Published at : 18 Jan 2023
Volume : IJtech
Vol 14, No 1 (2023)
DOI : https://doi.org/10.14716/ijtech.v14i1.4926
Denny Akbar Tanjung | Department of Agrotechnology, Faculty of Agriculture, Universitas Medan Area, Medan-20223, Indonesia |
Novesar Jamarun | Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Andalas, Padang-25163, Indonesia |
Syukri Arief | Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Andalas, Padang-25163, Indonesia |
Hermansyah Aziz | Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Andalas, Padang-25163, Indonesia |
Boy Isfa | Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Andalas, Padang-25163, Indonesia |
Ahmad Hafizullah Ritonga | Institut Kesehatan Medistra Lubuk Pakam, Deli Serdang-20512, Indonesia |
Vivi Sisca | Department of Biology Education, STKIP YPM Bangko, Jambi 37313-Indonesia |
The purpose of this
study was to improve the mechanical and physical properties, degradation
performance, and water absorption of a thermoplastic mixture of sago starch
with the addition of Linear Low-Density Polyethylene (LLDPE). The method used
is the grafting method where polyethylene is grafted onto Maleic Anhydride
(LLDPE-g-MA). In this research, Thermoplastics Sago Starch (TPSS) was made with
a mixture of Sago Starch (65%) and Glycerol (35%), added with water as a
solution. Compatibilizer (PE-g-MA) was made by reacting LLDPE (88%) and Maleate
Anhydride (9%) with an additional initiator of Benzoyl Peroxide (3%). The
concentration of LLDPE varied from 10,15, 20, 25, and 30%. Substances were
mixed into an internal mixer Thermo Haake Polydrive with a speed of 100 mm/minute, for 15
minutes. The concentration of 30% LLDPE produced the highest tensile strength
and elongation at a break of 4.30 N/mm2 and 2.15%, respectively. Simultaneously, as LLDPE concentration
increased, Young's Modulus decreased. This was powered by the morphology of the
sampling surface, with the occurred reaction of adhesion interface or
dispersion of LLDPE toward the whole surface with the assistance of
compatibilizer as connecting substance between hydrophilic polymer and a hydrophobic
polymer, which could improve the properties of mechanical. The formation of ester groups from the
reaction of inter groups of hydroxyls derived from the starch with the groups
of anhydride derived from the mixture of compatibilizer was visibly seen at the
peak of 1693 cm-1. The degradation performance of the TPSS: LLDPE
mixture with a ratio of 70:30 showed good performance where the degradation
continued to increase up to 42% on the 30th day of degradation in freshwater,
18% in seawater, and 17% in soil burial. While the water absorption test showed
that the higher concentration of LLDPE, the lower speed of water absorption.
Bioplastics; Compatibilizer, Coupling agent, Grafting, Starch
In 2018, the production of global plastic was nearly 360 million tons (Barnaba et al., 2020). Meanwhile, the production of bioplastic reached just 2.01 million tons or 0.56 percent of global plastic production (European Bioplastics, 2017). The increasing market of bioplastics could reduce dependency on fossil-based source and transform to be a biobased society (Imre et al., 2019; Geueke et al., 2018 ). Nowadays, approximately 80% of the world's plastic production is not recycled (Blank et al., 2020) and the usage of plastics polluting is on the rise (Sidek et al., 2019). Bioplastic, which by definition is biodegradable and/or gained from a renewable source, is a sustainable alternative to conventional plastic and its production capacity is estimated to increase to 2.43 million tonnes in 2024(European Bioplastics, 2018).
2.1.
Material
Sago starch Parang brand is a production of Warna
Jaya Indonesia. Obtained from the traditional market of Serpong-Tangerang,
Indonesia. Moisture content was 14%. Low Linear Density of Polyethylene (LLDPE)
UF 1810S1 Pellet with density: 0.922 g/m3, Melt Index (1900C/2.16
kg): 1.0g/10 min, melting point 1220C, obtained from PT.
Chandra Asri Petrochemical Tbk (TPIA) Cilegon-Indonesia. Maleic anhydride for
sinthesis Merck KGaA, 64271 Darmstadt Germany, Benzoyl peroxide Merck for
sinthesis Merck KGaA, 64271 Darmstadt Germany and Glycerol
Analytical Reagent merck Univar Produksi Ajax Finechem. These can beobtained
from the Rudang shop Medan-Indonesia.
