Physiochemical Characterization
In order to determine the functional groups, present in the bioplastic composites and the
molecular interaction of compounds, the samples were analyzed using Fourier Transform
Infrared Spectroscopy in Attenuated Total Reflectance mode (FTIR-ATR) using Thermo
Scientific Nicolet iS5. The device operated at a wavelength range of 4000-400 cm-1 with a total
of 64 conducted FTIR scans. FTIR is a powerful method of infrared spectroscopy that measures
the vibration properties of chemical functional groups of an unknown material by measuring the
vibration of an excited molecule through infrared radiation at a specific wavelength range.
Through quantitative analysis, FTIR spectroscopy provides information regarding the material’s
molecular structure and orientation, concentration and bond-structure formation of organic and
inorganic functional groups present in the material, and the conformation of polymer chains.
Modifications of this method include the implementation of attenuated total reflectance
technique which solves most common problems in infrared analysis, namely sample preparation
and spectral reproducibility. The amalgamated technique by determining the changes in the
internal reflectance occurring during the point of contact of the total internal reflected infrared
beam and the sample. This internal reflectance is measured when the infrared beam is aimed to a
dense crystal with an excellent refractive index. Upon contact, the reflectance creates an
evanescent wave that protrudes only a few microns (0.5 µ - 5 µ) beyond the crystal surface and
into the sample. As the sample absorbs the infrared energy, the evanescent wave is attenuated and
is passed back to infrared radiation beam wherein it exits the crystal and passes through the
interferogram in the FTIR spectrometer. Finally, the device will generate an infrared spectrum of
the sample.
Figure. FTIR spectra of PLA and PLA-bioplastic composites
The FTIR spectra of PLA along with PLA-bioplastic composites are presented in Figure.
Incorporation of PLA in the starch bioplastics composites lead to the formation of functional
groups of the materials, as observed from the formation of absorption peaks from both J-PLA 3%
and J-PLA 10% in comparison with J-PLA 0%. The spectra of both samples containing PLA
displayed a shifting absorption band between 1721 cm-1 to 1750 cm-1, which is ascribed to –C=O
stretching vibrations linked to the PLA. A shifting absorption bands from 1198 cm-1 – 1180 cm-1
was also observed in the spectra due to the -C-O stretching vibration of the carbonyl group of
PLA. In addition, a constructive peak formed at 1080 cm-1 was also ascribed from -C-O
stretching frequency, thereby increasing the absorption values of both composites containing
PLA compared to J-PLA 0%. The characteristic peak at 1450 cm-1 and 1370 cm-1 is related to the
stretching vibration of alkane chain (-CH3). However, a hydroxyl chain (-OH) bending could be
observed at the absorption band of 1020 cm-1, which could be derived from the starch
composition of the bioplastic. These variations between the amplitude of the absorption peaks
indicate the chemical interaction between the PLA and starch bioplastic composite. In the study
of Opedal et al. (2019), a bioplastic was formulated from spruce biomass and PLA.
Asymmetrical and symmetrical stretching of the methyl (-CH3) group was observed from the
wavelength peaks at 2995 and 2930. C=O stretching vibration was depicted at the intense peak at
1749. According to Maulida et al. (2018), bioplastics containing C=O and carbonyl ester group
are considered biodegradable.
Density Analysis
The densities of the PLA-bioplastic composites were determined using a calibrated
pycnometer with a reference liquid of distilled water and with total of three repetitions for
measurement analysis. Pycnometer can be an axcellent tool for determining the density og a
homogenous solid objects like bioplastics that are insoluble with the the reference liquid.
Initially, the mass of pycnometer together with the sample was measured. Distilled liquid was
then added and the weight of the composite could be deterimed from the total measured weight.
The density of the sample was calculated by the following equation:
msample
ρ sample=
V sample
The density of the PLA-bioplastic biocomposites are presented in Figure. Based from the
data, J-PLA 0% has the highest density at 1.3 g/cm3 while J-PLA 3% and J-PLA 10% exhibited
variations in their density measurement ranging from 1.2 -1.3 g/cm3. It can be observed that
increasing the PLA content of starch bioplastics decreases their density. Decreasing the density
value of bioplastics put them into the category of lightweigt bioplastics (Nag et al., 2020).
Similar studies show similar relationship between the PLA content and density of bioplastics.
According to Muller et al. (2017), increasing the amount of PLA in the formation of PLA/starch
biodegradable food packaging increases the material flexibility but reduces its tensile strength.
Increasing the flexibility of the material decreases its structural density. Moreover, both materials
have opposing attraction to water as PLA is hydrophobic while starch is hydrophilic, making
them incompatible with each other.
Figure. Densities of PLA-bioplastic composites
Solubility Analysis
Small portions of sample were obtained and dried at 105 oC. Then, the samples were weighed
and serve as the initial weight of the bioplastics (WO). After weighing, the samples were
submerged at 50 mL of distilled water for one day (24 hr) at room temperature. Finally, the
samples were dried at the same temperature before water immersion and weighed as the final
weight (WF). The solubility of the bioplastic composites was then calculated using the formula:
Solubility ( % )=
( W O −W F
WO )x 100 %
The solubility of the bioplastic biocomposites are shown on Figure. J-PLA 0% has the highest
solubility percentage among the three at 48 % followed by J-PLA 3 % and J-PLA 10% at 27%
and 25 % respectively. In general, all of the samples exhibit low solubility due to insolubility of
both polymer-matrix materials (starch and PLA) in water. However, it can indicate from these
values that adding PLA to starch bioplastic composites reduce the plastics solubility even more.
The surface of PLA exhibits strong hydrophobicity as its molecular are less able to form
hydrogen bonds which indicates it low water solubility. In addition, the results from the contact
angle analysis indicates the hydrophobicity of the biocomposites.
Figure. Solubilities of PLA-bioplastic composites
Application of PLA-Starch Bioplastic Biocomposites
Biomedicine Applications
PLA biocomposites provides innovative material applications for solving problems
related with PLA in biomedicine. Due to its unique structures, PLA biocomposites has
attract attentions in various fields of medicine for creating new technologies.
Tissue engineering implements both engineering and biology principles in creating
biologically-active substances for tissue restoration and homeostasis. Regeneration of
tissue starts with creation and application of engineered scaffolds that promotes cell
migration and growth on the targeted tissue. Utilization of PLA biocomposites provide
better thermal processability and long-haul mechanical integrity for engineering
scaffolds, making them suitable for both in-vitro and in-vivo applications. However,
some materials are added in order to solve some of the weakness of PLA composites
such as it’s hydrophobicity, brittleness and chemical inertness (Ozdil & Aydin, 2014). In
the study of Gutieerez-Sanchez, et al. (2019), an engineering scaffold was
manufactured from PLA/starch treated with Arginine-Glycine-Aspartic acid peptides
(RGD) through electrospinning method. Electrospunned polymer samples from PLA and
varying concentration of starch (0%, 2.5%, 5%, 10%) were exposed with RGD for cell
regulation. Biocompatibility of the scaffolds was only observed on hydrophilic scaffolds
containing PLA and PLA with 5 wt% starch that stimulate osteoblast growth and cell
proliferation. It can be observed that bigger cells accumulate in cells supported in the
cells supported by both of these scaffolds as osteoblasts have high affinity towards
both. In addition, decreasing the PLA percentage in the polymeric support increases
the chance of forming irregular surfaces on the scaffolds at the operating conditions.
Automotive Applications
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