Published at : 10 Jul 2024
Volume : IJtech
Vol 15, No 4 (2024)
DOI : https://doi.org/10.14716/ijtech.v15i4.5746
Dwi Setyaningsih | 1 Department of Agroindustrial Technology, IPB University, Bogor 16680, West Java, Indonesia 2 Surfactant and Bioenergy Research Center, IPB University, Bogor 16144, West Java, Indonesia |
Muhammad Syukur Sarfat | 1 Department of Agroindustrial Technology, IPB University, Bogor 16680, West Java, Indonesia 2 Surfactant and Bioenergy Research Center, IPB University, Bogor 16144, West Java, Indonesia |
Farah Fahma | Department of Agroindustrial Technology, IPB University, Bogor 16680, West Java, Indonesia |
Nastiti Siswi Indrasti | Department of Agroindustrial Technology, IPB University, Bogor 16680, West Java, Indonesia |
This research aims to identify the performance and mechanical characteristics of polypropylene-based antistatic bio-nano composites reinforced with 2% mono-diacylglycerols (M-DAG) and 0, 0.5, 2.5% cellulose nanocrystals (CNC) and compared to pure PP. Based on the results of SEM on cross-section, there was an agglomeration of M-DAG and CNC on the PP matrix. XRD diffractogram pattern of antistatic bio-nano composites showed peaks representing the diffraction structure of glycerol monostearate and cellulose I. The FTIR spectrum of each formulation was very similar to the characteristic peaks of PP and showed three distinct peaks compared to pure PP. The melting temperature of antistatic composites without CNC (176.54oC) was higher than pure PP (175.44oC). Thermal stability of antistatic bio-nano composites with 0, 0.5, and 2.5% CNC were 472.07, 470.25, and 475.15 oC, respectively, higher than pure PP (468.27oC). The best mechanical properties were 2.5% CNC with 11.071 MPa flexural modulus, 30.376 MPa tensile strength, 23.796% tensile elongation, 1.659 J/m2 impact strength, which were higher than pure PP, and it generated antistatic activity of 1010 - 1012 /sq resistivity.
Antistatic bio-nano composites; Biopolymers synthesis; Cellulose nanocrystals; Mono-diacylglycerols; Polypropylene
The trend of using synthetic polymer-based materials is predicted to increase in terms of fulfilling human needs. Synthetic polypropylene (PP) is known for having a high softening point or glass transition, high resistance to bending stress, low water absorption, good electrical resistance, light dimensional stability, high impact strength, non-toxicity properties, and the degree of crystallinity ranges from 40 to 60% with the melting temperature range from 130 to 171°C (Shubhra, Alam, and Quaiyyum, 2013). But PP is susceptible to high temperatures, flammable, prone to UV degradation, susceptible to oxidation, difficult to paint, and harmful to the environment due to its non-degradable nature (Purnomo, Baskoro, and Muslim, 2021; Shieddieque et al., 2021), but PP is recyclable (Jain and Tiwari, 2015). Therefore, to overcome the weakness, it is necessary to modify PP into bio-nano composites. Antistatic bio-nano composites are synthesized by adding natural antistatic materials.
Nanocomposites are multicomponent materials consisting of several
different phases in which at least one phase size is in the nanoscale (less
than 100 nm) (Sandri et
al., 2016). The antistatic bio-nano
composites synthesized using mono-diacylglycerols (M-DAG) as an antistatic agent (Salsabila et
al., 2021), cellulose nanocrystals (CNC) as a reinforcement, and PP
as a thermoplastic matrix (Clemons and
Rick, 2020; Sabaruddin, Md-Tahir, and Lee, 2019; Gwon et al., 2018).
A combination of M-DAG and CNC is expected to
produce a synergistic effect to improve the quality
of the antistatic bio-nano composites. The
addition of M-DAG and CNC to the PP matrix had a positive impact on
the characteristics of the resulting bio-nano composites and antistatic bio-nano composites (Sabaruddin, Md-Tahir, and Lee, 2019; Gwon et al.,
2018).
M-DAG
is an ester of glycerol and free fatty acid (FFA)
which has unreacted or free hydroxyl groups. MAG, or
monoglyceride, has a single fatty acyl chain, while DAG, or diacylglyceride,
has two fatty acyl chains (Sarfat et al., 2022).
This free hydroxyl group makes M-DAG a non-ionic surfactant that is degradable
and bio-compatible, so it is widely used in the food, cosmetic, and
pharmaceutical industries. This free hydroxyl group allows M-DAG to be used as
a stabilizer and an antistatic agent in bio composites or plastics (Salsabila et al., 2021).
