Nanotechnology in Pulp and Paper Industries: A Review

Abstract

Cellulose and lignocellulose have great potential as nanomaterials because they are abundant, renewable, have a nanofibrillar structure, can be made multi¬functional and self-assemble into well-defined architectures. New methods for liberating these materials, including nanodimensional cellulose fibrils, macromolecules and nanominerals will be needed in order to use the techniques developed for other nanomaterials as platforms for creating new wood-based materials and products. Research findings showed promising results in application of nanotechnology at different aspects of papermaking. Electrospinning; chemical treatment followed by mechanical techniques; or mechanical isolation methods were applied by different research groups to prepare cellulose nanofibres.

Full text

Nanotechnology in Pulp and Paper Industries: A Review
S.D Mohieldin
1,2
, E.S Zainudin
1,a
, M.T Paridah
1
and Z.M Ainun
1
1
Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products,
Universiti Putra Malaysia
2
The National Center for Research (NCR), Sudan
a
edisyam@gmail.com
Keywords: Nanotechnology, Wood Industry, Pulp, Paper, Nanofibres
Abstract. Cellulose and lignocellulose have great potential as nanomaterials because they are
abundant, renewable, have a nanofibrillar structure, can be made multifunctional and self-assemble
into well-defined architectures. New methods for liberating these materials, including
nanodimensional cellulose fibrils, macromolecules and nanominerals will be needed in order to use
the techniques developed for other nanomaterials as platforms for creating new wood-based
materials and products. Research findings showed promising results in application of
nanotechnology at different aspects of papermaking. Electrospinning; chemical treatment followed
by mechanical techniques; or mechanical isolation methods were applied by different research
groups to prepare cellulose nanofibres.
Introduction
Nanotechnology is an emerging area of science and technology that will revolutionize materials
use in the 21
st
century. The relatively crude and unsophisticated technologies on which we currently
depend will be replaced with highly efficient and environmentally friendly nanotechnologies [1].
The discovery of novel materials, processes, and phenomena at the nanoscale and the development
of new experimental and theoretical techniques for research provide fresh opportunities for the
development of innovative nanosystems and nanostructured materials [2]. Nanotechnology has
found an immediate spot on agendas of policy makers and industry leaders [3]. The nanotechnology
is important because of: 1) Less space, faster, less material, and less energy; 2) novel properties and
phenomena; 3) most efficient length scale for manufacturing; and intersection of living/non-living
[4]. A diverse array of ultra-small-scale materials, including metal oxides, ceramics and polymeric
materials, and wide-ranging processing methods including techniques that employ ‘self-assembly’
on a molecular scale, are either in use today or are being groomed for commercial-scale use. Other
examples, in various stages of development, focused on pollution prevention and treatment [5].
Malaysia has started its own microtechnology and nanotechnology development since the early
millennium year of 2000 and arise until this day. Nanotechnology R&D started by government in
2001 and categorized as a Strategic Research (SR) program under IRPA in the Eight Malaysia Plan
(8MP). Malaysian government has taken a serious concern over the development of nanotechnology
in the country. The third Industrial Master Plan (2005-2020) recognizes nanotechnology as the new
emerging field [6]. The National Nanotechnology Initiatives was launched in 2006. Malaysia
participated in different forums about nanotechnology [7].
Nanotechnology and the Forest Industry
Significant progress has been made in understanding the mechanical properties of bulk wood,
isolated fibres, and cellulosic fribrils; however, much remains to be understood about characteristics
of intact cell walls, interactions between cell wall layers, and properties of and interactions among
the nanoscale domains (cellulose, hemicellulose, and lignin) that provide the basis for properties we
observe in the system as a whole [8]. For the forest (lignocellulosic) products industrial sector,
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nanotechnology will be used to tap the enormous undeveloped potential that tree’s possess. The
vision for nanotechnology in the forest products is to sustainably meet the needs of present and
future generations for wood-based materials and products by applying nanotechnology science and
engineering to efficiently and effectively capture the entire range of values that wood-based
lignocellulosic materials are capable of providing [9]. Some possible application areas of
nanotechnology in papermaking includes: New materials; wet-end chemistry; Nanofiltration in
closure of water circulation; coating; calender rolls; sensors; microscopy; and nanoscale assemblers
[10]. Among the many possibilities suggested to date for new woodfibre-based products
incorporating nanomaterials are moisture-resistant cell-phone components, advanced membranes
and filters, improved loudspeaker cones, and additives for paints, coatings, and adhesives [11].
