Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120
ISSN: 2355-7079/E-ISSN: 2406-8195
UTILIZATION OF CITRIC ACID AS BONDING AGENT IN
SEMBILANG BAMBOO (Dendrocalamus giganteus Munr.
PARTICLEBOARD PRODUCTION Firda A.
Syamani1, *.
Agus Z.
Arifqi2.
Sasa S.
Munawar1.
Sudarmanto1.
Lilik Astari1.
Kurnia W.
Prasetiyo1, .
Mohamad Gopar1.
Ismadi1.
Sukma S.
Kusumah1.
Mohd Hazwan Hussin3.
Subyakto1.
Yusuf S.
Hadi2, and Kenji Umemura4 Research Center for Biomass and Bioproducts.
National Research and Innovation Agency.
Cibinong 16911.
Indonesia Forest Products Departement.
Faculty of Forestry and Environment.
IPB University.
Bogor 16680.
Indonesia Materials Technology Research Group (MaTReC).
School of Chemical Sciences.
Universiti Sains Malaysia, 11800 Minden.
Penang.
Malaysia Laboratory of Sustainable Materials.
Research Institute for Sustainable Humanosphere.
Kyoto University.
Gokasho.
Uji 611-0011.
Kyoto.
Japans Received: 23 August 2021.
Revised: 17 April 2022.
Accepted: 24 April 2022 UTILIZATION OF CITRIC ACID AS BONDING AGENT IN SEMBILANG BAMBOO (Dendrocalamus giganteus Munr.
PARTICLEBOARD PRODUCTION.
Citric acid was utilized as a bonding agent in the production of Sembilang bamboo particleboard.
The limitation in using bamboo for particleboard production is that the silica content in bamboo skin can accelerate particleboard processing machines' bluntness and reduce particle adherence in particleboard manufacturing.
This research aimed to investigate the influence of bamboo skin and citric acid content on the characteristics of sembilang bamboo Particleboards were prepared using bamboo particles .
ype A) and unskinned bamboo particles .
ype B).
The citric acid solution .
%) was sprayed over the surface of bamboo particles to obtain three different levels of citric acid, i.
, 15, 20, and 25% .
ased on bamboo particlesAo dry weigh.
The sembilang bamboo particleboards were manufactured using a hot-pressing machine at 200AC, 5 MPa for 10 min.
The particleboard targeted density was 0.
8 g/cm3.
The type B particleboardsAo internal bond (IB), modulus of rupture (MOR), water absorption (WA), and thickness swelling (TS) were superior compared to the type A particleboards.
This was influenced by the lower concentration of silica in type B particleboards, which tend to allow an intimate contact area among particles and citric acid then produced better quality particleboards compared to type A particleboards.
The type B particleboards met the obligation of JIS A 5908 for type 18 particleboard in terms of modulus of rupture, modulus of elasticity, and internal bond, however, only fulfilled the type 8 particleboard in terms of screw holding power.
The physical properties of Sembilang bamboo particleboard were also improved when using type B bamboo particles and adhered with citric acid at a level of 25%.
Keywords: Sembilang bamboo, particleboards, citric acid, physical properties, mechanical properties, silica
PEMANFAATAN ASAM SITRAT SEBAGAI AGEN PEREKATAN PADA PEMBUATAN PAPAN
PARTIKEL BAMBU SEMBILANG (Dendrocalamus giganteus Munr.
Asam sitrat digunakan sebagai agen perekatan dalam pembuatan papan partikel bambu Sembilang.
Keterbatasan penggunaan bambu untuk pembuatan papan partikel adalah kandungan silika pada kulit bambu dapat mempercepat ketumpulan mesin pengolah papan partikel dan mengurangi kerekatan antar partikel.
Penelitian ini bertujuan untuk mengetahui pengaruh kulit bambu terhadap karakteristik papan partikel bambu sembilang.
Papan partikel dibuat menggunakan partikel bambu lengkap dengan kulit bambu .
ipe A) dan partikel bambu tanpa kulit .
ipe B).
Larutan asam sitrat .
%) disemprotkan pada permukaan partikel bambu untuk memperoleh tiga kadar asam sitrat yang berbeda, yaitu 15, 20, dan 25% .
erdasarkan berat kering partikel bamb.
Papan partikel bambu sembilang diproduksi menggunakan mesin kempa panas pada suhu 200AC, 5 MPa selama 10 Corresponding author: firda.
syamani@brin.
A2022 IJFR.
Open access under CC BY-NC-SA license.
doi:10.
20886/ijfr.
Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120
ISSN: 2355-7079/E-ISSN: 2406-8195
Kepadatan papan partikel yang ditargetkan adalah 0,8 g/cm3.
Papan partikel tipe B menunjukkan keteguhan lentur (MOR), keteguhan tarik tegak lurus permukaan (IB), penyerapan air (WA) dan pengembangan tebal (TS) yang lebih baik dibandingkan dengan papan partikel tipe A.
Hal ini dipengaruhi oleh konsentrasi silika yang lebih rendah pada papan partikel tipe B, cenderung mempererat area kontak antara partikel dan asam sitrat sehingga menghasilkan kualitas papan partikel yang lebih baik dibandingkan dengan papan partikel tipe A.
Papan partikel tipe B memenuhi persyaratan JIS A 5908 untuk papan partikel tipe 18 dalam hal MOR, modulus elastisitas dan IB, namun hanya memenuhi papan partikel tipe 8 dalam hal keteguhan cabut sekrup.
Sifat fisik papan partikel bambu Sembilang tipe B dengan asam sitrat pada kadar 25%, lebih baik dibandingkan papan partikel bambu sembilang lainnya dalam penelitian ini.
