Expandable Polystyrene CAS 9003-53-6
Chelora Chemicals supplies insulation, packaging and block grades of expandable polystyrene to foam converters worldwide, including flame-retardant grades. Because EPS beads contain pentane, every consignment leaves with a batch-specific COA, the current SDS and full dangerous-goods documentation.
Also known as: EPS · Expandable polystyrene beads · Styropor type beads · Expanded polystyrene raw beads
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Price, lead time and a sample COA for Expandable Polystyrene, usually within one working day. We ship worldwide.
Request a Quote Email the DeskDocumentation
- Batch-specific COA (bead size, pentane content, expansion ratio)
- Safety Data Sheet (SDS)
- Transport and dangerous-goods documents
- Third-party inspection on request
- Certificate of origin
What is Expandable Polystyrene?
Expandable polystyrene is polystyrene produced as small beads impregnated with a pentane blowing agent, typically 4.5 to 6.5% by weight. The beads expand to many times their volume when heated with steam.
Converters pre-expand the beads, age them, then mould them into blocks or shapes. The two-stage process is what makes EPS economical: the material ships dense and expands at the point of use.
The two main markets are construction insulation and protective packaging, with flame-retardant grades required for most building applications.
The pentane content is what makes EPS a dangerous good in transport and what drives ventilation and ignition control at converting sites.
Why EPS specifically
- Ships dense, expands on site. Unexpanded beads carry far more material per container than finished foam, which transforms the logistics.
- Outstanding insulation per unit cost. Thermal conductivity around 0.033 to 0.038 W/mK at very low density.
- Mouldable to shape. Shape moulding gives protective packaging that fits the product exactly.
- 98% air. Finished foam is almost entirely air, which is why the material cost per cubic metre is so low.
How Expandable Polystyrene is Manufactured
EPS is made by suspension polymerisation of styrene with pentane impregnated during or after polymerisation.
- Styrene suspension polymerisation. Styrene droplets in water with a suspending agent and peroxide initiator form polystyrene beads.
- Pentane impregnation. Pentane is introduced during or after polymerisation and absorbed into the beads under pressure.
- Flame retardant addition. Building grades incorporate a polymeric brominated flame retardant, which replaced HBCD.
- Sieving and classification. Beads are classified into narrow size fractions, since bead size determines the minimum achievable density and detail.
- Coating. Antistatic and surface coatings are applied to control fusion and flow in the mould.
- Packing under containment. Beads are packed in sealed octabins or bags to retain pentane and limit emission.
Typical Commercial Specification
Figures below are representative of a packaging grade EPS. Insulation, block and flame-retardant grades differ — tell us the application and target density and we will send the matching sheet.
| Parameter | Typical Value |
|---|---|
| Appearance | White spherical beads, free flowing |
| Bead size range | 0.3 – 2.5 mm depending on grade |
| Pentane content | 4.5 – 6.5% by weight |
| Residual styrene monomer | To grade, typically 1000 ppm max |
| Minimum achievable density | Typically 10 – 25 kg/m³ depending on bead size |
| Flame retardant | Polymeric brominated FR for building grades |
| Moisture content | To grade, typically 0.5% max |
| Fusion quality | To grade, assessed on moulded samples |
| Expansion ratio | To grade data sheet |
Physical & Chemical Properties
| Property | Value |
|---|---|
| Chemical formula | (C₈H₈)ₙ with pentane blowing agent |
| Appearance | White spherical beads |
| Bulk density (unexpanded) | About 620 to 650 kg/m³ |
| Expanded density | Typically 10 to 35 kg/m³ |
| Thermal conductivity (expanded) | About 0.033 to 0.038 W/mK |
| Softening point | About 100 °C |
| Pentane flash point | About −49 °C — the hazard driver |
| Water absorption | Low in closed-cell foam |
| Chemical resistance | Attacked by hydrocarbons, ketones and esters |
| Service temperature | Up to about 75 °C continuous |
| Incompatibilities | Solvents, oils, oxidisers and ignition sources |
Behaviour in the process
EPS behaviour is dominated by the blowing agent and by bead ageing:
- Pentane release. Beads emit flammable pentane in storage, pre-expansion and ageing; ventilation and ignition control are essential throughout.
- Ageing requirement. Pre-expanded beads must age so air diffuses in and the cells stabilise before moulding; too short and parts shrink.
- Shelf life limited. Pentane diffuses out slowly, so old beads expand poorly and may not reach target density.
- Solvent sensitivity. Hydrocarbons and many solvents collapse the foam instantly.
