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D5644-23 – Standard Test Method Technical Guide
📐 Scope and Significance of ASTM D5644-23
ASTM D5644-23 establishes a standard test method for determining the average particle size distribution of recycled vulcanizate particulate rubber. Specifically designed for particles 90 µm (170 mesh) or larger, this method employs a mechanical vibratory sieve shaker to achieve consistent and reliable separations. The values stated in SI units are regarded as the standard, ensuring universal scientific applicability.
The significance of this test lies in its critical role in quality control and product characterization. The particulate size distribution is directly used to assign a product mesh or average particle size designation, which influences processing behavior, material handling, and end-use performance of the recycled rubber compound.
⚠️ Regulatory Compliance Note
This standard was developed in accordance with internationally recognized principles on standardization established by the WTO TBT Committee. Users are responsible for establishing appropriate safety, health, and environmental practices and determining the applicability of regulatory limitations prior to use.
This standard was developed in accordance with internationally recognized principles on standardization established by the WTO TBT Committee. Users are responsible for establishing appropriate safety, health, and environmental practices and determining the applicability of regulatory limitations prior to use.
⚙️ Test Procedure and Material Specifications
The mechanical vibratory sieve shaker method requires a specimen of 100 ± 1 g of recycled vulcanizate rubber. To prevent agglomeration of fine particles during the test, a fixed amount of flowing agent is combined with the specimen. Common flowing agents include hydrous magnesium silicate (talc), fumed aluminum oxide, fumed silica, or calcium carbonate.
The specimen is placed on top of a stacked series of mesh sieves, arranged with the coarsest sieve on the top and the finest at the bottom. The stack is then placed in a mechanical vibratory sieve shaker for a duration of 10 to 20 minutes, depending on the particle size classification of the material. Following the shaking period, the weight of the rubber retained on each individual sieve is recorded to calculate the size distribution.
| 🟦 Agent Type | 🔬 Chemical Nature |
|---|---|
| Talc | Hydrous Magnesium Silicate |
| Fumed Alumina | Aluminum Oxide (Al₂O₃) |
| Fumed Silica | Silicon Dioxide (SiO₂) |
| Calcium Carbonate | CaCO₃ |
💡 Anti-Agglomeration Strategy
The choice of flowing agent can be critical for accurate results, especially for very fine mesh sizes. The agent ensures that individual rubber particles do not stick together, allowing for precise separation and reliable weight retention data on the sieves.
The choice of flowing agent can be critical for accurate results, especially for very fine mesh sizes. The agent ensures that individual rubber particles do not stick together, allowing for precise separation and reliable weight retention data on the sieves.
📊 Classification and Particle Size Designation
The product designation for mesh size is based on specific retention limits defined in Classification D5603. No rubber particles shall be retained on the zero screen. For the designated sieve size, the method sets strict upper limits for the retained weight percentage to ensure consistent product grading.
| 📏 Particle Size Range | 🎯 Upper Limit Retained (max %) |
|---|---|
| Up to 850 µm (≥20 mesh) | 5% |
| 850 to 150 µm (20 to 100 mesh) | 10% |
| 125 to 20 µm (120 to 635 mesh) | 15% |
This classification system ensures that product specifications are consistently met. The weight percent retained on a specific screen is noted as a core metric of the test. Understanding these limits is essential for manufacturers and end-users who rely on the D5644 standard to characterize and specify recycled vulcanizate rubber.
❓ Frequently Asked Questions
🔍 What is the scope of this test method? The standard covers the mechanical vibratory sieve shaker test method for determining particle size distribution of recycled vulcanizate particulate rubber for particles 90 µm (170 mesh) or larger.
💡 Why must a flowing agent be added to the specimen? A flowing agent, such as hydrous magnesium silicate (talc) or fumed silica, is added to a 100 ± 1 g specimen to prevent the rubber particles from sticking together or agglomerating during the sieve shaking process.
⚡ What is the duration of the sieve shaker test? The mechanical vibratory sieve shaker runs for a duration of 10 to 20 minutes. The exact time depends on the particle size classification of the recycled rubber as defined in Classification D5603.
📌 How is the product mesh size designation assigned according to D5603? The designation is based on the size designation screen that retains a specific maximum percentage of material. The thresholds are 5% for particles up to 850 µm (20 mesh), 10% for 850 to 150 µm (20-100 mesh), and 15% for 125 to 20 µm (120-635 mesh). No rubber particles shall be retained on the zero screen.