1
Annals
Warsaw University
of Life Sciences
Forestry and Wood Technology No 107 Warsaw 2019
Contents:
PAWEŁ KOZAKIEWICZ, ROBERT BRZOZOWSKI, AGNIESZKA LASKOWSKA,
MARCIN ZBIEĆ
„Acoustic insulation properties of selected African wood species: padouk, bubinga, sapele.” 4
PIOTR F. BOROWSKI
„Bamboo as an innovative material for many branches of world industry.” 13
MARTA BABICKA, KRZYSZTOF DWIECKI, IZABELA RATAJCZAK
„A comparison of methods for obtaining nanocellulose using acid and ionic liquid hydrolysis
reactions.” 19
SŁAWOMIR KRZOSEK, IZABELA BURAWSKA-KUPNIEWSKA,
PIOTR MAŃKOWSKI, MAREK GRZEŚKIEWICZ
„Comparison results of visual and machine strength grading of Scots pine sawn timber from
the Silesian Forestry Region in Poland.” 24
ZUZANA VIDHOLDOVÁ, DOMINIKA KORMÚTHOVÁ, JÁN IŽDINSKÝ,
RASTISLAV LAGAŇA
„Compressive resistance of the mycelium composite.” 31
2
KATARZYNA MYDLARZ
„Corporate social responsibility in woodworking enterprises.” 37
BEATA FABISIAK, ANNA JANKOWSKA, ROBERT KŁOS
„Dual study possibilities in selected EU countries.” 45
IZABELA BETLEJ, BOGUSŁAW ANDRES
„Evaluation of fungicidal properties of post-cultured liquid medium from the Dual culture of
Kombucha microorganisms against selected mold fungi.” 54
IGOR NOVÁK, JURAJ PAVLINEC, IVAN CHODÁ, ANGELA KLEINOVÁ,
JOZEF PREŤO, VLADIMÍR VANKO
„The grafting of metallocene copolymer to higher polarity with acrylic acid.” 60
JOANNA WACHOWICZ, KLAUDIA WIERZBICKA, PAWEŁ CZARNIAK,
JACEK WILKOWSKI
„The influence of WC grain size on the durability of WCCo cutting edges in the machining of
wood-based materials.” 65
MAREK WIERUSZEWSKI, RADOSŁAW MIRSKI, ADRIAN TROCIŃSKI,
JAKUB KAWALERCZYK
„Influence of qualitative and dimensional classification of Pinewood raw material as an
efficiency indicator in the production of selected timber assortments.” 72
SZYMON NIECIĄG, TOMASZ ROGOZIŃSKI, JACEK WILKOWSKI,
BARTOSZ PAŁUBICKI
„Timber cross-cutting accuracy obtained with an automatic saw.” 80
MARTA DWORNIK, ANNA ROZANSKA, PIOTR BEER
„Traditional ornaments of Świdermajers’ style windows in the town of Otwock.” 84
DARIA BRĘCZEWSKA-KULESZA, GRZEGORZ WIELOCH
„Use of wood in the Baltic courses architecture on the example of Binz in Ruges.” 104
JOZEF KÚDELA
„Wood fibreboard paraffin hydrophobization and the impact of this treatment on the board
surface finishing quality.” 115
MAREK WIERUSZEWSKI, RADOSŁAW MIRSKI, ADRIAN TROCIŃSKI
„Raw material factors affecting the quota of structural wood in sawmill production.” 124
DONATA KRUTUL, ANDRZEJ ANTCZAK, ANDRZEJ RADOMSKI,
MICHAŁ DROŻDŻEK, TERESA KŁOSIŃSKA, JANUSZ ZAWADZKI
„The chemical composition of poplar wood in relation to the species and the age of trees.”131
EWA DOBROWOLSKA, DANIEL KUPIEC, ZBIGNIEW KARWAT
„Testing the tightness of a square joint between oak wood elements.” 139
ADAM KRAJEWSKI, PIOTR WITOMSKI, ANNA OLEKSIEWICZ
„The borings of Teredinidae in fossil wood of Taxodium Distichum Gothan, 1906.” 149
3
Scientific council:
Miroslav Rousek (Czech Republic)
Nencho Deliiski (Bulgaria)
Olena Pinchewska (Ukraine)
Loredana Badescu (Romania)
Iskandar Alimov (Uzbekistan)
Ján Sedliačik (Slovakia)
Ladislav Dzurenda (Slovakia)
Włodzimierz Prądzyński (Poland)
Kazimierz Orłowski (Poland)
Board of reviewers:
Bogusław Andres
Andrzej Antczak
Bogusław Andres
Piotr Beer
Izabela Betlej
Justyna Biernacka
Piotr Boruszewski
Piotr Borysiuk
Izabela Burawska-Kupniewska
Ewa Dobrowolska
Michał Drożdżek
Jarosław Górski
Emila Grzegorzewska
Agnieszka Jankowska
Teresa Kłosińska
Grzegorz Kowaluk
Paweł Kozakiewicz
Adam Krajewski
Krzysztof Krajewski
Sławomir Krzosek
Agnieszka Laskowska
Mariusz Mamiński
Mateusz Niedbała
Piotr Przybysz
Anna Różańska
Jacek Wilkowski
Piotr Witomski
Marcin Zbieć
Errata: The authors of the article: Broda M., Mazela B., Królikowska-Pataraja K., Siuda J. (2015): The state of
degradation of waterlogged wood from different environments. Annals of Warsaw University of Life Sciences -
SGGW, Forestry and Wood Technology 91, pp. 23-27, explain, that:
- at Table 1 a citation of the publication: Zborowska M., Królikowska-Pataraja K., Waliszewska B., Tekień P.,
Gajewska J., Kisiel I (2012): Condition of preservation and causes of degradation of bridge remains recovered
from the bottom of Gągnowskie lake. Physico-chemical analysis of lignocellulosic materials. Part II (ed. by J.
Zawadzki, B. Waliszewska) WULS-SGGW Press, Warszawa 2012, pp. 64-73 is missing,
- at Table 2 a citation of the publication: Zborowska M., Królikowska-Pataraja K., Waliszewska B., Tekień P.,
Gajewska J., Kisiel I (2012): Condition of preservation and causes of degradation of bridge remains recovered
from the bottom of Gągnowskie lake. Physico-chemical analysis of lignocellulosic materials. Part II (ed. by J.
Zawadzki, B. Waliszewska) WULS-SGGW Press, Warszawa 2012, pp. 64-73 is missing.
The missing citations were not a result of an intentional act of the authors but of an unfortunate oversight, and
the present errata intends to remedy this omission.
Warsaw University of Life Sciences Press e-mail:[email protected]
SERIES EDITOR
Ewa Dobrowolska
Anna Sekrecka-Belniak
Mateusz Niedbała
ISSN 1898-5912
Drukarnia POZKAL Spółka z o.o. Spółka komandytowa 88-100 Inowrocław, ul. Cegielna 10 – 12
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Annals of Warsaw University of Life Sciences - SGGW
Forestry and Wood Technology № 107, 2019: 4-12
(Ann. WULS - SGGW, For. and Wood Technol. 107, 2019)
Acoustic insulation properties of selected African wood species: padouk,
bubinga, sapele
PAWEŁ KOZAKIEWICZ1, ROBERT BRZOZOWSKI
1, AGNIESZKA LASKOWSKA
1,
MARCIN ZBIEĆ2
1Department of Wood Science and Wood Preservation;
2Department of Technology and Entrepreneurship in Wood Industry, Faculty of Wood Technology, Warsaw
University of Life Sciences - SGGW, 166 Nowoursynowska St., 02 - 787 Warsaw
Abstract: Acoustic insulation properties of selected African wood species: padouk, bubinga, sapele. The work determines the sound insulation properties of three wood species used in various types of acoustic partitions. The
tests were carried out in a small acoustic chamber after generating white acoustic noise for 5.5 s. The level of
sound intensity generated by the loudspeaker was 110 dB. The thickness of the wooden partitions was 20, 10 or
5 mm. The study was preceded by the determination of the moisture content, density and dynamic modulus of
elasticity of the tested wood samples. In the 20–600 Hz frequency range, the sound insulation characteristics of
the tested partitions changed dynamically but very similarly, while maintaining the mass law. In the higher
frequency range, the impact of the partition thickness on insulation was individual, different for each wood
species. Keywords: African wood, acoustic insulation, density, dynamic modulus of elasticity, small acoustic chamber
INTRODUCTION
Acoustic properties of wood determine its use, among other things, for the production
of sound absorbing materials. With the application of wood in various types of partitions, e.g.
wall elements (facades, cladding, panelling) and flooring, the sound insulation is taken into
account [Kozakiewicz et al. 2012]. Isolation, i.e. attenuation, is the ability to weaken the
intensity (silencing) of sounds passing through the material, expressed in decibels. Waves
with higher frequencies (high tones) are much easier to suppress than those with low
frequencies. The acoustic properties of wood are significantly affected by its density and
modulus of elasticity. In a simplified manner, with increasing wood density, the acoustic
insulation is also increasing [Kollmann and Côte 1968, Krzysik 1978, Bucur 2006,
Kozakiewicz 2012]. However, due to the diversity of wood structure and the complexity of
sound phenomena, including a number of accompanying effects (e.g. reflection, deflection
and penetration) [Kirpluk 2014], it is always desirable to experimentally verify its sound
insulation properties. Insulation is also proportional to the increase in the mass of a partition
and the sound frequency [Bucur 2006].
