The core team, a Jeep and an elephant...

Up to this moment, five compression tests have taken place, with altered variables the number of tested bottles (9/ 12), the bottles’ volume (0,5L/ 1,5L), the design specifications (For carbonated soft drinks CSD/ For non-CSD), the bottles’ condition (Used/ New), the cap sealing method (Teflon tape/ Epoxy adhesive) and the bottles’ distribution (Hexagonal/ Orthogonal array). The internal pressure of the bottles was kept constant for all samples, at a level of 6 atm, in order for the results to be comparable. The level of deformation of the samples and their mass loss were rated after the tests, and the factors leading to failure were analysed.

The new bottles for CSD that were sealed by applying epoxy adhesive around their caps’ threads, performed considerably better, regardless their volume. Specifically, during the fourth compression test, nine 0,5L PET bottles withstood a compression load of 7tn, and presented a total displacement of 140mm, until the bottles could no be seen anymore from the front Plexiglas opening of the safety container. At that point, the test was stopped for safety reasons (the Plexiglas sheet on the corner of the safety container started to bend outwards), but up to then, there was no bursting noted nor significant leaking that would lead to rigidity loss. After releasing the load, the bottles recovered their previous shape and remained rigid. All samples presented minor plastic deformation at the base (pleats on the petaloid’s surface), but no serious damage in any case.

Similarly, during the fifth compression test, nine new 1,5L PET bottles for CSD (adhesive sealing), withstood 8tn of loading and were displaced by 160mm. In this case, as well, the test was stopped for security reasons and no bursting or serious leaking was detected. The bottles, after unloading, returned to their previous shape but their base contained damages.

The results from the last two tests are very encouraging, yet more tests will be conducted the following months so that safe conclusions can be drawn.

The equivalent of the 4th compression test