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D5393-97 – Standard Test Method Technical Guide
📐 Test Scope and Material Conditioning
The ASTM D5393-97 test method evaluates the fogging tendency of vehicle interior trim materials, defined as the deposition of a light-scattering film on glass surfaces. This method is applicable under controlled conditions but has limitations for condensates with low surface tension or large quantities. Materials must be conditioned at 23 ± 2°C and 50 ± 5% relative humidity for 24 hours prior to testing and tested under the same conditions.
| 🟦 Conditioning Parameter | 📏 Required Value |
|---|---|
| Temperature | 23 ± 2°C |
| Relative Humidity | 50 ± 5% |
| Conditioning Duration | 24 hours |
⚙️ Test Procedure and Equipment
A test specimen is placed in a beaker and heated in a temperature-controlled unit. A clean glass plate, with its specular reflectance measured using a 60° glossmeter per ASTM D523, is mounted on the beaker with a silicone rubber seal. Volatile compounds from the material condense on the glass plate, which is then re-measured for gloss to determine the fogging deposit.
📊 Evaluation and Terminology
The fogging number is calculated as the ratio of the 60° glossmeter value of the glass plate with condensate to that of the clean plate, expressed in percent. This metric quantifies the fogging characteristics. Standard terminology defines fogging as the unwanted light-scattering film on interior glass surfaces.
| 🟦 Term | 📐 Definition |
|---|---|
| Fogging | Deposit of undesirable light-scattering film on glass |
| Fogging Number | (Gloss with condensate / Gloss without condensate) × 100% |
⚠️ Test Limitation: This method cannot accurately measure when condensate has low surface tension (forming thin transparent films) or when large quantities create heavy oily films, both causing false glossmeter readings.
💡 Standard Equivalence: ASTM D5393-97 is essentially equivalent to ISO 6452 for determining fogging characteristics of organic trim materials in motor vehicles.
❓ Frequently Asked Questions
🔍 What is the purpose of this test method?
It measures the tendency of interior trim materials to produce a light-scattering fog film on glass surfaces in a controlled environment.
💡 How is the fogging number calculated?
The fogging number is the quotient of the 60° glossmeter value of the glass plate with fogging condensate to that without condensate, expressed in percent.
⚡ What are the key limitations of this test?
The test is not accurate for condensates with low surface tension that form transparent films or for heavy deposits that form oily films, leading to inaccurate gloss measurements.
📌 Is this standard related to any ISO standard?
Yes, ASTM D5393-97 is essentially equivalent to ISO 6452, which addresses similar fogging tests for motor vehicle trim materials.