Plasma Functionalization of Multiwalled Carbon Nanotubes and Their Use in the Preparation of Nylon 6‐Based Nanohybrids

Abstract

The possibility to obtain carbon nanotubes (CNT)/polyamide 6 composites with excellent mechanical properties in a simple, industrially scalable way is investigated. Commercial CNTs are treated by plasma while changing some key parameters (exposure time, plasma power, type of gas) in order to optimize the process and to achieve a sufficient degree of functionalization. The treated samples are characterized by Fourier transform infrared spectroscopy, Raman spectroscopy and X‐ray photoelectron spectroscopy. The most interesting samples are selected to be used as reinforcing fillers, in different concentrations, in a polyamide 6 matrix. The mechanical tests show a dramatic increase of both tensile and impact properties, due to the achievement of a good wettability, and an efficient dispersion of the CNTs in the polymer matrix, as confirmed by scanning electron microscopy observations. magnified image

High performance PA6/CNTs nanohybrid fibers prepared in the melt

“…Surprisingly, the plasma functionalization causes a slight decrease of this property, despite the higher level of adhesion, dispersion and orientation achieved, as demonstrated by the above presented data. This unexpected result can be explained considering that the functionalization partially destroyed the graphenic sp 2 structure of the CNTs walls after introducing oxygen moieties as demonstrated by the increase of the ID/IG ratio as measured by Raman spectroscopy and discussed in our previous works [5,10]. Other authors [23][24][25] while studying PA12/CNT systems found some relationship between the rheological behaviour of PA12, its end groups and the electrical conductivity of the nanocomposites.…”

“…An increase of this ratio can be correlated with the degree of functionalization by the different vibration modes of carbon atoms in the presence of defects, generated during the functionalization process and associated to the presence of oxygen or other atoms in the nanotube structure. [5,17,18]. In Fig.…”

“…The nanotubes were dried under vacuum at 120°C overnight, fractionated in a mortar, put on a watch glass and then fed to the reactor, using oxygen as gas, a power of 120 W and a treatment time of 10 min, according to our previous studies [5,10].…”

“…Using nanoscaled fillers offers the possibility to achieve the aim by adding small amounts (even less than 1 wt.%) due to their high specific surface. Among these nanofillers, CNTs are interesting because of their unique combination of low density, large aspect ratio, good dimensional stability, high mechanical performance and electrical conductivity [1,2,4,5]. The ways to add CNTs into polymer matrices refer to two different inclusion approaches: in solution and in the melt.…”

“…According to our previous works [5,10], in this paper we chose to functionalize, in oxygen plasma, two samples of CNTs that differ for synthesis method and characteristics in order to introduce polar groups on the nanotubes walls thus promoting the adhesion with polyamide 6. The CNTs were then added to PA6 by melt mixing and fibres were subsequently obtained by melt spinning and characterized from a mechanical, morphological and electrical point of view, comparing the properties of composites prepared with neat or functionalized CNTs.…”