African species of wood have long been present on the European market and they find
various applications, also resulting from specific features and properties. High natural
durability of many African species, defined in EN 350:2016, and their high density
transforming into high strength parameters predestine them for external applications
[Kozakiewicz et al. 2010], such as sound absorbing and anti-glare screens in communication
arteries. The African wood species are also the material used for solid and layered flooring
materials – as horizontal partitions of buildings [Kozakiewicz et al. 2012].
The aim of the study was to determine the sound insulation properties of three African
wood species – padouk, bubinga and sapele – popular on the European market.
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MATERIAL AND METHOD
Samples of selected African wood species (padouk, bubinga, sapele) were used in the
study. The tested wood species are used as various types of acoustic barriers in buildings, as
well as in acoustic screens [Kozakiewicz 2007, Kozakiewicz et al. 2010]. Selected
information on the tested wood species was compiled in Table 1. To determine the sound
insulation properties, samples with planed surfaces of 500 mm (longitudinal) x 300 mm
(tangential) and the final thickness of 20 mm (radial) were used – samples with a dominant
tangential section were selected. After the initial determination of the insulation parameters,
the samples were planed down to a thickness of 10 mm, and then to 5 mm; and the acoustic
chamber test was repeated for each thickness.
Table 1. The basic information about investigated wood species from Africa [EN 13556:2003; Kozakiewicz and
Szkarłat 2004; Kozakiewicz 2006, 2007; Wagenführ 2007; Richter and Dallwitz 2009]
Latin name of wood
English trade name of wood
(and code) according to
EN 13556:2003
Description of wood (characteristic structure attribute)
Pterocarpus soyauxii
Taub., P. osun Craib
African padouk (PTXX) hardwood, diffuse-porous, stored structure,
small striped grain,
paratracheal parenchyma - wing-like, wing-streak
apotracheal - dispersed
Guibourtia tessmanii
(A.Chev.) J.Léon.
bubinga (GUXX) hardwood, diffuse-porous, stored structure,
small striped grain,
paratracheal parenchyma - one-sided
apotracheal - diffused
Entandrophragma
cylindricum (Sprague)
Sprague
sapele (ENCY) hardwood, diffuse-porous, stored structure,
strong regular striped grain,
paratracheal parenchyma - narrow around the vascular
apotracheal - banded
After bringing the samples to air-dry condition, the wood density was determined by
stereometric method in accordance with ISO 13061-2:2014, and moisture content was
controlled by electric capacitive method in accordance with EN 13183-3:2005. Prior to proper
sound insulation tests, the dynamic modulus of elasticity was also determined using the
original ultrasonic methodology. The tests were performed using a UMT-1 material tester
equipped with two cylindrical 40 kHz transmitting and receiving heads providing the required
signal range. The remaining settings were as follows: 50 dB gain, 60V energy, 12 Hz pulse
mode and 8.8 µs latency time. After placing the heads facing each other to the faces of the
wooden element covered with ultrasound gel, ultrasound was passed (the measurement was
repeated six times along the fibres, successively in lines evenly spaced from each other –
determined on the width of the element). Wave time was read via the UMT-LINK program.
On such basis, the following values were calculated:
– velocity of longitudinal waves:
c = L/t
where: L – sample length [m]
t = t1 - to – real time of longitudinal wave transition [s]
t1 – wave transition time read from the computer monitor [s]
to – latency time [s]
– dynamic modulus of elasticity:
E = c2 · g
where: g – density [kg/m3]
The testing of wood’s sound insulation properties was carried out in a small chamber
with full geometric similarity to large acoustic chambers (rooms). The results of the
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measurements in “small” model chambers do not differ significantly from the results obtained
in acoustic rooms [Godinho et al. 2010, Dukarska et al. 2014, Rey et al. 2019]. The test
conditions were based on the standards used for testing the sound insulation properties of
building materials [ISO 10140-1:2016 and ISO 10140-2,-3,-4,-5:2010].
The test stand included the following elements: EVENT sound column (sound source),
two Behringer ECM 8000 condenser microphones, FireWire 24-bit/96kHz-PreSonus3
interface, acoustic analyzer and EASERA 1.2.10 program for generating, recording and
processing acoustic data. Prepared solid wood samples were placed successively in a
measuring hole (partition) located between sending and receiving chambers. After placing the
samples, an acoustic field stimulated by white noise was generated for 5.5 s. The EASERA
program provided diagrams of the intensity of sound on both sides of the partition (samples)
in the audible frequency range, i.e. from 20 Hz to 20 000 Hz. Based on the obtained data, the
sound insulation (taking into account the background – the difference in the intensity of sound
measured without a partition in the transmitting and receiving chamber) was calculated from
the following formula:
R = SI - SII - So [dB]
where: R – sound insulation [dB],
SI – signal measured in the sending chamber [dB],
SII – signal measured in the receiving chamber [dB],
So – difference of signal reading in the sending and receiving chamber without
a partition [dB].
Based on the results of insulation performance expressed in decibels, the percentage
insulation factor was calculated from the formula:
CR% = (R/S) ·100 [%]
where: CR% – sound insulation coefficient [%],
S – sound level (110 dB).
RESULTS AND DISCUSSION
The moisture content of the wood to be tested ranged from 8% to 10% (typical for
wood used in rooms in the temperate climate zone). Due to strong saturation with non-
structural compounds, exotic species usually take lower equilibrium moisture content
compared to wood from a temperate climate [Kozakiewicz et al. 2012].
The results of the density, ultrasonic wave velocity and dynamic modulus of elasticity
are given in the Table 2. The density of sapele wood in the air-dry state was 694 kg/m3,
bubinga wood 858 kg/m3, and the largest African padouk 868 kg/m
3. The marked wood
densities are typical (representative) of those individual species. They are in the density
ranges given in the literature [Wagenführ 2007, Richter and Dallwitz 2009].
The obtained research results indicate that the velocity of propagation of ultrasonic
waves in two denser species of wood (bubinga, padouk) was similar and amounted on average
to 4900 - 5000 m/s. Sapele wood containing a striped fibre pattern was characterized by a
lower speed (about 4700 m/s) of ultrasonic propagation. Among the tested samples, the
bubinga wood sample – 22.07 GPa – had the highest average modulus of elasticity along the
fibres. Equally high value was obtained in padouk wood – 21.30 GPa, and the lowest in wood
sapele – 15.16 GPa. The last of the mentioned species was also distinguished by the highest
variability of the examined feature, which was most likely determined by the presence of a
striped arrangement of fibres. The obtained values of the modules marked with the dynamic
method are slightly higher than those found in the literature, which refer to the modulus of
elasticity determined during static bending [Kozakiewicz and Szkarłat 2004, Wagenführ
2007, Kozakiewicz 2006, 2007].