2.2. Preparation of TPSS
In order to prepare TPSS, sago starch and glycerol were reacted at a ratio of 65:35, and water was added at a concentration of up to 250% of the amount of sago starch. The mixture is heated to 100°C until it turns into gelatin. To reduce the water content in TPSS gelatin to 5%, it is oven-dried for 24 hours at 80°C (Majid et al,, 2009). Figure 1 depicts a flowchart of the process of TPSS preparation.
Figure 1 Flow diagram of the process of preparation of TPSS
2.3. Preparation of Compatibilizer
The blends were mixed with Haake Polydrive Thermo. LLDPE was first added into the mixing chamber, followed by Maleate Anhydride after 5 minutes of a mixture, then Benzoyl Peroxide (BPO) was added at last. The mixture was completed at 1500C and a speed of 100 rpm, with the mixture’s total time, being 15 minutes. The composition comparison of LLDPE: Maleate Anhydrous: Benzoyl Peroxide, the ratio was 88:9:3. The compound was removed, cooled, and cut into pellets. Figure 2 illustrates a Flow Diagram of the Compatibilizer (LLDPE-g-MA) Preparation Process.
Figure 2 Flow diagram of the process of preparation of
Compatibilizer (LLDPE-g-MA)
2.4. Preparation of TPSS/LLDPE/PE-g-MA
blends
The mixture preparation of TPSS / LLDPE/PE-g-MA was the final phase in this research, in which the whole phases that have been prepared above would be mixed here, such as TPSS, LLDPE, and compatibilizer. The compound was produced by mixing TPSS and LLDPE with the comparison of 90:10, 85:15, 80:20, 75:25, and 70:30. PE-g-MA was used with an amount of 10 wt. % based on the weight of TPSS (Majid et al., 2009). Figure 3 shows the process flow diagram of the TPSS/LLDPE/LLDPE-g-MA (compatibilizer) preparation.
Figure 3 Flow diagram of the process of preparation
of TPSS/LLDPE/LLDPE-g-MA (Compatibilizer)
2.5. Compression Molding
The
blend of TPSS / LLDPE was printed with hydraulic pressure compression at a
temperature of 1500C for 15 minutes. The pressure was increased to
its maximum every 5 minutes. All compression molded sheets by ASTM D638 Type
1.
2.6. Tensile Properties
A tensile test was carried out by examining the machine of
Universal Band Tensilon with the specimen of ASTM D638 Type 1. The
temperature in the chamber was 250C, humidity on 60% RHdn, 10mm
speed/minute. 3 Specimens were used to obtain the average value of Tensile Strength, Elongation
at Break, and Modulus Young.
2.7. Spectroscopy Fourier Transform
Infra-Red (FTIR)
Fourier transform infrared spectroscopy (FTIR; Perkin Elmer System
2000) was utilized to obtain qualitative information on the groups and chemical
characteristics of TPSS / LLDPE blends. For each spectrum, 45 scans with a
resolution of 4 cm-1 were recorded consecutively with Wd: 9:5 mm. The sample
was measured in the form of a 1-millimeter-thick layer produced through
hot-press molding.
2.8. Test of Morphology
The scanning test of Electron Microscopy (SEM) was carried out to
evaluate the morphology surface of the blended sampling of TPSS / LLDPE. The
sampling was dried up in the oven to reduce water content and avoid
electrostatic filling as well as worse resolution. By the time of sampling
surface inspection, it was installed on the piece of aluminum stubs and
sputter-coated with a thin layer of gold.
2.9. Test of Water Absorption
The sampling sheet was cut into a
dimension of 20mm x 20mm (Obasi et al., 2015) with a
thickness of 3mm. It was then washed with aquadest and dried up to 80% for 12
hours, cooled down in a desiccator, and weighed to gain initial weight. It was
then immersed into aquadest for ten days with a chamber temperature of 28-300C
and reweighed to gain weight afterward.
2.10. Test of Biodegradability
The compatible blend of TPSS / LLDPE with
a dimension of 20mm x 20mm with a thickness of 3 mm was examined with different
condition control (Spaccini et al., 2016; Maran et al., 2014). The
first sampling was stored in a container containing just fresh water. The
second one was immersed in seawater. The test for weight loss was done every
10, 20, and 30 days.
2.11. Test of Soil burial
The sampling was buried at a 10mm depth
from the surface of alluvial soil (Henry & Isaac, 2014) which was
placed in the holed box. Regularly wet it to keep its humidity. The weight loss
of the samples was monitored at regular intervals of 10, 20, and 30th days.