Kata kunci: Asam sitrat, bambu Sembilang, papan partikel, sifat fisis, sifat mekanis, silika
INTRODUCTION
Commercially, bonded with formaldehyde-based adhesive.
Unfortunately, during the use of particleboard, especially for interior furniture purposes, can be harmful to human health.
Therefore, the application of formaldehyde-free adhesives for particleboard production has become a critical concern.
Some biopolymers have been utilized as the main constituent in formaldehyde-free adhesives.
starch-based adhesive was applied as a binder in particleboard production, although its water resistance property has not met the requirement for application (Amini.
Hashim, & Sulaiman.
Salleh et al.
, 2.
Some lignocellulosic plants contain lignin or tannin that can be utilized as formaldehyde-free adhesives.
Lignin is known as the third largest biopolymer.
Lignin exists in the structure of lignocelluloses such as wood, agricultural residues, grasses, and other plants (Khalil et al.
, 2006.
Younesi-Kordkheili.
Lignin has a similar structure to phenol.
This means lignin can substitute phenol-based adhesive such as phenol-formaldehyde (PF) (Nasir.
Zakaria.
Sipaut.
Sulaiman, & Hashim.
However, one of the lignin-based adhesive disadvantages is low reactivity due to its complexity and the low number of reactive sites (Pizzi, 2.
Naturally, tannin is present in the skin of several trees, such as mimosa, pine, and quebracho (Fechtal & Riedl, 1993.
Kim, 2.
Tannin is a water-soluble compound.
TanninAos chemical structure is similar to phenolic compounds and can react with formaldehyde to replace phenolic resins (Faris.
Ibrahim, & Rahim, 2.
A tannin-based adhesive has been utilized as a binder in particleboard production (Cui et al.
, 2015.
El-Sayed.
El-Sakhawy.
Kamel.
El-Gendy, & Abou-Zeid, 2.
Nevertheless, the current use of commercial tannin for leather and in the beverages industries limits their availability as an industrial adhesive.
One of the bio-based wood adhesives that attract many researchersAo attention is citric acid-based adhesive.
Umemura et al.
began to study the potential of citric acid as a binder in molded products and as a wood adhesive (Munawar.
Umemura, & Kawai, & Kawai.
Umemura et al.
, 2011, 2.
A citric acidbased adhesive has been used for a binder in the production of particleboard made from Agave sisalana (Syamani & Munawar, 2.
, bamboo (Widyorini et al.
, 2013.
Widyorini.
Umemura, et , 2016.
, oil palm frond (Syamani & Munawar, 2.
, sugarcane (Liao et al.
, 2016.
Syamani et , 2.
, sweet sorghum bagasse (Kusumah et , 2016.
Kusumah.
Umemura, et al.
, 2017.
Imperata cylindrica (Syamani et al.
, 2.
, corn stalk (Prasetiyo.
Octaviana, et al.
, 2.
, and corn husk (Prasetiyo.
Gopar.
Kurniawati.
Syamani, & Kusumah, 2.
The advantages of using citric acid-based adhesive are renewable, non-toxic, produce particleboards with physical and mechanical properties that meet the standard application.
Nevertheless, some disadvantages need to be overcome, such as the required high temperature to set the bonding linkage between Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
particles, which can affect the particleboards processing machine due to adhesive acidity, and produce particleboards with a darker color than particleboards bonded with urea-formaldehyde Certain procedures were employed to increase the performance of the citric acid Additive agents, such as sucrose, can resolve the particleboard brittleness (Kusumah et al.
, 2.
, increase the number of ester groups to improve the bonding ability of citric acid adhesive (Widyorini, et al.
, 2016.
, increase the hydrogen bond, also the molecular linkage force between particles to produce stronger particleboards (Liao et al.
, 2.
There are 1,662 bamboo species in 121 genera spread worldwide (Canavan et al.
, 2.
Among them, 145 bamboo species belonging to 20 genera are found in Indonesia (Nurdiah.
Bamboo was utilized for furniture, handicrafts, chopsticks, and so on.
Moreover, bamboo used as a building material because bamboo culms are strong, tough, straight, easy to bend, and lithe (Widjaja, 2.
Bamboo can also be utilized as particleboard raw materials due to the limitation of wood as particleboard raw material.
Sembilang bamboo (Dendrocalamus giganteus Munr.
, has large biomass with a diameter of 20.
5 cm and 30.
5 m in height, and a thickness of 16.
5 mm (Park et al.
, 2.
, that has the potential to be utilized as particleboard raw material.
Furthermore, sembilang bamboo can be cultivated after 3 years, providing more sustainability and continuity regarding the availability of particleboard raw materials compared to wood plants.
On the other hand, compared to woods, most bamboo species contain much more silica .
5-4% w/.
(Ding et al.
, 2.
The silica is stored as amorphous hydrated silica (SiO2.
H2O) in bamboo with few crystalline phases (Motomura et al.
, 2.
(Yin et al.
, 2.
reported that 2-years-old bamboo (Neosincalamus affini.
outer skin contains a high concentration of silicon .
21%).
High silica content in some tropical wood species is still a challenge for the woodworking industry due to its abrasive action (Cristyvyo, 2.
Moreover, in particleboards production when using urea-formaldehyde resin, the high ash content, primarily silica, contributed to non-uniform resin distribution (Hiziroglu & Suzuki, 2.
This study aims to examine the properties of particleboards made from bamboo particles .
ype A) and unskinned bamboo particles .
ype B) of Sembilang bamboo using citric acid as Type A particles were obtained by directly processing bamboo slats with a ring While the outer skin of Sembilang bamboo was removed and then processed using a ring flaker to obtain type B particles.
Using these raw materials, the particleboards were manufactured by hotpressing.
The effect of bamboo particles types and citric acid content on particleboards properties were discussed.
II.