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Table 2. The results of the testing of the physical properties of wood
Wood species Density [kg/m
3]
Ultrasonic transition speed
average (standard deviation in parentheses) [m/s] – variation
coefficient [%]
Dynamic modulus of elasticity
average (standard deviation in parentheses) [MPa] – variation
coefficient [%]
African padouk 868 4950 (43) – 0.87 21.30 (0.37) – 1.74
bubinga 858 5070 (55) – 1.09 22.07 (0.48) – 2.17
sapele 694 4670 (296) – 6.34 15.16 (1.89) – 12.47
Figure 1. Acoustic insulation properties of padouk wood for three different thicknesses of the partition: 20, 10
and 5 mm
Figure 2. Acoustic insulation properties of bubinga wood for three different thicknesses of the partition: 20, 10
and 5 mm
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Figure 3. Acoustic insulation properties of sapele wood for three different thicknesses of the partition: 20, 10
and 5 mm
The material intended to fulfil the role of sound absorbing material must have the
highest possible absorption coefficient (internal attenuation), as high as possible for the
audible frequency range, i.e. 20–20 000 Hz. The law of mass allows approximation of the
sound insulation of a single homogeneous partition. This law shows that the increase in
insulation is proportional to the increase in bulkhead weight and sound frequency [Bucur
2006]. Generally, tested partitions show similar characteristics of the amount of sound
attenuation depending on the wave frequency expressed in dB (Fig. 1, Fig 2, and Fig. 3) and
in % in relation to the generated signal (Table 3). In the low frequency range, the
characteristics change very dynamically and attenuation can be considered as not very
effective. Above 200 Hz, a more even sound reduction characteristic begins. However, each
partition is characterized by so-called limit coincidence frequency (frequency band) at which
bent waves appear in the partition (resonance appears). Sounds of this frequency are
suppressed to a small extent – the so-called sound window occurs (frequency band that is less
attenuated compared to other frequencies) [Braune 1960]. In the conducted tests, this
phenomenon is visible at a frequency of approx. 300–350 Hz (clear lower insulation of
partitions). As the frequency increases further, the insulation increases, gradually reaching at
least 20% efficiency in all variants for frequencies above 2 kHz (Table 3). At higher
frequencies, there are also more marked differences between the tested wood species. The
most effective sound insulation is provided by padouk wood. An analysis of the influence of
partition thickness was also an important implication. It turns out that up to a frequency of
about 600 Hz, the results were in line with the expectations. Regardless of the type of wood,
the thickest partitions were the most effective in sound insulation. At higher frequencies,
along with the increase in sound insulation, the effect of partition thickness was no longer so
obvious; moreover, this characteristic was different for each species of wood (Fig. 1, Fig. 2,
and Fig. 3). It is likely that various anatomical features, in particular fibre arrangement and
wood parenchyma distribution, had an impact here. Perhaps in the case of padouk wood, the
sound insulation performance (Fig. 1, Table 3) was determined not only by high density but
also by the presence of banded parenchyma. Low-density parenchyma bands alternated with
thick-walled fibres formed a layered system difficult to overcome by sound waves. Probably
also non-straight fibre arrangement (strong, regular striped grain) in sapele wood was the
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reason for better insulation at high frequencies (Fig. 3, Table 3) compared to small striped
fibrous bubinga wood (Fig. 2, Table 3). There was no clear relationship between sound
insulation and the value of the modulus of elasticity along the fibres.
Table 3. Acoustic insulation coefficient CR [%] in individual frequency bands
Sound
frequency
[Hz]
Sound insulation coefficient CR [%]
African padouk bubinga sapele
partition thickness [mm]
20 10 5 20 10 5 20 10 5
12.5 9 9 11 7 7 11 11 7 6
16 9 12 10 10 12 11 9 9 11
20 10 9 10 11 7 9 11 12 9
25 15 16 16 18 16 17 16 16 16
31.5 28 27 26 28 27 27 27 26 24
40 28 30 27 27 29 27 28 29 25
50 41 42 40 39 42 38 42 44 31
63 36 38 32 31 34 28 36 36 21
80 16 16 12 23 16 13 18 15 17
100 16 12 15 19 18 17 21 15 16
125 19 12 12 21 15 12 21 13 15
160 18 7 12 16 12 11 16 13 14
200 20 20 15 22 21 15 21 18 16
250 26 23 20 24 23 20 24 22 18
315 18 17 15 17 17 14 17 16 13
400 25 24 20 24 24 20 24 23 18
500 27 25 21 27 24 22 25 23 20
630 27 24 21 27 23 22 26 23 20
800 21 25 21 21 25 19 21 24 18
1k 24 27 24 23 25 23 22 25 21
1.25k 24 30 25 23 28 25 23 29 23
1.6k 24 25 24 21 26 23 23 26 21
2k 24 24 26 18 22 24 24 26 20
2.5k 27 28 28 23 28 27 27 27 27
3.15k 27 27 28 22 23 27 29 30 24
4k 25 29 24 25 28 22 31 28 23
5k 28 31 27 28 31 27 33 32 25
6.3k 30 35 29 31 33 28 36 36 26
8k 31 35 28 25 31 29 31 34 27
10k 32 38 34 26 34 30 32 39 29
12.5k 31 41 37 27 34 34 33 43 35
16k 33 44 41 29 32 35 33 46 37
20k 34 38 42 28 31 34 32 46 39
CONCLUSIONS
Based on the tests of sound insulation of solid wood Afican padouk, bubinga, sapele
(air-dry planed elements 20, 10 and 5 mm thick) the following conclusions were drawn:
1. The density of padouk and bubinga wood was similar and brought over 850 kg/m3, and the sapele wood was clearly lower, less than 700 kg/m
3. The velocity of propagation of
ultrasonic waves with a frequency of 40 kHz in two denser wood species (padouk,
bubinga) was similar and averaged 5000 m/s. The lowest velocity (about 4700 m/s) of
ultrasound propagation was found in sapele wood containing a strong striped arrangement
of fibers. This also translated into the values of the dynamic modulus of elasticity.
10
2. In the frequency range from 20 to 600 Hz the sound insulation characteristics of the tested partitions changed dynamically, but very similarly while maintaining the law of mass.
Irrespective of the type of wood, thicker partitions were more effective than thinner ones.
3. In the higher frequency range, the impact of partition thickness on insulation performance was individual, different for each type of wood. In general, the highest insulation
properties were shown by the partition of padouk wood, which was probably determined
not only by the high density of this wood, but also by the presence of a banded parenchyma
alternated with thick-walled fibers that formed a layered system.
4. For partitions with a thickness of 10 mm and 20 mm, the largest differences in sound insulation between the tested species occurred in the frequency range 1 kHz - 20 kHz. In
the case of 5 mm thick partitions in the whole frequency range, these differences were at a
similar level.
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Streszczenie: Izolacyjność akustyczna wybranych gatunków drewna afrykańskiego: paduk,
bubinga, sapeli. Afrykańskie gatunki drewna obecne na rynku europejskim znajdują
różnorodne zastosowania wynikające również ze specyficznych cech i właściwości. Wysoka
naturalna trwałość oraz znaczna gęstość przekładająca się na wysokie parametry
wytrzymałościowe predestynuje je do zastosowań zewnętrznych między innymi na ekrany
dźwiękochłonne i przeciw olśnieniowe przy ciągach komunikacyjnych. Ze względu na walory
estetyczne są też stosowane w materiałach podłogowych i okładzinach ściennych.
W zastosowaniach tych istotna jest również izolacyjność akustyczna. Badania
przeprowadzono w małej komorze akustycznej po wytworzeniu pola akustycznego
pobudzonego szumem białym w czasie 5,5 s. Poziom natężenia dźwięku generowanego przez
głośnik wynosił 110 dB. W obrębie każdego gatunku grubość przegród wynosiła 20, 10 i 5
mm. Badania poprzedzono określeniem wilgotności, gęstości i dynamicznego modułu
sprężystości drewna. W przedziale częstotliwości od 20 do 600 Hz charakterystyki
izolacyjności akustycznej badanych przegród zmieniały się dynamicznie, ale bardzo podobnie
przy zachowaniu prawa masy. W zakresie wyższych częstotliwości wpływ grubości
przegrody na izolacyjność miał charakter indywidualny, odmienny dla każdego gatunku
drewna. Najwyższą izolacyjnością charakteryzowały się przegrody z drewna paduka, o czym
najprawdopodobniej zadecydowała nie tylko wysoka gęstość tego drewna, ale również
obecność miękiszu pasmowego ułożonego na przemian z grubościennymi włóknami, które
tworzyły układ warstwowy.
12
Corresponding author:
Agnieszka Laskowska
Department of Wood Sciences and Wood Preservation
Faculty of Wood Technology
Warsaw University of Life Sciences – SGGW
159 Nowoursynowska St.
02-776 Warsaw, Poland
email: [email protected], phone: +48 22 59 38 661
ORCID ID:
Kozakiewicz Paweł 0000-0002-2285-2912
Agnieszka Laskowska 0000-0001-6212-3100
mailto:[email protected]://orcid.org/0000-0002-2285-2912
13
Annals of Warsaw University of Life Sciences - SGGW Forestry and Wood Technology № 107, 2019: 13-18
(Ann. WULS - SGGW, For. and Wood Technol. 107, 2019)
Bamboo as an innovative material for many branches of world industry
PIOTR F. BOROWSKI Institute of Mechanical Engineering, Faculty of Production Engineering, Warsaw University of Life Sciences -
SGGW
Abstract: The article presents bamboo as a material that can be used in many branches of industry. The
widespread occurrence of bamboo, its rapid growth and very good physico-chemical properties make it a
convenient and easily available material in many countries all over the world. Results of some preliminary
research carried out in Ethiopia and Guinea show wide range of bamboo applications and the possibilities of its
use in Polish conditions. Secondary research based on available sources indicates the promising direction of
future development of the economy based on bamboo use.