The test was carried out by washing the sample with aquadest, drying it up at
chamber temperature until its weight remained constant, and then weighing
it.
2.12. Analysis of Thermogravimetric
(TGA)
The
implemented analysis of Thermogravimetric was STA module with channel TGDTA
7300. The measurement was done at 7.73 mg with a heating rate of 100C/minute. The heating was
begun at 30C to 6500C. The rate of nitrogen gas was 50 mL/min.
3.1. Mechanical Properties
The
Tensile Strength (TS), Elongation at Break (EB), and Young’s Modulus (YM) from
the blend of TPSS/LLDPE Compatibilized, as shown in Figure 1, showing the
affecting result of additional LLDPE, at the combination of PE –g-MA as a
compatibilizer on the tensile strength and elongation at break, experienced
continuous increase with the increased concentration of LLDPE from 3.20 N/mm2
become 4.30 N/mm2 and 0.72% to 2.15% at the maximum
concentration at LLDPE 30% concentration (Matzinos
et al., 2001) as can be
seen in Table 1.
When the young modulus decreased from 447N/mm2 to 201N/mm2 due to the higher
concentration of LLDPE, the young modulus decreased as well. Figure 4-6 illustrates
the Tensile Strength (TS), Young's Modulus (YM), and elongation break charts of
TPSS/LLDPE compatibilizer blends.
Table 1 Mechanical Properties Test of TPSS/LLDPE-Compatibilizer
LLDPE Content (%) |
Tensile Strength (N/mm2) |
Elongation at Break (%) |
Young Modulus (N/mm2) |
Reference |
0 |
1.80 |
0.38 |
479 |
(Majid et
al., 2009) |
10 |
3.20 |
0.72 |
448 | |
15 |
3.39 |
1.25 |
271 | |
20 |
3.60 |
1.43 |
252 | |
25 |
3.82 |
1.60 |
239 | |
30 |
4.31 |
2.50 |
205 |
Figure 4 Tensile strength (TS) and Young’s Modulus (YM) test of TPSS/LLDPE compatibilizer blends
Figure 5 Elongation at Break test of TPSS/LLDPE compatibilizer blends
Figure 6 Young Modulus test of TPSS/LLDPE compatibilizer blends
3.2. FTIR
Figure 7 The Spectra of TPSS, PE-g-MA, and TPSS/LLDPE
Compatibilized blends
3.3. Test of Morphology
Morphology
affects the mechanical properties of a product and polymer dispersion evenly,
indicating that interface and adhesion have increased. On the other hand, the
occurrence of agglomeration in the polymer, shows that there was a worse
interface reaction, in which agent dispersion, formed the copolymer with its
kind. Differences in polarity were one of the causative factors. As in this
TPSS/LLDPE blend, TPSS was the main component of the major blend on the
polarized matrix. While LDDPE was the minor component of the dispersed phase,
which was expected to be the non-polarizing reinforcing agent. Figure 8 shows
how the difference in polarity led to an uneven distribution, which shows that
the LLDPE is grouped or aggregated. (Rodriguez-Gonzalez et al., 2003; Yoo et al., 2001). To
unite the natural polymer of hydrophilic with the synthesis polymer, which is
hydrophobic, the coupling agent needs an ordinary connector, known as a
compatibilizer. In the case of LLDPE, this minor polymer was evenly distributed
throughout the blend, providing evidence of interface activity in a
heterogeneous polymer blend. This is supported by the fact that bioplastic's
mechanical properties increase when compatibilizers are added. Figure 9 shows
an SEM image of a compatible blend of TPSS/LLDPE at a 20% LLDPE concentration,
scaled to 1:150.
Figure 9 SEM Image of TPSS/LLDPE Compatibilized blends, (20% concentration of LLDPE) with scale 1: 150
3.4.
Water Absorption Test
The
balance of TPSS water absorption was increased to 120% as can be
seen in Figure 10. This resulted from the hydrophilic nature of the starch due to the
many hydroxyl groups available to react with the water (Vinhas et al., 2007). The
compatibilizer blend of TPSS and LLDPE demonstrates that the balance of water
absorption decreased as LLDPE concentration increased. This was probably due to
the decrease in the number of hydroxyl groups from starch as the concentration of
TPSS decreased, which could have reacted with a water molecule (Obasi et al., 2015; Majid et al., 2009; Gáspár et al., 2005).
