Mechanical Properties of Plastics Reinforced With Carbon Nanotubes

This paper describes the first steps in the area of prediction mechanical properties of nanotubes-plastic composites. Multi-level approach is used in order to take into account all the known data about all levels of composite material. Effective (macroscopic) mechanical properties are produced from solution of inverse boundary problem of continuum medium mechanics with coordinate-dependent elastic tensor. Theoretical results are compared with known experiment [1] on reinforcing polystyrene film.

Nanomodified Fibre Reinforced Polymer Composites and Adhesives: What Needs To Be Done?

The discovery of C60 bucky balls by Richard E Smalley and team that won them the Nobel Prize 1996, and the pioneering work by Thomas Ebbesen and Pulickel M Ajayan from the lijima Lab, on bulk production of CNTs, paved the way to worldwide research, in nanotechnology. Studies of researchers like, Koral Schulte, F.H. Gojny and several others, resulted in nanotube modified epoxy composites with improved fracture toughness and stiffness properties. Ray Boughman and group’s work may be considered as the first in the direction of CNT modified fibrous composites, when they produced the toughest ever SWNTs from a PVA dope. Alan Windles and team carried out rapid production of continuous CNT fibres. All these efforts while laying the foundation for use of CNTs in composites of particulate type, strongly reveal a big gap to be filled by nanoscientists and engineers alike, in extending the use of CNTs in structural grade composites. In this paper, therefore, an attempt has been made, to highlight the above efforts and explicitly bring out, the need to focus on scientific and technological aspects pertinent to the Nanotube-modified FRP Composites and adhesives, recognizing that the best of CNTs for the structural–composites is yet to come.

Characterization of Polyaniline Nanocomposite Using AC Electrochemical Impedance Spectroscopy

Silicate minerals have been found to improve physical and mechanical properties of polymers significantly through clay/polymer nanocomposites. This class of materials uses smectite-type clays, such as hectorite, montmorillonite, magadiite, and synthetic mica, as fillers to enhance the properties of polymers. One of the most important properties of smectite-type clays is their layered structure, in which each layer is constructed from tetrahedrally coordinated Si atoms fused into an edge-shared octahedral plane of either Al(OH)3 or Mg(OH)2. The layers exhibit excellent mechanical properties parallel to the layer direction due to the nature of the bonding between these atoms. It has been found that Young’s modulus in the layer direction is 50 to 400 times higher than that of a typical polymer [1–5]. The layers have a high aspect ratio and each one is approximately 1 nm thick, while the diameter may vary from 30 nm to several microns or larger. Hundreds or thousands of these layers are stacked together with weak van der Waals forces to form a clay particle. With such a configuration, it is possible to tailor clays into various different structures in polymer [1,6,7].