Keywords: bamboo, industry, energy, climate
INTRODUCTION
Bamboo is the widespread term applied to a wide group of large woody grasses
ranging from 10 cm to 40 m in height. They grow in the tropical and subtropical regions of
Latin America, Africa and Asia, extending as far north as the southern United States or central
China, and as far south as Patagonia. Bamboo also grows in the northern part of Australia
(Fig. 1).
Figure 1. Map of bamboo growth around the world
Note: Dark colour indicates countries with active bamboo growth. Source: based on bambooimport.com
Bamboo is already in everyday use by about 2.5 billion people, mostly for fibber and
food mostly in Asia. The subfamily Bambusoidaea consists of both woody and herbaceous
bamboos with 1575 identified species in 111 different genera. However, bamboo may have a
potential as a bioenergy or fibre crop for niche markets, although some reports of its high
productivity seem to be exaggerated. Literature on bamboo performance is still scarce (in
comparison with that on other materials), with most reports coming from various parts of
Asia. There is little evidence overall that bamboo is significantly more productive than many
other candidate bioenergy crops, but it shares a number of desirable fuel characteristics with
certain other bioenergy feedstocks, such as low ash content and alkali index. Its heating value
14
is lower than many woody biomass feedstocks but higher than most agricultural wastes and
residues, grasses and straws. Although non-fuel applications of bamboo biomass may be
actually more gainful than energy recovery, there may also be potential for co-production of
bioenergy together with other bamboo processing (Scurlock et. al., 2000).
Qualitative market research methods which include focus group studies, in-depth
interviews and observational techniques (Belk 2008) were applied. In this study, the following
market research methods were used: (1) observation, (2) primary research and (3) secondary
research (Creswell 2009). The author carried out series of research listed above on site in
Guinea and Ethiopia. Observations and primary research in Guinea were carried out directly
within April–May and August–September 2015, whereas desk research were realized as on-
going study. A research project in Ethiopia was realized in September 2014 and May–June
2016. In Guinea-Conakry bamboo and rattan stems are booming in the market of Conakry
(capital city) and some of the country’s major cities. Mainly bamboo is used to produce poles,
stakes and round woods. Bamboo is used for a wide variety of uses: roofing, scaffolding, dry
tapades, sheds, rustic bridges, barbed wire stands, etc. Currently there is no precise knowledge
about the annual production and consumption of this product (FOSA, 2001).
Ethiopia has over 60% of Africa’s natural bamboo, but it has never really been used.
Ethiopia has an estimated one million hectares of natural bamboo forest, the largest in the
African continent. It is green gold and should be given special attention. There 2 bamboo
species considered to be native of Ethiopia: Oxytenanthera abyssinica (lowland bamboo) and
Yushania arundinaria alpina (highland bamboo). In 2015, Ethiopia was the 9th
largest
exporter of bamboo raw materials in the world (King, 2019).
BAMBOO INLUENCE FOR THE CLIMAT PROTECTION
Bamboo is particularly suitable as a tool for carbon sequestration. Bamboo’s carbon
sequestration properties have been studied in Mexico and China, where it naturally forms wild
forests. The most effective solution to climate change is the abatement of CO2 (carbon
dioxide) emission by reducing our dependence on fossil fuels. As a result of its unbelievable
system of roots, bamboo continues to grow irrespectively after being harvested. In contrast to
most other plants bamboo are low cost plants, in meaning that they don’t require fertilizer,
chemicals or pesticides in order to grow. Bamboos can be called self-care plants because they
utilise their own fallen leaves to supply them with nutrients when disintegrated into the soil.
Due to its incredibly rapid growth cycle and the variety of areas in which it is able to grow,
bamboo is also extremely cheap. The first days of bamboo growing is shown in Figure 2.
y = 0.0012x3 - 0.0077x2 + 0.0268x + 0.0273R² = 0.9997
0
2
4
6
8
10
12
0 2 4 6 8 10 12 14 16 18 20 22 24
He
igh
t [m
ete
r]
Time [day]
Figure 2. The dynamics of bamboo growth. Source: https://lewisbamboo.com/growth-chart-of-bamboo/
15
The dynamics of bamboo growth is characterised with rapid increase in the second and
third week. It is observed that during the first 12 days a new bamboo can grow about 6 cm per
day, 37 cm in another 4 days, while the third week brings a daily growth of about 80 cm. Such
rapid growth requires the grass to absorb large quantities of CO2, meaning that its cultivation
as a building material would help reduce the rate of climate change. Over a period of 30 years,
bamboo plants and products can store more carbon than certain species of trees. This is
mainly because bamboo can be harvested regularly, creating a large number of durable
products which store carbon over several years, in addition to the carbon stored in the plant
itself. If the world planted an additional 10 million hectares of bamboo on degraded lands, it
is estimated that bamboo plants and their products could save over 7 gigatons of CO2 (carbon
dioxide) within 30 years. That is more than 300 million new electric cars could save in the
same time period. Importantly, this statistic does not include the emissions saved by
substituting aluminium, concrete, plastic, or steel for bamboo. Bamboo has huge strength and
flexibility making it an ideal building and construction material in many parts of Africa, Asia
and Latin America where it is native. Bamboo has a tensile strength greater than that of mild
steel, and withstands compression twice as well as concrete, making it a ready replacement in
roads, drainage pipes, housing and even wind turbine blades (King, 2019). In table 1 basic
strength properties for bamboo and other materials were presented.
Table 1. Mechanical properties of bamboo, spruce wood and steel
Properties [kN/cm2] Bamboo Spruce wood Steel
Modulus of elasticity 2000 1100 21000
Compressive strength 6.2–9.5 4.3 14.0
Tension strength 14.8–38.4 8.9 16.0
Bending strength 7.6–27.6 6.8 14.0
Shear strength 2.0 0.7 9.2
Source: GUTU, T. A study on the mechanical strength properties of bamboo to enhance its diversification on its
utilization. International Journal of Innovative Technology and Exploring Engineering, 2013, 2.5: 314–319.
CHALLENGES AND OPPORTUNITIES FOR BAMBOO PRODUCTION IN POLAND
Bamboo is a diverse plant that easily adopts to different climate and landscape
condition. It can grow in a wide variety of soil types, different temperatures and humidity
conditions. For Poland’s climate, there are dozens of varieties of cold hardy bamboo to
consider. Most of them belong to either the Phyllostachys or the Fargesia group (genus) of
bamboo. Phyllostachys is one of the most prevalent genera of bamboo, primarily native to
China and including about 50 distinct species.
Almost every species of Phyllostachys is a fast spreading runner (with an aggressive
rhizome root system), and many of them are cold hardy, down to minus 15–20 oC. Among the
varieties which can be grow in Poland are the following: Incense Bamboo (Phyllostachys
atrovaginata), fine-leaved Phyllostachys parvifolia, and Ink-finger (Phyllostachys nuda).
Fargesia is another major genus of bamboo, also indigenous to China and southeast Asia.
Unlike Phyllostachys, the Fargesia bamboos are chiefly dense growing clumpers. This and
their cold hardiness have made many varieties of Fargesia very popular among gardeners. In
Poland, the following varieties will cope well with the climate: Blue fountain bamboo
(Fargesia nitida), umbrella bamboo (Fargesia murielae), and Clumping bamboo, also called
“non-running bamboo” (Fargesia rufa).
16
It is worth noting that in Poland with a transient climate (between maritime and
continental climate) there are very clear differences in wintering conditions for plants in
individual regions. In the Pomeranian zone and in the western part of the country, down to
Lower Silesia, the conditions for growing a more sensitive plants are favourable, in the
majority of central Poland – moderate, and in the Podlasie province, Lublin, North East part
of the Masovia province, Mazury and in the mountains – difficult (see Fig. 3).
Figure 3. Conditions for wintering sensitive plants in Poland
Source: Hoser Sz. Fargesia www.ragesia.pl
Almost every species of Phyllostachys is a fast spreading runner (with an aggressive
rhizome root system), and many of them are cold hardy, down to minus 15–20 oC. Among the
varieties which can be grow in Poland are the following: Incense Bamboo (Phyllostachys
atrovaginata), fine-leaved Phyllostachys parvifolia, and Ink-finger (Phyllostachys nuda).
