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- Mechanical properties of alumina nanofilled polymeric composites cured with DDSA and MNAPublication . Amaro, Ana M.; Pinto, Deesy G.; Bernardo, Luís; Lopes, Sérgio; Rodrigues, João; Louro, Cristina S.Reinforced concrete is widely used in structures. New materials to replace both the steel and the concrete have been studied in many research centres. One of the possibilities for the reinforcement is the partial or total replacement of the steel bars by new composite materials. Nano composites are very promising, and an investigation line was developed to this end by an interdisciplinary team. On this work, the mechanical properties of epoxy resin nanocomposites (EPNCs) filled with α-Al 2 O 3 nanoparticles (NPs) with irregular shape and approximately 100 nm maximum diameter size was investigated. The variable study was the alumina NPs contents: 1, 3 and 5 wt.%. The NPs were previously pretreated with a silane agent (APTES). Two hardeners, 3-dodec-2-enyloxolane-2,5-dione (DDSA) and 8-methyl-3a,4,7,7a-tetrahydro-4,7-methano-2benzofuran-1,3-dione (MNA), frequently used in epoxy resin embedding tissues, were used simultaneously for this study. Unlike other hardeners, DDSA does not need curing treatment, constituting a novel application and a saving time-energy during the manufacturing process. Considering the mechanical behaviour, it was observed that the EPNCs filled with 5 wt.% of alumina NPs showed the maximum improvement in flexural modulus, around 14 % when compared to the pristine EP sample. No relevant effect was observed on the flexural strength by adding alumina NPs. Additionally, the maximum increase observed for hardness, and Young’s modulus were about 13 % and 28 %, respectively (the maximum increase was observed at 3 wt.%).
- Effect of irregular shaped nanoalumina on the enhancement of mechanical properties of epoxy resin nanocomposites using DDM as hardenerPublication . Amaro, Ana M.; Bernardo, Luís; Pinto, Deesy G.; Lopes, Sérgio; Rodrigues, João; Louro, Cristina S.This article presents experimental results on the mechanical properties of epoxy (EP) resin nanocomposites (EPNCs) reinforced with alumina nanoparticles. The nanoparticles consisted on alpha alumina with irregular shapes (100 nm maximum size) pretreated with a silane agent (3-Aminopropyl triethoxysilane, APTES). During the preparation process, silane-functionalized alumina nanoparticles, are covalently connected to the epoxy matrix by the reaction of the amine groups with the epoxy groups, creating stronger interfacial interactions between the nanoalumina (the filler) and the EP matrix. At the curing process, the amine groups of the 4,4′-Diaminodiphenylmethane (DDM (the hardener)) will react with the epoxy groups, creating/reinforcing the network interlock at the polymeric matrix. The weight fractions of alumina nanoparticles were as follows: 1, 3 and 5 wt.%. After testing, and when compared with the neat EP, the EPNCs containing 1 wt.% of alumina nanoparticles showed the maximum improvement on the mechanical properties. Better dispersion of nanoalumina particles was achieved for 1 wt.%.