Collaboration among industry, academia, and society must occur to overcome the challenges
associated with the future of nanotechnology in various sectors of application. Moreover, because
nanotechnology draws several fields, different sectors must contribute information and techniques
to further development of nanotechnology [12].
Preparation and Characterization of Cellulose Nanofibres
Fibre-fibre and fibre-additive interactions are main factors for physical paper properties. Control
and manipulation of these interactions are the focus of many research strategies. In particular
nanotechnology-modified fibre compounds and products are promising materials for improved
paper products [13]. Cellulose fibres on the nanoscale are prepared in four different ways: (1)
bacterial cellulose nanofibres, (2) cellulose nanofibres by electrospinning, (3) microfibrillated
cellulose plant cell fibres and (4) nanorods or cellulose whiskers. However, Table (1) summarise the
different methods of nanofibres preparation and charachterization. Structure and properties of
nanocellulose that are important include: morphology, crystalline structure, surface properties,
chemical and physical properties, and properties in liquid suspension [14]. The investigations
include the effect of the different pretreatments on chemical composition and structure of isolated
nanofibers beside thier dimensions and properties [15].
Table 1 Nanofibres preparation and characterization.[14]
Preparation
Electrospinning.
Chemical Treatment followed by
Mechanical techniques.
Chemical treatment
1.
Chemical Pulping and Bleaching.
2.
Sodium Hydroxide and acid hydrolysis.
3.
Acetylation of plant fibres.
4.
Solvent extraction followed by other
chemical treatments.
5.
Enzymatic degradation.
Mechanical Techniques
Refining/grinding/beating/blen
ding/cryo-crushing followed
by high pressure
homogenization
Characterization Structure
1.
Chemical Analysis.
2.
X-Ray Diffraction.
3.
Fourier Transform Infrared Spectroscopy.
Morphology and Dimensions
1.
Optical Microscopy.
2.
Transmission Electron
Microscopy.
3.
Atomic Force Microscopy.
4.
Scanning Electron
Microscopy.
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Nanofibres in the papermaking industry
Cellulose and lignocellulose have great potential as nanomaterials because they are abundant,
renewable, have a nanofibrillar structure, can be made multifunctional, and self-assemble into well-
defined architectures [9]. Cellulosic nanofibres present a very high surface area which makes the
adhesion properties the most important parameter to control for nanocomposite applications [14].
The contact angle measurements showed that the surface characteristics of nanofibres were changed
from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the
acetylation caused a swelling of the kenaf fibre cell wall and that the diameters of isolated
nanofibres were between 5 and 50 nm. The papermaking industry can benefit a lot from
nanotechnology. This versatile technolohy can also be used in the area of fillers for papermaking
wet end applications [16].
Improved Properties and New Paper Grades
The next evolutionary steps of paper in the form of cellulose nanofiber paper were shown in
many published articles. Ioelovich [17] reviewed that recent developments have shown the
possibility to increase paper strength with additive of nanocellulose particles or nanofibrillated
cellulose to paper composition. The potential of cellulose nanofibrils as a strength reinforcing agent
was also demonstrated by Ahola [18]. The nanofibrils are used with a cationic polyelectrolyte,
poly(amideamine) epichlorohydrin (PAE), to enhance paper strength. It is concluded that the paper
strength experiments and fundamental interaction studies showed that the use of nanofibrils as a
strength reinforcing agent together with PAE leads to superior improvements in strength properties.
Nogi [19] reported the inception of a new kind of paper made of cellulose nanofibres, as opposed to
micrometer-sized cellulose pulp fibres of ordinary paper. Nanopapers of different porosities and
from nanofibrils of different molar mass are prepared. The high toughness of highly porous
nanopaper is related to the nanofibrillar network structure and high mechanical nanofibril
performance [20]. The superiority of nanopaper is likely to be caused by higher fibril strength, more
favorable interfibril adhesion characteristics, and much smaller and more homogeneously
distributed defects (voids) [20]. More stable mass production of the nanofibres can be realized
because fibrillation methods are applicable to any natural fibre resource containing lignin such as
flax, sugarcane bagasse, and wheat straw [21], beside woody lignocelluosic materials. With these
potential the nanofibre paper could play the same role as or an even greater role than conventional
paper in information storage and transfer for perhaps another millennium to come [19].
