Key takeaways
- Family (HDPE / LDPE / LLDPE) and end-application (film, blow, pipe, injection)
- Density target and MFI window
- Comonomer (C4, C6, C8) for LLDPE; pressure class for HDPE pipe
- Origin preference — GCC, NEA, NA, or producer-agnostic
- Incoterms — [our Incoterms primer](/blog/incoterms-2020-for-polymer-buyers) covers the four that come up in PE trade
Polyethylene looks like one polymer in a textbook and three completely different commodities on a desk. The reason is geometry. HDPE chains run in long, almost unbranched lines and pack tightly. LDPE is densely branched and packs loosely. LLDPE is mostly linear with deliberate short branches, which is why it sits between the other two on every spec sheet.
That single difference shows up in density (HDPE is 0.94–0.96 g/cm³, LDPE 0.91–0.93, LLDPE 0.91–0.94), in tensile strength, and most importantly in how each grade processes. A buyer who orders the wrong family loses a week to scrap.
HDPE is what you specify when stiffness, chemical resistance, or pressure rating matter. Blow-moulded jerry cans and bottles, pressure pipe in the PE100 class, geomembranes, and the rigid layer of multi-wall packaging are all HDPE. The grade you actually want is signalled by MFI — we walk through that in detail here — and by the comonomer (butene, hexene, or octene) when you need extra environmental stress crack resistance.
On the supply side, HDPE is dominated by GCC, North American, and Northeast Asian producers. The largest dual-purpose plants swing between HDPE and LLDPE depending on margin, which means HDPE availability follows the resin spread more sensitively than the others.
LDPE is the historical first polyethylene — made in high-pressure tubular or autoclave reactors, not in the modern gas-phase units. Its long-chain branches give it the optical clarity, stretch, and tackiness that make it the default for shrink film, lamination film, and the soft handle of cosmetics tubes. It is also the easiest polyethylene to extrude on older lines.
LDPE is structurally short. Few new plants are being built. That alone keeps the price floor higher than LLDPE’s in tight markets, even when LLDPE is technically substitutable.
LLDPE was engineered to do most of what LDPE does, in a low-pressure reactor, at lower energy cost. It is the default for stretch film, heavy-duty sacks, and most general-purpose film. C4 LLDPE is the cheapest. C6 (hexene) is stronger and clearer. C8 (octene) is the premium tier, often blended into LDPE film to improve toughness without giving up gloss.
When a buyer asks for "PE film grade" without specifying further, what they almost always need is a blend — typically 70–80% LLDPE with 20–30% LDPE. Insisting on pure LLDPE often loses the optical properties the customer wanted; insisting on pure LDPE blows out the price.
- Family (HDPE / LDPE / LLDPE) and end-application (film, blow, pipe, injection)
- Density target and MFI window
- Comonomer (C4, C6, C8) for LLDPE; pressure class for HDPE pipe
- Origin preference — GCC, NEA, NA, or producer-agnostic
- Incoterms — our Incoterms primer covers the four that come up in PE trade
If a quote comes back with no comonomer or no MFI, send it back. Polyethylene at the bag level is fungible only within an exact spec window. Anything else is two grades pretending to be one.