Preparation and Characterization of Sound-Absorbent Based on Polystyrene Reinforced Primary Sludge and Fly Ash from Pulp Mill
Corresponding email: basuki@usu.ac.id
Published at : 09 May 2023
Volume : IJtech
Vol 14, No 3 (2023)
DOI : https://doi.org/10.14716/ijtech.v14i3.5131
Hiadayani, T.R., Wirjosentono, B., Nasution, D.Y., Tamrin, 2023. Preparation and Characterization of Sound-Absorbent Based on Polystyrene Reinforced Primary Sludge and Fly Ash from Pulp Mill. International Journal of Technology. Volume 14(3), pp. 649-658
| Tengku Rachmi Hiadayani | Department of Agribisnis Kelapa Sawit, Politeknik Teknologi Kimia Industri, Medan, Indonesia, 20288 |
| Basuki Wirjosentono | Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan, Indonesia, 20155 |
| Darwin Yunus Nasution | Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan, Indonesia, 20155 |
| Tamrin | Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan, Indonesia, 20155 |
Efforts to utilize and improve the value of pulp
waste have been done by using primary sludge (still containing cellulose) and
fly ash as a filler to produce composite foam polystyrene (PS)-based as sound
absorbent. In this study, the composite foam was produced by mixing primary
sludge and fly ash with several compositions such as PS, PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0), (80/10/7/3), (80/10/5/5), (75/10/10/5), and
(75/10/12/3). The composite was characterized based on ISO 11654:1997,
mechanical properties, thermal analysis using TGA and DSC, morphology using
SEM, crystallinity using XRD, and chemical analysis using FTIR. The results
showed that the band at 1600.63 cm-1 was sharper due to a chemical
reaction being formed between PS, primary sludge, and fly ash. The XRD analysis
showed a new diffraction peak in the 2
= 21-24o. The morphology analysis showed that primary
sludge and fly ash were uniformly dispersed into PS, increasing the mechanical
properties and decreasing the melting point of the PS foam composite. The sound-absorbing composite produced had
qualified ISO 11654:1997 on the rating level of the sound absorption
coefficient on materials for rooms with sound absorption classes D and C with
the value of 
w
0.328-0.793.
Fly ash; Polystyrene; Primary sludge; Pulp Mill; Sound-absorbing
Recycled porous material has comparable value to natural materials as a sound absorber. It also improves thermal insulation properties. A study reported that recycled materials from ethylene-vinyl acetate (EVA), polyvinyl chloride (PVC), polystyrene (PS), and polypropylene (PP), in different mixtures with a binding adhesive, can be considered as a good precursor of sound absorption suitable for room acoustic predictions (Biskupicová et al., 2021). In addition, PS is one of the widely used plastic materials for packaging and insulation purposes. However, its waste generates hazards for humans, animals, and the environment. Composite-based PS is a good solution to deal with the waste of PS and can be used for building insulation due to its low-cost property and its ability to provide a long-term solution for Styrofoam waste (Abir, Faruk, and Arifuzzaman, 2020). PS is also one of the most common polymers which benefit from low thermal conductivity, high optical transmission, good heat stability, and excellent moisture resistance (Zhao et al., 2021).
PS has been used as the most insulating
material in Europe. The market share is about 80% due to its low cost and ease
of processing (Heller and Flamme, 2020). PS and Portland cement as
aggregate and binder were mixed as masonry in the construction. ?The result shows that the
composite has efficient mechanical properties and meets the required
parameters. In addition, compared to the commercial one, the composite was
lighter, less permeable, and more economical
(Hernández-Zaragoza et al., 2013). It is also reported that
sawdust reinforced with extended PS composites is superior to the synthetic
fiber polymer as dumping sound material. ?Sound absorption of composite
foam increased with increasing sawdust with loading level of 80% (Abdel-Hakim et al., 2021). PS-fly ash composite is a
potential construction material to solve the environmental problem by recycling
waste fly ash and plastic material. ?It is reported that this composite material
bears the low cost and water insulation. Therefore, it has the potential to be
used as coating material on the walls and tiling in buildings (Bicer, 2020).
Fly ash, an agro-waste from any
industry, is a second layer by-product from the combustion of fuel. It has been
used as a precursor to producing nano-silica as filler for membranes, rubber
airbags, composite, and concrete materials. The study reported that the
presence of nano-silica improves the mechanical properties and durability of
composite material (Indrasti et al., 2020). ?While, it is stated that the relationship
between the content of nano-silica and the mechanical properties of concrete
needs further study to develop compressive strength that can be applied to any
concrete mixture (Eddhie, 2017).
Phosphate sludge is also used to ?prepare ceramic bricks by mixing
with kaolin (Muliawan and Astutiningsih,
2018). Therefore, this study aims to utilize the by-products, fly ash,
and primary sludge from the pulp industry as a filler to prepare PS composite
foam as a sound-absorbing material. The pulp industry has been the subject of a
long debate involving the local community due to the waste produced by
factories. Therefore, this study is expected to be a solution for the
utilization of waste. The new product is also expected to be a good formula to
prepare a biodegradable damping material.