M-DAG used in this research was produced from palm fatty acid distillates
(PFAD) from the refining process of crude palm oil (CPO) (Setyaningsih, Suwarna, and Muna, 2020; Setyaningsih et
al., 2020).
CNC
is a cellulose-based nanomaterial that has better mechanical characteristics
such as tensile strength (7.5 GPa) (Tang et al., 2017),
tensile modulus (100 - 140 GPa) (Tang et al., 2017),
high surface area (569 m²/g) (Brinkmann et al., 2016),
with a diameter average of 8 nm (Rochardjo et al., 2021) compared
to other cellulose-based nanomaterials such as cellulose nanofiber (CNF) which
has a tensile
strength of 0.3833 GPa (Kafy et al., 2017),
a tensile modulus of 23.9 GPa (Kafy et al., 2017) and
surface area of 430 m²/g (Moser, Henriksson,
and Lindström, 2016).
However, there are disadvantages of CNC, namely low stability starting from
283.55 0C, which causes CNC to be very
susceptible to high heat treatment when used as a reinforcing material in
polymer matrices. M-DAG can be used as a lubricant and stabilizer to protect CNC from thermal degradation during processing.
Therefore,
a combination of M-DAG and CNC as additive materials for the synthesis of
PP-based antistatic bio-nano composites has a prospect as next-generation
material
that is more flexible in use and exhibits superior
performance and mechanical characteristics compared to pure PP. There has never
been researched that combines M-DAG and CNC simultaneously as reinforcement in
the PP matrix. Therefore, this study aims to evaluate the performance and
mechanical characteristics of PP-based antistatic bio-nano composites
reinforced with varying concentrations of M-DAG and CNC, and compare them to
those of pure PP.
2.1. Raw
Materials
The raw materials for synthesizing
antistatic bio-nano composites were PP, M-DAG, and CNC. PP (PT Chandra Asri Petrochemical Tbk) has a melt
flow index of 10 g/10 minute and a density of 0.903 g/cm3.
M-DAG (SBRC-LPPM-IPB) has a crystallinity index of 92.85%, a diameter of 0.11–1.78 nm, and a thermal degradation rate of 200.50 oC. CNC (CelluForce Co.) has a density of 1.5 g/cm3, a crystallinity index of 98.95%, and diameter of 3.39–12.72 nm, a length of 44 – 108 nm, and thermal degradation of 296.96 oC. The supporting materials consist of maleic
anhydride polypropylene (MAPP)(BYK Chemie GmbH),
antioxidant (AO) (BASF Schweiz AG, Switzerland), and mineral oil (MO) (Arkema France).
2.2. Methodology
Figure 1 The Stages
of the synthesis of antistatic bio-nano composites
2.2. Antistatic
Bio-nano Composites Characterization
Infrared
spectrum analyzed using Fourier
transform IR (FT-IR) Thermo Fisher Scientific Nicolet iS5 spectrophotometer
with cleaning pump and wavelengths 300 cm-1 to 4000 cm-1,
128 accumulated scans, resolution 4 cm-1, in ATR and transmittance
module. Thermal properties analysis used differential scanning calorimetry
(DSC) TA Instruments, New Castle, UK model Q200. Dynamic DSC scans were conducted in the temperature range from 23 to 400 °C at a
heating rate of 10 °C/min. The crystallization and melting behaviors were
recorded in a nitrogen atmosphere, at the range mass used of 21.8 to 29.0 mg.
where W is the corrected energy absorbed by breaking the specimen (J), is the thickness of the specimen (mm), and is the width of the specimen (mm).
where is flexure strength
(N/mm2/MPa), is flexure
modulus (N/mm2/MPa),
where
3.1. Morphology
Analysis
Figure 2
Morphological analysis of antistatic bio-nano composites using SEM
Based on the results of the SEM analysis on the cross-section, M-DAG
agglomeration was found on the PP matrix because it shows a morphological form
of M-DAG, while the CNC is not visible. This indicates a chemical reaction or
physical interaction between M-DAG and the PP matrix. Physical interaction
occurs when the polar groups (palmitate) are oriented to the PP matrix. In
contrast, the polar groups (glyceryl) are oriented away from the PP matrix
towards the antistatic bio-nano composite surface, and it is possible to interact physically with CNC. Another
possibility is that the polar group (glyceryl) reacts with the O group of the
maleic anhydride during the synthesis process. In addition, there was no
fibrillation on the surface of the antistatic
bio-nano composites cross-section. This implies that
no significant plastic deformation occurred in the antistatic bio-nano composites layer during fracture, although the CNC concentration is increased. According
to Shojaeiarani, Bajwa, and
Chanda (2021), the
rheological properties of CNC-filled polymer melts depend on factors such as
the degree of CNC particle dispersion, their orientation state, and aspect
ratio. Consequently, the rheological properties of the antistatic bio-nano
composites in our study were also influenced by these factors. In particular,
the homogeneous dispersion of CNC particles led to more effective load transfer
to the reinforcements.
