Article pubs.acs.org/IECR
Imparting Cellulosic Paper of High Conductivity by Surface Coating of Dispersed Graphite Yanjun Tang,*,†,‡ Joseph Alexander Mosseler,‡ Zhibin He,‡ and Yonghao Ni‡ †
Key Laboratory of Advanced Textile Materials and Manufacturing Technology, Ministry of Education, Zhejiang Sci-Tech University, Hangzhou 310018, Zhejiang, China ‡ Limerick Pulp and Paper Centre, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3 ABSTRACT: Cellulosic paper, when imparted with strong conductivity, may have important applications. In the present work, graphite-based coatings were fabricated and directly applied onto the surface of a low-grade paper made of recycled fibers to produce conductive paper. Sodium dodecyl sulfate (SDS)-graphite aqueous dispersion was developed, in order to attain the graphite suspensions with high solid content and good dispersion. A coating formula consisting of graphite suspensions, styrene butadiene (SB) latex, and other ingredients was investigated to impart high conductivity to cellulosic paper. Effects of graphite dispersion on the coating viscosity and conductivity of surface coated paper were studied, and the microstructure of surface coated paper was characterized. Results showed that the optimum SDS addition promoted the graphite dispersion, decreased the coating viscosity, and facilitated the formation of uniform and compact coating network structures, all of which contributed to the increased coating layer density, decreased air permeability, and enhanced conductivity. from its tendency toward aggregation in aqueous systems.22 An effective approach to overcome the aggregation and stability issues is to optimize the dispersion process with the aid of dispersants. The use of dispersant/surfactant would provide an opportunity to enhance the graphite dispersion, decrease the coating viscosity, and improve the conductivity of surface coated paper. In the present study, the effect of sodium dodecyl sulfate (SDS), one of the popular anionic surfactants, on the aqueous dispersion of graphite was studied. Subsequently, the graphite-based coating formula was developed to produce highly conductive paper, based on the surface coating technology. These findings may lead to a cost-effective and easy scale-up manufacturing route for the production of cellulose-based conductive paper, particularly offering a way of adding high value to a low-grade paper made of recycled fibers.
1. INTRODUCTION Due to the concerns about environmental issues and economical aspects, the importance of recycled fiber utilization has been fully recognized in the papermaking industry. Nowadays, around 50% of paper used is recovered.1 How to make value-added products from the recovered/recycled fibers is of great commercial interest. Cellulose-based conductive paper has received great attention due to its potential wide range of technological applications in such areas as electromagnetic interference shielding,2,3 static electrical dissipation,4,5 electronic circuits,6 and energy storage.7 Significant progress has been made in the past few years toward the highly conductive paper. Overall, cellulose-based conductive paper can be produced via the wet-end formation process and/or surface coating. Various conductive fillers such as graphite,8 carbon black,9 carbon nanotubes (CNTs),2,10 and carbon fiber11 have been used to impart conductivity to cellulosic paper based on the wet-end formation process. Similarly, polypyrrole modified cellulosic fibers12−14 as well as polypyrrole modified kaolin clay15 were employed to produce conductive paper. It was proposed that the surface coating process can offer significant commercial production advantages over the wet-end formation process, for example, high filler retention (close to 100%), low overall production cost, and low-risk scale-up.16 In fact, the surface coating technology is well established for imparting excellent end-use properties.17−19 There are, however, limited studies regarding the surface application of conductive fillers, e.g., graphite, to produce conductive paper in the literature. Here, a conductive coating formula was designed/developed to impart high conductivity to the substrate made of recycled fibers. Graphite was selected as the conductive filler due to its low cost and high performance. Graphite suspensions can offer conductivity, electromagnetic shielding, or a low coefficient of friction.20,21 The main difficulty in utilization of graphite arises © 2014 American Chemical Society
2. EXPERIMENTAL SECTION 2.1. Materials. Graphite powder,
