This document summarizes a research article that studied the effect of adding nano silicon dioxide (SiO2) particles to polylactic acid (PLA) films on some mechanical properties. PLA films were produced with 0%, 1%, 3%, and 5% nano SiO2 by weight using solution casting. Tests showed that adding 5% nano SiO2 increased the tensile strength of PLA films by 35% and the Young's modulus by 25% compared to pure PLA films. Fourier transform infrared spectroscopy and X-ray diffraction characterization indicated good dispersion of the nano SiO2 particles in the PLA matrix. The improved mechanical properties are due to the uniform distribution of nano SiO2 particles in the PLA and

1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
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ISSN 0976 – 6359 (Online)
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EFFECT OF NANO SiO2 ON SOME MECHANICAL PROPERTIES OF
BIODEGRADABLE POLYLACTIC ACID
Nadia Abbas Ali1,
1
Ikram Atta AL-Ajaj1,
Farah Tariq Mohammed Noori1
Baghdad University, college science, physics Department
ABSTRACT
Effect of nano SiO2(13.69nm)with different weight percentage (1, 3, 5wt %)on some
mechanical properties of polylactic acid (PLA) is investigated .PLA film with thickness 100µm was
prepared by solution casting method .Chemical and crystal structure of PLA and its composites with
5% nano SiO2 are characterized by FTIR and X-ray diffraction techniques . Mechanical properties
(tensile strength and young modulus) of PLA and its composites are reported .Enhancement in above
mechanical properties are observed (35%for tensile strength and 25%for young modulus). The main
goal of this work is to study the influence of addition of different silica nanoparticles on the
mechanical properties of neat PLA in order to enhance its for brittleness to ductile stage.
Key Word: Biodegradable, Polylactic Acid, nano SiO2, Mechanical Properties.
1-INTRODUCTION
Natural polymers that are biodegradable and biocompatible has become increasingly
important. This is due to their amazing characteristics: natural abundance, low costs and wide range
of applications [1]. These polymers are being widely used in the biomedical area, including wound
dressing, drug delivery system and tissue engineering scaffolds . Polylactic acid (PLA) is prominent
among the polymers that are biodegradable and biocompatible due to versatility of its applications
and relatively low cost of production at industrial scale. PLA, is a linear aliphatic thermoplastic
polyester, produced from renewable resources, has several attractive properties such as
biocompatibility, high strength, and thermo plasticity. It has been used in medical applications, such
as surgical sutures, implants, tissue culture, and controlled drug delivery. Though PLA is
biodegradable and has been useful in various biomedical applications, the high stiffness and
brittleness at ambient temperatures associated with PLA must be improved to allow for more
applications [2,3]
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2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
The applications of nanomaterial are broad; some of them were used as nano-sensor in smart
nano
food packaging technology. It also could provide an antimicrobial mechanism by introducing nanonano
bulletin active packaging. The most popular purpose of this nano material is widely used as nano
reinforcement in composite polymer in fact, many studies on nano reinforcement were reported.
m
Nano-reinforcement that's been studied is such as clay and silicates [4].
reinforcement
2- EXPERIMENTAL WORK
1. Materials
Polylactic acid (PLA) (ESUN™ A
A-1001) [density = 1.25 g/cm3 was supplied by Bright China
Industrial Company. Ltd (Shenzhen, China .
.NanoSiO2 supplied by Sima-aldrch Company with
aldrch
particle size (13.69 nm)is shown in Fig(1)measured by (SPM) of nano SiO2 .
s
Fig(1)
Fig(1) Granuality normal distribution chart for nano SiO2particls
2. Preparation of PLA film and PLA nano SiO2 composites film.
PLA/
Neat PLA film is prepared by weight 2gm of PLA in 20 ml of chloroform , PLA films
composites with different weight percentage of nanosilica (1,3,5wt %) were prepared by solution
casting method in chloroform. Silica was added in chloroform and stirring in ultrasonic bath for 10
stirr
min. Nanoparticles were dispersed in the solvent using ultrasonic bath. Then PLA was added to
solvent/silica mixture and stirred with magnetic bar for 4 h hours at 40°C. After dissolving in
ed
chloroform, PLA/silica nanocomposites were poured into glass Petri dishes (10 cm diameter) and
vacuum dried for 2h and, additionally, 24 hours for total evaporation of solvent at room temperature.
The films were peeled off with thickness around 100µm.
3. (FT-IR) TEST
FT-IR was performed using a Perkin Elmer 1600 Infrared spectrometer. FT-IR spectra of the
IR
FT IR
samples were recorded by using Nicolet’s AVATAR 360 at 32 scans with a resolution of 4 cm and
cm-1
within the wave number range of 4000 to 400 cm-1.