Fargesia is another major genus of bamboo, also indigenous to China and southeast Asia.
Unlike Phyllostachys, the Fargesia bamboos are chiefly dense growing clumpers. This and
their cold hardiness have made many varieties of Fargesia very popular among gardeners. In
Poland, the following varieties will cope well with the climate: Blue fountain bamboo
(Fargesia nitida), umbrella bamboo (Fargesia murielae), and Clumping bamboo, also called
“non-running bamboo” (Fargesia rufa).
It is worth noting that in Poland with a transient climate (between maritime and
continental climate) there are very clear differences in wintering conditions for plants in
individual regions. In the Pomeranian zone and in the western part of the country, down to
Lower Silesia, the conditions for growing a more sensitive plants are favourable, in the
majority of central Poland – moderate, and in the Podlasie province, Lublin, North East part
of the Masovia province, Mazury and in the mountains – difficult (see Fig. 3).
BAMBOO AS A RENEWABLE SOURCE OF ENERGY PRODUCION
Bamboo may, indeed, have potential as a bioenergy or fibre crop for niche markets.
Bamboo has good fibre quality for paper-making, and it shares a number of desirable fuel
characteristics with certain other bioenergy feedstocks, such as low ash content and alkali
index. The principal ash-forming constituents in bamboo are silica (SiO2) and potassium
(K2O). It also contains calcium (CaO), chlorine (Cl) and magnesium (MgO) (Kumar,
Chandrashekar, 2014). To evaluate the quality of biofuels, it is important to know the content
17
of sulphur and chlorine. A high content of these elements is causing corrosion and
contamination of boilers and increased emissions of Cl2, SOx and HCl.
Since the plant’s health is improved by cutting, bamboo can be re-harvested every
three years without any harmful effects to the environment. With the average 500-year life
span of a redwood tree, a bamboo plant could be harvested and regrown more than 150
times. Bamboo biomass energy has great potential to be an alternative for fossil fuel. Biomass
of bamboo comes from culms, branches and leaves. Bamboo biomass can be processed in
various ways (thermal or biochemical conversion) to produce different energy products
(charcoal, syngas and biofuels), which can be substitutions for existing fossil fuel products.
Bamboo biomass alone cannot fulfil all the demand for energy. It needs to combine with other
sources to best exploit their potential and provide sustainable energy supply (Le, Truong,
2014). Bamboo biomass is characterized by a relatively higher heating value than other sorts
of biomass, which means it is a good material for direct combustion (e.g. co-combustion in
thermal power plant). Many projects on bamboo energy are operating or being implemented
all over the world. In African countries, bamboo biomass projects are very popular and mostly
used to replace firewood or produce charcoal for domestic use.
BAMBOO AS A ADDITIONAL MATERIAL FOR BIODEGADATION
In Europe, much research of biodegradable materials is conducted. In some materials,
pine wood dust is added to change the properties of biodegradable materials (Żelaziński et al.,
2019) but also bamboo can improve the results and properties of materials. The biocomposite
samples reinforced with raw bamboo fibre and treated showed different degree of
biodegradation with weight loss after 30 days of analyses. In general, the biodegradability
studies showed that raw bamboo fibre and the biocomposite reinforced with this fibre were
more resistant to the action of the microorganisms due to a higher contents of lignin and
hemicelluloses. In the plant tissue, lignin acts as a reinforcement, just like cement, between
the fibres (Junior et al., 2014).
CONCLUSION
In Europe, specifically in Poland, the cultivation of, but above all, the production of
bamboo can achieve a high level of innovation. Europe today has technological advances in
some areas of economy and industry such as the micro-propagation, the selection of superior
genotypes using molecular markers and biomass gasification for energy production. Any
widespread bamboo production implies an industrial use. In a short term perspective, bamboo
can be produced and used for soil stabilisation, riparian improvement, wind protection, poles
for viticulture or fruit trees, small sticks for horticulture. At medium term bamboo can find
utilisation for vannerie and furniture production. Also arts and craft could be considered as an
ideal utilisation for everyday equipment. In a long term perspective, bamboo utilisations for
industrial purposes require supplementary analyses and tests. Two of them seem of major
importance: determination of calorific value for gasification and defibration for the production
of boards or biodegradable textiles.
REFERENCES
1. BELK R.W. (2008): Handbook of Qualitative Research Methods in Marketing (Elgar Original Reference), Edward Elgar Publishing.
2. CICHY W., WITCZAK M., WALKOWIAK M., 2018: The assessment of fuel properties of pellets made from wood raw materials, Ann. WULS - SGGW, For. and
Wood Technol., 101, 85-90.
3. CRESWELL, J.W. (2009): Research Design: Qualitative, Quantitative and Mix Methods Approaches. Sage Publication Inc.
18
4. FOSA, 2001: L’Etude prospective du secteur forestieren Afrique (FOSA), l’Etude prospective du secteur forestieren Afrique – Guinée, Juillet, 07, 1-41.
5. GUTU T. A., 2013: study on the mechanical strength properties of bamboo to enhance its diversification on its utilization, International Journal of Innovative Technology
and Exploring Engineering, 2 (5), 314-319.
6. JUNIOR, A.E. C., et al., 2015: Thermal and mechanical properties of biocomposites based on a cashew nut shell liquid matrix reinforced with bamboo fibers. Journal of
Composite Materials, 49.18: 2203-2215.
7. KING Ch., 2019: Bamboo and Sustainable Development: A Briefing Note, INBAR, 1-8.
8. KUMAR R., CHANDRASHEKAR N., 2014: Fuel properties and combustion characteristics of some promising bamboo species in India. Journal of Forestry
Research, 25 (2), 471-476.
9. LE T.M.A., TRUONG H., 2014: Overview of bamboo biomass for energy production, halshs-01100209.
10. MEKONNEN Z., et al. 2014: Bamboo Resources in Ethiopia: Their value chain and contribution to livelihoods. Ethnobotany Research and Applications, 12: 511-524.
11. SCURLOCK J. M. O., DAYTON D. C., HAMES B., 2000: Bamboo: an overlooked biomass resource? Biomass and bioenergy, 19 (4), 229-244.
12. ŻELAZIŃSKI T., EKIELSKI A., TULSKA E., VLADUT V., DURCZAK K., 2019: Wood Dust Application for Improvement of Selected Properties of Thermoplastic
Starch, Inmatech – Agricultural Engineering, 58 (2), 37-43.
Streszczenie: Bambus jako innowacyjny materiał dla wielu gałęzi przemysłu światowego.
W artykule przedstawiono bambus, jako materiał, który można wykorzystać
w wielu gałęziach przemysłu. Powszechne występowanie bambusa, jego szybki wzrost
i bardzo dobre właściwości fizykochemiczne sprawiają, że jest to materiał wygodny i łatwo
dostępny w wielu krajach na całym świecie. Wstępne wyniki badań przeprowadzonych
w Etiopii i Gwinei pokazują szerokie możliwości wykorzystania bambusa i możliwości jego
implementacji w polskich warunkach. Badania wtórne oparte na dostępnych źródłach
wskazują na duży potencjał wykorzystywania bambusa w wielu branżach gospodarki.
Corresponding author:
Piotr F. Borowski
Institute of Mechanical Engineering, Faculty of Production Engineering, Warsaw University of Life Sciences -
SGGW
ul. Nowoursynowska 166
02-787 Warszawa
email: [email protected]
phone: +48225934557
ORCID ID:
Borowski Piotr F. 0000-0002-4900-514X
19
Annals of Warsaw University of Life Sciences - SGGW Forestry and Wood Technology № 107, 2019: 19-23
(Ann. WULS - SGGW, For. and Wood Technol. 107, 2019)
A comparison of methods for obtaining nanocellulose using acid and ionic
liquid hydrolysis reactions
MARTA BABICKA1, KRZYSZTOF DWIECKI
2, IZABELA RATAJCZAK
1
1Poznań University of Life Sciences, Department of Chemistry, Wojska Polskiego 75, PL-60625 Poznan, Poland
2Poznań University of Life Sciences, Department of Food Biochemistry and Analysis, Mazowiecka 48, PL-
60623 Poznan, Poland
Abstract: A comparison of methods for obtaining nanocellulose using acid and ionic liquid hydrolysis reactions. In this study, two methods were compared, i.e. acid hydrolysis using sulphuric acid (VI) and ionic liquid
hydrolysis using 1-methyl-3-butylimidazolium chloride to obtain nanocellulose from Sigmacell Cellulose Type
20. The efficiency of both processes was tested for weight loss of the material during the reaction. The study
showed that much more material can be obtained using ionic liquid hydrolysis than using acid hydrolysis. A
dynamic light scattering study was performed to determine material particle size before and after these
processes. Particles of nanometric size were recorded only for cellulose after the reaction with an ionic liquid. In
addition, Fourier transform infrared spectroscopy was performed to determine the chemical structure of the
materials tested.
