Polystyrene (nano)composites with possible antibacterial effect MERINSKA D., DUJKOVA Z.

Department of polymer engineering

Tomas Bata University in Zlin

Nám.TGM 275, Zlín 76272

CZECH REPUBLIC

merinska@ft.utb.cz http://web.utb.cz

Abstract: - The possibility of the preparation of PS (nano)composites with antibacterial properties was studied.

Mentioned polymer matrix was mixed with several types of (nano)fillers with the suppose of their antibacterial effect

in order to evaluate their influence on material properties of prepared samples with the regard of simultaneous

antibacterial effect. The XRD and TEM for nanoclays and hardness, tensile stress, permeability for oxygen and

nitrogen and antibacterial effect for all of them were evaluated. Generally, properties of PS were not significantly

influenced by any of added filler.

Key-Words: polystyrene, composite, nanocomposite, antibacterial effect, food packaging

1 Introduction Nanofiller/polymer nanocomposites have been studied

extensively during the last two decades, because they

have been expected to obtain improved properties in

the comparison with the neat polymer matrix and

commonly used fillers [1-6]. One of the used polymer

matrices for the preparation is polystyrene (PS). It is a

commonly used polymer with various applications,

e.g. insulation, packaging, in household and in

automotive industry. Unfortunately, PS also exhibits

some disadvantageous properties, i.e. relatively high

flammability. This is the reason why polystyrene

composites and later nanocomposites have been

studied because of the possibility of PS properties

improvement [7-11].

Lately PS in several forms has been used also in food

packaging industry. It is very well known the using of

PS for caps for coffee or bowls for hot food where the

good thermal isolation of expanded PS. Generally, in

the food packaging the hygienic quality of packed

food is important. Commonly this request is reached

by the addition of antibacterial agents. There are a few

types of these agents and the most used is silver in

different forms.

Polymer silver nanocomposites are advanced

functional materials composed of silver nanoparticles

dispersed inside the polymeric matrix [12-15] and/or

coated by polymer, thus forming a core-shell structure

[16-19].

As a result, the produced material combines the

suitable properties of both partners. Among the

numerous nanoparticles that have been used as

polymer functionalizing agent, silver nanoparticles

represent the most sought-after (nano)material. This is

mainly due to their unique catalytic [20-22], electric

[23–24], optical [25–26], and, particularly,

antimicrobial properties [27-31], which are well

established and extensively investigated mainly in

colloidal systems.

This work was focused on the comparison of several

additive types in order to evaluate their possible

antibacterial effect in PS matrix with the keeping of

mechanical properties and permeability with the aim to

find new applications for PS as food packaging

materials.

2 Experimental

2.1 Materials

Commercial polystyrene KRASTEN® 174 from

SYNTHOS Kralupy a.s., Czech Republic was used as a

polymer matrix. Unmodified clay CloisiteNa+

(Southern Clay Chemistry, US), as layered nanofiller.

Two different types of silver particles were used – Ag

powder, size of particles lower than 100 nm, and Ag

acetate, both from Aldridge. In addition, commercial

antibacterial compound Irgaguard B 5000 from BASF

was used. All fillers were added in 1wt %, resp. 3 wt%.

2.2 Preparation of composites and specimens Composites were prepared by mixing and compounding

in a Brabender kneader. Temperature was 170 °C and

the speed of the kneading parts was 30 rpm. Time of

mixing was 10 min.

The XRD measurement was performed on the

specimens prepared by pressing in a hot press at for 3

min at 210 °C followed by cutting of a circle shape.

The thickness was 1 mm.

Mathematical Methods and Techniques in Engineering and Environmental Science

ISBN: 978-1-61804-046-6 377

In order to prepare specimens for the mechanical

property evaluation the pellets were molded according

to ISO 294–1 at the equipment BATTENFELD 500

CD+, melt temperature 220 °C, form temperature 45

°C.

At the same conditions the samples for the

permeability evaluation were prepared, with the

thickness of 50 µm.