Biodistribution of Dendrimer Nanocomposites for Nano-Radiation Therapy of Cancer

Multifunctional nanocomposites have an enormous scientific and practical future in medicine, especially in biomedical imaging and targeted delivery. Multifunctional composite nanodevices (CND) possess chemical and physical properties of all components, while interactions with the environment of the nanoparticle are dominated by the contact surface of the host molecule. Thus, if the surface is dominated by the organic component of a nano-sized organic-inorganic composite particle, an inorganic particle property can be manipulated in a biologic environment as if it belonged to an organic macromolecule. Composition, charge, and size of are critical in determining nanoparticle trafficking and uptake by organs, and therefore this knowledge is crucial for the development of cancer imaging and therapies. Specific biokinetics and biodistribution then can be influenced by correctly selecting size, and modifying surface characteristics, such as covalently attaching various targeting moieties to the surface forming biohybrids, regulating the surface charge, etc. Dendrimer nanocomposites are recently developed nearly monodisperse hybrid nanoparticles composed of macromolecular hosts and very small, uniformly dispersed inorganic guest domains combining desirable properties of the components. The surface groups control the interaction of these nanodevices with the biological environment. As a result of various synthetic options, the interior and/or the exterior of the host can be cationic, anionic, or non-ionic, depending on their termini and interior functionalities and the pH, and may involve multiple targeting moieties. We have synthesized gold/dendrimer nanocomposites to carry payload radiation and/or diagnostic moiety to specific targets. We examined the biodistribution of the templates and the corresponding gold/dendrimer nanocomposites. We employed the same dendrimer template and systematically varied the size, the surface charge and the composition. Biodistribution of {Au} gold/dendrimer nanodevices of various size (5, 12 and 22 nm) and surface charge (positive, negative) was investigated in mice models (B16 melanoma and DU145 human prostate cancer). Isotope neutron activation analysis (INAA) was used to measure the presence of Au(0) in the tissue sample. All {Au} gold/dendrimer-nanocomposites were assayed for their quantitative short-term (1hr), intermediate (1 day) and long-term (4 days) biodistribution throughout organs for clinical toxicity. Delivery of radiation dose was achieved by radioactive {198Au} composites in a mice model. We have shown that modulating surface charge and composition will greatly change the biodistribution characteristics of the nanodevices. Rigorous testing of the principles that govern nanoparticle interactions with the complex environment of biological systems will be critical for an understanding of how these nanodevices will behave in vivo.

Fabrication of Laminated Nanocomposites by Vacuum-Assisted Deposition of Clay Onto Glass/Epoxy Prepregs

In this study we are presenting a novel method for introducing nanoclay in epoxy matrix composites. The method involves vacuum-assisted deposition of fine clay particles directly onto the surface of commercially available prepregs. A deposition chamber is developed that is capable of breaking down nanoclay particles by subjecting them to shear and depositing them uniformly onto prepregs at room temperature. By using the deposition chamber, a thin layer of nanoclay is deposited on 101.6mm×101.6mm woven glass/epoxy prepregs. Twelve of these prepregs are stacked and cured by an autoclave at a temperature of 121°C under a constant pressure of 0.2MPa (30psi) for 1 hour. After the curing is complete, the laminates are cut into 10.8mm×31.7mm samples for three-point bending tests, glass transition temperature measurements and microstructural characterization. The improvements in mechanical properties such as flexural strength, flexural stiffness, and glass transition temperature by the addition of nanoclay are presented. Nanocomposite morphology is studied by light microscopy and scanning electron microscopy. Marginal improvements in mechanical properties are observed with only 0.6% nanoclay content. The flexural stiffness improved by 4% while maintaining the flexural strength constant at around 400Wa. Glass transition temperature is measured as 128°C for samples with and without nanoclay. However, significant differences in microstructure are observed. Although both samples contain micro-voids, these voids are observed to be more extensive in samples involving nanoclay.

Cure Kinetics of Nanocomposites Prepared From Aqueous Dispersion of Nanoclay

The effect of nanoclay on the cure kinetics of glass/waterborne epoxy nanocomposites is investigated. First step in sample preparation involves dispersing Cloisite® Na+, a natural montmorillonite, in distilled water at 70°C with the aid of a sonicator. Then, desired amounts of dicyandiamide and 2-methyl imidazole, serving as cross-linkers, are mixed to the aqueous nanoclay solution. As the mixing continues, Epi-Rez 3522-W-60 waterborne epoxy resin is introduced to the solution and the compound is mixed for an additional 30 minutes. The nanoclay content of this batch is adjusted to be at 2wt%. An identical second batch, which does not comprise nanoclay, is also prepared to serve as the baseline data. Glass/waterborne epoxy prepregs containing 30% glass fibers are prepared from these batches and used to characterize the effects of nanoclay. The evolution of viscoelastic properties during curing are characterized by the APA2000 rheometer. Using the storage and loss moduli profiles during curing, gel time and maximum storage modulus are characterized. Effect of nanoclay on the glass transition temperature is determined by applying an additional temperature cycle following the cure cycle. In addition, mechanical performances of the samples are characterized by three point bending tests. Nanoclay is observed to yield 2-fold higher storage modulus during curing. Rate of curing is measured to be substantially slower for the samples comprising nanoclay. In addition, glass transition temperature improved by 5% to 99°C with the addition of nanoclay compared to 94.5°C for the samples without nanoclay. Flexural stiffness of the samples containing nanoclay is measured to be 20% higher than the samples without nanoclay while the strength remained virtually unaffected.

