Melt-blended polyaniline

A further variation was proposed by the Finnish company Neste Oy and is at the stage of being tested in various ESD applications by Panipol, which attempted to prepare a melt processable polyaniline [61 ]. It still remains a matter of debate what the melt behavior they observed resulted from, but it was evident that the resulting blend again is a two-phase system with nanosize network structures formed by the dispersed PAni phase. 

Soroudi, A., Skrifvars, M., 2010. Melt blending of carbon nanotubes/polyaniline/polypropylene compounds and their melt spinning to conductive fibres. Synth. Met. 160 (11), 1143-1147. http //dx.doi.Org/10.1016/j.synthmet.2010.02.038. 

Barra, G.M.O., Leyva, M.E., Soares, B.G., Mattoso, L.H., Sens, M., 2001. Electrically conductive, melt-processed polyaniline/EVA blends. Journal of Applied Polymer Science 82, 114-123. 

Hosier et at (2001) [25] prepared 2% (w/v) solutions of dodecylben-zene sulfonic acid doped polyaniline and PE separately in hot xylene. Appropriate volumes of the two solutions were then mixed and further refluxed to ensrue complete dissolution of the polymers. Finally, the blend solution was poured into cold acetone and the PE/polyaniline blends were precipitated as a green solid. Pereira da Silva et at (2001) [26,27] obtained PE/polyaniline blends by casting a mixture of hot solutions of camphor-sulfonic acid doped polyanihne in m-cresol and PE in decalin onto glass substrates. Melt blending usually involves dispersing the infusible ICPs into melt thermoplastic matrices [28]. Due to the insolubility of PE, as well... 

Electrically conducting polymer blends are also produced by blending another conducting polymer e.g., poly-3-octyl thiophene) with a matrix polymer e.g., PP, PVC, PS, PE, EVAc, PVC/ABS etc.) introducing a dopant e.g., iodine) [Kokkonen et al., 1994]. Several strategies were adopted in preparing ECPBs. In one example, polyaniline was blended with dodecylbenzene sulfonic acid, mixed with PS, PE or PP and then melt processed. In another case, polyaniline was mixed with protoning acid metallic salt. The conductive material was melt mixed with PE, PS, PP or ABS [Kama et al, 1994 a b]. 

It was not until 1984 and 1985 that we succeeded in comminuting polypyrrol and polyaniline in the melt by means of ultrasound and dispersing them in special polymer blends. Only two years later we were able to report to the world conference on Organic Metals in Kyoto (Japan) that dispersed conductive polymers displayed a conductivity breakthrough at a concentration of less than ten percent by volume in a thermoplastic polymer matrix—for example a polyvinylchloride (PVC), polyester or polyurethane—and could be processed in the form of such blends. 

T. Taka, P. Passiniemi, J.-E. Osterholm, Y. Cao, et al. Counter-Ion Induced Processibility of Polyaniline Conducting Melt Processible Polymer Blends. Synth. Met. 1995, 69,97-100. 

Electrospinning [29] is a facUe method to make almost any polymer into nano- and micro-fibers if the polymer can be solution-processed or melt-processed (Figure 7.4). However, due to the low solubility of polyaniline, it is very difficult to make polyaniline fibers thinner than 100 nm. To solve this problem, polyaniline is usually blended with a more soluble polymer to increase the weight percentage of polymer in solution. As a result, the obtained nanofibers are a polymer blend [29—33] this significantly reduces the conductivity of the polymer. Additionally, when the size of the fiber decreases, phase separation may occur, yielding a mixture of nanofibers of polyaniline and other polymers [33]. 

Similarly, Kim et al. [77] demonstrated that melt spinning of electrically conductive fibers is possible by blending doped the forms polyaniline and polypyrrole with either isotactic polypropylene or low-density polyethylene. Binary blends containing up to 40 wt% of the TCP were melt extruded into fibers at 150°C for low-density polyethylene, and at 200°C for isotactic polypropylene as the matrix polymers. 

As far as processing of ICPs is concerned, various methods have been developed to prepare electrically conductive composites [139], among which melt processing is quite popular for thermoplastics [140, 141]. Martins and De Paoli [142] prepared polystyrene and polyaniline blends in a double-screw extruder, giving a conductive thermoplastic with electrical conductivity of 10 to 10 S cm . In most cases, conducting polymers are incompatible with thermoplastic, so a fimctional dopant is needed to improve compatibility. For example, dodecylbenzenosulfonic acid... 

Zhang, Q.H., Wang, X.H., Chen, D.J., and (ing, X.B. (2004) Electrically conductive, melt-processed ternary blends of polyaniline/dodecylbenzene sulfonic acid, ethylene/vinyl acetate, and low-density polyethylene./. Pdym. Sci. B, 42, 3750-3758. 

A. Soroudi, M. Skrifvars, H. Liu, Polyaniline-polypropylene melt-spun fibre filaments the collaborative effects of blending conditions and fibre draw ratios on the electrical properties of fibre filaments, J. Appl. Polym. Sci. 119 (2011) 558—564. 

These blends have been reported to be useful as EMI shielding material [156] and have been prepared by dispersing polyaniline in a melt or a solution, or the thermoplastic method described by Wessling [157]. 

Melt mixing has been also used to disperse conductive polymers in SBS rubber. Polyaniline doped with dodecylbenzenosulfonic acid was mixed with SBS rubber in a Brabender mixer [119]. A conductivity of 2 S cm was achieved with a loading of 50% of the conductive polymer. According to the authors, this blend could be extruded. However, no supplementary data supporting this conclusion were provided. 

One of the main limitations of intrinsically conductive polymers (ICP s) towards their wide application as conductive additives for thermoplastics is their poor thermal-oxidative stability at typical melt processing temperatures (i.e., above 200 °C). On the other hand, the use of high surface area carbon blacks (CB) as conductive additives is limited due to the increased melt viscosity of their blends with thermoplastics. Eeonomers are a new class of thermally stable, chemically neutral, and electrically conductive composites made via in-situ deposition of conductive polyaniline (PANI) or polypyrrole (PPY) on CB substrates. Eeonomer composites are more stable (up to 300 °C) than pure ICP s and more easily processible with thermoplastics than CB. Use of Eeonomers as conductive additives for plastics lead to compounds with improved electrical, mechanical, and processing properties. By varying Ae conductive polymer to CB ratio, it is possible to fine tune the polarity of Eeonomer composites and achieve very low percolation thresholds. This control is possible because of preferred Monomer localization at the 2D phase boundary of the immiscible polymer blends. 

The major difficulties involved in making electrically conductive thermoplastic blends using polyaniline, polypyrrole, or their composites, are two-fold. The first is the thermal instability of doped polyaniline and polypyrrole at melt processing temperatures (1-3), The second is the chemical incompatibility of acidic conductive polyaniline with acid sensitive polymers such as the nylons. Conductive polyaniline is quite acidic and the adjustment of its acidity to neutral pH values eliminates its high conductivity (4,5). The authors present here thermal aging studies of conductivity and thermal gravimetric analysis - mass spectroscopy (TGA-MS) of Eeonomers which show pH independence of conductivity in acidic to neutral environments. The tunable surface properties of Eeonomer composites allows one to optimize the processibility as well as the electrical and mechanical properties of their blends with various thermoplastics. 

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