2.3 Instrumentation The level of exfoliation in the prepared samples

after compounding process was measured by XRD

patterns.

Compounded samples were analyzed by XRD powder

diffractometer (INEL) equipped with the curved

position sensitive detector CPS 120 (120° 2θ),

reflection mode with a germanium monochromator

(Cuα1 radiation). Samples were placed into holder and

exposed for 2000s.

For the transmission electron microscopy (JEM

200CX), the specimens were cut using Leica cryo-

ultramicrotome at sample temperature -100°C and

knife temperature -50°C to obtain ultra-thin sections

with the thickness approximately 50 nm and an

acceleration voltage of 100 kV was used.

Mechanical properties were measured according to

ISO 527-2/1A/X on the Zwick 145665. All presented

data are the arithmetic average taken from 10

measurements.

The permeability was measured for oxygen and

nitrogen, with the bodies cut from thin film. The

pressure was 2.10

5 Pa, at the temperature of 35°C.

Last evaluated property was the antibacterial effect

of added additives.

Agar media:

Mueller-Hinton agar (peptone 17.5 g/l, beef extract

4.0 g/l, starch 1.5 g/l, agar 20 g/l and distilled water)

was used for testing of antibacterial properties and

Sabouraud agar (casein peptone 5 g/l, meat peptone 5

g/l, glucose 40 g/l, agar 15 g/l and distilled water) was

used for testing of antifungal properties.

Procedure:

Petri plates with Mueller-Hinton agar were inoculated

by cell suspension of Staphylococcus aureus CCM

3953 or Escherichia coli CCM 3954 (50 µl were

spread onto each plate) and prepared plastic samples 2

x 2 cm were put on the surface. After 5 hours the

samples were removed and all the plates were

incubated for 48 hours at 37°C. After that, bacterial

growth or inhibition of growth was noted and

compared to blank test, in which plastic samples

without antimicrobial agent were used.

3 Problem Solution

3.1 XRD The XRD analysis was used for the evaluation of the

level of MMT exfoliation in the PS matrix in case of

clay nanofillers Cloisite 1 and 3wt%. The results are

summarized in the Fig. 1. From the XRD patterns it is

clear that the better level of exfoliation was achieved

in case of Cloisite Na+ with 1 % loading, where the

peak belonging to the MMT almost disappeared.

Patterns of 3wt% loading show that the significant

portion of MMT particles did not exfoliate. These

results are reflected in the following properties.

Fig. 1. XRD patterns of Cloisite /PS nanocomposite

(layered type of nanofiller).

3.2 TEM

TEM observation is presented by Fig. 2 A-B and it

was used only for layered type of nanofiller in order to

check the level of the exfoliation of nanoclays particles.

It is possible to see that in case of Cloisite Na+ with

1%wt loading, (Fig. 2 A) there was achieved better

dispersion in the PS matrix. The worse was found for

the same nanofiller type with higher loading (3wt %) –

particles of MMT are less exfoliated. (Fig. 2B)

a) PS b) PS + Cl Na+ 1%

c) PS + Cl Na+ 3%

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ISBN: 978-1-61804-046-6 378

A) B)

Fig. 2. TEM pictures: A) Cloisite Na+ 1%, B) Cloisite

Na+ 3%

3.3 Hardness The influence of nanofillers on the hardness was the next

observed fact. From the graph in Fig. 2 it is possible to

deduce that the hardness of prepared samples stayed

almost the same, it was observed only very slight

increasing. Thus, added nanofillers do not influence the

hardness.

0

10

20

30

40

50

60

70

80

90

neat

PS

3% IR

G

1%IR

G

3% C

l Na+

1% C

l Na+

3% A

g

1% A

g

3% A

g Ac

1% A

g Ac

samples

Sh

ore

A

1% 3%

Fig. 2. Hardness

3.4 Mechanical properties In the evaluation of mechanical properties, the tensile

strength, modulus and impact strength were measured.

Here the result of tensile strength is presented.

