Electrically conductive textiles by in situ polymerisation of conjugated polymers. CNR-ISMAC, Sede di Biella

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1 Electrically conductive textiles by in situ polymerisation of conjugated polymers CNR-ISMAC, Sede di Biella C.so Giuseppe Pella, Biella

2 Intrinsically conducting polymers (ICPs) Intrinsically conducting polymers are π-conjugated polymers able to conduct electricity. Polypyrrole (PPy) is one of the most used ICP because of its relatively good stability. It is difficult to process, but it can be easily produced by in situ chemical oxidative polymerisation in aqueous solutions of the monomer. After immersion in the polymerisation bath, textile materials were coated with an even and uniform layer of PPy. PPy layer enhances or does not change mechanical properties of textiles.

3 In some cases, polymerisation occurs also inside the fibre bulk, in particular with man-made cellulose fibres (e.g. viscose, lyocell, tencel). Patent TO2004A Along with polymerisation in solution, we studied two-step processes in order to save chemicals: Vapour phase polymerisation Spray deposition Man-made cellulose fibres treated with pyrrole in vapour phase show a partial penetration of PPy inside the fibre bulk. In spray deposition, oxidant and monomer are successively sprayed on a fabric. It is a fast and continuous process to produce thin conductive coating. C. Tonin, L. Dall Acqua, N. TO2004A (2004). L. Dall Acqua, C. Tonin, R. Peila, F. Ferrero, M. Castellani, Synth. Met. 146(2) (2004) L. Dall Acqua, C. Tonin, A. Varesano, M. Canetti, W. Porzio, M. Catellani, Synth. Met. 156(5-6) (2006) Cross-section of PPy/viscose fibres PPy/lyocell by vapour phase polymerisation PPy-coated cupro fibres by spray deposition

4 Applications of PPy on textile Antistatic garments Heating textiles EMI shielding fabrics Sensorised garments Anti-bacterial fabrics Flame-resistant textiles

5 Electrostatic discharge (ESD) Textile materials generally have high surface resistivity ( ohm/sq.). Excess of static charges can accumulate generating harmful discharges (damage of electronic devices), sparks (risk of explosions) and attraction of powder. For antistatic applications, surfaces with low resistivity ( ohm/sq.) are needed. PPy-coated wool fibres have been used in blend with untreated fibres to produce fabrics for ESD protection able to drain the electrostatic charges. A. Varesano, L. Dall'Acqua, C. Tonin, Polym. Degr. Stab. 89 (2005) wt. % PPy-coated wool 80 wt. % uncoated wool Surface resistivity: 10 kohm/sq.

6 Heat generation For resistivity below 1 kohm/sq., PPy-coated textiles can generate heat by heating Joule effect when electrical power is supplied. High temperature is achieved supplying high power for non-clothing applications (such as building textiles and geo-textiles). Low power generates midtemperature (3 7 C above ambient temperature) suitable for heated garments or automotive seats (heating lining and padding). Non-clothing Clothing A. Varesano, L. Dall'Acqua, C. Tonin, Polym. Degr. Stab. 89 (2005)

7 Fastness and stability Dry-cleaning is excellent for PPy-coated textiles (while domestic washing increases the electrical resistance). Abrasion resistance of PPy on wool (Patent TO2004A000654) and polyamides has been significantly improved by specific treatment before PPy deposition. On the contrary, light fastness and environmental stability have to be improved through new process of posttreatment. without pre-treatment pre-treated A. Varesano, N. TO2004A (2004). A. Varesano, L. Dall'Acqua, C. Tonin, Polym. Degr. Stab. 89 (2005) A. Varesano, A. Aluigi, C. Tonin, F. Ferrero, Fibers and Polymers 7(2) (2006)

8 Anti-bacterial property PPy-coated fabrics exhibit anti-bacterial activity against E. Coli (EN ISO 20645). Bacteria growth is inhibited by positive charges on PPy chains. Absence of an inhibition zone ensures that PPy is responsible for the anti-bacterial activity (PPy is linked to the fibre surface). Advantages: no dispersion of active substances in the environment or on the skin; no diminishing of antibacterial effect due to dilution of the active substance. PPy deposition can be a useful process for making anti-bacterial and anti-microbial textiles. Colony of bacteria Zone in contact with PPy No colony of bacteria A. Varesano, A. Aluigi, L. Florio, R. Fabris, Multifunctional cotton fabrics, Synth. Met. 159 (2009)

9 Thermal behaviour On PPy-coated fibres, degradation starts at lower temperature producing char. Oxidized PPy layer protects the substrate against the action of heat (coated textiles maintains the fibrous shape). Thermogravimetry at air of PET fabrics Uncoated fabric After heating for 30 min. above the PET melting point. PPy-coated fabric A. Varesano, C. Tonin, F. Ferrero, M. Stringhetta, J. Thermal Anal. Cal. 94 (2008) 2, A. Varesano, A. Ibarzabal Ferrer, C. Tonin, e-polymers 022 (2007).

10 Flame-resistancy 10 sec PPy-coated textiles resist to direct contact with fire for 10 s (EN ISO 15025). The flame persisted on the samples after the flame contact for ~1 s (textiles are selfextinguishing). No hole was produced on the surface: flame did not pass through the textile. No drop of molten polymer was observed. 11 sec 12 sec PPy-coated textiles are suitable as protective materials against flame and heat for limited flame spread. A. Varesano, C. Tonin, F. Ferrero, M. Stringhetta, J. Thermal Anal. Cal. 94 (2008) 2,

11 Future works The research is aimed to: Improve the stability of conductive performances to maintenance and use (post-treatments, stabilising agents); Improve the adhesion of PPy on synthetic fibres (e.g. PET) through pre-treatments; Set up processes (high temperature, swelling) to synthesise PPy inside the fibre bulk (other than cellulose-based fibres); Scale-up of the deposition process for industrial application.

12 Funding and collaborations Completed projects: Società Consortile Sinapsi a r.l. (Regione Piemonte, European Social Fund) and Filatura di Trivero spa European Commission Programme Alβan High level scholarships to Latin America Fondazione Cariplo Fibres on demand Politecnico di Torino, Laboratory of Engineering of Neuromuscular Systems (LISiN) Soltek spa Tessili tecnici elettroconduttivi Active project: HI-TEX (Regione Piemonte) Industrial partners: ARA spa Filatura di Trivero spa Filatura Marchi spa Sinterama spa INFA srl Soliani EMC srl Yanga snc Tintoria di Quaregna srl Research partners: Politecnico di Torino, Department of Materials Science and Chemical Engineering ITIS Q. Sella, Laboratorio Tessili Innovativi

13 Research group Alessio Varesano Annalisa Aluigi Claudio Tonin