MATERIALS AND METHODS
Sembilang bamboo (Dendrocalamus giganteus Munr.
was harvested from the bamboo garden of the Research Center for Biomaterial.
We prepared two types of bamboo particles:
bamboo particles .
ype A) and unskinned bamboo particles .
ype B).
Bamboo culms were cut into 40 cm lengths to obtain slats.
The bamboo slats were further processed using a planer to remove external layers of bamboo .
o obtain unskinned bamboo particle.
The bamboo particles were prepared by splitting and chopping bamboo slats, then treated using a ring flaker.
Subsequently, bamboo particles were separated with No.
4-mesh and No.
14mesh screens to obtain bamboo particles with size of 1.
41 O 4.
76 mm.
All of the bamboo particles were oven-dried at 60AC to reduce the moisture level of bamboo particles to below The technical grade of anhydrous citric acid .
anufacturer: Weifang Ensign Industry Co.
Ltd.
) was used without further purification.
The citric acid solution with a concentration of 59-60 wt% was obtained by dissolving the citric acid powder in a certain amount of distilled This liquid was used as the bonding agent in Sembilang bamboo particleboard Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120 Measurement of Bamboo Particles Size Distribution As many as 3 g bamboo particles were classified using a laboratory vibrating sieve shaker, with sieves of 18 mesh .
0 AA.
, 14 mesh .
0 AA.
, 10 mesh .
0 AA.
, 7 mesh .
0 AA.
, and 4 mesh .
0 AA.
Particles of 5 granulometric classes were used for bamboo particle size distribution: -18 mesh.
-18 14
-14 10 mesh.
-10 7 mesh and -7 4 Symbols (-) and ( ) indicate passage and retention of particles, respectively.
Afterward, the weight of each particle class was measured and presented.
Measurement of Bamboo Particles Geometry The length, width, and thickness of 100 bamboo particles were measured using a caliper (Mitutoyo Digital Caliper 500-170-.
Based on data of bamboo particle geometry, the slenderness ratio was calculated by dividing particlesAo length to particlesAo width.
The aspect ratio was calculated by dividing particlesAo length to particlesAo thickness of the two types of bamboo particles.
Measurement of Bamboo Particles Bulk Density ParticlesAo bulk density was calculated based on the proportion of the mass to the volume engaged (Cardoso et al.
, 2013.
Omoniyi & Olorunnisola, 2.
Bamboo particles were oven-dried for 24 h before calculation.
Firstly, the weight of the 50-mL cylinder was measured.
Bamboo particles were placed into the cylinder until they filled the cylinder to reach the 50mL mark, then the cylinder was re-weighed.
The bulk density was calculated based on the difference in weight between the bamboo particles loaded cylinder and the empty cylinder, then was divided by the volume loaded by the bamboo particles.
Measurement of Silica Content in Bamboo Particles The silica content in bamboo particles was measured using a modified method from ISSN: 2355-7079/E-ISSN: 2406-8195 previous research (Yuan, 2.
Five grams of dried Sembilang bamboo powder was placed in a weighted ceramic crucible, then entirely ashed at 525AC.
After cooling, crucible content bamboo ash was weighted to determine the ash content in bamboo.
A 10 mL of HCl .
mol/L) was poured onto the ash.
The acid-soluble ash solution was slowly boiled to near dryness using a boiling water bath.
HCl treatment was conducted for 10 min and repeated three times.
The other 15 mL of HCl .
mol/L) was added to the solution.
After 2 more minutes, the solution was filtered off through No.
42 ashless filter paper (Fisher Scientific.
Canad.
, weighted.
The precipitate .
was washed 5-6 times with 1 mol/L HCl solution, subsequently 5-6 times with hot deionized water (OO 50AC).
The filter paper with the precipitate and filter paper only .
s contro.
was put in a different ceramic crucible and put in a muffle furnace to be ashed at 600AC to reach a constant weight.
The difference in weight of ceramic contains filter paper residue and filter paper silica residue was calculated to determine silica content.
Measurement of Bamboo Particles Wettability Wettability of bamboo particles was conducted by dropping citric acid solution .
mL) on the outer part .
epresenting type A particle.
, and on the inner part .
epresenting type B particle.
of the bamboo slat.
The citric acid solution spread onto the bamboo surface was recorded for 3 minutes with a Digital Microscope (Dino-lite Basic AM2.
The contact angle was measured using Image J software every 10 sec.
Shi and Gardner .
presented a wettability model with the following .
Where:
yuE = contact angle yuEycn = initial contact angle yuEyce = equilibrium contact angle K = contact angle change rate constant t = time Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Production of Particleboard The citric acid solution was sprayed over the surface of Sembilang bamboo to obtain particles with three different levels of citric acid, which were 15, 20, and 25 wt% .
ased on dry bamboo particle weigh.
Afterward, the particles were oven-dried at 80AC for 6 h to reduce water content.
Following this, the particles were placed in a wooden forming mold with a dimension of 30 cm y 30 cm to form a mat.
The hot-pressing machine pressed the particle mat at 200AC for 10 min.
A 9-mm thick steel bar was positioned to control the board thickness during the hot-pressing process to produce particleboard with a target density of 8 g/cm3.
Once the upper part of the pressing plate reached the steel bar, the pressing pressure was 25 MPa.
Evaluation of Particleboards Surface Roughness Properties The surface roughness analysis was performed by using a fine stylus profilometer (Mitutoyo SJ-.
Triplicate measurements were conducted for each particleboard.
The average roughness (R.
as roughness parameters were determined.
The calculation of surface roughness parameters was based on digital information generated by the equipment.
The particleboard surface roughness in this study was measured with a sensitivity of 0.
AAm.
Pin diameter, pin top angle, and measuring the tool's speed were 4 AAm, 90Aand 0.
