A drop of liquid nitrogen injected into a PET bottle before capping evaporates and creates positive pressure inside. The pressure holds the shape of a thin-walled bottle in the same way CO2 does in a carbonated drink. This allows a lighter preform to be used for still beverages without losing container rigidity.
A thin-walled PET bottle with a still product has no internal pressure. In storage, the lower pallet layers are crushed under the weight of the upper ones; in transport, bottles deform. The usual solution is a thicker wall — a heavier preform and more plastic per unit.
After capping, the liquid nitrogen dose evaporates and expands roughly 700 times. The gas creates positive pressure in the closed bottle, and the walls work in tension. The bottle keeps its geometry on the pallet and in transport.
| Without nitrogen | With nitrogen dosing |
|---|---|
| Rigidity from wall thickness — heavier preform | Rigidity from pressure — a lighter preform can be used |
| Crushed containers in lower pallet layers | Shape retained in storage and transport |
| Claims and returns due to deformation | Fewer returns due to container deformation |
| Oxygen in the neck | Inert atmosphere above the product |
Yes. In hot filling, the product cools in the closed container, pressure drops and the bottle is drawn inwards. Nitrogen positive pressure compensates for this effect. For hot filling and containers with shallow headspace, the 3-D Technology option is used: it eliminates splash and holds target pressure within ±1% psi.
According to VBS, the investment in a doser typically pays back within the first year of operation. The period depends on line output, preform weight difference, PET prices and the share of returns. It is calculated for the specific production.
For lightweight containers, pressure stability from bottle to bottle is important. At speeds up to 2000 cpm, NITRODOSE G3 Pro (±3% of dose weight) and NITRODOSE G3 Servodoser (±1%) with the 3-D Technology option are used. Details are in How to choose a liquid nitrogen doser.
This depends on bottle shape, volume, product and storage conditions. The weight reduction is determined by trials with the preform manufacturer on the line (individually, on request).
In carbonated drinks, pressure is created by CO2. Nitrogen dosing for rigidity is used for still products: water, juices, tea, oils.
Sources: VBS Europe; Vacuum Barrier Corporation; VBS materials.
