POF Shrink Films: Beverage Multipack Case Study
Most buyers treat POF shrink film as a commodity. Pick a thickness, pick a width, compare the price per kilogram, place the order. Then the line runs at full speed and the packs come out crooked, or the film keeps breaking at the sealing bar — and nobody can explain why the exact same film runs perfectly at another plant.
Here is a case from our own production floor that explains what is really going on.
One product, two plants, two different films
AD calcium milk — the small-bottle dairy drink made famous in China by Wahaha — is sold everywhere in collated multipacks. The bottle is small, light, smooth-walled and slightly tapered. On paper it is one of the easiest products you could ever shrink wrap.
In practice, we supply two different films for it.
The reason is not the bottle. It is the machine. One plant runs the bottles upright through the packer. Another plant lays the bottles on their side and runs them lying down. Same drink, same bottle, same pack count — but two fundamentally different packaging scenarios.
Why the same film cannot serve both lines
It comes down to contact area and friction.
When the bottles travel lying down, the film wraps along the length of each bottle. The contact area between film and bottle is generous, so the bottles are naturally held in place. What matters most here is that the film moves freely through the machine — over the forming shoulder, through the film path, into the seal. A film that grips too aggressively creates drag: tension builds, feeding becomes unstable, and you get wrinkles, mis-seals and film breaks.
When the bottles travel upright, the situation reverses. The film touches only a narrow band of each bottle, so the contact area is small. Under acceleration and during shrinking, bottles can shift relative to the film — you get displaced bottles, skewed packs, crooked seals, and in the worst case bottles slipping out of the wrap. To hold everything in position, the film needs higher friction — a higher coefficient of friction (COF) — so it grips the bottle surface instead of sliding across it.
Now put those two requirements side by side. The high-COF film that solves the upright line is exactly the film that causes feeding problems and breakages on the lying-down line. The free-running film that keeps the lying-down line stable is exactly the film that lets bottles wander on the upright line.
One product. Two packing methods. Two films.
The lesson for buyers: the film should be built around your line
This is the part most sourcing conversations skip. A thickness and a width do not describe a packaging application. Before we quote, we would rather ask:
What is the product — shape, weight, surface, sharp edges or rounded?
Do the items travel upright or lying down through the packer?
What machine brand and model, and what is the line speed?
Side seal or hot-wire seal? What is the tunnel temperature and dwell time?
Single pack or collated multipack, and how many units per pack?
How are the finished packs stacked, stored and transported?
Are you trying to downgauge — run a thinner film to reduce cost and material use?
Answer those, and the specification almost writes itself: the right structure, the right COF, the right shrink force, the right thickness. Skip them, and you are buying film by the kilogram and hoping.
That is also why our film sometimes costs a little more than the cheapest quote on the table — and why customers stay. We develop the film around the packaging scenario, rather than asking the scenario to tolerate whatever is in stock.
Why we can tune a film instead of just selling one
Most people assume we are a film manufacturer. Strictly speaking, we are a company that builds its own film-blowing machines — we simply do not sell them. We use them ourselves, and we keep upgrading them. Our lines started at 1.8 m width, moved to 2.8 m, and today run at 3.3 m. Wider film means higher output and better consistency, and because the machines are ours, every improvement goes straight into the product.
That control over the process is what makes customised film structures realistic rather than theoretical:
Five-layer co-extruded POF shrink film
The workhorse structure, with high clarity, gloss and reliable shrink performance across a wide range of products.
Cross-linked POF shrink film
The same five-layer film treated with electron cross-linking, giving markedly higher tear and puncture strength, a higher shrink rate for a tighter finish, stronger seals for high-speed lines, and the option to downgauge.
Dedicated variants for specific problems
Low-temperature shrink for heat-sensitive goods, anti-fog film for fresh produce and chilled foods, and perforated film where breathability matters.
Behind that sits a provincial-level research institute with more than 80 engineers, 61 proprietary patents, 80,000 tonnes of annual capacity, participation in the drafting of China's national POF standards, and shipments to more than 60 countries. Zhejiang Zhongcheng has been listed on the Shenzhen Stock Exchange (002522) since 2010.
Frequently asked questions
Can one POF film handle both upright and lying-down bottle lines?
Sometimes, on slow lines with forgiving products. On fast lines, a compromise film usually underperforms on both — either bottles shift or the film drags. Two tuned films typically cost less than the downtime of one wrong film.
What is COF and why does it matter?
Coefficient of friction describes how easily film slides against itself and against your product. Too low and items shift inside the pack; too high and the film will not feed smoothly. It is a specification you can request — not something you have to accept by chance.
Can you match a film we already use?
Yes. Send us your current specification or a sample roll, along with your machine details, and we will match or improve on it.
Do you provide samples?
Yes — free samples for evaluation once the specification is agreed.
Tell us about your line
If you are packing bottles, cartons, trays, or anything awkward, the fastest way to a useful quotation is to send us:
Photos or a short video of your packaging line in operation
Machine brand, model and line speed
Your current film specification (thickness, width, roll length)
Estimated monthly or annual volume
We will come back with a recommended specification, a sample plan and a price — not just a price list.
Contact our team today for a specification review and free samples.