- Email: [email protected]
Electrically conductive compositions based on processible polyanilines — PANEPOL TM
ELSEVIER
Synthetic
Electrically
conductive
compositions
Metals 84 (1997)
113-114
based on processible polyanilines
- PANIPOLTM
E. Virtanen, J. Laakso, H. Ruohonen, K. Mkiparta, H. Jtirvinen, M. Jussila, P. Passiniemi and J.-E. &terholm weste Oy, Chemicals, P.O. Box 310, FIN-06101, Porvoo, Finland
Abstract Truly melt- and solution processible electrically conductive polyaniline (PANI) compositions can be produced commercially utilizing the technology originally developed some years ago in a joint-effort between Neste Oy and UNJAX Corporation. This technology, PANIPOLW, utilizes PANI protonated by functionalized protonic acids in combination with proprietary plasticizers. Neste has now tinther developed this technology and reached semi-industrial scale production capabilities. We briefly discuss some features of fusible, conductive PANIPOLTy compositions developed specifically for use in conductive products such as injection molded articles, extruded films and fibers. Keywords:
Polyaniline,
blends, processing, injection molding, films, fibers
1. Introduction Presently, commercially available plastics are made by adding conductive fillers in the form of particles, flakes or tibres. Depending on the aspect ratio of the filler material different percolation thresholds for the electrical conductivity can be obtained. Commonly, however, rather large amounts of intractable additives have to be added in order to assure reliable performance in end-products. Typical disadvantages using intractable fillers are sloughing (carbon blacks), difficulties in processing homogeneously conductive products, difficulties in controlling the invariably steep percolation behavior (i.e. control of conductivity) and cost (with the exception of carbon blacks and non-permanent antistatic agents). Conductive PANI offers the potential of providing properties to end products that are very difficult to obtain by existing commercial solutions. Recently conductive products based on PANT [l] and polypyrrole dispersions [2]have been reported. Neste has developed a new PANT technology PANIPOLN - based on the original inventions made some years ago by UNL4X Corporation and Neste. This technology is based on protonation of polyaniline using fimctionalized surfactant counter-ions [3,4] in combination with proprietary plasticizers
[51. 2. Experimental Fusible PANfPOLN compositions are produced by a reactive extrusion process [6]. The polyaniline salt, the plasticizer, and other optional additives are fed into a twinscrew extruder utilizing specific feeding port configurations. The temperature profile along the screw typically varies between 100 and 180 “C, the residence time typically being 510 minutes. During the extrusion process, the ingredients solidify into strands of conductive PANIFOLN which are 0379-6779/97/%17.00 0 1997 Elsevier PII 90379-6779(96)03861-1
S&me
S.A. All righta reserved
subsequently cooled, pelletized and packaged. The conductive pellets can then be compounded with commodity polymers and further processed into final products using conventional melt processing techniques.
