Overview
ISO 14631:2021 defines requirements and test methods for solid, flat extruded sheets of impact‑modified polystyrene (PS‑I) without fillers or reinforcing materials. It covers sheet and roll forms with nominal thicknesses from 0.25 mm to 20.0 mm and sets criteria for appearance, dimensions, mechanical and thermal properties, behaviour after heating and required test procedures. The standard is intended to support consistent material specification, quality control and conformity assessment for extruded PS‑I sheet products.
Key topics and technical requirements
- Material scope
- Applies to PS‑I extrusion compounds designated by ISO 19063‑1; additives such as stabilizers, colorants and processing aids are permitted but compounds of unknown identity are not.
- Appearance
- Sheets shall be substantially free from bubbles, voids, cracks, visible impurities and surface defects; colour must be homogeneous.
- Dimensional tolerances
- Thickness control with specified maximum deviations from nominal and from average actual thickness (formulas provided in the standard).
- Length and width tolerances (direction of extrusion is length unless agreed otherwise); rectangularity limits expressed as diagonal difference.
- Bow limits for rolled sheets (maximum permissible bow specified).
- Mechanical and thermal properties
- Minimum performance tables for types (PS‑N, PS‑R, PS‑H) including:
- Tensile stress at yield (e.g., ≥20 MPa for PS‑N)
- Nominal tensile strain at break
- Modulus of elasticity in tension
- Charpy impact strengths (notched and unnotched)
- Multiaxial impact energy (50% failure energy at specified thickness)
- Ball indentation hardness
- Vicat softening temperature ranges
- Behaviour after heating
- Shrinkage limits in the extrusion direction for thermoforming applications and requirements for absence of bubbles/cracking after heating.
- Test methods
Applications and users
ISO 14631:2021 is primarily useful for:
- Manufacturers and converters of extruded PS‑I sheets and rolls (product specification and quality control)
- Materials and process engineers developing extrusion and thermoforming processes
- Testing laboratories performing physical, mechanical and thermal characterization
- Procurement specialists and specifiers in industries that use PS‑I sheet for components, displays or thermoformed parts
- Product designers requiring reliable material data for design and compliance
Keywords: ISO 14631, impact‑modified polystyrene, PS‑I sheet, extruded PS‑I, dimensional tolerances, Charpy impact strength, Vicat softening temperature, thermoforming, material specification, test methods, quality control.
Related standards
Normative references used by ISO 14631 include ISO 179‑1, ISO 291, ISO 306, ISO 527‑1/2, ISO 1043‑1, ISO 1183‑1/2, ISO 2039‑1, ISO 2818, ISO 6603‑1, ISO 11501 and ISO 19063‑1. These provide the detailed test procedures and designation system referenced throughout ISO 14631.
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