Multiwalled carbon nanotubes (MWCNTs), both oxidized and amine functionalized (triethylenetetramine-TETA), have been used to improve the mechanical properties of nanocomposites based on epoxy resin. The TGA and XPS analysis allowed the evaluation of the degree of chemical modification on MWCNTs. Nanocomposites were manufactured by a three-roll milling process with 0.1, 0.5, and 1.0 wt % of MWCNT-COOH and MWCNT-COTETA. A series of nanocomposites with 5.0 wt % of reactive diluent was also prepared. Tensile and impact tests were conducted to evaluate the effects of the nanofillers and diluent on the mechanical properties of the nanocomposites. The results showed higher gains (258% increase) in the impact strength for nanocomposites manufactured with aminated MWCNTs. Optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to investigate the overall filler distribution, the dispersion of individual nanotubes, and the interface adhesion on the nanocomposites.Particularly, the epoxy resins are thermosetting polymers used in the development of structural composites due to their high tensile strength, good chemical resistance, high adhesion, and low shrinkage. 18,19 However, the cross-linked resins are generally brittle materials with low fatigue resistance to heat and impact, which limits their application. CNTs can contribute to the improvement of mechanical and thermal properties, such as tensile strength, modulus of elasticity, impact resistance, and increase in the glass transition temperature in high-performance nanocomposites. 19,20 Guo and co-workers dispersed 2.0, 4.0, 6.0, and 8.0 wt % of oxidized MWCNTs directly in epoxy resin Additional Supporting Information may be found in the online version of this article.
We observed the anti-UV action of beetroot extract in an ultra-high molecular weight (UHMWPE) matrix. The beetroot extract and the one prepared from annatto seed also acted efficiently as pigment to the same polymeric matrix. Neat UHMWPE and UHMWPE compounded with annatto and beet extract were compression molded and tensile specimens were obtained from the molded plates and submitted to UV radiation for up to 42 days. Tensile tests were performed and it was observed that the beet extract had a stabilizing action in the polymer compared to neat polymer and the one with annatto extract. Complementary analyses showed good homogenization of the extracts through the polymer matrix indicating the possibility of use as pigment, although the annatto extract appeared to be very unstable under irradiation. Spectroscopic characterization helped to explain the stability of the extracts before and after molding.
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