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					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
                             AND TECHNOLOGY (IJMET)

ISSN 0976 – 6340 (Print)
ISSN 0976 – 6359 (Online)                                                     IJMET
Volume 5, Issue 2, February (2014), pp. 01-07
© IAEME: www.iaeme.com/ijmet.asp
Journal Impact Factor (2013): 5.7731 (Calculated by GISI)                 ©IAEME
www.jifactor.com




     EFFECT OF NANO SiO2 ON SOME MECHANICAL PROPERTIES OF
                BIODEGRADABLE POLYLACTIC ACID

         Nadia Abbas Ali1,       Ikram Atta AL-Ajaj1,     Farah Tariq Mohammed Noori1
                     1
                         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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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME

                                                                              nano
        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 nano-
bulletin active packaging. The most popular purpose of this nano material is widely used as nano
                                               m
reinforcement in composite polymer in fact, many studies on nano reinforcement were reported.
       reinforcement
Nano-reinforcement that's been studied is such as clay and silicates [4].

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 .                                  aldrch
                                             .NanoSiO2 supplied by Sima-aldrch Company with
                         s          Fig(1)
particle size (13.69 nm)is shown in Fig(1)measured by (SPM) of nano SiO2 .




               Fig(1) Granuality normal distribution chart for nano SiO2particls

                                  PLA/
2. Preparation of PLA film and PLA nano SiO2 composites film.
        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
                                                                     stirr
casting method in chloroform. Silica was added in chloroform and stirring in ultrasonic bath for 10
min. Nanoparticles were dispersed in the solvent using ultrasonic bath. Then PLA was added to
                                ed
solvent/silica mixture and stirred with magnetic bar for 4 h hours at 40°C. After dissolving in
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
           IR                                                                FT IR
        FT-IR was performed using a Perkin Elmer 1600 Infrared spectrometer. FT-IR spectra of the
                                                                                       cm-1
samples were recorded by using Nicolet’s AVATAR 360 at 32 scans with a resolution of 4 cm and
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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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
                                                D                       a
at room temperature, according to the ASTM D-882 as shown in Fig 2a pure PLA , b, c, and d its
composites(1,3,5wt% ) respectively . A fixed crosshead rate of 10 mm/min was utilized in all cases
                                           o
and the results were taken as an average of five tests. Two metallic grips were attached for griping
both ends of the test specimen of the film. Tensile strength (σs), Young’s modulus (E) was
                                        equation
determined according to the following 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
                        known
        FT-IR is a well-known and widely used method to investigate the intermolecular interaction
                                                                                  PLA
and phase behavior between the polymers. In this study, the interaction between PLA/SiO2 was
                    IR                              Figure
investigated by FT-IR spectroscopy and is shown in Figure( 3) . FTIR spectrum of neat PLA shown
                                                         band                   3500
in (Fig 3(a)) clearly show the characteristic absorption bands in the region of 3500- 3600 cm-1,
                                   due
2946- 2999 cm-1 and 1757cm-1due to O                                 g           C-H asymmetric
                                           O-H bending and stretching vibration, C
                                                              ,
stretching vibration and C=O stretching vibration respectively, which agree well with the prepared
                                                F.
FTIR of PLA film reported by Cardoso, J. J. F.et. al., [5]. Fig3b is appear of PLA/5%SiO2 which
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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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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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
                                                                         SiO
             Fig(4):X-RAY diffraction patterns of a :PLA pure, b :PLA /5%SiO2

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
                                    .PLA
nano SiO2 which appear in Fig (5) .PLA is a biodegradable polymer that has been useful in various
                                                                            st
biomedical applications. High brittleness that are characteristic of PLA must be improved to allow
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
                 echanical               PLA-silica
dispersion,the mechanical properties of PLA silica by melt blending found that the tensile strength
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
                       composites                                                     polym
properties of the nano-composites improved because of their degree of dispersion and polymer filler
interaction.




                                                5
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                                                  PLA/nano5%SiO2




                 Stress MPa
                              35.0                                                  PLA/nano3%SiO2
                              30.0
                              25.0                                                  PLA/nano1%SiO2
                              20.0                                                  PLA
                              15.0
                              10.0
                               5.0
                               0.0
                                     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          Young modulus
                                                    strength(MPa)            (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.

REFERENCE

 1-   P. Qu, Y. Goa, G. F. Wu, and L. P. Zhang, (2010) “Nanocomposite of poly(lactid acid)
      reinforced with cellulose nanofibrils”, J .BioResources , vol. 5(3), 1811-1823.
 2-   B.K. Chen, T.Y. Wu, Y.M. Chang , A. F. Chen ,(2013)” Ductile polylactic acid prepared
      with ionic liquids” ,J.Chemical Engineering ,vol. 5 , 215–216.
 3-   B.H. Li, M.C. Yang,(2006)” Improvement of thermal and mechanical properties of
      poly(L-lactic acid) with 4,4-methylene diphenyl diisocyanate”, J. Polym. Adv. Technol.
      Vol.17, 439-443.
 4-   H.S. Mohd , S. Eraricar , I.M. Ida , N.H. Siti ,(2012) “ Cellouse nanofiber isolation and
      its fabracication into bio-polymer review “ International Conference on Agricultural and
      Food Engineering for Life (Cafei2012) 26-28.

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International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –
6340(Print), ISSN 0976 – 6359(Online) Volume 5, Issue 2, February (2014), © IAEME

 5-  J.J.F. Cardoso , Y..C. Queirós, K.J.A. Machado, J.M. Costa , F.E. ucas,(2013) ”
      SYNTHESIS, CHARACTERIZATION, AND IN VITRO DEGRADATION OF
      POLY(LACTIC ACID) UNDER PETROLEUM PRODUCTION CONDITIONS”
      BRAZILIAN JOURNAL OF PETROLEUM AND GAS v. 7 n. 2 , 057-069
 6- D. Battegazzore, S. Bocchini, A. Frache,(2011)” Crystallization kinetics of poly(lactic
      acid)-talc composites” eXPRESS Polymer Letters Vol.5(10),849-85 8.
 7- A.N. MOHAMMAD, S. MOHSEN, (2013) “Multi-component reaction on free nano-SiO2
      catalyst: Excellent reactivity combined with facile catalyst recovery and recyclability” J.
      Chem. Sci. Vol. 125(3) , 537-544.
 8- R.M. Izan , A.S. Robert , K. Ing ,(2011) ” Melting Behaviour and Dynamic Mechanical
      Properties of Poly(lactic acid)-Hemp-Nanosilica Composites”, Asian Transactions on
      Basic and Applied Sciences) ,Vol.3 Issue 2 ,556-561.
 9- G .Sanches, R.A.Lopez , J. M. Lagaron ,(2010) “Natural micro and nanobiocomposites
      with enchaced and novel functionalities for food biopackaging applications”, J.Trends in
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 10- S.Shankar, Dr.H.K.Shivanand and Santhosh Kumar.S, “Experimental Evaluation of
      Flexural Properties of Polymer Matrix Composites”, International Journal of Mechanical
      Engineering & Technology (IJMET), Volume 3, Issue 3, 2012, pp. 504 - 510, ISSN Print:
      0976 – 6340, ISSN Online: 0976 – 6359.
 11- Siddhant Datta, B.M. Nagabhushana and R. Harikrishna, “A New Nano-Ceria Reinforced
      Epoxy Polymer Composite with Improved Mechanical Properties”, International Journal
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      pp. 248 - 256, ISSN Print: 0976-6480, ISSN Online: 0976-6499.




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