SUBJECT: Ph.D. Proposal Presentation
BY: Mehdi Karevan
TIME: Friday, May 4, 2012, 1:00 p.m.
PLACE: MARC Building, 114
TITLE: Understanding Effects of Nano-reinforcement - Matrix Interphase on the Elastic Response of Polymer Nanocomposites
COMMITTEE: Dr.Kyriaki Kalaitzidou, Chair (ME)
Dr. Suman Das (ME)
Dr. Satish Kumar (MSE)
Dr. Vladimir V. Tsukruk (MSE)
Dr. Ting Zhu (ME)


The research focuses on understanding the effects of nano-reinforcement - polymer interactions on the elastic response of polymer nanocomposites (PNCs) in order to provide effective models that enable design and fabrication of PNCs with engineered properties for targeted applications. It is expected that nano-reinforcements can lead to PNCs with dramatic enhancement of mechanical properties. However, the unique properties of the nano-reinforcements cannot be fully realized in PNCs because of agglomeration and weak interface resulting in insufficient load transfer. In the other hand, it is noted that the micromechanical models assume homogeneous dispersion of nano-reinforcements and perfect contact at the nano-reinforcement polymer interface. These may be valid assumptions for micro-size reinforcements but fail in the case of the nano-reinforcements. The current approach in fabrication of PNCs is a trial and error one combined with elaborate, costly and time consuming experimental characterization of PNCs. Fundamental understanding of the nano-reinforcement- polymer interactions through an integrated approach including systematic experimental characterization of the interfacial interactions in PNCs and multi-scale modeling of PNCs is necessary for design and fabrication of PNCs with engineered mechanical properties. This is the goal of this research. In this study, the PNCs are fabricated using conventional methods such as extrusion injection molding and compression molding. Selective laser sintering (SLS) is also used to evaluate and compare the effects of processing-induced interfacial interactions. Interfacial interactions can lead to formation of interphase, change in the physical properties of the polymer including crystallization and secondary reinforcing mechanisms. The interphase properties such as amount, elastic modulus and thickness are characterized using dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and atomic force microscopy (AFM). The dependence of the interphase properties on the crystallization, characterized via X-ray diffraction, hot stage optical microscopy and DSC, and the state of agglomeration, characterized by scanning electron microscopy and rheometer, is evaluated. Finally, the results of the experimental study are used as an input to analytical models, such as Halpin-Tsai and Tandon-Weng.