Stretch Blow Molding of Mineral Filled PET
Résumé
Injection stretch blow molding (ISBM) is a two-step process that was designed and optimized mainly for unfilled PET resins. The present study focuses on stretch blow molding of a PET filled with different amounts of sub-micronic mineral fillers. The influence of fillers is analyzed thanks to DSC, DMA, tensile testing and processing in different configurations on a prototype apparatus and an industrial machine. It is demonstrated that fillers enhance crystallization kinetics, which leads to a reduction of the processing range. Differences in strain hardening induced by fillers make it necessary to adjust blowing temperature. However, the main effect occurs during the heating phase of the preforms. Temperature within a filled preform is much less homogeneous than in neat PET, making the temperature gradient totally different if the heating protocol is kept unchanged. Once the heating of filled preforms is controlled to reach equivalent temperature gradients, blowing is possible and rather equivalent to that of pure PET.