Online monitoring of thermoplastic crystallization with miniaturized interdigital sensors

Online in-process monitoring of the crystallization process of thermoplastic materials will significantly improve the production of structural parts of these materials and therefore expand their area of application. Several monitoring methods such as differential scanning calorimetry or scanning electron microscopy are available for this purpose, but they are not suitable for online monitoring. It was demonstrated that dielectric measurements are suitable for online monitoring. However, the sensors used so far were so big that they could not be applied in fabricated parts as they would harm the mechanical stability of the part. Here, we demonstrate that our flexible miniaturized interdigital sensor, which does not downgrade the mechanical stability of the part, can be successfully used for crystallization monitoring of polypropylene. We choose this material as representative of a crystalline thermoplastic material. For the first time such a small sensor was used to monitor the crystallization process of a thermoplastic material.