Overview
ISO 7246:1984 is an international standard developed by the International Organization for Standardization (ISO) that specifies the general requirements for moulding and extrusion materials based on acrylonitrile/styrene/acrylester (ASA) plastics. The standard focuses specifically on pipes and fittings made from ASA plastics, ensuring consistency in the quality and performance of these materials used in fluid transport systems.
This standard defines key material properties such as acrylonitrile content, Vicat softening temperature, melt flow rate, impact strength (Izod or Charpy), and flexural modulus. It serves as a comprehensive guideline for manufacturers and users to select ASA plastics suitable for pipe and fitting applications, enhancing reliability and safety in various industrial and commercial fluid conveyance systems.
Key Topics
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Material Composition
ASA plastics consist of a two-phase system where the continuous phase includes copolymers of acrylonitrile and styrene (or substituted styrene), and the dispersed phase is an elastomer based on a polymer or copolymer of acrylic ester. The acrylonitrile content in the continuous phase must be at least 20% to comply with the specification.
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Designation System
The designation of ASA plastics for pipe and fitting applications is based on five main properties:
- Acrylonitrile content (% in the continuous phase)
- Vicat softening temperature (minimum 90°C)
- Melt flow rate (MFR) at 220°C under 10 kg load (with maximum limits varying for pipes and fittings)
- Impact strength using Izod or Charpy tests
- Flexural modulus (minimum 1.5 GPa)
This system allows precise identification and classification of ASA materials tailored for different applications.
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Test Methods and Specifications
The standard references various ISO methods for property determination, including:
- ISO 178 for flexural modulus
- ISO 179 and ISO 180 for impact strength tests
- ISO 306 for Vicat softening temperature
- ISO 1133 for melt flow index
It also covers recommended specimen preparation conditions and prescribes drying procedures before testing to ensure accuracy.
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General Properties
ASA plastics for pipes and fittings exhibit specific characteristics such as:
- Average density of approximately 1.06 g/cm³
- Low thermal expansion coefficient (~0.8 × 10⁻⁴ K⁻¹)
- Thermal conductivity around 0.17 W/(mmK)
- High surface resistivity (> 10¹² Ω)
These contribute to the material’s durability and performance under varying environmental conditions.
Applications
ISO 7246:1984 is primarily intended for manufacturers and designers of:
- Plastic pipes used in fluid transportation systems
- Pipe fittings fabricated through injection moulding or extrusion processes
- Components in plumbing, chemical processing, irrigation, and industrial fluid handling systems
- Systems requiring standardized material properties that ensure mechanical strength, thermal stability, and resistance to environmental stressors
By adhering to ISO 7246 standards, stakeholders can improve product reliability, simplify material selection, and ensure compatibility across different pipe and fitting systems made from ASA plastics.
Related Standards
ISO 7246:1984 relates closely with other ISO standards that cover plastics and pipe materials:
- ISO 178: Methods for determining flexural properties of plastics
- ISO 179 and ISO 180: Standards for measuring impact resistance of plastics
- ISO 306: Determination of softening temperature using the Vicat method
- ISO 1133: Testing melt flow rate of thermoplastics
- ISO 2580/1 and 2580/2: Specifications and test methods for thermoplastics moulding materials necessary for specimen preparation and conditioning in compliance with ISO 7246
- ISO committees involved: ISO/TC 138 (Plastics pipes, fittings and valves for the transport of fluids), ISO/TC 61 (Plastics)
These complementary standards form a robust framework guiding the consistent quality assessment and classification of ASA plastics for pipe applications.
Keywords: ISO 7246, ASA plastics, acrylonitrile/styrene/acrylester, pipe materials, plastic fittings, moulding materials, extrusion materials, Vicat softening temperature, melt flow rate, impact strength, flexural modulus, plastic pipes, fluid transport systems, ISO standards for plastics.
Open preview (PDF)Pipes and fittings of acrylonitrile/styrene/acrylester (ASA) — General specification for moulding and extrusion materials