Deborah Dibbern Brunelli

Anomalous behavior of thermal stability of amino-carbon nanotube–epoxy nanocomposite:

Carbon nanotube–epoxy nanocomposite was obtained using amino-carbon nanotube and its thermal stability was compared with neat resin. The results showed that at lower temperatures (below 360℃), nanocomposite is more stable than neat resin. However, at higher temperatures (above 380℃), the contrary was observed: neat resin is more stable. In order to understand this anomalous behavior, a complete kinetic study of the cure process was performed. The precure degree of the nanocomposite was higher than that of the neat resin. However, both samples showed virtually the same final cure degree. The cure heat and activation energy were very similar for both samples. Nevertheless, the difference in thermal stability between nanocomposite and neat resin is not related to the cure process. This behavior must be associated with the good adhesion of amino-carbon nanotube–epoxy and to the presence of the functional groups linked to the carbon nanotube surface, especially oxygen molecules.

Study of Different Process Additives Applied to Polypropylene

There are several additives aimed on improving the processing characteristics as well as mechanical properties of the plastic materials. Being polypropylene is one of the main polymers used in the plastic processing industry due to its easy processability and application versatility, was chosen as the base resin for this study. Additives can aid the processing of polypropylene, either by promoting a better slip between the chains (lubricants), or by contributing to nucleation and crystallinity (nucleating). In this study, the raw materials copolymer polypropylene, lubricant (internal and external action), organic nucleating agent (metallic salt) and inorganic nucleating agent (metallic oxide) were considered. Mechanical tensile tests, Charpy impact and spiral flow to verify melt index were performed to characterize the samples with additives and standard (copolymer polypropylene). The interference of these additives with polymeric matrix was observed.

Understanding the water uptake in F-161 glass-epoxy composites using the techniques of luminescence spectroscopy and FT-NIR

This paper investigates the application of the luminescence spectroscopy technique in steady–state to study the moisture influence in glass fiber/epoxy prepreg and their laminates. The studies were monitored by intrinsic luminescence comparing the results with gravimetric analysis and near infrared with Fourier transform. Samples are cured and submitted to humidity controlled at 60 and 80 °C until 90 days. It is verified that the decrease in the maximum emission of the samples is directly related to the material moisture content. However, for very short periods, there is an increase in the relative intensity and blue shift of the emission band for all samples treated at 60 °C, which is related to an increase of the rigidity of the polymeric matrix. The results in this paper have a great significance because it brings a wide discussion on the interaction of water in epoxy composites materials.