The present review highlights the effect of different types of nanoparticles/nanotubes/nanolayers in polyamide nanocomposite properties. Polyamides belong to an important class of engineering polymers due to their interesting properties, such as temperature stability, good chemical resistance, relatively high tensile strength and stiffness. The availability of different types of nanoparticles and its functionalization, besides the improved knowledge on the integration with the polyamide matrix, has opened possibilities for developing new fields of applications and products. POLYM. COM-POS., 00:000-000, FIG. 12. TEM images of PA6/prisitine multi-walled carbon nanotubes (MWNT) (a) and PA6/amide like-3 MWNT nanocomposites (5 phr) by melt-compounding. Reprinted from [40], Copyright (2014), with permission from Elsevier.

The inorganic halloysite nanotube (HNT) is a promising type of naturally occurring fillers with many important uses in different fields. An HNT has a relatively low content of hydroxyl groups on its surface, which makes it relatively hydrophobic, although this is not always sufficient to guarantee good interfacial adhesion in composite systems. Further surface treatment is required to improve the compatibility of HNTs with polymer matrixes, maximizing interfacial interactions. The aim of the present work was to study a noncovalent functionalization of halloysite with 2,2′-(1,2-ethenediyldi-4,1-phenylene) bisbenzoxazole (EPB), based on electron transfer, for further use of EPB as a coupling agent in polymer/HNT compatibility. A set of characterization techniques were performed to evaluate the chemical and physical properties and evidence the functionalization. The results revealed the surface modification of halloysite upon functionalization. Emphasis was for powder wettability by tensiometry based on Washburn because no studies about halloysite powders using this technique could be found in the literature. The results demonstrate a reduction in the total surface energy of the system, usually accompanied by a reduction in the polar component upon HNT modification.

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L-menthol is an essential oil produced from Mentha arvensis. An experimental L-menthol solidliquid equilibrium in menthol oil constituents was determined in the temperature range between 271 K and 300 K, by the method of creating a saturated solution at a given temperature by using an excess of crystals in the suspension. The mole fraction of the experimental data, on a logarithmic basis, were fitted against T by the Apelblat equation and by a linear equation with good results. The equations were: ln(x) = [-52.45 + 1,170.70/T + 8.48.ln(T)] and ln(x) = 3.98 -1,249.65/T with T in K. Both equations give a good correlation with the experimental data. From the Apelblat equation the enthalpy of solution was also calculated as a linear function of temperature and has an average value of 150.31 J/mol in the temperature interval studied.

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