5 mm/ sec, respectively.
The length of the tracing line (L.
and cut-off were 12.
5 and 2.
5 mm .
, respectively.
The measuring force of the scanning arm on the samples was 4 mN .
Measurements were conducted at room temperature, and the pin was calibrated before the tests.
ParticleboardsAo Mechanical Properties Characterization The bamboo particleboards were tested to investigate the modulus of elasticity (MOE), modulus of rupture (MOR), internal bond (IB), by the Japanese Industrial Standards for particleboards (JIS A 5908:2.
The particleboard bending strength properties, including MOR and MOE, were measured by a three-point bending test method using Universal Testing Machine (Shimadzu Autograph 50kN).
The bending strength analysis was using a board specimen with dimension length x width of 200 mm y 50 and was tested in dry condition.
During the bending strength analysis, load cell speed was 10 mm/min, and the effective span was 150 mm.
Meanwhile.
IB analysis was conducted on sample test dimension of length x width of 50 mm y 50 mm, and with load cell speed of 2 mm/min.
ParticleboardsAo Physical Properties Characterization The bamboo particleboards were subjected to water absorption (WA) and thickness swelling (TS) analysis, based on JIS A 5908:2003.
Physical properties testing was conducted following 7 days of conditioning at room temperature.
The specimen size of 50 x 50 x 9 mm was applied to evaluate TS and WA.
Specimens were immersed in water for 24 h at room temperature.
The thickness and weight differences before and after immersion were calculated.
Statistical Analysis The mechanical and physical particleboards properties data were evaluated using a balanced analysis of variance (ANOVA) procedure for a completely randomized design.
The experimental design consisted of two parameters .
ype of particleboards and citric acid conten.
, and their interactions.
TukeyAos pairwise comparison test was performed to permit the separation of means.
Results were considered significant at 95% confidence levels, by using Minitab Software.
ParticleboardAos Durability Analysis by Cyclic Aging Treatment ParticleboardsAos durability was tested by treating sample specimens under successive severe conditions, based on the method by Kusumah et al.
with slight modification.
Cycling aging treatment involves five steps: .
Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120 soaking in water at room temperature for 24 h, .
oven-dry at 105AC for 8 h, .
immersion in warm water .
AC) for 10 h, .
oven-dry at 105C for 10 h, .
immersion in boiling water for 4 h, and .
oven-dry at 105AC for 16 h.
The changes in weight and thickness of the samples during the treatment were recorded.
Each experiment was performed with five The standard deviation and the mean values were calculated.
The thickness swelling (TS) and water absorption (WA) of the particleboard after each treatment cycle were Bonding adhesion of Bamboo Particles and Citric Acid Analysis by FTIR The edge of the particleboard was scratched to obtain particles.
The particles were ground into a powder, and the powder obtained was dried in a drying oven at 60AC for 16 h.
Infrared (IR) spectral data were obtained with an FTIR spectrophotometer (Spectrum Two.
Perkin
ISSN: 2355-7079/E-ISSN: 2406-8195
Elme.
using the Universal Attenuated Total Reflectance (UATR) method and were recorded by an average of 16 scans at a resolution of 4 i.
RESULT AND DISCUSSION
Particleboards Surface Roughness Bamboo particle size in this study was distributed unevenly, as demonstrated in Figure Most of them have particle size more than 2830 AAm .
83 m.
or passed through No 7-mesh screen, 90.
78% for type A bamboo particles and 74.
56% for type B bamboo Type B bamboo particles consist of more fine particles .
64%) than type A bamboo particles .
63%).
After bamboo slats were peeled off, the hardest parts of bamboo slats no longer existed.
So that during the processing in ring-flaker, type B bamboo slats produced extra fine particles (Figure .
While the width Figure 1.
Bamboo particles size distribution 20 mm 20 mm Figure 2.
Type A bamboo particles and Type B bamboo particles Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
and thickness of type A bamboo particles and type B bamboo particles show no significant difference (Figure .
The average of particle bamboo geometry from 100 particles of each type is presented in Figure 3.
Type B bamboo particles tend to split along the longitudinal direction.
The length of type B bamboo particles .
49 mm averag.
was longer than that of type A bamboo particles .
40 mm averag.
Based on data of particle geometry, we can calculate the slenderness ratio .
ength/widt.
and aspect ratio .
ength/ thicknes.
of the two types of bamboo particles (Table .
de Lira Bazzetto et al.
produced bamboo particleboards from bamboo (Dendrocalamus aspe.
particles with a size 210 mm0.
500 mm and classified them into 4 groups, which were -0.
mm, -0.
297 mm.
210 mm.
Symbols (-) and ( ) indicate passage and retention of particles, respectively.
Those bamboo particle sizes were relatively smaller than the size of bamboo particles used in this study.
Type B bamboo particlesAo slenderness ratio and aspect ratio are higher than of type A bamboo particles.
Thinner and longer particles yield a higher aspect ratio, larger surface area, and increased contact area in the glue line, contributing to better interaction and thus higher strength (Juliana et al.
, 2012.
Kasim et , 2.
Nonetheless, the bulk density of both types of bamboo particles shows no significant Smaller particles produced particleboard with improved surface smoothness nevertheless tend to reduce strength properties and dimensional stability and increase the difficulty in blending resin and mat-forming (Kelly, 1.
The particleboardsAo characteristics and properties are affected by the type of raw material, the particle geometry, the chemical content in the raw material, and the type and level of adhesive.
Particle geometry closely interacts with all these parameters, responsible for the particleboard properties (Maloney, 1.
Furthermore, the particleboard structures are defined by the conditions in which the pressing conditions and the mattress are formed.
Table 1.
The geometry ratio and bulk density of bamboo particles Type A bamboo particles Type B bamboo particles .
