Characterization of thermoplastic nonwovens of copolyamide hot melt adhesives filled with carbon nanotubes produced by melt-blowing method

Abstract

Thermoplastic nonwovens containing 2.5 wt% of multi-walled carbon nanotubes were manufactured by half-industrial melt-blowing process from two copolyamides belonging to the group of hot melt adhesives having different melt-viscosities. The initial masterbatches have been analyzed by their rheological and thermal properties to adjust the appropriate conditions of melt-blowing process which allowed to manufacture the nonwovens without structural defects. It was found using a scanning electron microscope that in 10 wt% masterbatches fewer agglomerates of the multi-walled carbon nanotubes occurred in less viscous coPA2 and their average diameter measured by ImageJ was 60 µm. For more viscous coPA1 some oval agglomerates with even 270 µm diameters have been detected but during the extrusion they were destroyed. Microstructural observations of the nonwovens showed that fibers occur in the entangled state and their average diameter is around 45 µm for each type of the copolyamides. Analysis of the electrostatic properties of the nonwovens with low and high areal weight showed that electrical surface resistivity is slightly higher for the nonwovens based on coPA2 and those with higher areal weight. Using high-resolution microscope, it was possible to ascertain that in the nonwovens made of coPA1 + 2.5 wt% the carbon nanotubes are well-dispersed with their visible alignment along the fiber axis, unlike those in the nonwovens made of coPA2 + 2.5 wt% which occur mainly as lightly connected bundles without any specific orientation. The developed nonwovens can be used as interlayers to increase the electrical and mechanical properties of composite structures in the aerospace and automotive sectors.

Fibers of Thermoplastic Copolyamides with Carbon Nanotubes for Electromagnetic Shielding Applications

“…Microwave dielectric spectroscopy was used to characterize the dielectric properties of the produced fibers according to the method described for thin cylindrical rods [ 24 ]. The moduli of microwave reflection and transmission coefficients were measured with an automatic dielectric spectrometer in the frequency range from 8 to 37 GHz.…”

“…This method prevented destruction of the waveguide channel to be rejected and made it possible to verify the calibration during the experiment. The complex dielectric permittivity of samples was calculated according to the method presented in [ 24 ]. For measurements at higher temperatures a home-made furnace was used, while for measurements at low temperatures liquid nitrogen was used.…”

“…A good microwave absorber should be thin and lightweight. The most common forms are foils, films or papers [ 21 , 22 ], coatings [ 25 , 26 , 27 ], fibers [ 23 ] or textile products such as woven or nonwoven fabrics or mats [ 24 , 25 ]. They were applied in fiber-reinforced composites as an alternative to metallic meshes or tapes [ 17 ].…”

“…Due to the modification of the processing parameters, the state of nanofillers' dispersion can be controlled, and the final composite properties have a tunable morphology [17,18]. This, together with the chemical and corrosion resistance, low weight, flexibility, ease of processing into various shapes, and inexpensiveness, is why polymer composites have the potential to replace the metallic materials in EMI shielding applications [2,17,[19][20][21][22][23][24]. It should be noted that the development process of innovative EMI shielding materials is also focused on their final form-ready-to-use in industrial applications.…”

Biodegradable hot melt adhesive based on partially saponified polyvinyl acetate/cellulose diacetate blend

“…EVA, a copolymer of ethylene and vinyl acetate (VAc), is most commonly used as the base polymer for HMAs. In addition, polyester, polyamide, and polyurethane are also used in the composition of HMAs 4–6 . In relation to the serious environmental issues caused by petroleum sourced polymers, the development of biodegradable HMAs has become a hotspot for many researchers.…”