PET has established itself as a material for making lightweight, clear and tough bottles. Ideally, one seeks to make a preform with zero or very low crystallinity (for purposes of clarity), while the final bottle should have high crystallinity (for enhancing gas barrier and mechanical properties). Monitoring crystallanity is thus important and in this work, we sought to evaluate methods of crystallanity measurement. We have used density, Differential Scanning Calorimetry (DSC) and Modulated Differential Scanning Calorimetry (MDSC) to study the crystallanity of preforms and bottles. The applicability and appropriateness of each technique for different PET sample types, and interpretation problems are also discussed.
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