Slenderness Ratio Aspect Ratio Bulk Density .
/cm.
Remarks:
Figure 3.
Bamboo particles geometry Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120
ISSN: 2355-7079/E-ISSN: 2406-8195
Remarks:
Figure 4.
The surface roughness of bamboo particleboards As explained in the previous section.
Type B bamboo particles have a higher slenderness ratio and aspect ratio than type A bamboo With small and thin characteristics, type B bamboo particles could transfer more easily to fill void spaces during hot pressing and create smooth surfaces.
Particle geometry has a considerable effect on panel surfaces and The small and thin particles result in smooth board surfaces.
The smooth surface is appropriate for different coating types due to their ability and flexibility to fill void spaces.
A standard commercially manufactured particleboard could have average surface roughness (R.
values of 3 to 6 AAm (Hiziroglu.
Type B bamboo particleboards show a smoother surface compared with type A particleboards (Figure .
The average roughness value was 400 AAm for type B bamboo particleboards and 558 AAm for type A particleboards when bonded with 15% citric At the same time, the surface roughness of bamboo particleboard bonded with 20% and 25% citric acid when using type A or type B bamboo particles showed no significant The higher amount of citric acid application for adhering bamboo particleboard produced smoother particleboards.
The average roughness of type B bamboo particleboards bonded with 20% and 25% citric acid were 435 AAm and 321 AAm, respectively.
Regrettably, it seems that the board surface characteristic of all the particleboards is very rough.
So, the sanding process needs to be applied when overlaying application is desired.
Particleboard made from fine particles had a smoother surface compared to that of coarse The usage of citric acid developed a better contact among bamboo particles.
therefore, better adhesion, producing a smooth particleboard surface.
Rising resin content level would cause the particleboard surface to become smoother or decrease Ra value (Widyorini.
Umemura, et al.
, 2016.
Other than particle geometry, silica in bamboo skin might also affect the particleboard surface roughness.
Silica content in type A bamboo particles was 1.
07 %, while in type B bamboo particles was 0.
93 %.
The effort of peeling off Sembilang bamboo slats can improve particleboard surface smoothness, particularly when applying lower content of citric acid.
Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Particleboards Wettability In this study, the contact angle between type A bamboo particles and water or citric acid was higher than the contact angle of type B bamboo particles and water or citric acid (Table Moreover, the bamboo skin's initial contact angle against the water was greater than 83A indicating that water could not spread easily on bamboo skin.
Yuan and Lee .
said contact angles greater than 90A commonly mean that wetting is critical, so the fluid will minimize its contact with the surface and form a dense Table 2.
The contact angle of water and citric acid on liquid droplet.
the bamboo surface The surface's wettability indicates the that determines the extent to which Contact angle (A) the fluid will be spread by the surface, affecting Water
Citric acid
the absorption, adsorption, penetration, and Type A bamboo particles 69 A 5
78 A 6
spread of adhesive (Marra, 1.
Wettability is Type B bamboo particles 35 A 13
52 A 11
an essential property of the wood surface, and K values of water and citric acid on the type it influences bonding properties directly (Tang B bamboo surface were higher than of type A et al.
, 2.
In the liquid wetting process, the bamboo (Table .
The higher the K value is, contact angle change as a function of time is a the more the contact angle is.
thus, the curve decreasing function (Shi & Gardner, 2.
Silica content in bamboo skin was higher is steeper (Figure .
, indicating the type B in unskinned bamboo, so bamboo skin was bamboo surface has higher wettability than type more hydrophobic.
The contact angle value is A bamboo.
also influenced by material surface macroscopic Table 3.
Bamboo dynamic wettability towards the water and citric acid (R= correlation coefficient, e = equilibrium contact angle, i = initial contact angl.
Type A particles Type B particles Water Citric acid Water Citric acid K (L.
e () i () Figure 5.
Citric acid and water contact angle change on the surface of type A and type B bamboo particles as a function of time Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120 properties such as porosity, surface smoothness, pH, and chemical compound (Lu & Wu, 2.
In bamboo culms, silica was considered as a major constituent of the epidermis with values between 1.
5 % (Bambusa vulgari.
and 4 % (Schizostachyum lumampa.
(Liese, 1.
Van Acker et al.
reported values of 066 % in the lower part and 0.
082 % in the upper part of Phyllostachys praecox culms and values of 0.
120 % in the lower part and 0.
% in the upper part of Phyllostachys nigra culms.
(Lybeer, 2.
indicated lower values between 04 and 0.
11 % Si for Phyllostachys nigra and Phyllostachys viridiglaucescens and 0.
08 to 0.
Si for the tropical species Gigantochloa levis and Dendrocalamus asper.
Compared to another genus of bamboo, as previously stated, the silica content in sembilang bamboo was quite high.
ISSN: 2355-7079/E-ISSN: 2406-8195
Particleboards Mechanical Properties Figure 6 shows the internal bond (IB) of Sembilang bamboo particleboards.
The range IB value of 0.
79 Ae 0.
97 N/mm2 was recorded in type B bamboo particleboards, and 0.
78 N/mm2 was recorded in type A bamboo The internal bond of sembilang bamboo particleboards bonded with citric acid was higher than the requirement .
3 N/mm.
for the Type 18 particleboard internal bond, based on JIS A 5908.
Analysis of variances shows.
P-value <0.
(Table .
, that the type of bamboo particle has a significant effect on the IB value of Further tests using the Tukey comparison method, with 95% confidence level, are presented in Table 5, showing that type B bamboo particles produce particleboards with Remarks:
Figure 6.
Internal bond of particleboards made from type A and type B bamboo particles Tabel 4.
Analysis of variance for particleboardAos internal bond Source Replication Particleboards type CA content Particleboards type*CA content Error Total Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Tabel 5.
