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

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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:wydawnictwo@sggw.pl

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.

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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.

REFERENCES

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sustainable acoustic solutions in a reduced sized transmission chamber. Buildings 9:60.

24. RICHTER H.G., DALLWITZ M.J., 2009: Commercial timbers: descriptions, illustrations, identification, and information retrieval. In English, French, German,

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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: agnieszka_laskowska@sggw.pl, phone: +48 22 59 38 661

ORCID ID:

Kozakiewicz Paweł 0000-0002-2285-2912

Agnieszka Laskowska 0000-0001-6212-3100

mailto:agnieszka_laskowska@sggw.plhttps://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: piotr_borowski@sggw.pl

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.

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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: izabela.ratajczak@up.poznan.pl

ORCID ID:

Babicka Marta 0000-0001-9844-3974

mailto:izabela.ratajczak@up.poznan.plhttps://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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