A new research has led to the development of conducting polymer coatings that can improve aircraft safety. Conducting polymer coatings are environmentally friendly coatings that are an appropriate substitute for heavy metal compounds. The conductive nature of these polymers provide an electroactive interaction with the metal surface and forms a passivation layer between the metal surface and the polymer coating, acting as a barrier coating as well. These coatings may also impact the internal components of the aircraft when exposed to lightening or ‘electrical thundering’. Gunjan Gupta, a research scholar at IITB-Monash Research Academy in Mumbai, has undertaken research on conducting polymer coatings. The research is looking at developing a conducting polymer coating using polyaniline, which provides adequate conductivity and protection against corrosion for aluminium allows and provides over 6 times more conductivity than other coatings. Polyaniline in particular has high environmental stability, is low cost and has a simple polymerisation process. When this is added to an epoxy resin - a binder with excellent adhesion, resistance to corrosion and good mechanical and thermal properties - it has been found that the properties of the epoxy resin are actually enhanced. One of the issues with using polyaniline is its poor level of solubility that can impact its level of conductivity. One option is to use organic dopants, such as 10-camphorsulfonis acide (CSA), dodecylbenzenesulfonic acid (DBSA) and lignosulfonic acid (LGS) that increases the solubility of the conducting polymer. As a result the conducting polymer can be easily dissolved or blended with other polymers. The research is important as it not only will provide an environmentally friendly coating system for aircrafts, but it the polymer will also incorporate properties of organic dopants and nanoparticles in the coating. Whilst this coating has been designed specifically to be used in aircraft coatings, it also may have various other uses. There are two other main applications for these conducting polymers. First, utilising it for its conductive property such as in electrostatic materials, conducting adhesives, printed circuit boards and active electronics (like transisitors). Secondly, it can also be used for its electroactivity in electrical displays, chemical , biochemcial and solid electrolytes, drug release systems, and “smart home” systems.
Carbon nanotubes have excellent mechanical properties, are very tough, very rigid and conduct electricity. "The problem with them is that they get dispersed, in other words, it's very difficult to get them to blend with polymers," explained Iñaki Eguiazabal, a member of the Polymer Technology Group. That is why it is essential to come up with methods that will enable the carbon nanotubes to have a high degree of dispersion and stability within the polymer matrix. A successful preparation of one of these materials has been achieved through a new research. The research aimed to improve the mechanical properties of poly(ether imide). Poly(ether imide) is a polymer that has very good mechanical and thermal properties and is used, among other things, to produce the internal parts of aircraft. However, like most polymers it is an insulating material from the electrical perspective. "By adding carbon nanotubes, we are not only able to improve the mechanical properties of the material even further, we can also turn it into a conductor of electricity," explained IñakiEguiazabal. This could enable them to be used in electrostatic painting applications, among other things.
The Polymer Technology Group, which is part of the UPV/EHU's Department of Polymer Science and Technology and the Institute for Polymer Materials, POLYMAT, has its recent line of work that is focusing on the study of nanocomposite systems consisting of thermoplastic polymers and organically modified laminated clays or carbon nanotubes. New nano-reinforced materials based on technical polymers, and in the case of systems with carbon nanotubes, conductors of electricity, have been developed in this line. Ternary systems based on polymer blends to which nanoparticles have been added have enabled the advantages offered by the blend to be combined with those provided by nanocomposites; this includes the obtaining of super-tough materials with an optimized range of properties. Authors of the paper are PhD-holders Imanol González and IñakiEguiazabal that deals with an application of the above-mentioned synergy between polymer blends and nanocomposites. For the case of poly(ether imide), they resorted to incorporating a blend based on poly(butylene terephthalate) into the polymer with a high concentration of dispersed nanotubes. In actual fact,"poly(butylene terephthalate) does not have the splendid properties displayed by the polymer we are trying to improve, but both polymers blend very well and that way we can get the dispersion to extend right across the blend," Eguiazabal pointed out. Although thermal stability is reduced, electrical conductivity is obtained by adding 1% of carbon nanotubes. The mechanical properties of the poly(ether imide) improve it even more. This is added the fact that the viscosity of the nanocomposites is seen to be significantly reduced thanks to the presence of the poly(butylene terephthalate), which constitutes a considerable improvement in the processability of the materials, despite the presence of the nanotubes that tend to increase viscosity. This reduction in viscosity makes it possible to obtain products with sections of very little thickness but with complex geometry.