Grouping information using the Tukey Method and 95% confidence Particleboards type Type B Type A N Mean Grouping Remarks: Means that do not share a letter are significantly higher IB values and are significantly different from type A bamboo particleboard.
The results of the wettability analysis were in accordance with the results of the IB analysis, which show that the particleboardAos IB values were not influenced by citric acid content but influenced by the type of bamboo particles.
values of particleboards made from Sembilang bamboo particles demonstrate an interesting It shows that 15 % of citric acid was enough to bond type A and type B bamboo particles to produce particleboards that fulfilled the Type 18 particleboard standard, based on JIS A 5908.
The citric acid solution can easily cover and fill the void of bamboo particles whether or not the skin bamboo is still attached to the bamboo particles.
Due to hot-pressing, citric acid was reacted with hydroxyl groups of bamboo particles, producing a strong internal bond .
xplained further in the bonding mechanism at the end of the articl.
The same bonding mechanism was observed in another grass family, such as Imperata cylindrica (Syamani et al.
, 2.
and sugarcane (Syamani et al.
, 2.
Citric acid is expected to act as a bonding agent in bamboo-based particleboard.
However, the presence of silica in type A boards drives citric acid to be reacted to destruct silica rather than reacted with hydrogen groups in bamboo Therefore, the internal bond in type A boards was lower than in type B boards.
MOR average values of two kinds of bamboo particleboards at various citric acid contents are presented in Figure 7.
It is indicated that the type of bamboo particles affected the particleboards MOR significantly.
Analysis of variances shows that the type of particleboard, has a value of P<0.
01 (Table .
, indicating that the type of bamboo particles has a very significant effect on the MOR value of particleboard.
Remarks:
Figure 7.
Modulus of rupture of particleboards made from type A and type B bamboo particles Tabel 6.
Analysis of variance for particleboardsAo modulus of rupture Source Replication Particleboards type
CA content
Particleboards type*CA content
Error
Total
2/31
Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120 Further tests using the Tukey comparison method, with 95% confidence level, are presented in Table 7, showing that type B bamboo particleboard produces a higher MOR value and is significantly different from type A bamboo particleboard.
Tabel 7.
Grouping information using the Tukey method and 95% confidence Particleboards type Type B Type A Mean Grouping Remarks: Means that do not share a letter are significantly The MOR values of type B bamboo particleboard, bonded with 15, 20, 25 % citric acid, were higher than type A bamboo particleboard, i.
0, 20.
7, and 20.
0 N/mm2, respectively, and fulfilled the requirement for type 18 particleboard by JIS 5908.
The high MOR values indicated that the type B bamboo particles developed good bonding strength with citric acid.
In contrast, particleboards made from type A bamboo particles showed lower
ISSN: 2355-7079/E-ISSN: 2406-8195
MOR values, considering that the adhesion between bamboo particles could be obstructed by the existence of silica in bamboo skin.
However, all particleboards made from type A bamboo particles could fulfill the obligation of Type 13 of JIS A 5908, where MOR of 13.
N/mm2 or more is obliged.
Regarding the citric acid amount applied to bond bamboo particles, the MOR values were not significantly affected.
In contrast to MOR value, particleboards made from type B bamboo particles showed a lower MOE value (Figure .
compared to particleboard made from type A bamboo particles when bonded with 15% or 20% citric acid.
Nonetheless, the MOE values of particleboards made from type A and type B bamboo particles were high that can fulfill the requirement of type 18 of JIS A 5908, where MOE of 3000 N/mm2 or more is Based on the analysis of variances, the interaction of particleboard type and citric acid content gave a significant effect on the MOE value of particleboard (Table .
Remarks:
Figure 8.
Modulus of elasticity of particleboards made from type A and type B bamboo particles Tabel 8.
Analysis of variance for particleboardAos modulus of elasticity Source Replication Particleboards type
CA content
Particleboards type*CA content
Error
Total
2,18
0,19
3,46
3,93
0,109
0,666
0,051
0,036
Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Further testing of the effect of particleboard type used the Tukey comparison method, with 95% confidence level is presented in Table 9 and Table 10, indicating that the type of particleboard or the level of citric acid does not affect the MOE value of the particleboard.
As reported by (Li & Beijing, 2.
and (Yuan, 2.
, in general, bending properties (MOR and MOE) decreased as the portion of the outer bamboo surface removed increased.
The outer bamboo surface shows higher bending properties than the inner part of bamboo.
line with Li's statement, this study result shows that the MOE of particleboards made from type B bamboo particles was lower than that of Tabel 9.
Grouping information using the Tukey method and 95% confidence Particleboardstype Type A Type B Mean Grouping Remarks: Means that do not share a letter are significantly Tabel 10.
Grouping information using the Tukey
Method and 95% confidence CA content
CA 15%
CA 20%
CA 25%
Mean Grouping Remarks: Means that do not share a letter are significantly MOE particleboard made from type A bamboo particles when bonded with 15% and 20% citric Type B particleboard, which no longer has bamboo skin, shows lower stiffness compared to type A particleboard.
Both types of Sembilang bamboo particleboards .
ype A and type B) demonstrate screw holding power (SHP) value greater than 300 N .
ulfilling type 8 particleboards based on JIS A 5.
when bonded with 15% and 20% citric acid.
However, the addition of citric acid until 25% causes particleboard SHP value to decrease (Figure .
Analysis of variances from the treatment of citric acid levels, has a value of P < 0.
01 (Table .
, indicating that the levels of citric acid have a very significant effect on the value of the screw holding power of the Further testing of the effect of citric acid levels using the Tukey comparison method, with 95% confidence level is presented in Table 12, showing that 15% citric acid content produces particleboard with higher SHP values and is significantly different from bamboo particleboard with a citric acid content of 20% and 25%.