Keywords: 1-butyl-3-methylimidazolium chloride, sulphuric acid(VI), acid hydrolysis, ionic liquid hydrolysis,
Dynamic Light Scattering, Fourier Transform Infrared Spectroscopy
INTRODUCTION
Nanometric size cellulose and the methods of its production are very popular research
topics, as evidenced by the number of publications in recent years (Ribeiro et al. 2019). This
is due to the increasing use of this material and attempts to develop a method that would be
cost-effective and safe for the environment (Bhat et al. 2019). Nanocellulose may be obtained
through affecting a factor capable of resolving strong interfibrillar hydrogen bonds within the
molecule. This ability is found in strongly corrosive acids and bases, some ionic liquids,
cellulose enzymes or mechanical forces (Jiang and Hsieh 2013).
Figure 1. Chemical structure of [Bmim] [Cl]
Nickerson and Habrle (1947) were the pioneers of nanocellulose production by acid
hydrolysis. It has been shown that sulphuric acid may be used for cellulose hydrolysis, but
different nanoparticle dimensions (from 3 to 70 nm wide and from 35 to 3000 nm long) were
obtained depending on the cellulose source and reaction conditions (Beck-Candanedo, et al.
2005; Elazzouzi-Hafraoui et al. 2008; Habibi et al. 2010). Strong acids, such as hydrochloric
acid and hydrobromic acid, also hydrolyze but usually providing low yields of less than 30%
(Jiang and Hsieh 2013). However, acids are dangerous for the environment and for its
protection various methods are being developed not involving toxic substances.
20
Ionic liquids are considered non-toxic and eco-friendly. Additionally, thanks to their
unique properties they have found numerous applications in new fields, including
nanocellulose production (Shak et al. 2018). In 2002, Swatlowski and his team proved that 1-
butyl-3-methylimidazolium chloride [Bmim] [Cl] is capable of dissolving cellulose with no
need for other solvents. Since this discovery there has been a growing interest in the use of
ionic liquids to dissolve and modify cellulose (Suzuki et al. 2014).
In this study two methods to obtain cellulose of nanometric size were compared. The
acid hydrolysis method, first proposed for the chemical preparation of nanocellulose, was
compared with hydrolysis of ionic liquid ([Bmim] [Cl]) (Figure 1). The experiments were
conducted on microcrystalline cellulose: Sigmacell Cellulose Type 20 with 20 μm particle
size.
MATERIALS
The research used microcrystalline cellulose – Sigmacell Cellulose Type 20 with 20
μm particle size (Sigma Aldrich). Moreover, the following chemical substances were used:
sulfuric acid (VI) 95% (Sigma Aldrich) was diluted to 64% with water, anhydrous NaOH
(Sigma Aldrich) for acid neutralization and 1-butyl-3-methylimidazolium chloride (≥98%)
(Sigma Aldrich) as ionic liquid, phosphorus pentaoxide (P2O5) (Sigma-Aldrich), acetonitrile
(Sigma-Aldrich), KBr (Sigma-Aldrich).
METHODS
Preparation of nanocellulose using acid hydrolysis reaction
Microcrystalline cellulose (Sigmacell) was mixed with H2SO4 (64%) at a 1:10 ratio (m/v).
The suspension was subjected to constant magnetic stirring (ChemLand, Poland). The
reaction was run at two temperatures (25 °C and 45 °C) for 1 min and 5 min. Cold water was
added to terminate the reaction and sulfuric acid (VI) was neutralized by sodium hydroxide.
The material was centrifuged and rinsed with water. The cellulose was dried in a dryer (Pol-
Eko, Poland) and, in the final stage, placed in a desiccator over P2O5.
Preparation of nanocellulose using ionic liquid hydrolysis reaction
Microcrystalline cellulose (Sigmacell) was added to the molten ionic liquid [Bmim] [Cl] at
a 1:10 ratio (w/w). The reaction was run for 9 hours at 90 °C, with intensive magnetic stirring
(ChemLand, Poland). After hydrolysis the reaction product was filtered and washed
thoroughly with acetonitrile to remove the ionic liquid. In the next stage of the study, the
cellulose material was left to dry at a room temperature and, in the final stage, it was placed in
a desiccator over P2O5.
Fourier transform infrared spectroscopy (FTIR)
The samples were mixed with KBr (Sigma Aldrich) at a 1:200 mg ratio and, in the form of
pellets, were analyzed by FTIR. Spectra were registered at a range of 4000-500 cm-1
, at
a resolution of 2 cm-1
and registering 16 scans using a Nicolet iS5 spectrophotometer (Thermo
Fisher Scientific, USA).
Dynamic light scattering analysis (DLS)
DLS was used to determine the particle size (hydrodynamic diameter) of the materials. The
samples were previously mixed (2 mg) with 5 ml deionized water, treated using an ultrasound
system (Polsonic, Poland) for 25 min and next centrifuged using an incubated shaker (Jeio
Tech, Korea) in order to remove the micrometric fraction of cellulose. Finally, the
hydrodynamic diameter of samples was determined with a Zetasizer Nano ZS-90 (Malvern
Instruments Ltd., UK) at room temperature, with the results presented as size distribution by
intensity.
21
RESULTS
The dried material was weighed to calculate the efficiency of the hydrolysis reaction
process. The results are shown in Table 1.
The efficiency of nanometric cellulose production in the hydrolysis reaction was
higher in milder reaction conditions. After a reaction of 1 min at 25°C, the reaction yield was
60%, while after a reaction of 5 min. at 25°C and 1 min at 45°C, the yield was close to
30%. The lowest result was registered for the 5 min reaction at 45°C (5%). A much higher
yield was obtained during hydrolysis with the ionic liquid (89%), despite a longer reaction
time and a higher temperature.
Another test was performed using FTIR spectra to determine the chemical structure of
the resulting materials (Figure 2).
Additional bands were recorded in the cellulose spectrum after hydrolysis with an
ionic liquid, which are not present in the spectra after acid hydrolysis. Wave numbers of
1575 cm−1
are due to C=N stretchings. The peak at the wave number of 757 cm−1
is due to
C–N stretching vibration. These bands correspond to the ionic liquid 1-butyl-3-
methylimidazolium chloride, which was not eluted from the cellulose sample, similarly as in a
study of Dharaskar et al. (2013). An increase in the intensity of the “crystallinity band”, which
corresponds to CH2 bending vibrations, was recorded at 1466 cm-1
for cellulose after
hydrolysis with the ionic liquid. At the same time, a decrease in the intensity of the
“amorphous band” was recorded at 815 cm-1
, which corresponds to the C-O-C tensile
vibration at β- (1 → 4) -glycosidic bonds.
Table 1. The efficiency of the acid and ionic liquid hydrolysis reactions
Hydrolysis reaction Conditions Efficiency [%]
Acid
1 min, 25°C 60
5 min, 25°C 35
1 min, 45°C 28
5 min, 45°C 5
Ionic liquid 24 h, 90°C 89
This indicates an increase in the crystallinity of the cellulose sample after hydrolysis
with the ionic liquid (Adsul et al. 2012). In the case of the cellulose sample after acid
hydrolysis, no changes in intensity were recorded in these areas, therefore it may be
concluded that cellulose crystallinity did not change, either.
Figure 2. FTIR spectra of cellulose (A); cellulose after the acid hydrolysis reaction (B) and the ionic liquid
hydrolysis reaction (C)
22
Another study was performed to determine the particle size of the materials. The
results are shown in Figure 3.
For samples following acid hydrolysis, no particles below 100 nm were recorded. The
result for cellulose after a reaction of 5 min. at 45°C was very similar to that for the native
material, while the particle size after hydrolysis with an ionic liquid was below 100 nm. This
showed that the ionic liquid hydrolysis was a better choice for obtaining cellulose nanometre
sizes. The limited weight loss of cellulose during this process further strengthens this belief.
Mao and his co-workers reported a very similar size of nanocellulose molecules using an
ionic liquid with the same cation, but at a much lower yield (Mao et al. 2015).
CONCLUSIONS
After analyzing the amounts and particle size of the material recovered after the
hydrolysis reaction, it may be concluded that the use of an ionic liquid to obtain nanocellulose
was more favourable than the use of sulphuric acid(VI).