Nanotechnology and Papermaking Process
The papermaking application of employing nanoparticle systems has evolved to become more of
a “properties” management system during papermaking, and beyond the mill at converting
operations and printers. Nano-technology developments in areas of fibre science, minerals and other
additives will give papermakers the means to put order and structure into the designs of a sheet [22].
Both lumen loading and in situ synthesis methods have been used in preparing magnetic papers.
Papers obtained via lumen loading process possess higher magnetic properties compare to in situ
synthesis method. This is due to its finite (nm) size of particles synthesized by using chemical
coprecipitation method, which shows super paramagnetic behavior. Finite size particles are tended
to aggregate and attach strongly between each other in order to minimize their surface energy and
resulting the low detachment rate during the washing and papermaking process [23]. The magnetic
particles deposited on the surface of the fibres had detrimental effects on the paper strength [24].
Agarwal [25] have demonstrated successful scale integration from nano to micro and macroscale
(nanocoating–microfibres–macropaper) in developing new paper material. The layer-by-layer (LbL)
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self-assembly technique was also applied to deposit organized multilayers of TiO
2
or SiO
2
nanoparticles of 30-80 nm diameter, and 50-nm diameter halloysite clay nanotubes on softwood
fibres [26]. Recently, Fahmy and Mobarak [27] have shown that the nanoadditive sucrose can
overcome the ultimate fate of deterioration in strength of paper, due to addition of inorganic fillers
such as kaolin. Incorporating the nanoporous structure of cellulose fibers with sucrose, which leads
to incorporation beating of the fibers, increases the strength of the produced paper nanocomposites.
Nanofibres in Composite Reinforcement
Cellulose micro/nanofibril (CMNF) as a reinforcing material for composites is becoming more
and more attractive to researchers in composite science because of its potential lightweight and high
strength [28]. Nakagaito and Yano [29] stated that a completely new kind of high-strength
composite was manufactured using microfibrillated cellulose derived from kraft pulp. Iwamoto [30]
reported that the nanofibres exhibit great potential as reinforcement material for optically
transparent composites. Graham [31] explored the theoretical and practical benefits of using
nanofibres in composite filter media and have been concluded that, nanofibres can provide an
improvement in filter efficiency without a substantial increase in filter pressure drop. They have
proven to enhance the life of filters in pulse-clean cartridge applications for dust collection, and
increase the efficiency of air filters for personnel cabins of mining vehicles. Bhatnagar and Sain
[32] prepared a polymer/nanofibres matrix where the nanofibres reinforcement content was 10% in
90% PVA. They observed that even 10% nanofibres provide a remarkable reinforcing potential.
Peresin [33], obtained very smooth nonwoven mats with homogeneous nanofibers, of PVA
reinforced with cellulose nanocrystals by the electrospinning technique. These fiber
nanocomposites had shown enhanced thermomechanical properties. According to Zimmermann
[34], the strength of the composites reinforced with the nanofibres is equivalent to that of mild steel
or magnesium alloy. Due to the light weight of the microfibrillated cellulose, substantial reduction
in automobile weight can be achieved when they replace that alloys. However, the use of
biopolymers has been limited because of their usually poor mechanical and barrier properties,
which may be improved by adding reinforcing compounds (fillers), forming composites [35].
Nanoparticles have proportionally larger surface area than their microscale counterparts, which
favors the filler-matrix interactions and the performance of the resulting material. Besides
nanoreinforcements, nanoparticles can have other functions when added to a polymer, such as
antimicrobial activity, enzyme immobilization and biosensing. Nanocomposite edible films were
developed by adding cellulose nanofibers (CNF) in different concentrations as nanoreinforcement
to mango puree based edible films and chitosan films [36].
Summary
Cellulose and lignocellulosic materials have great potential as nanomaterials because they are
abundant, renewable, have a nanofibrillar structure, can be made multifunctional and self-assemble
into well-defined architectures. Different aspects of papermaking process can benefit from
nanotechnology application either utilizing nanofibres and/or other nanomaterials (fillers, sizing and
coating minerals) to improve the quality of the produced paper or producing new types of paper.
Cellulose nanofibres could be generated successfully from different fibrous raw materials through
chemical and mechanical treatments. Cellulose nanofibres has shown great potentiality as
reinforcing materials in composites and especially in reinforcing biopolymers to produce
biodegradable films favoring the environmental issues. Sufficient attention and plans of action was
given to research and development activities in nanotechnology in Malaysia.
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