Low-density polyethylene is the oldest polyethylene in the trade and still one of the most widely moved, both as virgin resin and as recovered film. It is defined by how it is made: high-pressure polymerisation produces long-chain branching, which is what gives LDPE its softness, clarity and famously easy processing. That same structure is why it cannot simply be swapped for LLDPE. This is a plain-English reference for buyers and sellers of LDPE in any condition.
How are LDPE grades defined?
Two numbers carry most of the specification. Melt flow index, quoted at 190°C under 2.16 kg, tells you how easily the resin flows: low MFI grades have higher molecular weight and give tougher, stronger film, while high MFI grades flow freely and suit coating and moulding. Density sits in a narrow band, roughly 0.910 to 0.925 g/cm³, and nudges stiffness and clarity.
Beyond those, the additive package matters more than people expect — slip and antiblock additives, which stop film layers sticking, are routine in film grades and unwelcome in some applications. It is a fair question to ask of any offer.
What are the main LDPE grade families?
- Film — the dominant use, typically MFI around 0.3 to 2. Shrink film, lamination film, bags, agricultural and construction sheet.
- Extrusion coating — high MFI grades, often 4 to 8 or higher, designed to draw down thin onto paper, board or foil.
- Injection moulding — mid-to-high MFI for lids, closures and flexible mouldings.
- Cable and wire — grades formulated for insulation and sheathing, where electrical properties and cleanliness dominate.
- Blends with LLDPE — extremely common in film, combining LDPE's processability and optics with LLDPE's strength.
How is recycled LDPE traded?
Recovered LDPE film moves in a form the virgin trade does not use, and the vocabulary is worth knowing:
- Bales — baled post-industrial or post-commercial film, described by a quality split such as 98/2 or 95/5, meaning the percentage of target material to contamination. Clear or natural film sits well above coloured or mixed.
- Regrind and flake — shredded and usually washed, sold by the tonne, priced on cleanliness, moisture and colour.
- Regranulate or repro pellets — washed, extruded and pelletised. The most finished and highest-priced recycled form because it drops straight into a machine.
- Agricultural film — silage and mulch film, typically heavily contaminated with soil and moisture, priced well below clean commercial film.
Moisture is the quiet value killer in recycled film. Material sold by weight that carries water is material you paid resin prices for, and it causes bubbles and degradation on extrusion.
What is the difference between LDPE and LLDPE?
They sit at similar densities but are structurally different polymers. LDPE is made at high pressure and has long-chain branching, which makes it easy to process, glossy and clear, with good melt strength but modest tensile and puncture resistance. LLDPE is made catalytically by copolymerising ethylene with an alpha-olefin, giving short-chain branching, much better tensile, puncture and tear performance, poorer optics and a stiffer melt that is harder to extrude.
In practice film producers blend them rather than choose. If you are offered "LDPE film scrap", it is worth asking whether it is genuinely LDPE or an LDPE/LLDPE blend, because it changes what the buyer can do with it.
What drives the price of LDPE?
- The virgin resin market, which recycled grades track at a discount that moves with supply.
- Colour and clarity — clear and natural film runs above coloured, which runs above mixed and printed.
- Form — regranulate above washed flake above baled film, reflecting the processing already done.
- Contamination and moisture, including print, labels, tape, soil and residual water.
- MFI and additive package for virgin and near-prime resin, since grade fit narrows or widens the buyer pool.
- Quantity, location and incoterm — bales are bulky, so freight is a larger share of the delivered cost than it is for pellets.
Because these move independently, no fixed price list holds for long. LDPE is best priced against live offers for the same form, colour and cleanliness.
How does Prime Polymers handle LDPE?
LDPE listings state form, grade, condition, quantity, location, incoterm and the seller's own asking price per tonne, so bales, flake and regranulate can be compared side by side rather than lumped together. 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 does 98/2 mean on an LDPE film bale?
- It is a quality split: roughly 98% target material to 2% contamination or off-grade content. Common splits are 98/2, 95/5 and 90/10, and the number materially changes the price. Treat it as the seller's description and confirm it against photos or a sample before committing.
- Is LDPE the same as LLDPE?
- No. LDPE is made at high pressure and has long-chain branching, giving clarity, gloss and easy processing. LLDPE is made catalytically with an alpha-olefin comonomer and has short-chain branching, giving much better tensile and puncture strength but poorer optics. Film producers commonly blend the two.
- Why is clear LDPE film worth more than coloured?
- Clear and natural film can be reprocessed into a wider range of end products, including ones where appearance matters, so it serves more buyers. Coloured, printed and mixed film is committed to darker or less visible applications and prices accordingly.
- What MFI is typical for LDPE film grade?
- Film grades usually sit around 0.3 to 2 g/10min at 190°C and 2.16 kg. Extrusion coating grades run much higher, often 4 to 8 or above, because they need to draw down thin. Always confirm the test condition alongside the number.
- How can I see what LDPE is trading at?
- Compare live offers of the same form and quality rather than relying on a dated figure. On Prime Polymers each LDPE listing shows the seller's asking price per tonne next to form, condition, quantity, location and incoterm. If nothing matches, post a Wanted requirement and let sellers come to you.