Citric acid affected the power of the screw to hold the particleboard due to its acidity.
Based on this data, it is suggested to use not more than 20% citric acid content to bond the particle, especially when the particleboards are intended to be used as furniture.
The SHP of type A Remarks:
Figure 9.
Screw holding power of particleboards made from type A and type B bamboo particles Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120
ISSN: 2355-7079/E-ISSN: 2406-8195
Tabel 11.
Analysis of variance for particleboardAos screw holding power Source Replication Particleboards type CA content Particleboards type*CA content Error Total Tabel 12.
Grouping information using the Tukey
method and 95% confidence CA content
CA 15%
CA 20%
CA 25%
Mean Grouping Remarks: Means that do not share a letter are significantly particleboards was higher than that of type B particleboards.
Particleboard strength, nail, and screw withdrawal resistance are important characteristics of particleboards and are mainly affected by particle geometry.
As stated in Table 1, the slenderness ratio and aspect ratio of type A bamboo particles were lower than of type B bamboo particles.
It means that the shape of type A bamboo particles is wider and thicker than of type B bamboo particles.
Therefore, particleboards made from type A bamboo particles have more power to hold the screw.
Particleboards Physical Properties ParticleboardsAo water absorption and thickness swelling characteristics were analyzed to explain bamboo particleboardsAo physical It is obvious from Figure 10 that the resistance of the particleboards to absorb water was improved significantly when using type B bamboo particles.
The water absorption (WA) values were 19.
35 % for type B bamboo particleboards bonded with various citric acid On the other hand, the particleboards using type A bamboo particles show WA values in a range of 32.
53 %.
The influence of bamboo particle type was more significant compared to citric acid content.
Analysis of variances due to particleboard type has a value of P<0.
01 (Table .
, indicating that particleboard type has a very significant effect on the water absorption (WA) value of particleboard.
Further testing of the effect of particleboard type using the Tukey comparison method, with Remarks:
Figure 10.
Water absorption of particleboards made from type A and type B bamboo particles Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Tabel 13.
Analysis of variance for particleboardsAo water absorption (%) Source Replication Particleboards type CA content Particleboards type*CA content Error Total Tabel 14.
Grouping information using the Tukey method and 95% confidence Particleboards type Type A Type B Mean Grouping Remarks: Means that do not share a letter are significantly a 95% confidence level is presented in Table 14, showing that type B bamboo particles produce particleboard with a lower water absorption value than type A particleboard.
This indicates the stability of the type B particleboard is better than the type A particleboard.
(Widyorini et al.
, 2.
applied 15% and 30% citric acid content to bond various bamboo species with different sizes of particles.
She explained that citric acid content was more principal on particleboards dimensional stability than bamboo species or particle size.
The WA values were 35%, 17%, and 26% for particleboards made from 15% citric acid and fine particles of petung, wulung, and apus Then the WA values were improved to 15%, 13%, 12% for particleboards made from 30% citric acid and fine particles of Petung.
Wulung.
Apus bamboo, respectively.
In this study, the citric acid amount varied at 15%, 20%, and 25%, and has not significantly influenced particleboard WA value.
The difference of bamboo particles type influenced wettability properties, as mentioned before.
Type B bamboo particles which have lower silica content, have superior wettability properties than type A bamboo particles, thus causing the improved bonding then resulted in enhanced dimensional stability.
As demonstrated in Figure 11, the thickness swelling (TS) values of the particleboards bonded with citric acid fulfilled the requirement Remarks:
Figure 11.
Thickness swelling of particleboards made from type A and type B bamboo particles Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120
ISSN: 2355-7079/E-ISSN: 2406-8195
Tabel 15.
Analysis of variance for particleboardAos thickness swelling Source Replication Particleboards type CA content Particleboards type*CA content Error Total of JIS A 5908 .
ax 12 %), demonstrating that bamboo particleboard had good dimensional Analysis of variances due to citric acid content has a value of P<0.
01 (Table .
, indicating that citric acid content has a very significant effect on the value of thickness expansion (TS) of particleboard.
Further testing of the effect of citric acid levels using the Tukey comparison method, with 95% confidence level is presented in Table 16, showing that particleboard with 25% citric acid content produces particleboard with a lower thickness expansion value than particleboard with 15% and 20% citric acid This shows that the stability of the bamboo particleboard bonded with citric acid at a level of 25% is better than that of the bamboo particleboard bonded with citric acid at a concentration of 15% and 20%.
Tabel 16.
Grouping information using the Tukey
Method and 95% confidence CA content
CA 15%
CA 20%
CA 25%
Mean Grouping Remarks: Means that do not share a letter are significantly The TS value was 8.
98% for type A particleboard bonded with 15% citric acid.
The TS value was improved to 7.
63% and 6.
31% by adding 20% and 25% citric acid, respectively (Figure .
Moreover, the TS value of type B particleboard was also improved when applying higher citric acid content, with a range of TS values of 5.
This occurrence is possible because type B bamboo particles might deliver a more intimate contact area among particles, and in contrast with type A bamboo particles due to the lower concentration of silica in type B bamboo particles, resulting in more intense bonding.
The same trend was also found by (Widyorini.
Nugraha, et al.
They reported that bamboo-citric acid particleboards have TS value in a range of 7 9% when bonded with 15% citric acid and 2 4% when bonded with 30% citric acid.
Particleboards Durability Analysis by Cyclic Aging Treatment The thickness change of particleboards made from type A and type B bamboo particles after cyclic aging treatment are depicted in Figure 12.