3.2. Degree of Crystallinity and
Particle Size Analysis
Crystallinity analysis was carried out on AS-BNC using XRD analysis to observe changes in the crystal structure as a function of chemical treatment and to measure the degree of crystallinity (CrI) using the deconvolution method with a ratio between the area corresponding to the crystal peak and the total area (Park et al., 2010). Figure 3A shows the XRD diffractogram of AS-BNC. XRD diffractogram patterns were recorded using Cu K irradiation, = 1.5418 A.
The results of the XRD diffractogram analysis of AS-BNC showed with seven peaks with peak heights ranging from 87.09 – 1000 I rel of AS-BNC-5, 84.61 – 1000 I rel of AS-BNC-0.5, and 90.91 – 1000 I rel of AS-BNC-2.5 (Table 2). The XRD diffractogram pattern showed peaks representing the diffraction structure of glycerol monostearate and cellulose I. The diffraction characteristic of glycerol monostearate can be observed in the peak range between 5o to 30o (Yusuf et al., 2013). The diffraction characteristics of cellulose I could be observed around peaks at 15o (001), 22.5o (002), and 34o (040) (Park et al., 2010), Couret et al. (2017) said the peaks at 15o (1-10), 17o (110), 21o(102/012), 23o (200), and 34o (004) represent the diffraction structure of cellulose I.
The XRD diffractogram of PP showed the pattern, which has seven peaks with peak heights ranging from 85.41 – 1000 I rel. According to Guerra, Wan, and McNally (2019), the XRD patterns showed the most intense peaks for PP at = 16.5o (100), 19.2o (300), 20o (040), 22o (130), and for the GNPs at = 32o (002).
The identification results of the
particle size, degree of crystallinity, and percent of amorphous components in
AS-BNC showed the average particle
sizes between 15.84 to 16.01
nm, 89.81
to 91.10 % degree of
crystallinity, and 8.90 to 10.19
% amorphous components (Table
2). The
particle size of AS-BNC was increased with the increase in CNC concentration.
The degree of crystallinity of AS-BNC-2.5 is higher than that of pure PP.
3.3. Infrared Spectrum Analysis
The FTIR spectrum of each treatment (Figure 3B) was very similar to the characteristic peaks of PP and depicted distinct
tri peaks for the antistatic bio-nano composites compared to the pure PP. The
first distinct absorption peak ranging from 1200 cm-1 to 1000 cm-1
were primarily assigned to C–O–C bond, C–C bending, and ring structures (with
typical sharpening at 1071.50 cm-1 with %T of 85.14% and 1166.98 cm-1
with %T of 69.93% (AS-BNC-0), 1080.18 cm-1 with %T of 83.03% and
1166.02 cm-1 with %T of 64.77% (AS-BNC-0.5), and 1085.01 cm-1
with %T of 74.86% and 1166.02 cm-1 with %T of 51.02% (AS-BNC-2.5),
which correspond to typical cellulose and glycerol compound (Al-Haik et al. 2020). In the band around 1080 cm-1, the %T decreased as the
concentration of CNC added to the PP matrix increased, while the %T in Pure PP
was lower than each of the AS-BNC, which was 70.79%. This indicated the
presence of an increasing C–O–C bond due to ring deformation of maleic acid compounds
or ring widening and C–O stretching. The same phenomenon occurred in the band
around 1166 cm-1, which showed a decrease of %T with increasing
concentration of CNC addition to the PP matrix, but lower than Pure PP (68.11%),
except for AS-BNC-0. This indicated the presence of an increasing C–C bending.
