Information on the most widely used ASTM standards within the materials testing industry
Thermal insulation boards are rigid panels designed to reduce heat transfer, available in various materials like PIR, XPS, EPS, stone wool, and microporous boards, each suited for specific construction or industrial applications.
EPS (Expanded Polystyrene) Board: Rigid cellular plastic insulation made by pre-expanding polystyrene beads, then molding and fusing them under heat. It has a semi-open/partially closed cell structure.
XPS (Extruded Polystyrene) Board: Rigid insulation produced by melting polystyrene resin with blowing agents, then continuously extruding, cooling and forming. It has a dense, continuous closed-cell structure (closed-cell rate >95%).
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| EPS (Expanded Polystyrene) Board | XPS (Extruded Polystyrene) Board |
Details test methods, test equipment, requirement for EPS & XPS Instruction Thermal Insulation Board:
| Test method | Test requirement | Standard | Test Equipment (UnitedTest Brand) |
| Compressive Strength Test | Core strength index; resists static/dynamic load without crushing. EPS: 60 kPa–≥800 kPa; XPS: ≥150 kPa–≥900 kPa Specimen Size: 100 mm × 100 mm × original thickness. | ISO 844 | Universal testing machine + Compression test platen |
| Thermal Conductivity Test | The material's ability to resist heat transfer is measured at average temperatures of 10°C and 25°C. XPS is categorized into 024, 030, or 034 grades (referring to their max W/(m·K) value). EPS is categorized into 033 or 037 grades. Lower numbers indicate superior insulating power. | ISO 8302 ISO 8301 | Thermal Conductivity Tester |
Flexural Performance | Assists in judging structural toughness and construction adaptability. (Cross-breaking) | ISO 1209-1 ISO 1209-2 | Universal testing machine + Bending test fixture |
| Water Absorption Test | XPS is strictly required to absorb no more than 1.0% to 2.0% of its volume; whereas EPS can absorb up to 6.0%, depending on its density grade. XPS performs far better than EPS. Samples are fully submerged in 23°C water for 96 hours. | ISO 2896 | Rigid Foam Plastic Water Absorption Tester |
| Dimensional Stability Test | Specimens are baked in an oven at 70°C ± 2°C for 48 hours. The percentage change in length is measured afterward. High-performance XPS allows a maximum change of 3.0%;while standard grades must stay under 1.5%. EPS ranges from 1% to 4% depending on density. | ISO 2796 | Constant temperature and humidity test chamber |
| Water Vapor Transmission Coefficient | Measures how much water vapor passes through the board. High-grade XPS must block vapor transmission almost entirely (≤ 2.0 to 3.5 ng/(m·s·Pa)). | QB/T 2411 | Water Vapor Transmittance Tester(Weight method) |
Melt Bonding Test (3 points bending) | For EPS only, Because EPS is made of fused beads, this test ensures the beads are strongly bonded. A "breaking bending load" is applied; if the beads separate too easily, the board will crumble during handling. | ISO 1209-1 | Universal testing machine + Bending test fixture |
After test use UnitedTest machine, you can easily identify the difference of performance of EPS and XPS board:
| Item | EPS (Moulded Polystyrene Foam) | XPS (Extruded Polystyrene Foam) |
|---|---|---|
| Production Process | Expandable polystyrene beads → pre-foaming → moulded heating forming | Polystyrene resin → melting → extrusion → continuous closed-cell forming |
| Cell Structure | Mixed open/closed cells; closed-cell rate ~90% | Full closed-cell structure; closed-cell rate ≥98% |
| Thermal Insulation | Worse; higher thermal conductivity | Better; lower thermal conductivity |
| Water Resistance | Medium; higher water absorption | Excellent; extremely low water absorption |
| Compressive Strength | Low–medium (60–≥800 kPa) | Medium–high (≥150–≥900 kPa) |
| Dimensional Stability | Average; easy to deform at high temperature | Excellent; small deformation at high temperature |
| Water Vapor Permeability | High | Extremely low (good vapor barrier) |
| Combustion Grade | B1, B2, B3 | Only B1, B2 (no B3) |
| Cost | Lower | Higher |
Related standard:
ASTM E2430 Standard Specification For Expanded Polystyrene (“EPS”) Thermal Insulation Boards For Use In Exterior Insulation and Finish Systems (“EIFS”)
BS 3837-1 Expanded polystyrene boards-Boards and blocks manufactured from expandable beads. Requirements and test methods.
IS 4671 Expanded Polystyrene for Thermal Insulation Purposes – Specification
GB/T 10801.1 Moulded polystyrene foam for thermal insulation(EPS)
GB/T 10801.2 Extruded polystyrene foam for thermal insulation(XPS)
Typical Applications
1, EPS Board
Building exterior wall external insulation (thin plastering system)
Roof insulation, floor heating insulation layer
Lightweight partition walls, indoor thermal insulation
Low-humidity cold storage, packaging buffer materials
Civil building insulation with general load-bearing requirements
2, XPS Board
Inverted roof insulation, basement wall/slab insulation
Roadbed, bridge, airport runway insulation (high compression resistance)
High-humidity cold storage, swimming pool insulation
High-performance exterior wall insulation, floor heating (high-load scenarios)
Cold-chain logistics, industrial insulation with strict waterproof/load requirements
Related products and device
Related Standard
ASTM D790: Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
ASTM D790 test methods are used to determine the flexural properties of unreinforced and reinforced plastics, including high modulus composites and electrical insulating materials utilizing a three-point loading system to apply a load to a simply supported beam (specimen). The method is generally applicable to both rigid and semi-rigid materials, but flexural strength cannot be determined for those materials that do not break or yield in the outer surface of the test specimen within the 5.0 % strain limit.
ISO 178 Plastics - Determination of flexural properties
ISO 178 specifies a method for determining the flexural properties of rigid and semi-rigid plastics under defined conditions. A standard test specimen is defined, but parameters are included for alternative specimen sizes for use where appropriate. A range of test speeds is included.
ISO 178 test method is used to investigate the flexural behaviour of the test specimens and to determine the flexural strength, flexural modulus and other aspects of the flexural stress/strain relationship under the conditions defined. It applies to a freely supported beam, loaded at midspan (three-point loading test).
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