Investigation and control of the static electrification in polypropylene

Abstract

The electrostatic charging of polymers due to friction is such a common phenomenon in daily usage of polymers that can be a problematic issue for various applications, such as in electronic devices, textile, space industry and so on. Hence, understanding and controlling of the mechanism behind the static electrification, which is basically because of the charge accumulation on the material, is an important subject in terms of the applications. In the way to understand static electrification of bulk materials, examining the physical and morphological properties is crucial. On the other hand, when the physical properties are considered, the structure of polymer plays a significant role, yet there is a lack of knowledge in the literature about the relation between these structural properties and triboelectricity. As a reason of this, it can be pointed out that in the proposed mechanisms about the frictional electrification the structure-property relation could not get sufficient attention so far. In this thesis, the crystalline structure of polymer, which plays a crucial role in the determination of physical properties of polymeric materials, was studied and by using different treatment techniques, such as microwave radiation and mechanical stress, and the relation between the degree of crystallinity and triboelectric charging was investigated. Due to its economical cost and heat-sensitive degree of crystallinity that can be changed in a significant way polypropylene (PP) which is a semi-crystalline polymer was used in this study. Hence, by utilizing different spectroscopic and microscopic techniques the relation between physical properties and triboelectrification of polypropylene was investigated in detail. In order to understand the physical and chemical changes taking place in untreated and treated polypropylene X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Differential Scanning Calorimetry (DSC) are the techniques that were employed. In this study, by considering the mechanism behind static electrification the potential link between electrification and degree of crystallinity was designated. Furthermore, the generation of charge on the surface of mechanically treated polypropylene film was observed for the first time by this current work. The results lead to the fact that it is possible to convert mechanical energy into electrical energy without any contact between the objects by introducing physical forces onto the insulating materials and the reasons behind non-contact electrification was investigated. Therefore, in the light of the results obtained from this study, more efficient triboelectric generators can be designed to harvest electrical energy from mechanical energy.