3. Discussion The major driving force behind the development of the PANIPOLTU technology was to achieve economically feasible routes to produce truly soluble and fusible conductive PANI compositions that would overcome the drawbacks of traditional fillers when further blended with commodity polymers. Andreatta et al. [7] previously showed that conductive PANI is soluble in strong acids. Cao et al. [3,4] demonstrated soluble and fusible PANI in the presence of excess amounts of functionalized protonic acids such as alkylbenzene sulphonic acids. Highly acidic compositions are, however, not acceptable in common melt processing equipment because of the very high corrosion rate. In order to overcome the intractability of conductive PANI salts effective plastization is necessary. We have specifically identified two classes of feasible plasticizers to yield fusible PANIPOLTu compositions: (i) compounds that form coordination complexes with the nitrogens of the doped PANl chains [5] and, (ii) compounds that sterically allow for a combination of strong hydrogen bonding and phenyl-phenyl interactions with the PANI salt [S,9]. We fmd furthermore, that the introduction of sufficiently long alkyl chains to the protonating acid and to the plasticizer allow the formation of phase separated conductive PANI networks to be formed particularly in non-polar and weakly polar commodity polymers such as polyolefins [lO,ll]. 3. I Conductive
thehoplnstic
blends
We have previously reported about conductive polymer blends containing PANIPOLTM [lo]. The final optimum
114
E. Rrtanen
et al. /Synthetic
properties of these blends, specifically the conductivity, will depend on many parameters such as the weight fraction of PANIPOLn’, the level of plastization, the processing temperature and shear stress. In addition, the surface activity of PANKPOLTu as well as the viscosity ratio of PANIPOLTU and the matrix polymer at a selected processing temperature will greatly influence the conductivity of the blend as described elsewhere in these proceedings [12]. Tailoring the melt viscosity of PANIPOLTU is conveniently done by adjusting the degree of plastization of the PANI salt to achieve the correct visosity ratio for optimal blend performance. PANIPOLTu also exhibits useful properties during processing with thermoplastics by acting as a processing aid, thus lowering the needed maximum processing temperature by several tens of degrees. This shortens injection molding cycles and effect the output capacity of extrusion of films and fibers as well as enables the design of more demanding and complex shaped articles. 3.2. Conductive thermoplastic products The primary focus of Neste’s development work has been in three different areas: to develop fusible PANJPOLTU compositions and thermoplastic compounds suitable for use in (i) injection molded shaped articles; (ii) blow molded and extruded films and; (iii) fibers. The compositions have been tailored to match especially polypropylenes, polyethylenes, polystyrenes, PVC and some non-polar &i-block elastomers. The frost target products have been in the area of ESD protection. Excellent overall ESD protection properties in packaging and transportation boxes for electronic components made of PANIPOLW - polypropylene compounds have been observed. A desirable conductivity profile can be achieved through the thiches of the walls of the boxes giving, simultaneously, a high and uniform surface resistance of ca. 10’ No and a bulk resistivity of less than IO4 !&cm. The high surface resistance ensures a controlled discharge and, at the same time, the lower bulk resistivity provide adequate ESD shielding properties. Similar boxes containing carbon black have similar shielding properties but, due to much lower surface resistances, usually exhibit too fast and less controlled dissipation characteristics [131. PANIPOLW - polypropylene fibers and PANIPOLTU - low density polyethylene films have been spun and blow molded, respectively, on industrial scale processing equipment. The fibers have been spun at speeds of up to 1000 mlmin with subsequent orientation. The fibers, characterized by TEM and WAXS [ Ill, show a unique morphology with a phase separated continuous conductive PANI-network embedded in the polypropylene matrix . These products target the textile, carpet and packaging industries. 3.3. Thermosets and solutions Ln addition to fusible compositions, the PANPOLTu technology also provide solution processible compositions. PANI-surfactant counter-ion complexes dissolve readily in organic solvents, such as xylene and toluene, in the presence of
Metals
84 (1997)
113-l 14
proprietary solubility promoters, to yield viscous solutions from which highly conductive films can be made by solution casting [3, 4,]. Conductive thermosets, specifically phenolformaldehyde and melamine type resins [14], as well as acid curable epoxy formulations based on PANIPOLTu have been demonstrated [ 151. Acknowledgement The authors thank especially Hannu Hohna, Hannu Nousiainen, Isto Eilos and Jar-i Rautio for their excellent work on process upscaling. Dr. Olli II&ala and his coworkers are acknowledged for invaluable discussions and cooperation.
