Preparation of conductive paper by in-situ polymerization of pyrrole in a pulp fiber system

This study explored and demonstrated one possibility of the "fiber engineering" concept via an in-situ chemical polymerization methodology, specifically, to deposit polypyrrole on fiber surface and thus render cellulose fibers electrically conductive: not only a novel functionality was imparted to pulp fibers but processability of the intrinsically conducting polymer (ICP) was greatly improved. Reaction and processing conditions were optimized in terms of the electrical and mechanical properties of the paper sheets prepared from such modified fibers. Typically, conductivity of 3.2×10-2 S/cm was achieved with pyrrole dosage of only 0.06g per gram of BCTMP fibers and a 5 minutes reaction time at 25°C. Good adhesion of the conductive polymer deposition to fibers was accomplished. The engineered fibers were then characterized by FT-IR (Fourier Transform Infrared Spectrometer), optical microscopy, epi-fluorescence microscopy and TEM-EDX (transmission electron microscopy coupled with energy dispersive X-ray analysis) with respect to the chemistry as well as the polypyrrole distribution. As the final product, electrically conductive paper composites were prepared by two methods, (1) exclusively from the polypyrrole engineered pulp fibers; (2) from a mixture of such modified fibers and unmodified fibers. Both composites were investigated in terms of their conductivity and strength properties as a function of monomer dosage or percentage of treated fibers in mixture. It was found that, by mixing treated fibers with untreated ones (i.e. adding treated fibers as a conductive filler), less amount of monomer (i.e. conductive polymer) was needed to achieve the same conductivity while attaining higher tensile strength in the paper compared with paper obtained exclusively from treated fibers. The percolation model was adopted for the first time to describe such paper-conducting polymer composites, and the much lower percolation threshold achieved through the mixing method can be well explained by a multiple-percolation-theory. The long-term environmental aging stability of these composites was also monitored, and attempts were made to interpret the observed conductivity decay through existing kinetic models. Such conductive ICP-fiber/paper composites can be used for electrostatic dissipation packaging, electromagnetic shielding and even more potential applications. The current research may have potential industry application, and it also lays a foundation for further work on the ICP-fiber composites aiming at other properties of ICPs and sets a prototype for future research in the field of fiber engineering.