change in ASTM Oil No. 2, and F1 requires low-temperature brittleness at –40 °C. They are specified singly or in combination after the grade number.
How should test films be prepared for compliance?
Standard test films are made using the same coagulation, leach, dry, and cure processes as production parts, but with thickness strictly controlled to 0.63–0.75 mm. For durometer hardness, multiple plies are stacked to achieve 4.5–6.3 mm thickness.
Why was J19 cancelled and what are the alternatives?
The standard was cancelled because the industry showed no interest in revising it, and the committee lacked the expertise to maintain it. For new automotive rubber specifications, refer to SAE J200 (classification system for rubber materials) or ASTM D2000, which provide a more modern and comprehensive framework.
