Marcio Rodrigo Loos

Effect of carbon nanotubes addition on the mechanical and thermal properties of epoxy matrices

In this work, nanocomposites were prepared by adding a small amount of single walled carbon nanotubes (SWCNTs) to an epoxy resin aiming to study the resulting mechanical, viscoelastic and thermal properties of the nanocomposites. To optimize the processing of the nanocomposites and to favor a homogeneous dispersion of the SWCNTs on the matrix, acetone was used to reduce resin viscosity, increasing diffusion of the SWCNTs in the solution. The epoxy/SWCNTs/acetone systems were also sonicated in order to minimize entanglement of the SWCNTs. The systems were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, thermogravimetry, differential scanning calorimetry and dynamic mechanical analysis. The results indicated that the addition of small amounts of SWCNTs to epoxy leads to slight structural changes in the epoxy matrix which, together with the presence of SWCNTs, may reflect on its mechanical and viscoelastic properties

The Effect of Acetone Addition on the Properties of Epoxy

In this work, a varied amount of acetone was employed to dissolve an epoxy resin and then a route was followed to remove the acetone, simulating a frequently used method to disperse nanofillers in thermoset matrices. Analyses were then carried out to address the influence of residual acetone on the curing process and on the epoxy properties. The results showed a detrimental effect on the mechanical properties of the cured epoxy due to the presence of residual acetone and also a less brittle-like fracture of the specimen. Fourier transform infrared spectroscopy and thermogravimetric analyses were additionally used to characterize the cured resins and have also indicated the presence of a small amount of acetone. Nevertheless, rheological measurements indicated that 10.0 wt.% acetone addition on the resin causes a significant decrease in viscosity (around 50%) which may promote a better dispersion of nanofillers.

The Effect of Sulfonation Level and Molecular Weight on the Tensile Properties of Polyoxadiazoles

The tensile properties of sulfonated polyoxadiazoles were studied as a function of molecular weight and sulfonation level. All sulfonated polyoxadiazoles synthesized through a polycondensation reaction of the hydrazine sulphate salt and a dicarboxylic acid in poly(phosphoric acid) exhibit rigid-ductile behavior with high Young’s modulus (3—4 GPa) and with larger elongations at break (up to 120%). Sulfonated polyoxadiazoles with maximum reproducible tensile strength (190 ± 6.9 MPa) could be synthesized in the frame of time of 4—5 h.

Polymer Matrix Nanocomposites and Nanostructured Materials

1 Center for Technological Sciences, State University of Santa Catarina, 89223-100 Joinville, SC, Brazil 2 Department of Macromolecular Science and Engineering, Case Western Reserve University, Cleveland, OH 7202, USA 3 Institut für Kunststoffe und Verbundwerkstoffe, Technical University of Hamburg-Harburg, 21073 Hamburg, Germany 4 CINVESTAV-Querétaro (Materials Science & Technology), Libramiento Norponiente 2000, 76230 Santiago de Querétaro, QRO, Mexico

Chapter 8 – Is It Worth the Effort to Reinforce Polymers with Carbon Nanotubes?

The effectiveness of carbon nanotubes (CNTs) and carbon fibers (CFs) as reinforcing agents is ranked. The strongest, the stiffest, and the cheapest CFs commercially available are compared with CNTs. We show that CNTs are the most viable strengthening option, whereas CFs are the most viable stiffening option. To achieve the true potential of nanotubes, several challenges have to be faced.

Chapter 9 – Reinforcement Efficiency of Carbon Nanotubes—Myth and Reality

We demonstrate that the critical filler volume fraction where a percolating network of carbon nanotubes is forming marks a “turning point” in the reinforcement efficiency. Expectations for the reinforcing effect of carbon nanotubes at concentrations above a percolating threshold with the current technology are mostly unrealistic.