Figure 10 Equilibrium of water uptake test for TPSS/LLDPE Compatibilized blends
3.5. Biodegradability Test
In this degradation test, the three
conditions were shown in figure 11-13, namely, freshwater immersion,
seawater immersion, and being buried in the ground. In general, it could be
said that the sample size weight of compatible blend-based bioplastics made
from TPSS and LLDPE was going down as the quantity of concentrated LLDPE and
time went up. For example, the sampling weight of freshwater decreased from 46
to 42% at concentrated LLDPE 10 to 30% of concentrated LLDPE until the 30th
Day. Meanwhile, the decrease of seawater sampling weight from 56 to 18% at a
concentrated LLDPE of 10- 30%, as well as the decreased percentage of soil
buried sampling achieved 50% at a concentrated LLDPE of 30%, with the
decomposition of 17% at the 30th Days. The
more concentration of LLDPE contained in bioplastic, the smaller percentage of
degradation rate (Abdullah et al., 2013). Table
2 contains specific data.
Table 2 Performance of degradation in 3 conditions
Condition |
Time (day) |
LLDPE Concentrations |
Reference | |||||
0% |
10% |
15% |
20% |
25% |
30% | |||
Fresh
Water |
10 |
17 |
46 |
43 |
40 |
38 |
36 |
(Ashok et
al., 2018) |
20 |
33 |
58 |
53 |
49 |
44 |
40 | ||
30 |
56 |
64 |
57 |
53 |
48 |
42 | ||
Sea Water |
10 |
15 |
47 |
43 |
38 |
11 |
9 | |
20 |
31 |
52 |
48 |
45 |
17 |
14 | ||
30 |
52 |
56 |
52 |
49 |
21 |
18 | ||
Soil
Burial |
10 |
14 |
34 |
32 |
23 |
15 |
13 | |
20 |
29 |
47 |
43 |
37 |
19 |
15 | ||
30 |
49 |
50 |
47 |
46 |
23 |
17 |
Figure 11 Degradation
test of TPSS/LLDPE Compatibilized
blends in
freshwater
Figure 12 Degradation test of TPSS/LLDPE
Compatibilized blends in Seawater
Figure 13
Degradation test of TPSS/LLDPE
Compatibilized blends in Soil Burial
3.6. Analysis of
Thermogravimetric (TGA)
The Thermogravimetric Analysis
technique was used to determine the thermal decomposition and stability of the
mixed TPSS/LLDPE compatibilizer film. Thermal decomposition occurs in four
stages. The initial stage of degradation occurs at a temperature of 201.10C
with a mass loss of 17.1%. At this stage, there is evaporation or dehydration
of water into H2 and O2 gases at a temperature of 1000C
with a mass loss of 6.36%. According to the findings (González Seligra et al., 2016),
plasticizer compounds (glycerol) evaporate between the first and second stages
at temperatures between 125 and 290°C. This thermal decomposition will continue
along with the increase in temperature into compounds to other compounds. The
initial thermal decomposition of plasticized starch occurs at around 3000C,
during the second stage. At this stage, hydrogen groups are removed, and the
starch carbon chain is decomposed and depolymerized (Nascimento et al., 2012).
Furthermore, in the third stage, polyethylene begins to degrade at a
temperature of 400°C, producing gas and hydrocarbon oil (Abdullah et al., 2013). The curve of TGA shows that degradation of TPSS
/LLDPE compatibilized blends does not show a significant reduction in each
phase. This indicates that the amount of mass loss in each temperature increase
at each stage is almost the same (stable). The results of the TGA curve are
presented in Figure 14.
Figure 14 The TGA Spectrum of TPSS/LLDPE Compatibilized blends
The
addition of LLDPE as a strength agent followed by a compatibilizer between the
blend of TPSS and LLDPE could inadvertently rectify the weaknesses of
bioplastics, such as their low mechanical properties and high water absorption.
The increase in concentrated LLDPE or the decrease in concentrated TPSS could
reduce the water absorption percentage. Meanwhile, the degradation rate of
blended TPSS/LLDPE decreased because the hydroxyl groups of TPSS getting less
reacted with water molecules or were degraded by water. In this case, dispersed
particles of LLDPE in the compatible blend are significantly better than those
in the incompatible one. Future studies will focus on TPPS/LLDPE/Compatibilizer
blends.
Thank
you to LPDP for funding this research (2020).
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