12 Current Nanoscience, 2010, 6, 12-39 1573-4137/10 $55.00+.00 © 2010 Bentham Science Publishers Ltd. Carbon Nanotubes Composites: Processing, Grafting and Mechanical and Thermal Properties Ana L. Martínez-Hernández 1,2 , Carlos Velasco-Santos 1,2,* and Víctor. M. Castaño 1 1 Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro, 76230, México 2 Departamento de Metal Mecánica, Ingeniería en Materiales, Instituto Tecnológico de Querétaro, Av. Tecnológico s/n, Col. Centro, Santiago de Querétaro, Querétaro 76000, México Abstract: Carbon nanotubes represent one of the most important materials in nanoscience and nanotechnology today. The exceptional properties that these materials possess open new fields in science and engineering. Additionally, the chemistryassociated to these materi- als starts to play an important role, inasmuch, new moieties insert by different chemical routes, inside and outside of carbon nanotubes surfaces, have shown able to modify their structure and properties. To this date, new properties have been found in chemically-modified nanotubes and diverse potential applications are suggested for these materials. One of the most frequent applications for these carbon ma- terials is their inclusion as reinforcement in polymer matrices, due to the amazing structural, mechanical, electrical, chemical and thermal properties that carbon nanotubes possess, suggesting that these materials are ideal to produce new polymer nanocomposites. In this con- text, carbon nanotube nanocomposites have been developed by numerous research groups around the world aiming to produce new novel strong and light composite materials. Also, electrical conductivity and thermal properties have been studied for this kind of nanocompo- sites. However, new challenges to create a new age of multifunctional composite materials with these nanometric forms arise and, there- fore, the study of new properties in these nanocomposites has increased significantly in the last few years. In this review we discuss a range of methods to properly utilize nanotubes in poymer-based composites, from the solubility behavior of carbon nanotubes, the proc- essing methods to develop carbon nanotube polymer composites, interactions produced between carbon nanotubes and polymer grafted, to the most recent results on the mechanical and thermal properties of carbon nanotubes polymer composites, synthesized with different types of carbon nanotubes. In addition, we discuss the effect of different chemical modifications on nanotubes, with special focus on those developed to improve the compatibility between these nanostructures and engineering polymers, as well as their effect on the final composites properties. The significance of understanding, enhancing and controlling the behavior at the interface between nanotubes and polymer matrices towards the development of novel multifunctional applications with these composites, is also discussed in detail. Keywords: Carbon nanotubes, chemical functionalization, polymer nanocomposites, polymer grafting, mechanical properties, thermal prop- erties. INTRODUCTION Carbon nanotubes are one of the most studied nanomaterials in the last fifteen years. Due to their extraordinary physical and chemical properties that this carbon allotrope posseses has emerged as novel nanometric material, promising in most areas of science and engineering. These materials have their own features and prop- erties related to structural arrangement and therefore the carbon nanometric materials find new specific research fields that are raised constantly. Nowadays, the carbon nanotubes research has been focused on diverse fields, inasmuch as no previous material has displayed the combination of outstanding mechanical, thermal, and electronic properties. The combination of these properties makes nanotubes appropriate for an extensive range of applications. One of these possible applications is certain their incorporation as reinforcement of polymers matrices in order to develop a novel strong, light, conductive, smart and multifunctional new age of nanocomposite materials. The properties of carbon nanotubes col- lectively with their size provide a unique material competent to form more interactions in various polymer matrices at molecular level. In this context different researches have been focus to synthe- size polymer composites with as-obtained carbon nanotubes and modified nanotubes. Several experimental researches are directed to find the better compatibility between carbon nanotubes and poly- mer matrices, inasmuch as, there are many factors that play an im- portant role in carbon nanotubes dispersion in polymers. However, chemical functionalization in carbon nanotubes has improved nota- bly the compatibility of these materials with diverse solvents and polymer matrices. This later has allowed diversify the applications of carbon nanotubes and take advantage of their properties in vari- *Address correspondence to this author at the Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro, 76230, México; Tel: +52 442 2 38 11 50; Fax: +52 442 2 38 11 65; E-mail: carlosv@fata.unam.mx ous polymeric matrices. Thus, in this paper are reviewed the disper- sion of carbon nanotubes in different solvents, oxidation in nano- tubes is also introduced, inasmuch as this approach is the base of several functionalizations with other chemical moieties, in addition is reviewed the functionalization with other chemical groups in- serted on carbon nanotubes surface using other methods. The tech- niques used in the literature to produce polymer composites rein- forced with carbon nanotubes are reviewed before to analysis the mechanical and thermo-mechanical properties of these kinds of nanocomposites reinforced with as-synthesized nanotubes. In addi- tion are presented the polymer grafting nanotubes researches with the grafting to and grafting from techniques, follows of the review of mechanical properties reported to polymer composites developed with modified carbon nanotubes. Finally comments of the reviewed researches and advances in the field of carbon nanotubes polymer nanocomposites are also discussed. 1. DISPERSION OF CARBON NANOTUBES IN ORGANIC SOLVENTS AND WATER Recently, research to synthesize Carbon Nanotube Polymer Composites (CNPN) has focused on different routes aiming to ade- quately disperse these nanomaterials in a number of polymer matri- ces. Carbon Nanotubes (CNs) dispersion is influenced by the sur- face nature of these materials, which normally agglomerate due to the interactions between carbon nanotubes with each other. To get good dispersion during polymer composites processing is funda- mental in order to aspire to all mentioned multifunctional properties desire in polymer composites, adequate dispersion improve conduc- tive, mechanical, thermal properties and allows to access to other features in these kind of novel polymer nanocomposites. Thus, to disperse CNs in organic solvents solutions or polymer is an open area of R&D, with fundamental questions, unsolved yet. However, important advances have been achieved when CNs are modified by chemical or physical approaches, in order to change their surface nature, thus improve their solubility properties and therefore, their