0

5

10

15

20

25

30

neat P

S

3% IR

G

1%IR

G

3% C

l Na+

1% C

l Na+

3% A

g

1% A

g

3% A

g Ac

1% A

g Ac

samples

Te

ns

ile

str

en

gh

t (M

Pa

)

1% 3%

Fig. 3. Mechanical properties – tensile strength

The evaluation of tensile strength brought a little bit

different data. In almost all cases it can be seen that the

value of the tensile strength is lower in the comparison

with the neat PS matrix. The decrease is higher for

samples with 3 wt % loading, which can be caused by

worse dispersion of MMT or Ag agglomerates.

Generally, the decrease is not significant; it is only about

5%. To sum up, the tensile strength is not influenced

significantly.

3.5 Permeability

Barrier properties of prepared samples were

evaluated because the possible using of this type of

material in packaging. The most common gases -

oxygen and nitrogen - were observed. The results of

measurement are summarized in the graph in Fig. 4.

0,00E+00

1,00E-16

2,00E-16

3,00E-16

4,00E-16

5,00E-16

6,00E-16

7,00E-16

8,00E-16

9,00E-16

neat PS

IRG

Cl Na+ Ag

Ag Ac

samples

Perm

. co

ef.

(m

ol/s.m

.Pa)

O2 N2

Fig. 4. Permeability coefficient for O2 and N2

The result is very similar to the previous

measurements. The permeability coefficient is not

significantly different for neat and filled PS matrix

for both evaluated gases. Also here the barrier

property is not negatively influenced by used

nanofillers.

3.6 Antibacterial effect

As it was mentioned earlier, the aim of this work

was to compare several additive types in order to

evaluate their possible antibacterial effect in PS matrix

with the keeping of mechanical properties and

permeability. The mostly researched types of bacteria are

two the most widened - Escherichia coli or

Staphylococcus aureus (see Fig 5).

100 nm 100 nm

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ISBN: 978-1-61804-046-6 379

Fig. 5. Escherichia coli and Staphylococcus aureus

Samples of PS with nanofillers were prepared under

the steps described in the 2.3 chapter. Samples were

taken out from Petri plates after 5 hours and used

agars were consequently checked after 19 hours and

the observation was finished after 48 hours when the

photos of samples in Petri plates were taken. The

pictures are shown in the Fig. 6.

A) B)

C) D)

E) F)

Fig. 6. Pictures of the antibacterial test – A is neat PS

in Escherichia coli, B is neat PS in Staphylococcus

aureus, C is PS/AgAc 3wt% in Escherichia coli, D is

PS/AgAc 3wt% in Staphylococcus aureus, E is

PS/Irgaguard 3wt% in Escherichia coli, D is

PS/Irgaguard 3wt% in Staphylococcus aureus

Unfortunately, how it is possible to see from the

presented pictures, when the neat and filled PS matrix is

compared, no efficiency of added nanofillers can be seen.

The development of bacteria was not restricted or

reduced nor by Ag acetate present or by Irgaguard

compound present. The reason of it can be the fact that

the chosen way of samples mixing was not suitable for

these nanofillers.

4 Conclusion

Samples of polystyrene composites containing

different nanofillers with supposed antibacterial effect.

The concentration of nanofillers was from 1 and 3 wt. %.

The influence on barrier and mechanical properties was

studied simultaneously with the antibacterial testing.

TEM observation confirmed intercalation and partial

exfoliation of layered nanofiller Closite Na +.

Mechanical properties exhibited no significant change

in values for both evaluated – hardness and tensile

strength in the comparison with neat PS matrix. Added

nanofillers do not worse the samples properties.

The similar result was obtained in case of

permeability measurement – values of permeability

coefficients for O2 and N2 are not significantly different

or even worse in the comparison with the neat PS matrix.

Unfortunately, the main aim of this work was not

fully obtained. No one from used added nanofillers,

where the antibacterial effect was supposed, showed the

influence on the growth of used bacteria. Probable reason

cans be not suitable way of composite preparation.