EPS Grades and Alternative Insulation
EPS is bought by bead size and by whether flame retardancy is required, and the application decides both.
| Material | Origin / type | When it is the right choice |
|---|---|---|
| Packaging-grade EPS | Medium to coarse beads | Protective packaging, shape moulding and void fill |
| Insulation-grade EPS | Fine beads, flame retardant | Building insulation board and panels |
| Block-grade EPS | Coarse beads | Large block moulding and cut shapes |
| XPS | Extruded polystyrene board | Higher compressive strength and moisture resistance at higher cost |
| Polyurethane board | PIR and PUR insulation | Better thermal performance per thickness, higher cost |
Stated plainly: EPS gives the most insulation per unit cost and is the default where thickness is available. XPS and PIR win where space is constrained or where moisture exposure is severe.
Industries We Supply Expandable Polystyrene To
EPS reaches construction, packaging, cold chain and civil engineering.
Where Expandable Polystyrene is Used
Construction insulation and protective packaging take most EPS, with cold chain and civil engineering behind them.
Pre-expansion and ageing
Beads are pre-expanded with steam to the target density, then aged in ventilated silos for several hours to a day so air can diffuse into the cells and the pentane partially vent. Too little ageing gives parts that shrink after moulding; too much gives beads that will not fuse. Getting this cycle right matters more to part quality than the resin grade.
Flame retardant grades
Building applications require flame-retardant EPS, now based on a polymeric brominated flame retardant after HBCD was restricted under the Stockholm Convention. FR grades are not interchangeable with packaging grades, and building regulations generally require documented compliance with the relevant reaction-to-fire classification.
Need a specific grade, purity and packing format?
Tell us the grade, the application, target density and whether flame retardancy is required, the packing format you can receive and the annual quantity. We will come back with a price, a lead time, a sample COA and the full documentation set.
Quality Control & Testing
Every lot is released against a batch-specific Certificate of Analysis with bead size, pentane content and expansion data, so your pre-expansion settings can be matched to the actual material.
- Bead size distribution — by sieve analysis, defining achievable density and surface detail.
- Pentane content — the blowing agent level, which determines expansion capacity.
- Expansion ratio — confirming the minimum density achievable from the lot.
- Residual styrene monomer — reported for food contact and packaging applications.
- Flame retardant content — for building grades, with reaction-to-fire documentation.
- Moisture and fusion quality — confirming processing behaviour.
Common Process Problems & Likely Causes
When EPS causes trouble, it is usually bead age, pre-expansion or ageing time. This table is the shortcut our technical desk works through before anyone opens a complaint file.
| Symptom | Likely cause | What to check |
|---|---|---|
| Cannot reach target density | Pentane loss from aged beads or wrong bead size | Pentane content, lot age and bead size |
| Parts shrinking after moulding | Insufficient bead ageing after pre-expansion | Ageing time and silo ventilation |
| Poor fusion between beads | Over-aged beads or inadequate steam | Ageing time, steam pressure and mould condition |
| Surface detail poor | Bead size too coarse for the part | Bead size against part geometry |
| Pentane odour in the work area | Normal emission with inadequate ventilation | Ventilation rate, silo venting and gas monitoring |
| Fire classification not met | Non-FR grade used, or FR content below specification | Grade documentation and flame retardant content |
Packaging, Storage & Shipping
- Standard packing. Sealed octabins and bags with pentane containment, typically 500 to 1000 kg.
- Ventilation. Store in well-ventilated areas; beads continuously emit flammable pentane.
- Ignition control. No ignition sources, earthed equipment and gas monitoring in storage and pre-expansion areas.
- Temperature. Cool storage below 20 °C slows pentane loss and extends usable life.
- Stock rotation. First in, first out. Pentane diffuses out over months and old beads will not reach low density.
- Segregation. Keep away from solvents, oils and oxidisers.
- Shelf life. Typically three to six months depending on grade and storage temperature.
- Transport classification. UN 2211, polymeric beads expandable, Class 9, evolving flammable vapour.
Hazards & Safe Handling
EPS beads are inert polystyrene, but the pentane blowing agent is highly flammable and is released continuously in storage and processing. Ventilation and ignition control are the central safety measures.
- Flammable pentane. Beads emit pentane with a flash point near −49 °C. Vapour is heavier than air and accumulates at low level.
- Ventilation. Storage, pre-expansion and ageing areas all require forced ventilation and gas monitoring.
- Ignition control. Earth equipment, use flameproof electrical fittings and prohibit hot work in bead handling areas.
- Fire behaviour. EPS foam burns readily unless flame retarded, producing dense black smoke; building grades must be FR.
- Static. Bead transfer generates static charge; earthing and antistatic coating both matter.
- Low toxicity. The polymer itself is inert; pentane is a simple asphyxiant and narcotic at high concentration.
- Environment. Bead and foam loss to the environment is a recognised litter source; containment at every transfer point is expected practice.
