Correlations between blowability and uniaxial stretchability of PET before and after mechanical recycling

Abstract

In the literature, previous studies have linked the behaviour of PET under stretch-blowing and under uniaxial stretching thanks to the time-temperature equivalence principle. Other works showed variations of microstructural, thermal and mechanical properties of PET submitted to mechanical recycling, but blowability was not measured. In this article, the behaviour during free stretch-blowing tests was investigated for a virgin commercial PET before and after mechanical recycling with a step of solid-state post-condensation. For the same physical state, the lower stretch-blown volumes obtained for the recycled PET were correlated with a sooner nucleation leading to a lower Natural Draw Ratio, as observed during uniaxial tensile tests. Our results confirm that the uniaxial stretching tests used in the past to discriminate the behaviours of neat PET resins in blowing, can also be used to predict variations of blowability under mechanical recycling.