Polystyrene is really four trades under one name. Crystal polystyrene is a hard, glass-clear commodity resin; high-impact polystyrene is a rubber-modified opaque one; expanded polystyrene is a foam sold by volume as much as by weight; and extruded polystyrene foam is a construction product. They share a monomer and very little else. This is a plain-English reference for buying and selling polystyrene in each of its forms.
What is the difference between GPPS and HIPS?
General purpose polystyrene (GPPS, often called crystal) is unmodified: glass clear, hard, rigid, cheap and notably brittle. It goes into disposable cups and cutlery, clear packaging, CD cases, optical and diffuser sheet, and laboratory ware.
High impact polystyrene (HIPS) is GPPS with polybutadiene rubber dispersed through it. The rubber makes it opaque and slightly less stiff, but dramatically tougher. It goes into refrigerator liners, thermoformed packaging, appliance and television housings, and point-of-sale display. The rubber content is effectively the grade: more rubber, more impact, less stiffness and gloss.
Melt flow for polystyrene is commonly quoted at 200°C under 5 kg. As always, the condition belongs with the number.
How are EPS and XPS different, and how are they traded?
- EPS (expandable polystyrene) — supplied as beads containing a blowing agent, then steam-expanded and moulded. Protective packaging, fish boxes, insulation board, void formers. Graded by bead size and by the density it is expanded to.
- XPS (extruded polystyrene) — foamed continuously through an extruder into board. Denser, stronger and more moisture resistant than EPS, used in construction insulation.
The commercial fact that dominates recovered EPS is that it is almost all air — typically well under 2 per cent polymer by volume. Moving loose EPS any distance costs more than the material is worth, so it is compacted or thermally densified into blocks or ingots at source. An offer of recovered EPS should say what form it is in, because loose, compacted and densified are three different propositions with three different freight profiles.
What should I check when buying recycled polystyrene?
- Which polystyrene it actually is — GPPS, HIPS, EPS or XPS. They are not interchangeable and the word alone does not identify the material.
- Source stream — fridge liner and appliance HIPS regrind is well defined; mixed post-consumer packaging is not.
- Colour — natural and white above mixed above black, on the usual recolouring logic.
- Contamination — labels, adhesive, food residue, and for EPS in particular moisture and expanded polypropylene mixed in by mistake.
- Density and form for foam material, which govern freight as much as value.
- Any legacy flame retardant question on construction-derived foam, where older insulation board may contain restricted substances.
What drives the price of polystyrene?
- The styrene monomer market, which the virgin price tracks and recycled follows at a discount.
- Type — GPPS, HIPS and foam grades price separately and serve different buyers.
- Rubber content and impact class for HIPS; clarity and flow for GPPS.
- Colour and cleanliness in recycled material.
- Form and density for foam, since freight is a large share of delivered cost on anything not densified.
- Quantity, location and incoterm.
These move independently, so a fixed list dates quickly. Polystyrene is best priced against live offers of the same type, form and colour.
How does Prime Polymers handle polystyrene?
Polystyrene listings state the type, form, condition, quantity, location, incoterm and the seller's own asking price per tonne, so crystal, high impact and foam are compared as the distinct materials they are rather than under one label. Prices are shown exactly as sellers enter them — never computed, adjusted or benchmarked by us. Browsing is free and open without an account. If nothing on the board fits, a Wanted post puts your specification in front of sellers. Prime Polymers is operated by ARC Polymers Ltd, a UK polymer trading company.
Frequently asked questions
- What is the difference between GPPS and HIPS?
- GPPS, or crystal polystyrene, is unmodified — glass clear, hard and brittle. HIPS is the same polymer with polybutadiene rubber dispersed through it, which makes it opaque and slightly less stiff but far tougher. The rubber content effectively defines the HIPS grade.
- Why is recovered EPS compacted or densified before sale?
- Because expanded polystyrene is mostly air — typically well under 2 per cent polymer by volume. Transporting it loose costs more than the material is worth, so it is compacted or thermally densified into blocks or ingots at source. Always establish which form is being offered.
- Is EPS the same as XPS?
- No. EPS is moulded from steam-expanded beads and is used for packaging and insulation. XPS is extruded as a continuous foam board, denser, stronger and more moisture resistant, used mainly in construction insulation. They are different products with different markets.
- Can HIPS and GPPS be recycled together?
- They can be processed together in some applications, but a mixed stream is worth less than a clean single-type one because it limits what the buyer can make. HIPS regrind from a known source such as fridge liner is markedly easier to sell than an unsorted polystyrene mix.
- How can I see what polystyrene is trading at?
- Compare live offers of the same type, form and colour. On Prime Polymers each polystyrene listing shows the seller's asking price per tonne next to grade, condition, quantity, location and incoterm. If nothing matches, post a Wanted requirement and let sellers approach you.