The microwave synthesis of Ag nanoparticles on zinc stearate (ZnSt/Ag) was performed to obtain an antimicrobial additive for a polypropylene matrix. Thermoplastically prepared polymer composites contained (1, 3, 5 and 10) % of mass fractions of ZnSt/Ag. The effect of the presence of additives on the morphology and mechanical properties of composites was studied by scanning electron microscopy and stress-strain analysis. The antimicrobial activity of the composites was studied according to the ISO 22196 standard. The results showed that sufficient antimicrobial activity of the composites against both Gram-positive and Gram-negative bacterial strains was observed in the case of the composites with the highest filling studied.grant of Technology Agency of the Czech Republic [TE02000006]; Ministry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2015/004

Holčapková, Pavlína

Hrabalíková, Martina

Jandíková, Gabriela

Machovský, Michal

Sedlařík, Vladimír

English

Institutional repository of Tomas Bata University Library

G. JANDIKOVA et al.: ANTIMICROBIAL MODIFICATION OF POLYPROPYLENE WITH SILVER NANOPARTICLES ...869–871ANTIMICROBIAL MODIFICATION OF POLYPROPYLENE WITHSILVER NANOPARTICLES IMMOBILIZED ON ZINC STEARATEPROTIMIKROBNO SPREMINJANJE POLIPROPILENA ZNANODELCI SREBRA, IMOBILIZIRANIH NA CINKOVEMSTEARATUGabriela Jandikova, Pavlina Holcapkova, Martina Hrabalikova,Michal Machovsky, Vladimir SedlarikTomas Bata University in Zlin, University Institute, Centre of Polymer Systems, tr. Tomase Bati 5678, 76001 Zlín, Czech Republicsedlarik@cps.utb.czPrejem rokopisa – received: 2015-06-30; sprejem za objavo – accepted for publication: 2015-12-01doi:10.17222/mit.2015.152The microwave synthesis of Ag nanoparticles on zinc stearate (ZnSt/Ag) was performed to obtain an antimicrobial additive for apolypropylene matrix. Thermoplastically prepared polymer composites contained (1, 3, 5 and 10) % of mass fractions ofZnSt/Ag. The effect of the presence of additives on the morphology and mechanical properties of composites was studied byscanning electron microscopy and stress-strain analysis. The antimicrobial activity of the composites was studied according tothe ISO 22196 standard. The results showed that sufficient antimicrobial activity of the composites against both Gram-positiveand Gram-negative bacterial strains was observed in the case of the composites with the highest filling studied.Keywords: antibacterial, polypropylene composite, zinc stearate, Ag nanoparticlesIzvedena je bila sinteza nanodelcev Ag na cinkovem stearatu (ZnSt/Ag) z mikrovalovi, da bi dobili protimikrobni dodatek poli-propilenski osnovi. Termoplasti~no pripravljeni kompozit polimera je vseboval (1, 3, 5 in 10) % masnega dele`a ZnSt/Ag. Vplivprisotnosti dodatkov na morfologijo in mehanske lastnosti kompozitov je bil prou~evan z vrsti~no elektronsko mikroskopijo inanalizo napetost-raztezek. Protimikrobna aktivnost kompozita je bila prou~evana skladno s standardom ISO 22196. Rezultati sopokazali, da je primerna protimikrobna aktivnost pri sevih, gram pozitivnih in gram negativnih bakterij, dose`ena v primerukompozita z najve~jim prou~evanim dodatkom.Klju~ne besede: protibakterijsko, polipropilenski kompozit, cinkov stearat, nanodelci Ag1 INTRODUCTIONAntimicrobial modifications of polymers are used toprevent or inhibit the growth of microorganisms on itssurface. Such a modification may find utilization in foodpackaging, medical applications and especially in hygi-enic materials or textile production. Nowadays, acommonly used method for the modification of polymersis an addition of an antimicrobial agent/additive directlyinto the polymer matrix. Currently, silver-based (Ag)additives have received significant attention due to thelow toxicity of the active Ag ion to human cells as wellas for being a long-lasting biocide with high thermal sta-bility and low volatility.1,2 Microwave (MW) synthesis isone of the well-known effective methods for the prepa-ration of Ag NPs.3,4 The immobilization of Ag NPs byMW synthesis on various organic substrates has beenstudied by P. Bazant et al.2 The authors successfullyimmobilized nano-silver, nanostructured ZnO and hybridnanostructured Ag/ZnO on a wood flour (WF) surface byMW synthesis. Subsequently, the modified WF wascompounded into a PVC matrix (5 % of mass fractionsloading) and the antimicrobial activity was tested whilethe most efficient system was the hybrid nanostructuredAg/ZnO. N. Iqbal et al.1 described the surface