Figure 3. The average particles size of the cellulose before and after treatment with ionic liquid and acid
The yield for the ionic liquid reaction was higher than in all the acid tests. Nanometric
particles were registered only for the material after ionic liquid hydrolysis. Based on the
analysis of FTIR spectra, it may be stated that the degree of cellulose crystallinity after the
ionic liquid hydrolysis increased, while no changes were recorded for cellulose after the acid
hydrolysis. In the FTIR spectra of samples after hydrolysis with ionic liquid, bands
corresponding to the ionic liquid were recorded, which may be due to insufficient washing of
the material.
REFERENCES
1. ADSUL M., SON S.K., BHARGAVA S.K., BANSAL V. 2012: Facile Approach for the Dispersion of Regenerated Cellulose in Aqueous System in the Form of
Nanoparticles. Biomacromolecules 13(9): 2890-2895
23
2. BECK-CANDANEDO S., ROMAN M., GRAY D. G. 2005: Effect of reaction conditions on the properties and behaviour of wood cellulose nanocrystal suspensions.
Biomacromolecules 6(2): 1048-1054
3. BHAT A. H., KHANB I., USMANI M. A., UMAPATHI R., AL-KINDY S. 2019: Cellulose an ageless renewable green nanomaterial for medical applications: An
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4975
Corresponding author: Izabela Ratajczak
Poznań University of Life Sciences
Department of Chemistry
Wojska Polskiego 75
PL-60625 Poznan, Poland
e-mail: [email protected]
ORCID ID:
Babicka Marta 0000-0001-9844-3974
mailto:[email protected]://orcid.org/0000-0001-9844-3974
24
Annals of Warsaw University of Life Sciences - SGGW Forestry and Wood Technology № 107, 2019: 24-30
(Ann. WULS - SGGW, For. and Wood Technol. 107, 2019)
Comparison results of visual and machine strength grading of Scots pine
sawn timber from the Silesian Forestry Region in Poland
SŁAWOMIR KRZOSEK, IZABELA BURAWSKA-KUPNIEWSKA,
PIOTR MAŃKOWSKI, MAREK GRZEŚKIEWICZ
Faculty of Wood Technology, Warsaw University of Life Sciences – SGGW
Abstract: Comparison results of visual and machine strength grading of Scots pine sawn timber from the
Silesian Forestry Region in Poland. The paper presents an analysis of the strength grading results performed by
two methods – visual (appearance) and machine, carried out for sawn timber obtained from the Silesian Forestry
Region in Poland. Visual strength grading was performed in accordance with PN-D-94021:2013, while the
machine strength grading with the use of MTG device from Brookhuis Electronics BV. As a result of the tests, it
was confirmed that the machine grading results in a very small share of sawn timber classified as rejects. At the
same time, during machine strength grading there were some sawn timber pieces that were not classified for any
class or a reject. Based on its visual appearance, such timber elements should be graded as rejects.
Keywords: strength grade, Scots pine sawn timber, Polish structural timber, visual grading, mechanical grading
INTRODUCTION
The importance of timber used in construction increases year by year. From the
material fulfilling auxiliary functions in traditional construction and used mainly on roof
trusses and for interior finishing, wood has become a construction material. In modern timber
structures several main techniques can be distinguished: classic frame buildings, assembled
from scratch at the building site or made in prefabrication technology. Prefabrication involves
the production of complete building components in a factory, and then assemble on the
construction site. In terms of prefabrication, panel prefabrication can be distinguished, which
results in finished walls as well as volume prefabrication, in which the outcome is ready-made
modules, which, after being transported to the construction site, allow for the immediate
assembly of a whole, even a multi-storey building. In Poland prefabrication technology is
already used to build timber structures with 4 floors (Beśka 2018).
Cross-linked structural slabs (CLT) are getting more and more popular. Buildings with
14 storeys were built in the world using these modern materials, e.g. in Norway (Abrahamsen
and Malo 2014), then 18 storeys in Canada (Fast 2016) or in Norway (Abrahamsen 2017).
One of the necessary conditions for safe building with timber is the use of wood with
adequate strength parameters. Sawn timber used in construction for structural purposes must
be subjected to strength grading. There are two methods for strength grading of structural
sawn timber: visual and machine.
Strength grading by visual methods consists of a thorough examination of each piece
of sawn timber and its qualification into specific grade classes on the basis of noticed wood
structure defects, and shape and processing defects. In visual grading, the following wood
features and defects are taken into account: knots, grain deviation, cracks and fissures, resin
pockets, bark pockets, rot and insect tunnels, shape deviations, etc. Shape and processing
defects are wanes, longitudinal (sides and planes) curvatures, transversal curvatures, twists
and other cutting defects, such as mechanical damage or exceeding dimensional tolerances.
As a result of visual grading, timber is sorted into specific sorting classes. Each of the EU
countries has its own national regulations regarding strength grading of sawn timber by the
visual method. Following this, there are distinct sorting classes in different countries and there
are different methods of assessing timber features, e.g. knottiness. These standards are
25
historically conditioned, they differ in terms of grading criteria and the number of grade
classes. Strength grading by visual method in Poland is carried out on the basis of PN/D-
94021:2013. Conifer constructional timber graded with strength methods. As a result
of grading sawn timber is qualified into KW – high quality, KS – medium and KG – low.
Sawn timber that does not meet the requirements of KG grade class is not suitable for
structural applications and call a reject.
Strength grading by the visual method is a slow and time-consuming process. The
efficiency of such grading in m3 per hour is low. Moreover, it is always burdened, to a greater
or lesser extent, with a subjective “human factor” – the result of such grading depends on who
grades the timber. If two graders sort the same batch of timber, the grade results may not be
identical. Graders are aware of the responsibility and consequences of making an error;
in ambiguous situations (so-called border pieces), they tend to lower the grade class of timber
subconsciously. Therefore, the first machines for strength grading of sawn timber were
designed already in the middle of the last century. Such machines should meet several basic
requirements, the most important are:
a possibility to grade full-size structural timber,
ensuring of non-destructive grading. Due to the second requirement, machines for the strength grading of timber are based
on the measurement of certain characteristics of wood, which can be determined in a non-
destructive manner and which are known to correlate with the bending strength. The higher
the correlation between the wood characteristic tested by the machine and its bending
strength, the more reliable sorting results of this machine.
Because of the use of grading machines, the obtained results are objective; moreover,
modern automated machines sort with efficiency much higher than human. Automatic,
computer-controlled, very efficient machines (e.g. feed speed of up to 200 m/min) can be
integrated into automatic technological lines for the production of, for example, laminated
timber (German: BSH – Brettschichtholz, English glulam), solid timber construction glued to
length (German: KVH – Konstruktionsvollholz) or CLT (Cross Laminated Timber). In such
automatic lines grading machines are joined with the following circular saws, which cut out
fragments of boards with unacceptable wood defects.
Mechanical strength sorting has already been in use for over 50 years. For the first
time, on an industrial scale, devices dedicated to strength grading were used in 1963 in the
United States. In Europe, many different designs have been developed and applied on an
industrial scale over the past years, some of them have already been the subject of
publications by various authors (Denzler et al. 2005, Glos 1982, Krzosek 1995, Krzosek 2009,
Krzosek and Bacher 2011).
The most important advantage of strength grading by machine method is classifying of
sawn timber directly to grades C, according to EN 338:2016 (in Poland PN-EN 338:2016
Timber structures – Strength classes). This standard introduced the following classes for
coniferous timber: C14, C16, C18, C20, C22, C24, C27, C30, C35, C40, C45 and C50, and
for hardwood: D30, D35, D40, D50, D60 and D70. Poplar wood is treated as coniferous, thus,
it is placed into the C classes. This standard also defines the characteristic values of strength
properties, elastic properties and density of wood for each C and D class. Characteristic
values of strength properties for several selected strength C classes (lowest: C14, highest C50
and C18, C24 and C30) are presented in table 1. If the board is qualified as a given C class,
it is assumed that it meets the minimum values of strength and stiffness properties as well as
density. If the designer of a wooden roof truss knows, for example, the strength class of
timber (e.g. C24), then he has a guarantee that the board has such properties as given in EN
338:2016, i.e. bending strength 24 MPa.
