Finite element analysis for container approval
10-10-2018 | Posted by Principia
Plastic, especially PET, containers must satisfy the progressively tougher quality requirements that transformers and final clients impose on their suppliers.
And those requirements are not arbitrary. If you want to play in the big league, aiming at large contracts with brand owners (Coca-Cola, PepsiCo, Orangina, etc.) to give stability to your business, you must prove that your product complies with the health and safety standards of organisations such as FDA or EFSA, apart from other more stringent ones that may be specified by the client.
The key word is approval, a fearsome exercise because the necessary analyses are protracted, cumbersome and costly; that is certainly the case in the migration tests conducted with PET bottles, in which various liquids (water, oil, etc.) must be used in different storage conditions to guarantee that the shelf life specified by the brand owner is actually attained.
In the case of carbonated soft drinks (CSD), apart from the possible migration from the container to the product, the permeability of the container must be checked to limit the leakage of contents; after all, who would care for a coke that is not bubbly?
Placing fruit juices in PET containers presents even more challenges: hot filling implies that the material must be able to sustain elevated temperatures without excessive deformation, which requires additives to improve the thermal behaviour without compromising the barrier or migration properties. In brief, a true challenge.
A standard laboratory test takes one or two weeks at best and must be repeated for a number of material configurations (single or multiple layers, with nanocomponents, etc.), thereby multiplying the number of tests required (as well as time and cost), without much guarantee of success beyond a pass/fail conclusion and the observations that the tests might provide.
Realistic simulations by finite elements can yield faster and less expensive answers to those questions.
With adequate software one can design a virtual container and carry out virtual tests in a couple of hours, sometimes in minutes, with the added advantage that shapes and materials can be easily modified as a function of the type of drink and the conditions to consider. Furthermore, the same virtual bottle can be subjected to other tests, such as accidental drops, stacking or crushing.
Thus, simulation software can be used for discarding, quickly and efficiently, large numbers of unsuitable designs and for selecting the more promising shapes, materials and dimensions, leading to prototypes that can be tested with good chances of success.
We will not obviate the approval process, but the life of PET producers and transformers can be made much simpler… if only the right tools are activated.
