IJCS 18 36 - Ghorbani
IJCS 18 36 - Ghorbani
IJCS 18 36 - Ghorbani
net/publication/327776733
CITATIONS READS
0 228
3 authors:
Maryam Afsharpour
Chemistry & Chemical Engineering Research Center of Iran
35 PUBLICATIONS 134 CITATIONS
SEE PROFILE
Some of the authors of this publication are also working on these related projects:
EVALUATION OF POLYVINYL BUTYRAL AND ZINC OXIDE NANO-COMPOSITE FOR CONSOLIDATION OF HISTORICAL WOODS View project
Reading about the conservating modern or contemporary artifacts (in particular those containing polymers) and at the same time,
translating a book in persian on the same topic. View project
All content following this page was uploaded by Mahdi Ghorbani on 20 September 2018.
CONSERVATION SCIENCE
ISSN: 2067-533X Volume 9, Issue 3, July-September 2018: 389-400 www.ijcs.uaic.ro
Abstract
One of the most important issues for treatment of paper works is use of long-lasting
(endurable) materials. In this study, Mechanical properties of Bacterial cellulose Nanofibers
(BCN) for preservation of paper works are investigated. For this purpose, Suspension of BCN
in Klucel-G polymeric matrix with doses of 0.5, 1, and 2 Wt% of dry matter were prepared and
were coated on the pure cellulose paper (filter paper) by hydro-soluble casting method, and
then tensile strength (TS) and folding endurance (FE) mechanical tests were performed. Also,
in order to evaluate durability properties (long-lasting) of the cellulose fiber bio-
nanocomposite, accelerated aging test was conducted in moist heat conditions. After
performing mechanical test, obtained results were investigated and it was observed that the
presence of this nanofibers in Klucel-G matrix, although lowers the initial mechanical
properties (before aging), but increases durability of bio-nanocomposite compared to pure
Klucel-G polymer matrix, and hence, as protective coatings, results in prevention of early
aging. As a result, this prepared nanocomposite would have applications as a new reinforcing
and endurable polymeric coating for preservation of paper works and prevention from further
loss of their strength, and also there would be less need for retreatment.
Introduction
Paper works, due to their organic nature are constantly threated by various damaging
agents (such as temperature, humidity, and light), which oxidize and hydrolyze the paper
structure and hence lower their mechanical strength. So, conservators treat these damages and
inhibit their growth utilizing a vast variety of protective materials and different reinforcing
techniques. Among them, several developed approaches can be named including: silking
method [1], Parylene method in plasma atmosphere [2], paper splitting [3], and some other
scientific researches performed for reinforcing paper works [4, 5]. Also, wide application of
conventional and common methods such as resizing by polymer adhesives (e.g. cellulose ether
adhesives), lining by tissue or Japanese papers [6, 7] can be mentioned. In preservation of paper
works, both durability and inertness of materials are of prime importance [8]. Sometimes
deterioration and degradation of materials on the paper work may function as catalyst for
decomposition, and hence, may lead to the higher speed of damaging. Thereupon, application of
suitable and endurable materials for reinforcing of paper works have always been a very
*
Corresponding author: Samanian_k@yahoo.com
V.K. RATHIA et al.
important consideration for conservators, and therefore many researchers have been focused
their studies in this field. Exploitation of nanotechnology for preservation of cultural heritage
with several years of experiments has endowed researchers with significant accomplishments
among which preservation of paper work have received much attention. Including application
of Calcium Hydroxide (Ca(OH)2 ) nanoparticles for de-acidification [9, 10], de-acidification by
Magnesium Hydroxide (Mg(OH)2) nanoparticles [11], improvement of light resistant features
and antibacterial properties by Titanium dioxide (TiO2) [12], and also using a mixture of two
polymers (CMC/MC) with calcium hydroxide nanoparticles for enhancement of mechanical
properties of paper works [13], etc.
