The target was to design square stackable large size containers in PET in order to save space and to reduce palletizing cost.
In order to keep the same packaging standards as with HDPE jerry cans (most common material conversion) the container must be vertically stackable also with a neck handle. Conversion is possible also from tinplate cans.
Stackable containers need to have the right design combination between customized base and neck/shoulder. It is important to choose the right neck finish and preform design and stretching ratios (radial and specially axial) have to be within certain limits to ensure an optimum thickness/material distribution and blowability of the container. Special attention must be paid on bottom design: special pattern, special vents, special cooling. The particular shape of the base must be high and wide enough to contain the capped neck (and handle, if present) of the lower container.
We have developed different designs and performed several blowing trials. To produce a good container, it is necessary to respect some limitations:
- The weight range depends on the complexity of the container and on customer specifications including logistic;
- A larger neck finish (i.e. 77mm vs 63 or narrower) improves the blowability, enhances stretching ratio by using optimum preform drawing and facilitates lightweighting;
- Handles and closures availability must be evaluated.