References [l] B. Wessling, Proceedings, 6. Symposium, Elektrisch Ieitende Kunststoffe, Technische Akademie Esslingen Germany (1995) ; Zipperling Kessler 62 Co., Technical Data Sheet, Internet http://www.zipperling.dc, July (1996). [2] DSM Research, Product sheet - “Conquest - Waterborne Conductive Coatings”, Geleen, The Netherlands (1996). [31 Y. Cao, P. Smith and A. J. Heeger, Synth. Met., 48 (1992) 91. [41 Y. Cao, P. Smith and A. J. Heeger, U. S. Patent No. $232,631 (1993). [51 T. K&n& J. Laakso, T. Niemi, H. Ruohonen, E. Savolainen, H. Lindstrom, E. Virtanen, 0. I&ala and A. Andrea!&, U. S. Patent No. $340,499 (1994). [61 T. K&n&, J. Laakso, E. Savolainen and K. Levon, U. S. Patent No. $346,649 (1994). VI A. Andreatta, Y. Cao, J. C. Chiang, A. J. Heeger and P. Smith, Synth. Met., 26 (1988) 383. PI 0. II&ala, L.-O. Pietila, P. Passiniemi, Y. Cao and A. Andre-at& European Patent Application EPO 643 397 AI (1993). PI 0. T. II&ala, L.-O. Pietila, P. Passiniemi, T. Vikki, H. Csterhohn, L. Ahjopalo and J.-E. Gsterholm, These proceedings. [lOI 0. II&ala, J. Laakso, K. Vsikiparta, E. Virtanen, H. Ruohonen, H. J&-vinen, T. Taka, P. Passiniemi, J.-E. Gsterhohn, Y. Cao, A. Andreatta, P. Smith and A. J: Heeger, Synth. Met., 69 (1995) 97. [l l] P. Passiniemi, J. Laakso, H. Osterholm and M. Pohl, Theseproceedings. [ 121 J. Tanner, 0. T. II&ala, P. Passiniemi and J.-E. Gsterhohn, These proceedings. [13] K. Vakiparta, P. Kirmanen, J. Laakso, P. Passiniemi, T. Taka and E. Virtanen, Proceedings, 17th EOSLZSD Symposium, Phoenix, U. S. A. (1995). [14] J. Laakso, H. Jarvinen and J.-E. Gsterholm, to be published. [15] J. Peltola, Y. Cao and P. Smith, Adhesive Age, May Issue (1995).
Synthetic
Electrically
conductive
compositions
Metals 84 (1997)
113-114
based on processible polyanilines
- PANIPOLTM
E. Virtanen, J. Laakso, H. Ruohonen, K. Mkiparta, H. Jtirvinen, M. Jussila, P. Passiniemi and J.-E. &terholm weste Oy, Chemicals, P.O. Box 310, FIN-06101, Porvoo, Finland
Abstract Truly melt- and solution processible electrically conductive polyaniline (PANI) compositions can be produced commercially utilizing the technology originally developed some years ago in a joint-effort between Neste Oy and UNJAX Corporation. This technology, PANIPOLW, utilizes PANI protonated by functionalized protonic acids in combination with proprietary plasticizers. Neste has now tinther developed this technology and reached semi-industrial scale production capabilities. We briefly discuss some features of fusible, conductive PANIPOLTy compositions developed specifically for use in conductive products such as injection molded articles, extruded films and fibers. Keywords:
Polyaniline,
blends, processing, injection molding, films, fibers
1. Introduction Presently, commercially available plastics are made by adding conductive fillers in the form of particles, flakes or tibres. Depending on the aspect ratio of the filler material different percolation thresholds for the electrical conductivity can be obtained. Commonly, however, rather large amounts of intractable additives have to be added in order to assure reliable performance in end-products. Typical disadvantages using intractable fillers are sloughing (carbon blacks), difficulties in processing homogeneously conductive products, difficulties in controlling the invariably steep percolation behavior (i.e. control of conductivity) and cost (with the exception of carbon blacks and non-permanent antistatic agents). Conductive PANI offers the potential of providing properties to end products that are very difficult to obtain by existing commercial solutions. Recently conductive products based on PANT [l] and polypyrrole dispersions [2]have been reported. Neste has developed a new PANT technology PANIPOLN - based on the original inventions made some years ago by UNL4X Corporation and Neste. This technology is based on protonation of polyaniline using fimctionalized surfactant counter-ions [3,4] in combination with proprietary plasticizers
[51. 2. Experimental Fusible PANfPOLN compositions are produced by a reactive extrusion process [6]. The polyaniline salt, the plasticizer, and other optional additives are fed into a twinscrew extruder utilizing specific feeding port configurations. The temperature profile along the screw typically varies between 100 and 180 “C, the residence time typically being 510 minutes. During the extrusion process, the ingredients solidify into strands of conductive PANIFOLN which are 0379-6779/97/%17.00 0 1997 Elsevier PII 90379-6779(96)03861-1
S&me
S.A. All righta reserved
subsequently cooled, pelletized and packaged. The conductive pellets can then be compounded with commodity polymers and further processed into final products using conventional melt processing techniques.