Mixing of these used nanofillers with the polymer matrix

in the melt should be replaced in the future work by some

other way of preparation.

ACKNOWLEDGEMENTS

This project was supported by the Academy of

Sciences of the Czech Republic (projects KAN

100400701 and AVOZ40500505). Authors would like

also to thank to Microbiology laboratory UTB in Zlin.

References:

1. K.Chen, M.A. Susner, S. Vyazovkin, Effect of

the brush structure on the degradation mechanism of

polystyrene-clay nanocomposites, Macromolecular

Rapid Communications, 26, 9, 2005, pp. 690-695

2. K.Chen, S. Vyazovkin, Mechanistic differences

in degradation of polystyrene and polystyrene-clay

nanocomposite: Thermal and thermo-oxidative

degradation, Macromolecular Chemistry and Physics,

207, 6, 2006, pp. 587-595

3. W.H.Awad, High-throughput method for the

synthesis of high performance polystyrene

nanocomposites, Polymer-Plastics Technology and

Engineering, 45, 10, 2006, pp. 1117-1122

4. A.B.Morgan, J.W.Gilman, Characterization of

polymer-layered silicate (clay) nanocomposites by

transmission electron microscopy and X-ray diffraction:

A comparative study, J. Appl. Polym.Sci., 87, 8, 2003,

pp. 1329-1338

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ISBN: 978-1-61804-046-6 380

5. J.M. Yeh, C.P. Chin, Structure and properties of

poly(o-methoxyaniline)-clay nanocomposite materials,

J. Appl. Pol. Sci., 88, 4, 2003pp. 1072-1080

6. S.J.Ahmadi, Y.D. Huang, W. Li, Synthetic routes,

properties and future applications of polymer-layered

silicate nanocomposites, J. Mat. Sci., 39, 6, 2004, pp.

1919-1925

7. S.Su, D.D. Jiang, C. A. Wilkie, Novel

polymerically-modified clays permit the preparation of

intercalated and exfoliated nanocomposites of styrene

and its copolymers by melt blending, Pol. Degr, Stab.,

83, 2, 2004, pp. 333-346

8. K.Chen, C.A. Wilkie, S. Vyazovkin,

Nanoconfinement revealed in degradation and relaxation

studies of two structurally different polystyrene-clay

systems, J.Phys. Chem., 111, 2007, pp. 12685-12692

9. G. Chigwada, D.Y. Wang, C.A. Wilkie, Pol.

Degr. Stab., 91, 4, 848-855, (2006).

10. G. Chigwada, D.Y. Wang,D.D. Jiang, C.A.

Wilkie, Styrenic nanocomposites prepared using a novel

biphenyl-containing modified clay, Pol. Degr. Stab., 91,

4, 2006, 755-762

11. S.Nazarenko, P. Meneghetti, P. Julmon, Gas

barrier of polystyrene montmorillonite clay

nanocomposites: Effect of mineral layer aggregation, J.

