POF is the general-purpose choice for retail packs: clear, food-safe and forgiving in the tunnel. PVC shrinks at lower temperature and holds sharp detail but is less tolerant of heat variation. PE is tougher and suits bundling heavy items rather than presentation packs.
Film properties drive machine settings
Each film has a temperature window where it shrinks cleanly. Below it the pack stays loose; above it the film scorches or splits. Changing film without re-setting the tunnel is one of the most common causes of a line that ran fine last week and does not today.
Film comparison
| POF (polyolefin) | PVC | PE (polyethylene) | |
|---|---|---|---|
| Clarity | High | High, sharp detail | Lower, often opaque |
| Tunnel temperature | Moderate window | Lower, narrower window | Higher |
| Toughness | Good | Moderate | High |
| Typical use | Retail food and consumer packs | Print-sensitive presentation packs | Bundling, heavy multipacks |
| Tolerance to setting error | Forgiving | Less forgiving | Forgiving but needs heat |
Film thickness and the seal
Thicker film needs more energy at the seal and more dwell in the tunnel. If you move up a gauge for durability, expect to re-set both stages. A seal that was reliable at one gauge will show intermittent failures at the next without adjustment.
What to change first when the pack looks wrong
- Confirm the film is the one the settings were made for.
- Check tunnel temperature against the film's window before anything else.
- Check conveyor speed: it sets dwell, and dwell and temperature trade off.
- Only then adjust air flow or product centring.
Films and consumables are listed with the machines they suit in the full catalogue.
Figures in this article are drawn from the 137 machine series SilverSeal currently supplies, not from generic industry averages. Specifications vary by model — check the individual series page before specifying.
Frequently asked questions
Can I run POF settings on PVC film?
No. PVC shrinks at a lower temperature and in a narrower window. Running POF settings will scorch it.
Which film is best for food?
POF is the usual choice for food retail packs because it is food-contact suitable and tolerant in the tunnel. Confirm the specific grade against your regulatory requirement.
Why did my seal quality drop after changing film supplier?
Sealant layers differ between suppliers even at the same nominal gauge. Re-set seal temperature and dwell after any film change.
