The Woodruff School

SUMMARY

Current technology of polymer nanocomposites (PNC) emphasizes the need for fundamental understanding of the links between manufacturing method and bulk properties in order to engineer processing and performance of PNCs. Manufacturing method is one key variable that dramatically defines interfacial interactions on the nano-scale and thus properties of polymer near the interface of nanomaterial/polymer or interphase, level of dispersion and crystallization behavior of semi-crystalline PNCs. These factors in particular govern reinforcing mechanisms at the interface and consequently impart important properties to PNCs. Therefore, a fundamental insight into the links among manufacturing method, interfacial interactions and bulk properties is essential in order to construct effective structure-property models to design PNCs with engineered performance. The main goal of this study was to provide a fundamental understanding of effect of manufacturing method on the bulk properties of PNCs with a focus on the role of interfacial interactions that can lead to fabrication of engineered PNCs with multifunctional performance. The objectives of this research were to: i) determine detail correlations among manufacturing methods, nano- and microstructure and macroscopic properties of multifunctional exfoliated graphite nanoplatelets/polyamide 12 polymer nanocomposites with enhanced mechanical and electrical performance through a systematic experimental methodology, ii) provide a scientific methodology in order to understand the possible correlations among nano-scale interfacial interactions, physical and structural properties of the polymer at the interface and macroscopic behavior of PNCs, iii) provide a comprehensive methodology to qualitatively and quantitatively characterize an interfacial zone (interphase) formed between the reinforcement and polymer, and iiii) provide a scientific knowledge for introduction of engineered and directionally dependent functionalities to PNCs. This study demonstrated key correlations among manufacturing techniques, interfacial interactions and macroscopic properties of PNCs. A successful methodology was introduced to determine the properties of the interfacial zone such as thickness, amount and modulus. Finally, the study illustrated superior mechanical, electrical and morphological properties of SLS processed parts over injection molded PNCs and thus confirmed capability of SLS in development of electrically conductive PNCs that exhibit multifunctional performance. In conclusion, the study provided insight into the links among process, nano-scale interfacial interactions and microstructure to better understand effects of manufacturing technique on macroscopic properties of PNCs.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Mehdi Karevan

TIME:	Tuesday, June 4, 2013, 3:00 p.m.

PLACE:	MARC Building, 201

TITLE:	Understanding Effects of Nano-reinforcement -Matrix Interphase on the Elastic Response of Polymer Nanocomposites

COMMITTEE:	Dr. Kyriaki Kalaitziou, Chair (ME) Dr. Suman Sad (ME) Dr. Satish Kumar (MSE) Dr. Ting Zhu (ME) Dr.Vladimir V. Tsukruk (MSE)

SUMMARY Current technology of polymer nanocomposites (PNC) emphasizes the need for fundamental understanding of the links between manufacturing method and bulk properties in order to engineer processing and performance of PNCs. Manufacturing method is one key variable that dramatically defines interfacial interactions on the nano-scale and thus properties of polymer near the interface of nanomaterial/polymer or interphase, level of dispersion and crystallization behavior of semi-crystalline PNCs. These factors in particular govern reinforcing mechanisms at the interface and consequently impart important properties to PNCs. Therefore, a fundamental insight into the links among manufacturing method, interfacial interactions and bulk properties is essential in order to construct effective structure-property models to design PNCs with engineered performance. The main goal of this study was to provide a fundamental understanding of effect of manufacturing method on the bulk properties of PNCs with a focus on the role of interfacial interactions that can lead to fabrication of engineered PNCs with multifunctional performance. The objectives of this research were to: i) determine detail correlations among manufacturing methods, nano- and microstructure and macroscopic properties of multifunctional exfoliated graphite nanoplatelets/polyamide 12 polymer nanocomposites with enhanced mechanical and electrical performance through a systematic experimental methodology, ii) provide a scientific methodology in order to understand the possible correlations among nano-scale interfacial interactions, physical and structural properties of the polymer at the interface and macroscopic behavior of PNCs, iii) provide a comprehensive methodology to qualitatively and quantitatively characterize an interfacial zone (interphase) formed between the reinforcement and polymer, and iiii) provide a scientific knowledge for introduction of engineered and directionally dependent functionalities to PNCs. This study demonstrated key correlations among manufacturing techniques, interfacial interactions and macroscopic properties of PNCs. A successful methodology was introduced to determine the properties of the interfacial zone such as thickness, amount and modulus. Finally, the study illustrated superior mechanical, electrical and morphological properties of SLS processed parts over injection molded PNCs and thus confirmed capability of SLS in development of electrically conductive PNCs that exhibit multifunctional performance. In conclusion, the study provided insight into the links among process, nano-scale interfacial interactions and microstructure to better understand effects of manufacturing technique on macroscopic properties of PNCs.