26
Table 1. Characteristic values of strength properties for selected strength classes of sawn timber (in acc. with EN
338:2016)
Strength class (selected)
C14 C18 C24 C30 C50
Strength properties [MPa]
Bending fmk 14 18 24 30 50
Tension parallel ft,0,k 8 11 14 18 30
Tension perpendicular ft,90,k 0.4 0.5 0.5 0.6 0.6
Compression parallel fc,0,k 16 18 21 23 29
Compression perpendicular fc,90,k 2.0 2.2 2.5 2.7 3.2
Shear fv,k 1.7 2.0 2.5 3.0 3.8
Stiffness properties [MPa]
Mean modulus of elasticity parallel E0, mean 7000 9000 11000 12000 16000
5 percentile modulus of elasticity parallel E0.05 4700 6000 7400 8000 10700
Mean modulus of elasticity perpendicular E90, mean 230 300 370 400 530
Mean shear modulus Gmean 440 560 690 750 1000
Density [kg/m3]
Characteristic ρk 290 320 350 380 460
Mean Ρmean 350 380 420 460 550
It can be noticed that the number at the C letter in a given strength class corresponds to
the bending strength of sawn timber. In practice, in order to qualify the sawn timber for
a given C class using sorting machines, its modulus of elasticity and density should be
determined. Other characteristic values can be calculated on the basis of mathematical
relations and correlations between these parameters. Therefore, modulus of elasticity and
density are the key parameters when sorting sawn timber using the machine method.
Additionally, they can be determined non-destructively on a full-size sawn timber when using
a grading machine. Scaling such a machine, i.e. its release for use, is carried out according to
strictly defined procedures and involves examining a certain amount of sawn timber first on
a tested machine and then checking the results on the strength testing machine. The results
obtained from non-destructive testing are verified by results obtained in traditional,
destructive manner of timber testing. After obtaining satisfactory consistency of results, it is
assumed that the grading machine is calibrated and can be approved for use (under many
additional conditions – see EN 14081-4:2009, in Poland PN-EN 14081-4:2009 Wooden
structures – Strength graded structural timber with rectangular cross section – Part 4: Machine
grading – Grading machine settings for machine controlled system).
In Polish sawmills, the method of visual grading is used almost exclusively. It wasn’t
until 2015 when a device for the machine strength grading of sawn timber was installed in the
first Polish sawmill – in Tartak Janina i Wacław Witkowscy (Bekas 2016, Krzosek et. all
2015). Another sawmill – Tartak Abramczyk – purchased a machine for the sawn timber
strength grading in 2018.
According to the research carried out so far, a large share of rejects is obtained during
sorting sawn timber when using the visual method, and only a small amount of timber of high
strength grade is obtained. With the applying of strength grading by machine method, much
more sawn timber of high strength grades is obtained and far less rejects (Diebold 2009,
Karlsson 2009). According to research conducted at Faculty of Wood Technology (WULS-
SGGW), as a result of visual strength grading up to 52.9% of sawn timber in the tested batch
was classified as reject, and only 4.4% to the highest strength grade KW. When sorting the
same batch of sawn timber using the MTG device, only 17.5% of the tested batch was
classified as a reject (Krzosek 2009). Further studies on pine sawn timber from selected
27
natural forest regions of Poland are currently ongoing at the Faculty of Wood Technology,
within the Biostrateg 3 research project,.
RESEARCH MATERIAL
The research material consisted of sawn Scots pine (Pinus sylvestris L.) timber from
the Silesian Forestry Region in Poland. The sawn timber was cut of raw materials with age
classes IV and V, obtained from the young, mixed forest within the Regional National Forest
Directorate of Katowice (Olesno Forest Disctrict, Sternalice Forest Subdistrict, forest
compartament 14d, geographic coordinates: 50.898629, 18.423915). The timber was dried in
industrial conditions in a chamber drier, up to the humidity of ca. 12%, and planed. The
nominal dimensions of timber after drying and planing were: 40 x 138 x 3500mm. There were
210 pieces of timber in the batch under research. The timber was prepared at a sawmill in
Kalisz Pomorski.
RESEARCH AIM AND SCOPE
The aim of research was to verify what the differences are between results of visual
(appearance) and machine strength grading. The scope of research included strength grading
of sawn timber with both methods.
METHODS
Strength grading by visual method was carried out in accordance with PN-D-
94021:2013 Structural sawn timber sorted by strength methods. As a result of the grading, the
sawn timber was assigned to sorting classes KW, KS, KG or classified as reject. The results of
strength grading are presented in table 2. Strength grading by the machine method was carried
out with the use of MTG (Mobile Timber Grader) device from Brookhuis Electronics BV.
The dynamic modulus of elasticity is measured by the vibration method which measures the
natural frequency of vibration after a short impact. The MTG device has already been used in
previous studies conducted at the Faculty of Wood Technology (Krzosek and Grześkiewicz
2008; Krzosek 2009). The results of strength grading with the use of the MTG device are
presented in table 3.
RESULTS AND ANALYSIS
The results of strength grading results by visual and machine method are presented in
table 2 and 3.
As a result of sawn timber grading (210 pieces) by the visual method, 41 pieces were
assigned to the KW strength grade (19.5% of the whole batch), 24 pieces to KS grade (11.4%
of the whole batch), 62 pieces to KG grade (29.5% of the whole batch), whereas 83 pieces
(39.5%) were classified as rejects. With reference to the research conducted in previous years,
timber originating from the Silesian Forestry Region was characterized by the highest
mechanical properties in comparison to the other regions (table 2). Particularly noteworthy is
the large share of sawn timber of KW strength class, many times higher than the average
share from the previous studies and twice as high as for the best forest region analysed in the
previous studies (10.6% for sawn timber from the Baltic Forestry Region). The percentage
share of sawn timber in KS strength grade class in the described studies (11.4%) was also
higher than the average from previous studies (7.2%). The percentage share of sawn timber in
KG strength grade class (29.5%) was lower than the analogous average share obtained in
previous studies (35.5%). Rejects in the analysed batch of timber from the Silesian Forestry
Region were about 39.5%, its amount was significantly smaller than the average number of
rejects found in the earlier studies (52.9%).
28
Table 2. Results of sawn timber strength grading by visual method in accordance with PN-D-94021:2013
Visual strength grade acc. to PN-D-94021:2013
KW KS KG Reject
[no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%]
41 19.5 24 11.4 62 29.5 83 39.5
On the basis of the obtained results of visual strength grading, it can be noticed that
pine sawn timber from the Silesian Forestry Region has the highest quality in comparison
with the five others forest lands analysed in the previous studies at the Faculty of Wood
Technology of Warsaw University of Life Sciences – SGGW (Krzosek 2009).
Table 3. Results of strength grading of sawn timber by machine method with the use of MTG device
Strength grade acc. to EN 338
C40 C35 C30 C24 C18 Reject
[no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%] [no of
pieces]
[%]
21 10.0 47 22.4 58 27.6 63 30.0 15 7.1 3 1.4
As a result of sawn timber grading by the machine method (MTG), 10% of the batch
was in C40 strength class, 22.4% in C35 class, 27.6% in C30 class, 30% in C24 class, 7.1% in
C18 class and only 1.4% rejects were noticed. It is worth noting that a large number of sawn
timber – 32.4% in total – was assigned to classes that are unachievable at visual strength
grading (i.e. C40 and C35). On the basis of the obtained results of machine strength grading,
it can be noticed that pine sawn timber from the Silesian Forestry Region has the highest
quality in comparison with the five other forest lands analysed in the previous studies at the
Faculty of Wood Technology of Warsaw University of Life Sciences – SGGW (Krzosek
2009).
A shortcoming of the MTG device is the inability to grade sawn timber with knots
occurring on its face side, in cases where an extremely large twist of fibres is present and
when planks faces are not precisely cut. In such situations, according to authors’ assumptions,
a wave caused by an impact to the board forehead does not reach the other side because of the
mentioned defects, neither is it reflected from it nor returns to the vibration detector. In such
cases, the MTG device displays the message: ERROR. During the tests described, 3 of a total
number of 210 sawn timber boards were not classified into strength grades (1.4% of the
batch). Practice indicates that such boards should be described as rejects.
CONCLUSIONS
1. Scots pine sawn timber from the Silesian Forestry Region was characterized by the highest quality, determined both during visual and machine strength grading (KW
strength grade 19.5%; C40 and C35 in total 32.4%).
2. The assumption that the machine strength grading results in low share of sawn timber considered as rejects has been confirmed.
3. There are sawn timber elements which were not assigned to any class or marked as rejects during the machine strength grading. Such timber should be classified as rejects
based on its visual appearance.
ACKNOWLEDGMENTS: The authors are grateful for the support of the National Centre for Research and
Development, Poland, under the “Environment, agriculture and forestry” – BIOSTRATEG strategic R&D
programme, agreement No. BIOSTRATEG3/344303/14/NCBR/2018.
29
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