Thermoplastic nanocomposites with enhanced electrical conductivity

Paulina Latko ,  Anna Boczkowska 

Warsaw University of Technology, Faculty of Materials Science and Engineering (InMat), Wołoska 141, Warszawa 02-507, Poland

Abstract

     During recent years, there has been a growing demand for composite materials with integrated multifunctional capabilities. The promising substitutes for traditional composites are nanocomposites consist of polymers and filler with nanosize. One of the most known nanofillers are carbon nanotubes. These hollow, low dense three-dimensional structures demonstrate extraordinary mechanical and electrical properties capable to reach the functionality of composites. However, their great industrial potential cannot be fully realize due to current manufacturing challenges. It happens because even the small addition of carbon nanotubes into polymer matrix alters the properties of polymer significantly. On the one side, the improvement of mechanical and electrical behavior of polymer is observed. However, on the other side, the jump of viscosity and decrease in macromolecules flowability lead to many hindrances in their processing. Hence, a lot of efforts is put to overcome these obstacles  to find the possible way of nanocomposite's processing on industrial scale.

      The conducted research are focused on the three levels. The first one is the fabrication of thermoplastic composites with carbon nanotubes from polyamides and thermoplastic elastomers using laboratory mini extruder. Polymers used in the study are commercially available and show the wide range of melt-flow index. Samples were produced in the form of strips and fibers. The process conditions were found and then optimized to make the manufacturing route continuous. Afterwards, the factors affecting electrical conductivity of nanocomposites are deeply investigated. First and foremost, the significant increase in electrical conductivity. The higher amount of carbon nanotubes the higher conductivity is achieved. However, this is necessary to achieve the percolation threshold which is different for various polymer. It was found, that the differences in carbon nanotubes arrangement in strips and fibers lead to completely dissimilarities in the conductivity values. Moreover, the carbon nanotubes available on the market did not give the same results what is dependent on their dimensions and purity.   

   The second area of the study is related to development of processing route of nanocomposites towards products which could be commonly used in different industrial sectors. Aerospace and aviation fields are mainly under our interests because the novel lightweight multifunctional nanocomposites  are still desired.  They potential usage include lighting strike protection and improvement of the mechanical properties.  The most needed form of the final product is non-woven fabric called veil. It is understood as a thin textile material with random distribution of fibers characterized by low aerial weight (GSM factor). The method of fabrication thin veils with carbon nanotubes on the laboratory scale was the main challenge within this area of interest. The production starts with nanocomposites fibers extrusion with carbon nanotubes using mini-extruder. Then fibers with different carbon nanotubes content and with diameters from 80µm to 300µm were fabricated. They were further cut and press together into the veil without using of any binders or additional chemical compounds. The temperature and time of pressing were adjusted resulting in good quality veils. Non-woven fabrics doped with carbon nanotubes were used in the laminate infusion process as an interlayer. The improvement of electrical and mechanical performance of laminate was observed.

      The third area of study is connected to development of veils manufacturing process on the half-industrial scale. For this purpose, melt-blow technique was chosen as a well known in the polymers processing. This one step approach possesses higher capacity and is much faster than others. Thermoplastic polymer with carbon nanotubes was loaded into the hopper and melted. Then, owing to high speed hot air the material is going through the head equipped with small nozzles on the moving drum. As a result, veils with carbon nanotubes were obtained. Veils with 5wt.% of nanofiller with minimum areal weight 7g/m2 were successfully fabricated. They were used as a interlayers in the laminate infusion process.

      The main motivation of our work is the lack of non-woven veils with carbon nanotubes on the market. Moreover, their huge potential and demand from different industrial sectors. 

    The part of the study was supported by ESA as a contract no. 4000107904/13/NL/KML

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Presentation: Oral at Nano PL 2014, Symposium A, by Paulina Latko
See On-line Journal of Nano PL 2014

Submitted: 2014-06-30 07:00
Revised:   2014-06-30 07:09
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