Regulatory & Compliance Notes
EPS is regulated for transport because of its pentane content and for building use through fire classification. The notes below are orientation rather than legal advice.
- GHS classification. Classified for flammable vapour emission; the polymer itself is not hazardous.
- Dangerous goods transport. UN 2211, polymeric beads expandable, Class 9. ADR, IMDG, IATA and DOT rules apply to packaging and ventilation.
- Flame retardant regulation. HBCD is restricted under the Stockholm Convention and has been replaced by polymeric brominated flame retardant in building grades.
- Building fire classification. Insulation must meet reaction-to-fire classification such as EN 13501 Euroclass or equivalent national standards.
- Food contact. Food packaging grades must comply with applicable migration limits for residual styrene.
- Single-use restrictions. Some jurisdictions restrict EPS food service items, which affects application mix rather than insulation use.
We Supply Expandable Polystyrene Worldwide
Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Expandable Polystyrene from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.
- Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
- Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
- Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
- Flexible volumes. From a single octabin up to repeat bulk shipments on a supply contract.
- Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.
Buying Expandable Polystyrene from Chelora
We are an independent sourcing and supply partner. For EPS that means settling three things at enquiry: the target density and part geometry that set the bead size, whether flame retardancy and fire classification documentation are required, and the delivery schedule, because shelf life is limited.
- Documentation on every lot. Batch-specific COA (bead size, pentane content, expansion ratio), plus SDS and the full transport paperwork.
- Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
- Quantities. From a single octabin through to full bulk shipments on contract supply.
- Grade matching. Packaging, insulation or block grade at the bead size and flame retardant level your application requires.
- Inspection. Independent third-party inspection available at loading when the contract requires it.
- Related products. Polystyrene, Styrene Monomer, Acrylonitrile Butadiene Styrene Resin and other feedstocks alongside Expandable Polystyrene from one supplier.
How ordering works
- Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
- We quote. Price, lead time, packing format and a sample COA, normally within one working day.
- Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
- Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
- Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
- Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.
Expandable Polystyrene — Common Questions
The questions our technical desk is asked most often about Expandable Polystyrene. If yours isn't here, call or email and you will reach someone who knows the chemistry.
What is the CAS number of expandable polystyrene?
The CAS number for polystyrene is 9003-53-6. EPS is classified under HS code 3903.11 and ships as UN 2211 because of its pentane content.
What is EPS used for?
For building insulation board and panels, protective packaging, cold chain boxes, geofoam lightweight fill, insulated concrete formwork and moulded consumer foam products.
Do you supply EPS worldwide?
Yes. Chelora Chemicals supplies and exports expandable polystyrene beads worldwide — across Asia Pacific, Europe, the Middle East, Africa and the Americas, as well as throughout India, in sealed octabins and bags.
Why does EPS contain pentane?
Pentane is the blowing agent. It is absorbed into the beads during manufacture and vaporises when the beads are steamed, expanding them to many times their original volume at the converter's site rather than at the resin plant.
How is EPS manufactured?
By suspension polymerisation of styrene into beads, with pentane impregnated during or after polymerisation, followed by sieving into narrow size fractions and surface coating. Building grades also receive a polymeric brominated flame retardant.
How do I choose bead size?
By target density and part detail. Fine beads give the lowest densities and the finest surface detail; coarse beads expand faster and suit large block moulding. Using the wrong size is the commonest reason a converter cannot hit target density.
Why does EPS have a shelf life?
Because pentane diffuses out of the beads over time, faster in warm storage. Old beads will not expand to the same low density, so stock rotation and cool storage both matter.
Is EPS hazardous?
The polystyrene itself is inert, but the pentane blowing agent is highly flammable and is released continuously. Ventilation, ignition control and gas monitoring are required in storage, pre-expansion and ageing areas.
What are the UN number and transport class?
UN 2211, polymeric beads expandable evolving flammable vapour, Class 9. ADR, IMDG, IATA and DOT rules apply to packaging and ventilation during carriage.
What flame retardant is used in EPS now?
A polymeric brominated flame retardant, which replaced HBCD after the latter was restricted under the Stockholm Convention. Building grades require it and must meet the relevant reaction-to-fire classification.
Why do pre-expanded beads need ageing?
So air can diffuse into the cells and stabilise them before moulding. Too little ageing gives parts that shrink; too much gives beads that will not fuse properly. The ageing cycle usually matters more to part quality than the grade.
What packing sizes are available?
Sealed octabins and bags, typically 500 to 1000 kg. Orders run from a single octabin up to full container loads, with delivery scheduled against your shelf life.
Ready to source Expandable Polystyrene?
Send us your specification, grade and annual volume. You will get a price, a realistic lead time and a sample COA from someone who understands what the material has to do in your process — delivered anywhere in the world.