Assembly at the Nanoscale: Towards Functional Nanostructured Materials (Invited)

This paper reports the self assembly of functional nanostructured materials including multi-walled Carbon Nanotube-Quantum Dot (CNT-QD) heterojunctions using the Ethylene Carbodiimide Coupling procedure (EDC). Thiol stabilized ZnS capped CdSe quantum dots containing amine terminal groups (QD-NH2) were conjugated with acid treated Multi-Walled Carbon Nanotubes (MWCNT) ranging from 400 nm to 4μm in length. SEM, TEM, EDS and FTIR were used to characterize the conjugation process.

Factors Influencing the Morphology Development of Epoxy Nanocomposites

Polymer nanocomposites draw great interest due to their unique nanostructures and improved properties [1–2]. Epoxy is a widely-used thermosetting material. The research on the epoxy layered-silicate epoxy nanocomposite has exploded in the last decade [3–9]. The morphology of nanocomposites is the key to making high-performance nanocomposites. In this presentation, the factors influencing the morphology development behavior of epoxy nanocomposites will be discussed. The factors to be investigated include organoclay, epoxide, and curing agent. In this study, the aliphatic diamine (Jeffamines) with different molecular weights and aromatic diamine were selected as the curing agents, S30B (quaternary onium-montmorillonite) and SC18 (primary oniummont-morillonite) as the organoclays, and Epon 862 and Epon 828 as epoxides. In situ small-angle x-ray scattering (SAXS) was utilized to study the morphology development of the epoxy nanocomposite.

C/SiC Composites by Electrophoretical Infiltration

Due to its high thermodynamical stability carbon fiber reinforced silicon carbide is an interesting material for high temperature applications. Studies are described to find an innovative route for fabricating C/SiC composites by using electrophoresis for infiltrating carbon fiber mats with non-aqueous suspensions of mixtures of silicon carbide powders, stabilizers and sintering aids. The suitability of nano-scaled and submicron powders is discussed. Based on investigations of the interaction between the SiC particle surfaces and the carbon fibers essential technological parameters of the electrophoretic infiltration are defined. The fabrication of C/SiC composites by lamination of single infiltrated fiber mats and a subsequent thermal process is demonstrated.

Zeta Potential Studies of Titanium Dioxide and Silver Nanoparticle Composites in Water-Based Colloidal Suspension

We determine the zeta potential (ZP) by using electrophoretic laser light scattering and Laser Doppler Velocimetry (LDV). Particle sizes are measured by photon correlation spectroscopy (PCS). We studied the ZP for colloidal suspensions of TiO2 and Ag metal particles in order to determine the kinetic interaction and charge exchange between the particles. We investigated the natural tendency of the particles for aggregation and varied the pH of the solution. It was found that the ZP versus pH curve for the mixed TiO2/Ag did not behave as the average of the individual TiO2 and Ag curves as one would expect, and instead there was a slight horizontal shift towards higher pH values which implies that the particles in the mixed TiO2/Ag colloid are interacting with the result of charge exchange. The average particle size was measured in terms of effective diameter, for the TiO2, Ag and the mixed TiO2/Ag particles. The results indicated an increase of approximately 100 nm in the effective diameter of the mixed TiO2/Ag particles size compared to the size of the individual TiO2 particles. This can be explained as the fact that 50 nm Ag particles are adsorbed on the surface of the TiO2 particles.