A practical guide to polyethylene comonomer grades
If you work in flexible packaging, you have almost certainly heard a resin described as “C4,” “C6,” or “C8″ — usually right before a price gap appears on the quote. For anyone new to polyethylene (PE), it is one of the most confusing bits of jargon in the industry. For a buyer, those three letters are the difference between a bag that survives the journey and one that does not.
At XH PACK we walk customers through this every week. So here is a plain-English breakdown of what those letters actually mean — and why one extra carbon atom can matter far more than it sounds.
Start with a simple picture
Imagine weaving a fishing net. You could build it from short ropes, longer ropes, or the longest ropes available. A net made from short ropes is stiffer and cheaper to produce; a net made from long ropes is softer, tougher, and drapes far better.
Polyethylene behaves the same way. During polymerization, manufacturers add a “helper” called an alpha-olefin comonomer. The shorthand the industry uses — C4, C6, C8 — is simply a count of how many carbon atoms that comonomer carries. More carbons means a longer side chain, which makes the finished film more flexible and more resilient. The performance trend runs cleanly: C4 → C6 → C8, step by step.
What each grade really is
- C4 — Butene (“The workhorse”): lowest cost, very stable to process, biggest volume worldwide. Moderate toughness; easier to puncture. Typical uses: everyday shopping bags, agricultural film. Common grades: 7042, 218WJ.
- C6 — Hexene (“The sweet spot”): clearly better drop, tear and puncture resistance than C4, with only a modest price step up. Typical uses: heavy-duty and industrial packaging. Common grades: 2607G, 2645.11G.
- C8 — Octene (“The premium player”): exceptional toughness and impact/puncture resistance; enables downgauging (same performance, less thickness). Typical uses: frozen-food, liquid and high-end laminated films. Common grades: 5401G, 5401GT, 3518.PA and various POE products.
Useful stat: butene (C4) copolymers are still the largest-volume LLDPE family on the planet, while hexene is the fastest-growing — overseas, roughly 94% of newly launched PE grades now use hexene.
So which one should you actually choose?
Customers rarely buy a “C6.” They buy outcomes: Will the bag break in transit? Can we make the film thinner and save material? Will the end user ever complain? Our rule of thumb:
Everyday packaging → C4 is plenty.
Heavy-duty / industrial → C6 earns its keep.
High-end or critical protection → C8′s advantages are clear.
Stretch film: machine-grade leans C6/C8; hand-wrap usually C4.
The paradox: if C8 is so good, why is C4 everywhere?
Two reasons keep C4 on top of the volume chart:
1. Cost vs. payoff — octene resins don’t always deliver a dramatic leap over hexene, yet they cost meaningfully more.
2. Supply — locally, large-scale hexene and octene production is limited, so imported comonomers carry a premium. That is why most domestically produced LLDPE runs on butene, while the high-end imported grades skew C6/C8.
The line we use with customers: C4 is the reliable economy car, C6 is the comfortable mid-range sedan, and C8 is the luxury SUV. They will all get you to the destination — the difference is the ride and the capability. The most expensive option is not automatically the best. The right one is.
The XH PACK takeaway
From C4 to C8 is really a roadmap of polyethylene moving from “good enough” to “high performance.” The skill in material selection is not chasing the highest grade — it is matching the resin to what your product genuinely demands.
It is exactly the kind of decision we help our customers make every day: securing the performance you need without paying for the performance you don’t.
What grade are you running today, and has it ever let you down? I would love to hear about it in the comments.
Post time: Aug-14-2026