The second distinct band is related to the wavelength near 2900 cm-1. This broadband was assigned to stretching vibration of C–H hydroxyl groups asymmetric stretching of cellulose and glycerol. In this band, % transmittance (T) decreased as the concentration of CNC increased, while %T in pure PP was higher than AS-BNC. The presence of these bands confirmed the interaction of CNC and the distribution of M-DAG in the PP matrix. Due to this interfacial adhesion, the overall mechanical properties were enhanced for the AS-BNC. Hobuss et al. (2020) determined the asymmetric and symmetric C–H stretching mode of the fatty acid chain methylene group at 2922 cm-1 and 2853 cm-1. The third distinct peak was 3315 cm-1, which is related to O–H [ (O–H)] stretching, a characteristic of hydroxyl groups. This band showed that %T decreased as the concentration of CNC increased, while %T of pure PP was higher than AS-BNC. Hobuss et al. (2020) set the O–H stretch at 3360 cm-1.
The
bands at 1377.23 cm-1 and 1457.28 cm-1 in all treatments
were characteristics of PP (Fang et al., 2012).
The absorption bands at 1738.90 cm-1 (Pure PP), 1742.76 cm-1
(AS-BNC-0), 1738.90 cm-1 (AS-BNC-0.5), and 1742.76 cm-1
(AS-BNC-2.5) were observed, which were assigned to the absorption of carbonyl
groups (C=O) of maleic anhydride
(MA) (Rahman, Hassan, and Heidarian, 2018; Zhou et al., 2013). Finally, the spectrum on the peak 1166.02 cm-1 indicated
the C-C bending, which was the backbone of PP (Fang et al., 2012).
The
infrared (IR) spectrum of the antistatic bio-nano composites revealed several
characteristic peaks. Specifically, peaks between 3300 cm-1 and 3250
cm-1 were assigned to O–H stretching modes, while those between 3000
cm-1 and 2750 cm-1 corresponded to the stretching modes
of CH, CH2, and CH3 groups. The peak at 1750 cm-1
was indicative of carbonyl stretching (C = O).
The peaks between 1500 cm-1 to 1250 cm-1 were
characteristic of the deformation of the CH2 and CH3
groups. The peaks between 1250 cm-1 to 1150 cm-1 were
referred as the C–O and C–C bonds. The peak at 1100 cm-1 was also
characteristic of the strain of the C–O bond and ester group (–C–O–C–). The
"wag" vibration and asymmetric angular deformation of CH and CH2
groups were found at 750 cm-1 (Hobuss et
al., 2020).
3.4. Thermal Properties and Melt
Flow Index Analysis
Based on the identification results of the thermal
properties (Figure 3C and Table 3),
it was found that the melting temperature
of AS-BNC-0 was 176.54oC
higher than that of pure PP 175.44 oC.
The melting temperature of AS-BNC-0.5
and AS-BNC-2.5 were 171.70oC and
174.38oC,
respectively, slightly lower than that of pure PP. However,
when compared between AS-BNC-0.5 and AS-BNC-2.5, AS-BNC-2.5 had a higher
melting temperature than AS-BNC-0.5. This indicated an opportunity for
increasing melting temperature with an increase in CNC concentration. According to Al-Haik et
al. (2020) and Hejna et al. (2017),
the melting temperature of bio-nano composites with the addition of 2%, 4%, and
5% CNC on the PP matrix showed a higher value when compared to pure PP and the
addition of 4% CNC had the higher melting temperature than 3% CNC. According to
Yousefian and Rodrigue (2016),
the distribution of CNC particles in the polymer matrix greatly influenced the
thermal properties of the resulting bio-nano composites.
Thermal stability of AS-BNC-0, AS-BNC-0.5,
and AS-BNC-2.5 was 472.07 oC, 470.25oC, 475.15oC respectively, higher
than pure PP (468.27 oC).
Therefore, the addition of 2.5%
CNC and 2% M-DAG to
the PP matrix can increase the thermal degradation of the resulting antistatic
bio-nano composites. The higher the degree of crystallinity of the antistatic
bio-nano composites, the higher the thermal stability, except for the
antistatic bio-nano composites treated with AS-BNC-0. According to Al-Haik et al. (2020),
the thermal stability of bio-nano composites with the addition of 1%, 2%, and 3
% CNC on the PP matrix showed a higher value when compared to pure PP and the
addition of 4% and 5 % CNC. It showed that the addition
of 3 % CNC has the highest thermal
stability. CNC particles were thought to increase the thermal
resistance of AS-BNC by inhibiting the diffusion of volatile decomposition
products or by forming a charred CNC surface that
dissipates heat by absorbing it in the inorganic phase (Thomas et al., 2018; Ng et al.,
2017).
In addition, the presence of M-DAG can inhibit the thermal degradation of
AS-BNC. The reduced thermal resistance in AS-BNC with 2% M-DAG and 0.5% CNC may have been due to the non-uniform dispersion of the CNC particles (Ng et al.,
2017).