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Posted: Mar 20, 2013
Nanotechnology in the pulp and paper industry
(Nanowerk Spotlight) During the past few decades, nanotechnology has had tremendous advances in several areas of research and development. Every week we are witnesses to hundreds of articles and scientific publications reporting new pathways for nanoparticle/nanofiber production, modification and use in modern and high-tech applications. In this respect, the pulp and paper industry has not been absent of this development, which has motivated massive research about nanocellulose. This wonderful material, which is synthesized naturally in wood, is composed of nanofibrils with widths usually less than 20 nm, high aspect ratio and remarkable strength.
Cellulose nanofibrils on the surface of a wood pulp fibre. (Photo: Gary Chinga Carrasco, Nanoscale Research Letters 2011, 6:417)
Being a flexible research institute, which can adapt rapidly to new research and development trends, PFI has made substantial contributions to this area. Some of the most important contributions are summarized in this article. Researchers from PFI were among the first to propose and prove the benefits of using nanocellulose in TMP-based and filled paper, where the strength was considerably improved. However, due to the large capacity of nanocellulose for adsorbing water, drainage in the wet web of a paper machine has been considered a limiting factor for using nanocellulose in an industrial scale. Such challenge has also been addressed by PFI and NTNU researchers, with promising results.
Moving forward the development of conventional paper, nanopaper has appeared as a keyword. Nanopaper has been reported to have extremely high barrier properties, comparable and superior to conventional oil-based plastics. One of the first scientific articles, which reported the advantages of a nanopaper concept for barrier applications, was published by PFI and NTNU researchers. Due to the intrinsic strength of cellulose nanofibrils and their ability to self-assemble, dense and strong nanobarriers and nanocomposites can be manufactured.
In addition considerable advances have been made to surface modify cellulose nanofibrils and films and thus control the surface hydrophobicity, which is an important aspect to consider in food packaging applications. Surface modification of cellulose nanofibrils is also most important for novel applications, such as stabilization of emulsions, which has been demonstrated to be promising in diesel emulsions fuels.
A necessary step to realize the above-mentioned applications requires the development of effective industrial production of nanocellulose, with affordable production costs. PFI and industrial project partners demonstrated that nanocellulose can be produced industrially, in large scale (1.5 tonne/day) and with low energy consumption (1600 kWh/tonne). This is considered a significant achievement and implies that nanocellulose from wood can be produced in large quantities, which is a major advantage compared to e.g. bacterial cellulose. However, adequate production and utilization of nanocellulose requires a comprehensive understanding of nanocellulose chemistry and structure. This is an area where PFI actively has contributed to the research community, shedding light into structural terms and characterization based on optical methods and electron microscopy.
In the short run, we foresee novel applications in this promising area of nanotechnology, e.g. functional additives, oil-recovery and in drilling muds. Additionally, paper electronics is appearing as a potential application of nanocellulose due to the smooth surface and low porosity of nanopapers. In this respect, a strong and transparent nanopaper was proposed by researchers from PFI and Åbo Akademi as a biodegradable and renewable substrate for printing electronics, which obviously will widen the applicability of nanocellulose in functionalized nanostructures.
On the biomedical area, PFI is contributing with comprehensive assessments of biocompatibility of nanocellulose, presently in-vitro, but also in-vivo tests are expected. This is most important, as an adequate and necessary verification of biocompatibility will enable novel applications of nanocellulose as a biomaterial for biomedical applications.
In a few words, the potential is big for this wonderful and naturally occurring nanomaterial, which motivates to continue making major efforts and move in the right direction in this promising era of nanotechnological development.
By Gary Chinga Carrasco, Paper and Fibre Research Institute