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D6339-11 – Standard Test Method Technical Guide
This classification system, formally titled ASTM D6339 – 11 (Reapproved 2019), establishes a standardized framework for specifying syndiotactic polystyrene (SPS) materials intended for molding and extrusion. Encompassing homopolymers, copolymers, blends, and impact-modified grades, this standard provides a precise language for material communication via a structured line callout system aligned with the broader ASTM D4000 specification infrastructure for plastics.
📐 Scope and Material Designation
The scope of D6339 covers SPS materials suitable for molding and extrusion. It is intended to provide a means of calling out plastic materials used in the fabrication of end-use items or parts. A critical caveat within the scope explicitly clarifies that this system is not intended for the initial selection of materials, which requires expert consideration of design, environment, and economics. The primary identification of a given composition relies on the properties defined in the standard’s cell table, while additional requirements for specialized applications are designated using the suffix system detailed in Section 5. Notably, the standard contains a specific note indicating there is no known ISO equivalent to this standard.
⚙️ Key Properties and Referenced Test Methods
The backbone of the classification system is the suite of standardized test methods used to measure the relevant properties of SPS materials. The table below summarizes the principal mechanical, thermal, and physical tests referenced in the standard.
| 📏 Property Category | ⚡ Standard Test Method | 🎯 Significance for SPS |
|---|---|---|
| Tensile Properties | ASTM D638 | Critical for mechanical design calculations |
| Flexural Properties | ASTM D790 | Measures material stiffness in end-use parts |
| Izod Impact Resistance | ASTM D256 | Determines toughness and durability under stress |
| Deflection Temperature (HDT) | ASTM D648 | Indicates heat resistance under a flexural load |
| Vicat Softening Temperature | ASTM D1525 | Defines the upper service temperature limit |
| Melt Flow Rate (MFR) | ASTM D1238 | Essential for processing flow characterization |
| Ash Content | ASTM D5630 | Determines filler or reinforcement level |
| Density / Specific Gravity | ASTM D792 | Material identification and weight calculation |
⚠️ Important Testing Prerequisites: All test specimens must be conditioned according to Practice D618 and molded per Practice D3641 before testing. Accurate adherence to these preparatory standards is vital for obtaining reproducible and representative mechanical and thermal data for SPS materials.
📊 Suffix System and Specification Details
While the primary cell table assigns broad classifications for base SPS grade properties, the standard’s comprehensive suffix system (Section 5) allows for precise customization. This enables a specifier to demand exact performance criteria for properties like impact strength (using either Izod per D256 or Charpy per ISO 179-1) or a specific flexural modulus. The specification relies heavily on the reporting of significant digits per Practice E29. For quality assurance, the standard references sampling plans per MIL-STD-105 and packaging/packing per Practice D3892.
💡 Application Guidance: SPS materials classified under this standard are typically chosen for applications requiring high heat resistance, excellent chemical resistance, and dimensional stability, such as automotive under-hood sensors and electrical connectors. The suffix system allows precise tailoring of impact resistance and flow properties for these specific applications.
❓ Frequently Asked Questions
🔍 What specific material types are covered by ASTM D6339-11?
This standard covers syndiotactic polystyrene (SPS) homopolymers, copolymers, blends, and impact-modified grades suitable for molding and extrusion. Recycled SPS materials are explicitly excluded from this version and are reserved for a separate standard.
💡 Does ASTM D6339-11 have an international (ISO) equivalent?
No. The scope of the standard includes a specific note stating, “There is no known ISO equivalent to this standard.” While it does reference supporting ISO test methods for impact (ISO 179-1) and Vicat softening (ISO 306), the classification framework itself is uniquely an ASTM standard.
⚡ How does the line callout system facilitate the specification of SPS materials?
The system uses a cell table format under the ASTM D4000 umbrella to define broad material classes. For precise definitions, the suffix codes in Section 5 allow specifiers to single out specific values for key properties like tensile