In this research, the applicability of mechanical properties of bacterial cellulose
nanofibers (BCN) is evaluated to be used in nanocomposite as protective coatings for paper
works. The previous scientific studies show that cellulose nanofibers provided polymeric
Nanocomposite with desirable mechanical properties. Specific physical and mechanical features
of cellulose nanofibers have been evaluated and confirmed by researchers who are specialized
in other science fields (such as polymer and paper industry), and numerous articles have been
published in this field [14-19]. Also, another well-known and important feature of cellulose
nanofibers is their biocompatibility with surrounding environment and with nature [20, 21],
which guarantees health being of conservators. Additionally, their same chemical characteristics
and hence compatible nature with the environment and also similar chemical composition with
substrate materials (i.e. paper works) make them to be much reliable. And this is while
inertness, compatibility, and durability of materials used for treatment are of prime importance
in the field of reinforcing of paper works [8, 22]. The present study investigates mechanical
properties of BCN containing nanocomposite coatings. BCN nanofibers was produced through
bottom-up method by bacterial biosynthesis (microbial culture) with a non-pathogenic bacteria
such as Acetobacter xylinum [23-25]. Presence of multiple crystalline regions into the BCN
chemical structure leads to high porosity and hence low tensile strength [26].
Introducing the cellulose nanofibers as reinforcing agents in polymer matrices and
preparation of nanocomposite is a relatively new research field. The first approach in this
regard, purposed about 20 years ago, was the use of cellulose micro and Nano-whisker as
additives in polymeric nanocomposite (latex) [16, 17], and thereafter use of cellulose
nanoparticle were commonly used as additives in various polymeric matrices. The purpose of
these approaches was to reinforce and enhance physical properties of polymers so that to
become more suitable to serve as protective coatings. Thus, BCN nanofibers was added to
Klucel-G matrix and attempts have been made to evaluate the properties of prepared protective
coatings to be used for paper works and develop an innovative advanced approach to improve
conventional preservation method (resizing with Klucel-G which is commonly used in
preservation of paper works).
Experimental part
Materials
BCN cellulose nanofiber suspension (having the average particle dimensions of 37nm
diameter and 2µm lentgh) with the concentration of 1 wt% (bought from Nano Novin Co., Iran)
(Fig. 1) were prepared in a solution of Klucel-G cellulose ether in ethanol (Lasco Co.) via
hydrosoluble casting method [15]. Klucel-G is favorably micissible and compatible with
cellulose nanofibers owing to its same cellulosic chemical structure. Solid content of cellulose
nanofiberes suspensions was determined from the below equation:
Dw - (Dw + Dm) = Dm (1)
where: Dw is the weight of empty dish and Dm is the weight of dry matter.
Pure cellulos filter papers (MN brand) were used as the substrate to be coated by
prepared nanocomposite. Formation of nanocomposite films onto the paper samples with
thickness of 100µm was conducted by a coater machine (K-Control coater model) at the speed
of 2m/min, in order to obtain a uniform thickness of coating layer. Finally, once coating was
completed, all treated samples were dried at room temperature, and an specific code was
assigned to each sample (Table 1).
http://www.ijcs.uaic.ro 391
V.K. RATHIA et al.
Methods
Accelerated Aging
In order to evaluate the quality and and long-term effects of nanocomposite coatings on
paper works, aging environment was designed to be moist heat having the relative humidity of
50±5% and the temperature of 90±2°C [27] for two time periods of 14 days (336 hours) and 24
days (576 hours) in the oven chamber.
decreased by increasing the aging time periods as compared with the case in which cellulose
nanofibers are added into the polymer matrix.
Table 2. Tensile strength (TS) results of paper samples listed in N and N/m
Fig. 4. Comparison of TS results between paper samples coated by BCN-based by bar chart
http://www.ijcs.uaic.ro 393
V.K. RATHIA et al.
Fig. 5. Comparison the relations between TS values and aging time periods
for paper samples coated by BCN-based nanocomposites
These foundings were obtained while it was expected to observe an increased tensile
strength due to the presence of numerous OH functional groups as well as high aspect ratio
(surface area to volume ratio) of cellulose nanofibers added as reinforcing additives in the
Klucel-G polymer matrix [14-21]. Loading further content, more than 0.1%, of cellulose
nanofibers in polymer matrices results in decreased mechanical strength of the matrix due to the
aggregation and agglomeration of nanofibers [18] and hence their inhomogeneous distribution
throughout the polymer matrix. As a consequence, irregular distrubution of mechanical stresses
will be generated in the coatings leading to a decreased mechanical strength of polymer matrix.
Favorable durability of properties of prepared cellulose fiber containing coatings could
be attributed to the increased physical entanglement and also increased interfacial interactions
(bonding points) between cellulose nanofibers arising from their nano-scale dimensions. This
phenomenon decreases physical contact of coating with environment, and finally, generates
prevention behavior for these nanocomposites.