3. Discussion The major driving force behind the development of the PANIPOLTU technology was to achieve economically feasible routes to produce truly soluble and fusible conductive PANI compositions that would overcome the drawbacks of traditional fillers when further blended with commodity polymers. Andreatta et al. [7] previously showed that conductive PANI is soluble in strong acids. Cao et al. [3,4] demonstrated soluble and fusible PANI in the presence of excess amounts of functionalized protonic acids such as alkylbenzene sulphonic acids. Highly acidic compositions are, however, not acceptable in common melt processing equipment because of the very high corrosion rate. In order to overcome the intractability of conductive PANI salts effective plastization is necessary. We have specifically identified two classes of feasible plasticizers to yield fusible PANIPOLTu compositions: (i) compounds that form coordination complexes with the nitrogens of the doped PANl chains [5] and, (ii) compounds that sterically allow for a combination of strong hydrogen bonding and phenyl-phenyl interactions with the PANI salt [S,9]. We fmd furthermore, that the introduction of sufficiently long alkyl chains to the protonating acid and to the plasticizer allow the formation of phase separated conductive PANI networks to be formed particularly in non-polar and weakly polar commodity polymers such as polyolefins [lO,ll]. 3. I Conductive
thehoplnstic
blends
We have previously reported about conductive polymer blends containing PANIPOLTM [lo]. The final optimum
114
E. Rrtanen
et al. /Synthetic
properties of these blends, specifically the conductivity, will depend on many parameters such as the weight fraction of PANIPOLn’, the level of plastization, the processing temperature and shear stress. In addition, the surface activity of PANKPOLTu as well as the viscosity ratio of PANIPOLTU and the matrix polymer at a selected processing temperature will greatly influence the conductivity of the blend as described elsewhere in these proceedings [12]. Tailoring the melt viscosity of PANIPOLTU is conveniently done by adjusting the degree of plastization of the PANI salt to achieve the correct visosity ratio for optimal blend performance. PANIPOLTu also exhibits useful properties during processing with thermoplastics by acting as a processing aid, thus lowering the needed maximum processing temperature by several tens of degrees. This shortens injection molding cycles and effect the output capacity of extrusion of films and fibers as well as enables the design of more demanding and complex shaped articles. 3.2. Conductive thermoplastic products The primary focus of Neste’s development work has been in three different areas: to develop fusible PANJPOLTU compositions and thermoplastic compounds suitable for use in (i) injection molded shaped articles; (ii) blow molded and extruded films and; (iii) fibers. The compositions have been tailored to match especially polypropylenes, polyethylenes, polystyrenes, PVC and some non-polar &i-block elastomers. The frost target products have been in the area of ESD protection. Excellent overall ESD protection properties in packaging and transportation boxes for electronic components made of PANIPOLW - polypropylene compounds have been observed. A desirable conductivity profile can be achieved through the thiches of the walls of the boxes giving, simultaneously, a high and uniform surface resistance of ca. 10’ No and a bulk resistivity of less than IO4 !