Segregated Conductive Network of MWCNT in PA12/PA6 Composites

Significance 

Electrically conductive polymer composites are widely used for various industrial applications today. They can be formed from a dispersion of conductive fillers in either a polymer blend or matrix through extrusion or injection molding. A good example of commonly used conductive filler are the carbon nanotubes (CNT), which has a good electrical conductivity and high aspect ratio so could promote low percolation thresholds in the composite. As matrix, the blends of polyamide 12 and polyamide 6 (PA12/PA6) have added advantages such as better dimensional stability as compared to using a single polyamide 6.

However, various factors determine the nanocomposite morphology in the case of use immiscible blends as PA12/PA6 blends. They include viscosity ratio of the polymers, kinetic effects, and thermodynamics. On the other hand, evaluation of the rheological behaviors and electrical conductivity of the nanocomposites can be used to investigate their percolation threshold. It also provides an in-depth understating of the organization structure of the MWCNTs in their polymeric matrices.

A group of researchers at the University of Coruna in Spain: Dr. Laura Arboleda-Clemente, Assistant Professor Ana Ares-Pernas, Mr. Xoan Garcia, Dr. Sonia Dopico and Assistant Professor Maria Jose Abad designed a carbon nanotube nanocomposite with low percolation threshold and excellent electrical conductivity. They used an immiscible PA12/PA6 blend as matrix. This was in a bid to understand and explain the macroscopic properties of nanocomposites. Their research work is currently published in the research journal, Polymer Composites.

The authors used rheological tests and alternating current measurements to deduce the percolation threshold. Furthermore, to investigate the carbon nanotubes localization and the nanocomposite morphology in the polymer matrix, transmission electronic microscopy and light microscopy were used. Lastly, they calculated the electrical and rheological percolations using graphical methods.

The authors observed from rheological tests, a liquid-like to solid-like transition that takes place between 0.15% and 0.31% of the entire MWCNT volume. On the other hand, a 0.09% of the MWCNT was estimated using the power-law relationship. Additionally, it was found that the insulation to conduction transition of the material was also located between 0.15 and 0.31 of the MWCNT percentage volume, but in this case,the electrical threshold, using the power-law relation, was found to be 0.26%. The obtained results were similar to those obtained in the previous studies.

The sequence of mixing of PA12, PA6 and MWCNTs during processing promoted the development of a segregated conductive network. The preferred localization of the CNTs is the interface of the two used polyamides. This morphology explains the low percolation thresholds obtained for the PA12/PA6/MWCNT composites. Besides, a lower rheological percolation than electrical percolation was observed. This was attributed to the fact that the electrical percolation depends on the network created by carbon nanotubes while the rheological percolation depends on both nanotube-nanotube and nanotube-polymer networks.

 

Segregated Conductive Network of MWCNT in PA12/PA6 Composites: Electrical and Rheological Behavior. Advances in Engineering

About the author

Dr. María José Abad-López is an Associate Professor at the Department of Physics and Earth Sciences, University of A Coruña (UDC), Spain. She develops his research in the Group of Polymers and, at the present, is the technical manager of the Plastics Laboratory in the Center for Technology Research belonging to UDC. She manages different R&D& I projects financed by public or private funds focused on polymer science and technology.

Her current research interests are in polymer processing and polymer characterization, specifically, on conducting polymers and composites. She received her Ph.D (1999) in Physics from University of Santiago de Compostela (Spain). She has authored over 80 scientific articles and has supervised four PhD thesis.

About the author

Dr. Ana Isabel Ares-Pernas is an Assistant Professor at the Department of Physics and Earth Sciences, University of A Coruña (Spain). Her research is performed in the Group of Polymers in the same university.

Her expertise and research activities are in the area of polymers; polymers characterization, epoxy resins, cure kinetics, thermal degradation, water absorption, mechanical and impact tests. She is mainly involved in the study of composites processability and rheology and the last studies are focused on thermal and electrical conductive composites. Dr. Ares collaborates on research activity at the Plastics Laboratory of Center for Technology Research of the University of A Coruña, participating as a research in R& D& I projects funded through public calls both national and international. In addition, she collaborates in technical assistances and projects that the Laboratory done to companies in the plastics processing sector.

About the author

Dr. Laura Arboleda-Clemente was a PhD student at the Plastics Laboratory of Center for Technology Research, University of A Coruña. Her doctoral thesis was focused on the study of conductive nanocomposites based on carbon nanotubes and polyamide blends, focusing mainly on their electrical and rheological properties and their morphology. During her stage in the Laboratory the Dr. Arboleda collaborated as a researcher in several projects funded through public calls and in technical assistances or projects with companies in the plastics processing sector. Nowadays she works in one of these companies.

About the author

Xoán García Fonte holds a degree in Biological Sciences from the University of Santiago de Compostela. He worked for two years as Production Manager at the CGAP (Centro Galego do Plástico). Since then, he joined the technical team of Plastic Laboratory, University of A Coruña, where he has participated in different R & D projects focused on the design and development of polymer composites, optimization processing parameters for new materials or manufacturing techniques, etc. At present, he develops his thesis work centered on the design of new conducting composites and their physical-chemical characterization.

Reference

Arboleda-Clemente, L., Ares-Pernas, A., García, X., Dopico, S., & Abad, M. (2015). Segregated conductive network of MWCNT in PA12/PA6 composites: Electrical and rheological behavior. Polymer Composites, 38(12), 2679-2686.

Go To Reliability Polymer Composites

Check Also

fatigue resistance of polymers and their molecular weight

Uncovering the relation between fatigue resistance of polymers and their molecular weight