Effect of Functionalization on the Crystallization Behavior of MWNT-PBT Nanocomposites
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Effect of Functionalization on the Crystallization Behavior of MWNT-PBT Nanocomposites Gaurav Mago1, Carlos Velasco-Santos2, Ana L. Martinez-Hernandez2, Dilhan M. Kalyon3, and Frank T. Fisher1 1 Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 2 Centro de Fisica Aplicada y Technologia Avanzada, Universidad Nacional Autonoma de Mexico, Queretaro, Mexico 3 Department of Chemical, Biomedical and Materials Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 ABSTRACT There is tremendous interest in using low loadings of multiwalled carbon nanotubes (MWNTs) to enhance the multifunctional properties of polymers, with functionalization often pursued to increase the dispersion and effective reinforcement of MWNTs within the polymer. In our interest to understand the effect of MWNT functionalization on Poly (butylene terephthalate) (PBT) crystallization kinetics, morphology and mechanical properties, nanocomposites were fabricated with both as-received and carboxyl group (-COOH) functionalized MWNTs. Initial results indicate as-received and functionalized nanotubes alter the crystallization temperature and crystal size for quiescent samples. In addition, isothermal crystallization studies using an Advanced Rheometric Expansion System (ARES) show that the addition of MWNTs increases the rate of PBT crystallization. However, functionalization was found to decrease the rate of nanocomposite crystallization as compared to nanocomposites samples prepared using pristine MWNTs, suggesting that nanotube functionalization weakens the nucleation effect observed in the nanocomposite samples. These results suggest that semicrystalline polymer nanocomposite crystallization kinetics and morphology can be significantly influenced by nanoparticle functionalization and chemistry. Further study of how these changes impact the rheological and multifunctional properties of semicrystalline nanocomposite systems are ongoing. INTRODUCTION Poly (butylene terephthalate) (PBT) is a semicrystalline thermoplastic with a wide range of applications due to its fast crystallization rate, good moldability and mechanical properties. Meanwhile, the use of carbon nanotubes (CNTs) within polymeric materials has drawn considerable interest in the polymer industry as a means to impart multifunctional properties to various polymers. In particular, multiwalled carbon nanotubes (MWNTs) have stimulated great interest in the field due to their high aspect ratio, low density, high tensile modulus and strength, and high electrical conductivity. Effective properties of polymer-CNT nanocomposites are greatly affected by the dispersion of CNTs in polymer matrix, and the interface adhesion between the CNTs and the matrix [1-4]. In addition, the physical, chemical, and mechanical properties of semicrystalline polymers depend on the crystalline structure and the degree of crystallinity within the polymer. Further, it is well known that under quiescent crystallization, nanoparticles within a semicrystalline pol
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