4. X-ray Diffraction TEST
X-ray Diffraction patterns were measured in a Brüker Advance instrument, at 40 KV, 40 mA
using target Cu Kα ( λ= 1.54A° ) with secondary monochromator (Karlsruhe, Germany)
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3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
5. Tensile Properties
Mechanical test was performed using the Instron 4400 Universal Tester to measure the tensile
strength at the point of breakage for each sample. Tensile specimens cut were used were carried out
at room temperature, according to the ASTM D-882 as shown in Fig 2a pure PLA , b, c, and d its
D
a
composites(1,3,5wt% ) respectively . A fixed crosshead rate of 10 mm/min was utilized in all cases
and the results were taken as an average of five tests. Two metallic grips were attached for griping
o
both ends of the test specimen of the film. Tensile strength (σs), Young’s modulus (E) was
determined according to the following equation:
equation
σs =F /(A)……… 1
E =F L0/A L…………2
Where: F: force exerted on an object under tension, L0: original length, A :cross section area, L:
:
length of the object changes
a
b
c
d
a
Fig(2) : samples of PLA and its composites (1,3,5%) nano SiO2
a
3. RESULTS AND DISCUSSION
1. (FT-IR) characterization
FT-IR is a well-known and widely used method to investigate the intermolecular interaction
known
and phase behavior between the polymers. In this study, the interaction between PLA/SiO2 was
PLA
investigated by FT-IR spectroscopy and is shown in Figure( 3) . FTIR spectrum of neat PLA shown
IR
Figure
in (Fig 3(a)) clearly show the characteristic absorption bands in the region of 3500- 3600 cm-1,
band
3500
2946- 2999 cm-1 and 1757cm-1due to O
due
O-H bending and stretching vibration, C
g
C-H asymmetric
stretching vibration and C=O stretching vibration respectively, which agree well with the prepared
,
FTIR of PLA film reported by Cardoso, J. J. F.et. al., [5]. Fig3b is appear of PLA/5%SiO2 which
F.
bonds of PLA and SiO2 appear that mean good distribution of nano SiO2 in composites film because
that bond appear and no different in pure PLA .
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4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
a
b
Fig(3):FTIR of a :PLA pure, b : PLA /5%SiO2
2.X-ray Diffraction
X-ray diffrction pattern of polylactic acid shows two peaks located at 2θ= 16°.5 and 19°
with sharp peak for first peak indicating high crystalline structure which agree well with results
reported by Batteazzone et.al [6] as reported of PLA finds that pattern of PLA is characterized by a
broad band with maximum at 2θ = 16.6º, 19.1° . The XRD pattern of composites (PLA/5%SiO2 )
exhibits broad diffraction peak at 2θ = 22ºdue to addition nano SiO2 for silica which agree well with
results reported by A.N. Mohammed et al and find this peak centered at a 2θ = 23◦[7].
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5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
2θ
a
2θ
b
Fig(4):X-RAY diffraction patterns of a :PLA pure, b :PLA /5%SiO2
SiO
3-Mechanical peoperties
Tensile test provides an indication of the tensile strength calculated in eq.1 and young
modulus in eq.2 of the films and find both tensile strength and young modulus increased when add
nano SiO2 which appear in Fig (5) .PLA is a biodegradable polymer that has been useful in various
.PLA
biomedical applications. High brittleness that are characteristic of PLA must be improved to allow
st
for more applications [8].
Table 1 shows the values of tensile strength of pure PLA film prepared and its composites
films using nanosilica enhanced about 35% and young modulus enhanced about 25% . Mechanical
properties of prepared nanocomposites were improved by addition of 5 wt.% of silica comparison to
neat PLA matrix, this result
agree with ref.[8] is probably due to achievement of good
dispersion,the mechanical properties of PLA silica by melt blending found that the tensile strength
echanical
PLA-silica
and modulus of the composites were enhanced by incorporation of nanoparticles. The silica
nanoparticles were uniformly distributed in the PLA matrix for filler contents bel
below 5 %·w/w,
whereas some aggregates were detected with further increasing filler concentration .The mechanical
properties of the nano-composites improved because of their degree of dispersion and polymer filler
composites
polym
interaction.
5

6. Stress MPa
International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME
45.0
40.0
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
PLA/nano5%SiO2
PLA/nano3%SiO2
PLA/nano1%SiO2
PLA
0.0
2.0
4.0
6.0
8.0
Strain % 10.0
Fig(5):Stress-Strain of PLA and its composites PLA/5%SiO2
Table (1) Mechanical properties of PLA and its composites films
Sample
Tensile
strength(MPa)
Young modulus
(GPa)
PLA
29
2.3
PLA/1%SiO2
32
2.5
PLA/3%SiO2
36
2.9
PLA/5%SiO2
43
3.1
CONCLUSIONS
1- PLAfilm was successfully prepared by casting method.
2- Maximum enhancement in 35%of tensile strength and 25% in young modulus of PLA as
observed by adding 5%nano SiO2, due to their good dispersion in PLA matrix. Obtained results
could be further used for future research in the field of PLA/silica nanocomposites, as
important materials due to their good and satisfying mechanical properties for food packaging
application.
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