PS EPS (Expanded polystyrene foam)
Grade
GB GB/T 4454 · ISO 1043-1 PS · also Styron, Polystyrol
Pick for low-cost thermal insulation, protective packaging and lost-foam patterns where mechanical loads are light.
Values for the EPS condition
Other PS grades and fills
PS is listed in 6 conditions; see the grade overview at PS.
Compare all 6 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
EPSThis page Expanded polystyrene foam | Pick for low-cost thermal insulation, protective packaging and lost-foam patterns where mechanical loads are light. | — | 0.28 | — | — |
Antistatic / ESD HIPS | Pick for electronics trays, carriers and IC packaging where surface charge must be dissipated. | 21 | 24 | 25 | 70 Shore D |
High-impact polystyrene | Pick when parts must survive handling/drop loads or be thermoformed into tough opaque housings, refrigerator liners and packaging trays. | 24 | 25 | 40 | 100 HRR |
PS-FR | Pick for TV/appliance housings and electrical enclosures needing UL 94 V-0 at 1.5–3 mm; accept lower impact, higher density and reduced light stability. | — | 26 | 20 | — |
Medium-impact polystyrene | Compromise grade when some toughness is needed but GPPS-like stiffness and translucency must be kept. | 28 | 33 | 15 | 78 Shore D |
GPPSDefault General-purpose (crystal) polystyrene, unfilled transparent | Pick for clarity, stiffness, gloss and lowest cost where impact loading and solvents are absent. | — | 46 | 2.5 | 75 HRM |
What is PS EPS?
PS EPS is PS in the EPS grade — pick for low-cost thermal insulation, protective packaging and lost-foam patterns where mechanical loads are light. PS EPS has a yield strength of 45 MPa (6.53 ksi) and a tensile strength of 0.28 MPa (0.0406 ksi) — weaker than 58% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi). PS EPS has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F). GPPS is the default condition FabDigit quotes; EPS is available on request or by drawing note.
Advantages
- Lightweight — 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), better than 97% of polymer grades
- Polishes to a fine finish — 80/100, better than 89% of polymer grades
- Easy to machine — 85/100, better than 88% of polymer grades
- Low embodied carbon — 3.4 kg CO₂/kg, better than 76% of polymer grades
Limitations
- Absorbs moisture — dry before molding — 2%, worse than 97% of polymer grades
- Needs corrosion protection — 55/100, worse than 94% of polymer grades
- Poor heat conductor — 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades
- Limited ductility — 2.5%, worse than 89% of polymer grades
- Low fracture toughness — 1 MPa·√m (0.91 ksi·√in), worse than 87% of polymer grades
PS EPS properties
Typical room-temperature values for PS EPS; 11 are specific to this condition. Other listed values are PS reference data and may not represent this condition. Bars are the position among polymer grades.
Physical6
PS EPS has a density of 0.02 g/cm³ (7.95×10⁻⁴ lb/in³), lighter than 97% of polymer grades. Its glass-transition temperature is 100°C (212 °F).
Mechanical17
PS EPS has a yield strength of 45 MPa (6.53 ksi) and a tensile strength of 0.28 MPa (0.0406 ksi) — weaker than 58% of polymer grades. Elongation at break is 2.5% and the elastic modulus is 0.01 GPa (8.7×10⁻⁴ Msi).
Thermal11
PS EPS is rated for continuous service to 75°C (167 °F). It conducts heat at 0.04 W/m·K (0.0208 BTU/hr·ft·°F), worse than 92% of polymer grades. Thermal expansion is 70 µm/m·K (38.9 µin/in·°F).
Electrical7
PS EPS is an electrical insulator with a dielectric strength of 22 kV/mm (558.8 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (55/100), worse than 94% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of PS EPS takes about 87 MJ of energy and emits 3.4 kg of CO₂ — less than 77% of polymer grades. Typical recycled content is 2%.
Manufacturability8
PS EPS's machinability is excellent (85/100, better than 88% of polymer grades); weldability very good (70/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with PS EPS
Is PS easy to machine?
