Papers by Author: Celeste M.C. Pereira

Abstract: An overview of the effects of different nanoscale materials on the flammability of two thermoset polymers is presented and discussed in this paper. Its goal is to bring together our recent experimental results obtained for different material systems of nanoclays, nano-magnesium hydroxide (nano-Mg(OH)2) and carbon nanotubes (CNT) in epoxy and unsaturated polyester resins; some of these results have already been published elsewhere. It is shown that these nanoparticles can be used to lower the heat release rate (HRR) of the polymers when exposed to a fire situation. On the other hand, in the majority of the cases this low flammability of polymer nanocomposites is only achieved in terms of HRR, but fails in terms of time-to-ignition or the extent of smoke released.

Abstract: In this work the effect of nano-magnesium hydroxide (nano-Mg(OH)2) on the flammability of epoxy composites is presented and compared with the traditional flame retardant used in just small amounts for epoxy resins, ammonium polyphosphate (APP). The fire reaction properties of epoxy composites were obtained by cone calorimeter tests. It was observed that the flammability of the unfilled resin is significantly changed with nano-Mg(OH)2 addition and reductions of 33, 22 and 23% in the epoxy composite heat release rate peak (PHRR) by incorporating 10%, 5 % and 1% of nano-Mg(OH)2, respectively, were achieved. Cone calorimeter analyses confirm the better behavior of APP composites compared with nano-Mg(OH)2 composites. SEM micrographs show some agglomerations on the distribution of nano-Mg(OH)2 in the epoxy matrix.

Abstract: This work reports the effects of nanoclays and aluminium hydroxide (ATH) on the thermomechanical properties of an unsaturated polyester resin. Dynamic mechanical thermal analysis in the temperature range from 25 to 150 °C has indicated the formation of different structures for the different clay (1, 5 and 10 wt. %) and ATH loadings (50 and 100 wt. %) investigated. The rubbery modulus increases with nanoclay and ATH content which indicates that both nanoclays and ATH act positively on the final network density and consequently lead to systems showing higher stiffness at higher temperatures. The mechanical loss peak value decreases with either nanoclay or ATH content which seems to indicate that both nanoclays and ATH improve network density. The glass transition temperature and the mechanical loss peak value changes linearly with ATH content.