modifica-tion by the MW synthesis of Ag NPs on the surface ofinorganic substances. The Ag NPs were successfullybonded on hydroxyapatite and caused antimicrobialactivity of the prepared system.The antimicrobial modification of polypropylenewith Ag NPs prepared by MW synthesis and immobi-lized on a zinc stearate surface was studied in this work.The prepared composites were characterized by scanningelectron microscopy, stress-strain analysis and antimicro-bial testing according to the ISO 22196 standard.2 EXPERIMENTAL PART2.1 MaterialsPolypropylene (PP) resin (C706-21 NA HP, density =0.9 g.cm–3, MFR = 21 g.10 min–1) used in this work wasa product of the Braskem company (Brazil). Zinc steara-te (ZnSt) was supplied by Sigma Aldrich (USA). Silvernitrate (AgNO3), Hexamethylenetetramine (HMTA) andethanol were purchased from PENTA, Czech Republic.2.2 Preparation of hybrid ZnSt/Ag particles and PPcompositesHybrid ZnSt/Ag particles were prepared under refluxin the MW open vessel system MWG1K-10 (RADAN,Materiali in tehnologije / Materials and technology 50 (2016) 6, 869–871 869UDK 620.1:678.742.3:669.22:669.5:661.8'075.3 ISSN 1580-2949Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 50(6)869(2016)Czech Republic; 1.5 kW, 2.45 GHz) operating in conti-nuous mode (zero idle time) with an external cooler.First, 200 mL of AgNO3 (0.85 g) solution in water and450 mL of ZnSt (11.02 g) dispersion in ethanol weretransferred into a 1000 mL reaction bottle. The reactionmixture was heated in a MW oven for 2 min. After that,100 mL of HMTA (7.00 g) solution in water was addedand the MW heating continued for 10 min under conti-nuous stirring (250 min–1). The reaction product wascollected by suction microfiltration and left to dry in alaboratory oven (50 °C) up to the constant weight. Theprepared ZnSt/Ag system contained 2.4 % of mass frac-tions of Ag (determined by atomic absorption spectro-scopy, Agilent DUO 240FS/240Z/UltrAA). The preparedhybrid particles were incorporated into the PP matrix bytwin screw micro-compounder DSM Xplore (15 mLchamber volume). The temperature of all three zoneswas 200 °C, speed 100 min–1 and time of mixing 10 min.The concentration of the filler was from 1 % to 10 % ofmass fractions.2.3 Characterization methodsThe structure of the prepared samples was observedby scanning electron microscopy (VEGA IILMU,TESCAN). The specimens were coated with a thinAu/Pd layer. The microscope was operated in vacuummode at an acceleration voltage of 10 kV.The mechanical characterization of the samples(dog-bone shaped specimens) was performed with aM350-5 CT Materials Testing Machine. The cross-headspeed was 10 mm/min. Each test consisted of seven re-plicate measurements. Antimicrobial testing was per-formed according to the ISO 22196:2007 internationalstandard against Escherichia coli and Staphylococcusaureus.3 RESULTS AND DISCUSSIONSEM micrographs of the ZnSt/Ag additive and PP10 % ZnSt/Ag composite are shown in Figure 1. Immo-bilized Ag particles with a size below 100 nm are visiblein the case of the pure additive (Figure 1a) as well in thecomposite (Figure 1b). The size and shape of the MWprepared Ag NPs correspond to the results published byBazant et al.2 where Ag NPs were immobilized on awood flour. Furthermore, the SEM analysis reveals thatimmobilized Ag NPs have good cohesion to the ZnStsubstrate, even after thermoplastic processing.The mechanical properties of the composites werenoticeably influenced when the loading of the filler wasabove 5 % of mass fractions. However, the addition of1 % of mass fractions of ZnSt/Ag improved the tensilestrain by approximately 16 % in comparison with neatPP, while the tensile strength remained unchanged. In thecase of the composites containing 10 % of mass fractionsof ZnSt/Ag the Young’s modulus, tensile strength andtensile strain were reduced by approximately 35 %,20 %, and 81 %, respectively (Table 1). The mechanicalproperties of the composites are most dependent on theG. JANDIKOVA et al.: ANTIMICROBIAL MODIFICATION OF POLYPROPYLENE WITH SILVER NANOPARTICLES ...870 Materiali in tehnologije / Materials and technology 50 (2016) 6, 869–871Table 1: Summary of stress-strain analysis results of prepared PP/ZnSt/Ag compositesTabela 1: Zbir rezultatov analiz napetost-raztezek pripravljenih kompozitov PP/ZnSt/AgYoung’s modulus (MPa) Tensile strength (MPa) Strain at break (%)PP 217 (± 27) 22 (± 1.7) 187 (± 47)PP 1 % ZnSt/Ag 179 (± 25) 22 (± 0.5) 217 (± 23)PP 3 % ZnSt/Ag 172 (± 12) 22 (± 1.1) 68 (± 