The thickness change of bamboo particleboards at each phase of the cyclic aging treatment decreased with the increase of citric acid content, regardless of the type of bamboo The particleboard dimensions have remained stable during all steps of cyclic aging The results demonstrate that boards with a 25% citric acid content performed better dimensional stability than the boards bonded with 15% or 20% citric acid.
The percentage of thickness-change of type A and type B bamboo particleboards bonded with 25% citric acid after being boiled in water for 4 h was 15% and 12.
31%, respectively.
This value of particleboard thickness-change was lower than those bonded with 15% or 20% citric The result suggests that 25% of citric acid effectively produced good dimensional stability Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
Figure 12.
Thickness swelling of bamboo particleboards during cyclic aging treatment Figure 13.
Weight changes of bamboo particleboards during cyclic aging treatment The change of particleboards weight after cyclic aging treatment is illustrated in Figure 13, indicating that the weight change decreased with the increase of citric acid level.
This outcome demonstrates that the increase of citric acid levels enhances the inhibition of water absorption.
The type B bamboo particleboards weight changes due to the following hot-water immersion treatment .
33%) were higher than those of type A bamboo particleboards after the first phase of water immersion treatment .
46%).
This occurrence is affected by the water resistance of the adhesive decreased due to hot-water immersion treatment, thus enhancing the water infiltration into the boards.
The type A bamboo particleboard weight bonded with 25% citric acid changed by approximately Oe4.
61 to Oe15.
74% with the following drying treatment.
The scale of type B bamboo particleboard weight change is similar to that of type A bamboo particleboards.
Nevertheless, the type B bamboo particleboards weight changes due to each phase of drying treatment were lower, approximately Oe3.
83 to Oe9.
This outcome demonstrates that the bonding between type B Indonesian Journal of Forestry Research Vol.
9 No.
April 2022, 99-120 bamboo particles and citric acid was superior to type A bamboo particles, thus more dominant to resist water due to a more intimate contact area among particles with citric acid, by the lower concentration of silica in bamboo skin.
Bonding Adhesion of Bamboo Particles and Citric Acid Analysis by FTIR The bonding mechanisms of bamboo particleboards with various citric acid levels were evaluated using FT-IR spectroscopy.
The ISSN: 2355-7079/E-ISSN: 2406-8195 board infrared (IR) spectra are presented in Figure 14 and Figure 15.
In the FTIR analysis, the peak intensity at approximately 1714 cmOe1 is typically ascribed to C=O stretching due to carboxyl groups and/ or C=O ester groups (Yang et al.
, 1996.
agar & Grdadolnik, 2.
Kusumah.
Arinana, et al.
, .
and Kusumah.
Umemura, et , .
mentioned that carbonyl groups were represented as ester linkage between hydroxyl groups of sweet sorghum bagasse Remarks:
Figure 14.
FTIR spectrogram of type A bamboo particles and particleboards made of type A bamboo particles bonded with 25% citric acid before and after cyclic aging treatment Remarks:
Figure 15.
FTIR spectrogram of type B bamboo particles and particleboards made of type B bamboo particles bonded with 25% citric acid before and after cyclic aging treatment Utilization of Citric Acid As Bonding Agent In Sembilang Bamboo .
(Firda A.
Syamani et al.
ignocellulosic material.
and carboxyl groups of citric acid.
As described in Figure 14.
FTIR spectra of Type A bamboo particles show no peak at 1713 cm-1.
On the other hand.
FTIR spectra of particleboard made from type A bamboo particles show a peak at 1713 cm-1 before and after cyclic aging treatment.
has proven the forming of ester linkage in According to the results presented in Table 4, band characteristics were changed from type A and type B particleboards before and after cyclic treatment.
The peak at nearly 1714 cmOe1 was assigned to the C=O stretch in esters.
The IR spectra of type B bamboo particleboards exhibit that the intensities of the transmittance peaks at nearly 1714 cmOe1 representing that carboxyl groups in citric acid reacted with the hydroxyl groups of type B bamboo particles to form ester linkages (Figure .
The bonding mechanism is very similar to that detected in wood particleboards bonded with citric acid (Umemura et al.
Accordingly, ester linkages formation would cause good adhesiveness and convey superior physical characteristics to the bamboo IV.
CONCLUSION
The effects of bamboo particle type and citric acid level on the mechanical and physical properties of Sembilang bamboo particleboards bonded with citric acid were evaluated.
The type B particleboardsAo internal bond (IB), modulus of rupture (MOR), water absorption (WA), and thickness swelling (TS) were superior compared to the type A particleboards.
This was influenced by the lower concentration of silica in type B particleboards, which tend to allow an intimate contact area among particles and citric acid then produced better quality particleboards compared to type A particleboards.
On the other hand, type A particleboard shows higher quality, in terms of modulus elasticity, due to bamboo outer skin contributing to particleboardsAo Furthermore, the MOR.
MOE, and IB values of type B bamboo particleboards satisfied the type 18 requirements of JIS A Although, the screw holding power of type B bamboo particleboards only satisfied type 8 of JIS A 5908.
The physical properties of Sembilang bamboo particleboards were also improved when using type B bamboo particles and bonded with 25% citric acid.
Based on the infrared spectra, ester linkages appeared clearly in Sembilang bamboo particleboards manufactured with type B bamboo particles and bonded with 25% citric acid.
This means that removing bamboo skin containing silica affected the mechanical and physical properties of Sembilang bamboo particleboards bonded with citric acid.
ACKNOWLEDGEMENT
This research was partly supported by JASTIP Program on Collaborative Bioresources and Biodiversity Studies for the ASEAN Region.
The authors acknowledge facilities, scientific and technical support from Advanced Characterization Laboratories Cibinong - Integrated Laboratory of Bioproducts.
Indonesian Institute of Sciences through E-Layanan Sains Lembaga Ilmu Pengetahuan Indonesia.
REFERENCES