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Silicon nanocomposites were prepared with unmodified and modified magnetite nanoparticles in order to study the effect of the fatty acid modification on the curing reaction and thereafter on the mechanical and magnetic properties of the filled silicon‐based elastomer. Magnetite nanoparticles were first surface modified with oleic and stearic acid. Silicon nanocomposites with unmodified and modified magnetite nanoparticles were prepared by predispersing the nanoparticles in the silicone with the curing agent using toluene and ultrasound assisted mixing. The effect of the magnetite on the crosslinking reaction was studied in a rubber process analyzer instrument. At first, the addition of 1 wt% of magnetite decreased the induction time and increased the maximum torque, but upon increasing the magnetite content, this time increased and the maximum torque decreased. However, all the nanocomposites showed an induction time much lower than that of the pure silicon and a maximum torque much higher than that of the pure silicon. Unmodified magnetite nanocomposites showed a heterogeneous saturation magnetization when magnetite nanoparticles were modified with oleic and stearic acid. This resulted in homogeneous and replicable properties, attributed to the improvement in nanoparticles dispersion and distribution within the polymer matrix. The high saturation magnetization values of composites with unmodified magnetite compared with those with modified magnetite confirm that modified magnetite presented the best dispersion and more homogeneous magnetic properties. The Fourier‐transform infrared spectroscopy analysis suggests that the magnetite nanoparticles coating could be reacting with the silicon hydrosilane group which in turn decreases the attainable crosslinking level. With respect to the tensile properties, the tensile stress, as well as the elongation at the breakpoint decrease, in general, with increasing the magnetite content. POLYM. COMPOS., 40:3981–3988, 2019. © 2019 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Maleic anhydride-grafted polypropylene (PP-g-MA) was reacted with aniline (NH2C6H5) to produce PP-g-NHC6H5 and used as a compatibilizer in polypropylene/carbon nanotube composites. Infrared spectroscopy (FTIR) and nuclear magnetic resonance confirmed the reaction between PP-g-MA and aniline. PP-g-NHC6H5 resulted a better compatibilizer than PP-g-MA, producing good dispersion and homogeneous distribution of the carbon nanotubes with less agglomerates, as observed by SEM analysis. Improved dispersion and distribution is assumed to be due to the π-π interactions between the -C6H5 ring in the prepared compatibilizer and the hexagonal carbon structure in the nanotubes. In addition, a higher degree of crystallinity (12%) was promoted, since it was favored by π-π interactions. This achieved higher crystallinity promoted an increase in tensile modulus, with only slight changes in tensile strength but with an adverse effect on elongation at break. [ABSTRACT FROM AUTHOR]

Poly( l‐lactic acid) nanocomposites based on silver nanoparticles (PLA/AgNP) were prepared by melt blending using a twin screw extruder. Nanocomposites at low concentrations were prepared with 0.1, 0.2, and 0.3 wt% of AgNP to enhance the crystallinity and improve the thermal and mechanical properties of PLA. AgNPs smaller than 100 nm which increased the crystallinity of PLA upon the addition were detected by UV–Vis. Crystallinty index of nanocomposites was estimated reaching a maximum of 0.52, where the AgNPs acted as heterogeneous nucleating agent which is correlated with the Ag content. The α and α′ crystals were observed by temperature modulated differential scanning calorimetry and wide angle X‐ray diffraction, thus lattice spacing of more ordered and distorted crystals were corroborated obtaining a higher fraction of α structures when a high content of nanoparticles was added. Moreover, strain at break and toughness of pure PLA were increased from 4.3% to 16.9% and 2.1 to 7.3 MJ/m3, respectively, modifying the inherent brittleness of PLA. Finally, with the obtained results a correlation was established where more disordered crystals show less resistance to deformation that lead to an enhancement of elongation at break observed in the nanocomposites. POLYM. COMPOS., 39:2368–2376, 2018. © 2016 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]