12)PP 5 % ZnSt/Ag 155 (± 29) 21 (± 1.2) 54 (± 17)PP 10 % ZnSt/Ag 143 (± 10) 18 (± 0.8) 35 (± 3)Figure 1: Scanning electron micrographs of: a) ZnSt/Ag particles and b) PP 10 % of mass fractions of ZnSt/Ag composite. The Ag nanoparticlescan be recognized as white dots.Slika 1: Posnetka z vrsti~nim elektronskim mikroskopom: a) ZnSt/Ag delci in b) kompozit PP z 10 % masnega dele`a ZnSt/Ag. Nanodelci Ag seka`ejo kot bele to~ke.ZnSt content without the effect of the Ag NPs presenceon it. Changes of the mechanical properties correspondto the results observed in the case of the compositesbased on PP and unmodified ZnSt.5The antimicrobial activity of the composites issummarized in Table 2. There is a slight inhibition ofgrowth of both bacterial strains when the concentrationis 5 % of mass fractions of ZnSt (corresponding to0.08 % of mass fractions of Ag). The samples with thehighest filling studied (0.16 % of mass fractions of Ag)exhibit a noteworthy activity against Escherichia coliand Staphylococcus aureus. Antimicrobial activity is inagreement with studies describing incorporation of AgNPs into hydrophobic polymer matrices.24 CONCLUSIONSThe hybrid systems of ZnSt and Ag nanoparticleswere prepared by MW synthesis and incorporated into aPP matrix. The prepared composites showed a promisingantimicrobial activity at concentration above 5 % ofmass fractions. The mechanical properties were notice-ably influenced at 10 % of mass fractions of the ZnSt/Agloading into the PP matrix. However, a noticeable impro-vement of tensile strength of the composites was ob-served already at 1 % of mass fractions of ZnSt/Ag,while the tensile strain remained unchanged in com-parison with the unmodified PP.The proposed antimicrobial modification of com-monly used additives, such as zinc stearate, represents apromising way of nanoparticle handling and applica-tions.AcknowledgmentsThis work was supported by the grant of TechnologyAgency of the Czech Republic (grant No. TE02000006),the Ministry of Education, Youth and Sports of theCzech Republic – Program NPU I (grant No. LO1504)and by Internal Grant Agency of the Tomas BataUniversity in Zlín (grant No. IGA/CPS/2015/004).5 REFERENCES1 N. Iqbal, M. R. Abdul Kadir, N. A. N. Nik Malek, N. HumaimiMahmood, M. Raman Murali, T. Kamarul, Rapid microwave assistedsynthesis and characterization of nanosized silver-doped hydroxy-apatite with antibacterial properties, Material Letters, 89 (2012),118–122, doi:10.1016/j.matlet.2012.08.0572 P. Bazant, L. Munster, M. Machovsky, J. Sedlak, M. Pastorek, Z.Kozakova, I. Kuritka, Wood flour modified by hierarchical Ag/ZnOas potential filler for wood–plastic composites with enhanced surfaceantibacterial performance, Industrial Crops and Products, 62 (2014),179–187, doi:10.1016/j.indcrop.2014.08.0283 D. Breitwieser, M. M. Moghaddam, S. Spirk, M. Baghbanzadeh, T.Pivec, H. Fasl, V. Ribitsch, C. O. Kappe, In situ preparation of silvernanocomposites on cellulosic fibers--microwave vs. conventionalheating, Carbohydrate Polymers, 94 (2013), 677–686, doi:10.1016/j.carbpol.2013.01.0774 X. Zhao, Y. Xia, Q. Li, X. Ma, F. Quan, C. Geng, Z. Han, Biopoly-mers regulate silver nanoparticle under microwave irradiation foreffective antibacterial and antibiofilm activities, Colloids and Sur-faces A: Physicochemical and Engineering Aspects, 444 (2014),180–188, doi:10.1016/j.colsurfa.2013.12.0085Ñ. V. Panin, L. A. Kornienko, T. Nguyen Suan, L. R. Ivanova, M. A.Poltaranin, The effect of adding calcium stearate on wear-resistanceof ultra-high molecular weight polyethylene, Procedia Engineering,113 (2015), 490–498, doi:10.1016/ j.proeng.2015.07.341G. JANDIKOVA et al.: ANTIMICROBIAL MODIFICATION OF POLYPROPYLENE WITH SILVER NANOPARTICLES ...Materiali in tehnologije / Materials and technology 50 (2016) 6, 869–871 871Table 2: Antimicrobial activity of prepared composites determined according to ISO 22196Tabela 2: Protimikrobna aktivnost pripravljenih kompozitov, dolo~ena po ISO 22196SampleS. aureus E. coliCFU/cm2 R CFU/cm2 RPP 2,4E+05 – 7,2E+05 –PP + 5 % ZnSt 1,1E+05 0.4 1,9E+05 0.6PP + 10 % ZnSt 9,6E+04 0.4 5,0E+04 1.2PP + 5 % ZnSt/Ag 1,6E+05 0.2 5,5E+04 1.1PP + 10 % ZnSt/Ag 9,5E+02 2.4 0,0E+00 7.0

Antimicrobial modification of polypropylene with silver nanoparticles immobilized on zinc stearate

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Antimicrobial modification of polypropylene with silver nanoparticles immobilized on zinc stearate

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