Pol. Sci., Part B: Pol. Phys., 45, 2007, pp. 1733-1753

12. G. F. Prozorova, S. A Korzhova, T. V Kon'kova.

et al., Specific features of formation of silver

nanoparticles in the polymermatrix, Doklady Chem., 437,

2011, pp. 47-49

13. Ch. Triebel, S. Vasylyev, C. Damm et

al.Polyurethane/silver-nanocomposites with enhanced

silver ion release using multifunctional invertible

polyesters

J Mat Chem, 21, 12, 2011, pp. 4377-4383

14. M. A Kudryashov, A. I. Mashin, A. S. Tyurin et

al., Morphology of a silver/polyacrylonitrile

nanocomposite

Tech Phys, 56, 1, 2011, pp. 92-96

15. P. Dallas, V. K. Sharma, R. Zboril, Silver

polymeric nanocomposites as advanced antimicrobial

agents: Classification, synthetic paths, applications, and

perspectives

Adv in Colloid and Interface Sci, 166, 1-2, 2011, pp. 119-

135

16. R. Gunawidjaja, T. Myint, H. Eilers, Synthesis

of silver/SiO(2)/Eu:Lu(2)O(3) core-shell nanoparticles

and their polymer nanocomposites, Powder Technology,

2, 2011, pp. 157-166

17. R P Jose; A Urrutia; J Goicoechea; et al. An

antibacterial coating based on a polymer/sol-gel hybrid

matrix loaded with silver nanoparticles, *anoscale Res

Lett, 6, 2011, Article Number: 305

18. S. Pyne, P. Sarkar, S. Basu et al.Synthesis and

photo physical properties of Au @ Ag (core @ shell)

nanoparticles disperse in polyvinylalcohol matrix,

J.*anoparticle Res, 13,4, 2010, pp. 1759-1767

19. S.K. Tripathy, J.-N. Jo, H.-M. Song et al.,

Fabrication and optical study of Ag@SnO(2) core-shell

structure nanoparticle thin films, App. Phys. A-Mat. Sci

& Proc., 104, 2, 2010, pp. 601-607

20. A. Roucoux, J. Schulz, H. Patin, Reduced

transition metal colloids: A novel family of reusable

catalysts? Chem Rev, 102, 10, 2002, pp. 3757-3778

0 21. N. Severin, S. Kirstein, S.M. Sokolov, J.P. Rabe,

Rapid Trench Channeling of Graphenes with Catalytic

Silver Nanoparticles, *ano Lett , 9, 1, 2009, pp.457

22. A.M. Signori, K.D.O. Santos, R. Eising, B.L.

Albuquerque et al., Formation of Catalytic Silver

Nanoparticles Supported on Branched Polyethyleneimine

Derivatives, Langmuir, 26, 22, 2010,pp. 17772-17779

23. M. E. Leyva, F. G. Garcia, A. A. Alencar de

Queiroz et al.,Electrical properties of the DGEBA/PANI-

Ag composites, J Mater Sci-Mater in Electronics, 22, 4,

2011, pp. 376-383

24. M. K. Abyaneh, S. Jafarkhani, S. K.Kulkarni,

Electrical transport behaviour of silver-PMMA

nanocomposite films at low temperature, J Experimental

*anoscience, 6, 2, 2011, pp. 159-173

25. C. K. Rowan, I. Paci, Optical Properties of

Ag/Polyvinylidene Fluoride Nanocomposites: A

Theoretical Study, J Phys Chem C, 115, 16, 2011, pp.

8316-8324

26. V.Chaudhary, A. K. Thakur, A. K. Bhowmick,

Improved optical and electrical response in metal-

polymer nanocomposites for photovoltaic applications

J Mater Sci, 46, 2011, pp. 6096-6105

27. M. Y. Mamaghani, M. Pishvaei, B. Kaffashi,

Synthesis of latex based antibacterial acrylate

polymer/nanosilver via in situ miniemulsion

polymerization, Macromol Res, 19, 3, 2011, pp. 243-

249

28. Q. Shi, N. Vitchuli, J. Nowak et al., One-step

synthesis of silver nanoparticle-filled nylon 6 nanofibers

and their antibacterial properties

J Mat Chem, 21, 28, 2011, pp. 10330-10335

29. V. Melinte, T. Buruiana, I. D. Moraru et al.,

Silver-Polymer Composite Materials with Antibacterial

Properties, Digest Journal of *anomaterials and

Biostructures, 6, 1, 2011, pp. 213-223

30. S. Lischer, E. Koerner, D. J. Balazs et al.,

Antibacterial burst-release from minimal Ag-containing

plasma polymer coatings, Journal of the Royal Society

Interface, 60, 2011, pp. 1019-1030

31. H. Stara; Z. Stary, H. Muenstedt, Silver

Nanoparticles in Blends of Polyethylene and a

Superabsorbent Polymer: Morphology and Silver Ion

Release, Macromol Mater Eng, 296, 5, 2011, pp. 423-

427

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