&cm. The high surface resistance ensures a controlled discharge and, at the same time, the lower bulk resistivity provide adequate ESD shielding properties. Similar boxes containing carbon black have similar shielding properties but, due to much lower surface resistances, usually exhibit too fast and less controlled dissipation characteristics [131. PANIPOLW - polypropylene fibers and PANIPOLTU - low density polyethylene films have been spun and blow molded, respectively, on industrial scale processing equipment. The fibers have been spun at speeds of up to 1000 mlmin with subsequent orientation. The fibers, characterized by TEM and WAXS [ Ill, show a unique morphology with a phase separated continuous conductive PANI-network embedded in the polypropylene matrix . These products target the textile, carpet and packaging industries. 3.3. Thermosets and solutions Ln addition to fusible compositions, the PANPOLTu technology also provide solution processible compositions. PANI-surfactant counter-ion complexes dissolve readily in organic solvents, such as xylene and toluene, in the presence of
Metals
84 (1997)
113-l 14
proprietary solubility promoters, to yield viscous solutions from which highly conductive films can be made by solution casting [3, 4,]. Conductive thermosets, specifically phenolformaldehyde and melamine type resins [14], as well as acid curable epoxy formulations based on PANIPOLTu have been demonstrated [ 151. Acknowledgement The authors thank especially Hannu Hohna, Hannu Nousiainen, Isto Eilos and Jar-i Rautio for their excellent work on process upscaling. Dr. Olli II&ala and his coworkers are acknowledged for invaluable discussions and cooperation.
References [l] B. Wessling, Proceedings, 6. Symposium, Elektrisch Ieitende Kunststoffe, Technische Akademie Esslingen Germany (1995) ; Zipperling Kessler 62 Co., Technical Data Sheet, Internet http://www.zipperling.dc, July (1996). [2] DSM Research, Product sheet - “Conquest - Waterborne Conductive Coatings”, Geleen, The Netherlands (1996). [31 Y. Cao, P. Smith and A. J. Heeger, Synth. Met., 48 (1992) 91. [41 Y. Cao, P. Smith and A. J. Heeger, U. S. Patent No. $232,631 (1993). [51 T. K&n& J. Laakso, T. Niemi, H. Ruohonen, E. Savolainen, H. Lindstrom, E. Virtanen, 0. I&ala and A. Andrea!&, U. S. Patent No. $340,499 (1994). [61 T. K&n&, J. Laakso, E. Savolainen and K. Levon, U. S. Patent No. $346,649 (1994). VI A. Andreatta, Y. Cao, J. C. Chiang, A. J. Heeger and P. Smith, Synth. Met., 26 (1988) 383. PI 0. II&ala, L.-O. Pietila, P. Passiniemi, Y. Cao and A. Andre-at& European Patent Application EPO 643 397 AI (1993). PI 0. T. II&ala, L.-O. Pietila, P. Passiniemi, T. Vikki, H. Csterhohn, L. Ahjopalo and J.-E. Gsterholm, These proceedings. [lOI 0. II&ala, J. Laakso, K. Vsikiparta, E. Virtanen, H. Ruohonen, H. J&-vinen, T. Taka, P. Passiniemi, J.-E. Gsterhohn, Y. Cao, A. Andreatta, P. Smith and A. J: Heeger, Synth. Met., 69 (1995) 97. [l l] P. Passiniemi, J. Laakso, H. Osterholm and M. Pohl, Theseproceedings. [ 121 J. Tanner, 0. T. II&ala, P. Passiniemi and J.-E. Gsterhohn, These proceedings. [13] K. Vakiparta, P. Kirmanen, J. Laakso, P. Passiniemi, T. Taka and E. Virtanen, Proceedings, 17th EOSLZSD Symposium, Phoenix, U. S. A. (1995). [14] J. Laakso, H. Jarvinen and J.-E. Gsterholm, to be published. [15] J. Peltola, Y. Cao and P. Smith, Adhesive Age, May Issue (1995).