Evaluation of Folding Endurance (FE)
In this test, folding endurance of paper samples was investigated and evaluated (Table
3).
The foundings obtained from this test were similar to those obtained from tensile test,
wich by increasing the concentration of cellulose nanofibers in Klucel-G matrix, the folding
endurance of paper samples was decreased (Fig. 6). Durability of properties in aging condition,
however, was increased in the presence of cellulose nanofibers (Fig. 7), and such increased
durability is in direct relation with concentration of this Nano-additive.
Incresing the concentration of Klucel-G matrix (without any additive) in the aging
condition results in decreased folding endurance as compared with the case in which cellulose
fiber nano additives are added.
Fig. 6. Comparison between FE resultes of paper samples coated by BCN-based by bar chart
http://www.ijcs.uaic.ro 395
V.K. RATHIA et al.
Fig. 8. Comparison between BCN's concentrations as nanoadditive into Klucel matrix and
rate of changes in its mechanical behavior, before and after aging; A. TS; B. FE
It is worthy to mention that foundings obtained from this test make the enhancement
conditions in far more suitable state compared to the results obtained from tensile test. On the
other hand, it was observed that once BCN nanofibers are added in Klucel-G matrix, by
prolonging the aging time period, folding endurance was almost maintained at higher
concentration of BCN. In fact, BCN-containing nanocomposite exhibited a fairly well
durability. Such higher mobility of BCN nanofibers is caused due to the formation of lower
physical bonds. Folding endurance characteristics of BCN-based samples are maintained maybe
for the same reason to which tensile strength characteristics was related, i.e. lower interface for
exposure of coating to environment caused by the nano-scale dimensions.
Reversibility
The amount of reversibility of materials have always been of the great importance [8].
Owing to their similar chemical characteristic and compatible nature with the surrounding
environment and with the substrate materials, cellulose nanofibers are able to minimize the
degradation probability as well as serious damage to paper works. Nevertheless, the following
procedure is followed for making this coating reversible. Paper samples were immersing and
subsequently washed by a mixture of 1:3 water ethanol solution (one part water with 3 parts
ethanol) for 5 minutes. Thus, dissolution of this coating will be possible for Klucel-G polymeric
and this cellulose-based composites resulting from reversibility of Klucel films in alcohol
solvents [12] and to some extent in water [30].
Conclusion
Reinforcing paper works is one of the most important factors for their preservation.
Utilization of endurable and resistant materials for this purpose is of prime importance. The
http://www.ijcs.uaic.ro 397
V.K. RATHIA et al.
results obtained in the present study shows that nanocomposite coatings prepared by adding
Bacterial cellulose nanofibers in Klusel-G polymer matrix exhibited increased durability of
mechanical properties as well as resistance to aging process; but on the other hand, showed
decreased initial properties compared to those of pure Klucel-G matrix. however, paper works
having the medium strength can be treated and protected by these nanocomposite coatings.
Also, this composite coating limit the need of re-treatments for paper works.
Results indicate that BCN nanocomposite coatings show more improved properties once
samples are exposed to folding stresses. In sum, application condition of this nano-
biocomposite coating is mainly focoused on their preventive function as endurable and
protective coatings for paper works. For other preservation conditions to be studied,
complementary researches must be performed. Regarding to the type of accomplishments
gained in the present study, attentions will be directed toward achieving more effective
mechanical properties of this cellulose nanofiber as a new method for reinforcment of paper
works.
Acknowledgement
References
http://www.ijcs.uaic.ro 399
V.K. RATHIA et al.
[27] * * *, Standard Test Method for Effect of moist heat on properties of paper and board,
TAPPI T544 SP-03, Technical Association of the Pulp and Paper Industry, 2003,.
[28] * * *, Standard Test Method for Tensile properties of paper and paperboard: using
constant rate of elongation apparatus, TAPPI T494 om-01, Technical Association of the
Pulp and Paper Industry, 2006.
[29] * * *, Standard Test Method for Paper-Determination of folding endurance, ISO 5626,
International Organization for Standardization, 1993.
[30] Henry, Walter, et al., Consolidation/Fixing/Facing, (Chap. 23), Paper Conservation
Catalog, Washington D.C.: American Institute for Conservation Book and Paper Group,
1988, pp. 1-20. http://cool.conservation-us.org/coolaic/sg/bpg/pcc/ [accessed on
04.02.2016]
______________________________________