2.1. Materials
The
materials used in this experiment were PS (C8H8)n
type GPPS (General Purpose Polystyrene) injection grade, benzoyl peroxide (C14H10O4),
xylene (CH3)2C6H4, maleic anhydride
(C4H2O3), which were purchased from Merck
(Darmstadt, Germany). Primary sludge and fly ash were obtained from Indah Kiat
Pulp & Paper Tbk., Riau, Indonesia.
2.2.
Preparation of Primary Sludge and Boiler Ash
Primary sludge was dried under the sun
for 7 days and then dried in the vacuum oven at 100o C for 6 hours.
After drying, it was blended with a blender and sieved on a 400-mesh sieve.
Meanwhile, fly ash was pulverized with a size of 200 mesh. It was purified
using a 2 M HCl solution with fly ash: HCl ratio, 1:10, then distilled for 2
hours. The fly ash HCl solution was filtered and then washed using distilled
water until pH-neutral. It was then
calcinated at 600o C for 2 hours to decompose and remove amorphous
content. The calcinated fly ash was allowed to cool at room temperature and put
into a ball mill (Planet PM 200) for 10 hours.
2.3.
Preparation of Sound-Absorbing Polystyrene
Figure 1 A flowchart of PS composite foam preparation
2.4.
Characterization
The sound-absorbing composite of
PS-reinforced primary sludge and fly ash was characterized using analytical
techniques as follows. The morphology of the samples was investigated using
scanning electron microscopy (SEM) Hitachi TM3030 (JEOL, Ltd., Tokyo, Japan) at
an accelerating voltage of 10 kV. To reduce charging during analysis, the
sample was first coated with a thin layer of gold. The chemical structure in
the samples was analyzed using a Fourier-transform infrared (FTIR) spectrometer
(Nicolet 380, Thermo Scientific, Boston, USA) in a transmission mode with a
resolution of 2 cm-1 and 100 scans. The crystallinity of the samples
was analyzed using X-ray diffraction (XRD) Bruker D8 advanced X-ray
diffractometer (Bruker Optik GmbH, Ettlingen, Germany). The thermal properties
of the samples were characterized using Thermogravimetric analysis (TGA),
DTA/TG Exstar SII 7300 (Hitachi medical system, Tokyo, Japan) heated between 30
and 600° C with a heating rate of 10° C/min. It was also studied via a
differential scanning calorimetry (DSC) X-DSC7000 (Hitachi medical system,
Tokyo, Japan) in a range temperature from 30° to 600° C using a heating rate of
10° C/min. The mechanical properties of the sample ?were
tested with a dead load hardness tester, shore A, at room temperature according
to ASTM D 2240. Finally, the sound absorption of the samples was carried out
using an impedance tube according to ASTM E-1050-98. The amplitude from the
graph was obtained by looking at the maximum value of each channel, and the
sound absorption coefficient value was calculated using MATLAB software.
3.1. FTIR and X-ray Analysis
Figure 2 FTIR spectra of primary sludge, fly ash, PS, PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0), (80/10/7/5), (80/10/5/5), (75/10/10/5, and
(75/10/12/3)
The peak at the band 3000–3500 cm-1
indicates the OH stretching vibrations in all samples (Kusrini et
al., 2021). In the sludge
sample, the OH wave number was at 3744.40 cm-1 with a fairly wide
peak. This is due to the large amount of water in the sample. The band at
2850.31 cm-1 attributed to H-C-H stretching (alkyl, aliphatic),
1623.65 cm-1 corresponded to OH-fibers (water absorption), and
1414.47 cm-1 was vibrations of HCH and OCH bonds (methyl groups). In
the primary sludge, there was a band at 706.52 cm-1 indicating 1b crystalline cellulose polymorph from the pulp (Risnasari et
al., 2018).
For PS, there was a peak at
1492.25 cm-1 indicating the absorption of the indentation of the
(C-H) group as alkyl. The peak at 1600.63 cm-1 is attributed to the
bond in benzene with strong to weak intensity. The band at 2922.36 cm-1
and 3059.46 cm-1 corresponded to C-H bonds with benzene and Ar-H. In
the fly ash, it can be seen that the absorption at 1621.90 cm-1
presented C=O stretching on the ketone. The peak of 1064.25 cm-1 and
796.10 cm-1 attributed to C=C stretching of hemicellulose and C=C
stretching of vinylidene alkenes, respectively. The aromatic ring in fly ash
was seen at the band 777.60 cm-1 (Reza et
al., 2020; Huan et al., 2015).
Furthermore,
PS/PS-g-MA/primary sludge/fly ash (80/10/10/0), (80/10/7/5), (80/10/5/5),
(75/10/10/5), and (75/10/12/3) showed a decrease in the peak in the absorption
area of 3059.46 cm-1. The band at 1600.63 cm-1 also
looked sharper. From the FTIR results, it can be concluded that PS, primary
sludge, and fly ash have been physically blended, and there were chemical
reactions formed during the mixing process as reported by previous studies (Oromiehie, Ebadi-Dehaghani, and Mirbagheri, 2014).