Machines fast with sharp positive-rake tools, high speed and light feeds; use air blast (no solvent/oil coolants) and avoid stress risers to prevent crazing and chip-out.
Can PS be welded?
Excellent solvent cementing (MEK, toluene, dichloromethane) and ultrasonic/hot-plate welding; do not attempt to weld to non-styrenics without adhesives.
Can PS be formed, bent or molded?
Very easy injection molding at 190–250 °C melt / 20–70 °C mold with 0.4–0.7 % shrinkage; HIPS and GPPS sheet thermoform and vacuum-form readily above ~130 °C.
What surface finishes work on PS?
Molds to high gloss and can be printed, hot-stamped, vacuum-metallized or painted with PS-compatible (non-aggressive-solvent) systems; anneal machined parts near 70–80 °C to relieve stress before contact with solvents.
PS chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| polybutadiene rubbergraft rubber phase in HIPS only | 4 – 12 | 7 |
| mineral oil / lubricantinternal lubricant/flow aid in HIPS and easy-flow GPPS | 0 – 3 | 1.5 |
| residual styrene monomerfood-grade limits per GB 4806.6 / EU 10/2011 | ≤ 0.1 | 0.03 |
| styrene (polystyrene homopolymer)GPPS: amorphous atactic polystyrene, Mw typically 200,000–300,000 g/mol | balance | — |
PS EPS — frequently asked
What is PS EPS used for?
PS EPS is typically used for disposable cutlery and cups, CD/DVD cases, packaging inserts, lab-ware, optical light diffusers and model kits. In short: lowest-cost clear thermoplastic; stiff but notch-sensitive; best solvent-cementing styrenic.
What is the yield strength of PS EPS?
PS EPS has a typical yield strength of 45 MPa (6.53 ksi) and a tensile strength of 0.28 MPa (0.0406 ksi) — weaker than 58% of polymer grades. Strength varies by condition: see the 6 listed tempers.
Is PS EPS easy to machine?
Yes — machinability is rated excellent (85/100, better than 88% of polymer grades). Machines fast with sharp positive-rake tools, high speed and light feeds; use air blast (no solvent/oil coolants) and avoid stress risers to prevent crazing and chip-out.
Can PS EPS be welded?
Yes — weldability is rated very good (70/100). Excellent solvent cementing (MEK, toluene, dichloromethane) and ultrasonic/hot-plate welding; do not attempt to weld to non-styrenics without adhesives.
What surface finishes work on PS EPS?
Molds to high gloss and can be printed, hot-stamped, vacuum-metallized or painted with PS-compatible (non-aggressive-solvent) systems; anneal machined parts near 70–80 °C to relieve stress before contact with solvents.
Can PS EPS be formed, bent or molded?
Very easy injection molding at 190–250 °C melt / 20–70 °C mold with 0.4–0.7 % shrinkage; HIPS and GPPS sheet thermoform and vacuum-form readily above ~130 °C.
What is the maximum service temperature of PS EPS?
PS EPS is rated for continuous use to about 75°C (167 °F), and briefly to 85°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between PS GPPS and PS ESD?
GPPS is the default condition — pick for clarity, stiffness, gloss and lowest cost where impact loading and solvents are absent. ESD: pick for electronics trays, carriers and IC packaging where surface charge must be dissipated. Yield strength is 45 MPa in GPPS versus 21 MPa in ESD.
Sources
- ISO 1043-1 Plastics — Symbols and abbreviated terms — ISO (2011)
- ASTM D4549 Standard Classification System for Polystyrene Molding and Extrusion Materials — ASTM (2020)
- Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
- STYRON / Trinseo GPPS and HIPS grade datasheets — Trinseo (2023)
- CAMPUS plastics database — PS/HIPS entries — CWFG (2024)
- PlasticsEurope Eco-profile: General Purpose Polystyrene — PlasticsEurope (2020)
- GPPS/HIPS (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.