= 21 – 24o corresponding to the
crystalline region. The increase in the crystallite value for the
sound-absorbing composite foam PS/PS-g-MA/primary sludge/fly ash contributed to
the mechanical properties of the resulting sound-absorbing composite foam.
Figure 3 XRD pattern of PS, PS/PS-g-MA/primary sludge/fly ash (80/10/10/0)
and (75/10/10/5)
3.2. Morphological Characterization
Figure 4 SEM micrograph of
(a) primary sludge, (b) fly ash, (c) PS, and (d) PS/PS-g-MA/primary sludge/fly
ash (75/10/10/5) with magnification 3.5 kX and scale bar 2 µm
3.3. Thermal Analysis
The
thermal properties of the sample in this study were characterized using TGA and
DSC. The TGA curve for all samples is presented in Figure 5, and the DSC
thermogram for PS, PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0) and (75/10/10/5) is shown in Figure 6.
Figure 5 shows that all samples had three
main distinct degradations. The first step was at 100o C with a mass
loss of around 2% for PS, and almost 10% for PS/PS-g-MA/primary sludge/fly ash (80/10/10/0), (80/10/7/5), (80/10/5/5),
(75/10/10/5), and (75/10/12/3). The second step was from 200 to 350 oC
for PS, PS/PS-g-MA/primary sludge/fly
ash (80/10/10/0), (80/10/7/5), (80/10/5/5), (75/10/10/5). However, PS/PS-g-MA/primary sludge/fly ash
(75/10/12/3) experienced a lower temperature between 131 and 371o C.
At this step, all samples lost about 20% of their mass. Finally, PS decomposed
at 349-434o C with a residual mass of 0,6%.
Figure 6 DCS thermogram for
PS, PS/PS-g-MA/primary sludge/fly ash (80/10/10/0) and (75/10/10/5)
3.4. Mechanical Properties
Figure
7 shows the strain and stress curves of all samples. In general, the tensile
strength of a composite foam significantly increased after the addition of
filler. PS and PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0) had a tensile of 6.526 MPa and 5.841 MPa, respectively.
PS/PS-g-MA/primary sludge/fly ash (80/10/7/3) had a tensile of 6.043 MPa which
was the highest value compared to all samples.
The
increase in tensile strength after the addition of primary sludge/ash with
composition 7/3 was because the filler was well and uniformly dispersed into
the matrix. The addition of filler increased the tensile strength and Young's
modulus indicating that sufficient dispersion of the filler into the matrix has
occurred. In addition, as the filler concentration increased, the sample
deformation decreased. A previous study reported that the wall panel with the
presence of sludge increased the tensile strength by 0.61 N/mm2
compared to without sludge, 0.59 N/mm2 (Hidayani et al., 2021).
Figure 7 Stress-strain curve
for PS, PS/PS-g-MA/primary sludge/fly
ash (80/10/10/0), (80/10/7/5), (80/10/5/5), (75/10/10/5), and (75/10/12/3)
3.5. Sound Absorption Properties
Figure 8 The sound absorption
coefficient of the composites
Regarding
Figure 8, it can be seen that the absorption coefficient of PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0) decreased from a frequency of 200 Hz to 400 Hz. On the
other hand, PS and PS/PS-g-MA/primary sludge/fly ash (75/10/10/5) increased in the
absorption coefficient at the range frequency. The highest
value for PS was 0.793 at a frequency of 500 Hz and then experienced a dramatic
decrease. Although the absorption coefficient of PS/PS-g-MA/primary sludge/fly ash
(75/10/10/5) had decreased at a frequency of 500 Hz, it increased again and had the
highest peak at a frequency of 1000 Hz with a value of 0.328. For PS/PS-g-MA/primary
sludge/fly ash (80/10/10/0), the absorption coefficient continued to
decrease. The sound-absorbing composites produced have qualified ISO 11654:1997
about the rating level of the sound absorption coefficient on materials for
rooms with sound absorption classes D and C with the value of aw 0.328-0.793.
Sound-absorbing composite PS-based filled with primary sludge and
fly ash from a pulp mill has been produced by using a
compression press. From the results, primary sludge and fly ash are dispersed
uniformly onto the PS polymer matrix which increases the mechanical properties.
It also shows that chemical bonds
formed during the mixing process due to the grafting procedure between PS and
maleic anhydride. The sound-absorbing composite has the value of aw 0.328-0.793 which is
qualified based on ISO 11654:1997 and sufficient for sound absorption for
rooms. The composite produced is potentially used as a green and biodegradable
sound absorber material. For future work, fly ash will be modified into
nano-silica so that the mechanical properties of the composite increase and
bear the parameter of the commercial damping sound.
The authors thank the Indonesian Ministry of Industry for research funded by DRPM 2021 PDUPT scheme with contract number 235/UNS.2.3.1/PPM/KP-DRPM/2021.
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