Received: 1 March 2017
Revised: 16 May 2017
Accepted: 16 May 2017
DOI: 10.1002/pat.4089
RESEARCH ARTICLE
Antimicrobial, mechanical, barrier, and thermal properties of bio‐based poly (butylene adipate‐co‐terephthalate) (PBAT)/Ag2O nanocomposite films for packaging application Raja Venkatesan1
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Natesan Rajeswari1
|
Alagumuthu Tamilselvi2
1
Department of Printing Technology, College of Engineering, Guindy, Anna University, Chennai, Tamil Nadu 600025, India
2
Centre for Human and Organisational Resources Development, CSIR—Central Leather Research Institute (CLRI), Adyar, Chennai, Tamil Nadu 600020, India Correspondence Raja Venkatesan, Department of Printing Technology, College of Engineering, Guindy, Anna University, Chennai, Tamil Nadu 600025, India. Email:
[email protected]
Bio‐based nanocomposites of poly (butylene adipate‐co‐terephthalate) (PBAT)/silver oxide (Ag2O) were prepared by the composite film casting method using chloroform as the solvent. The prepared Ag2O at different ratios (1, 3, 5, 7, and 10 wt%) is incorporated in the PBAT. The PBAT nanocomposite films were subjected to structural, thermal, mechanical, barrier, and antimicrobial properties. The electron micrographs indicated uniform distribution of Ag2O in the PBAT matrix. However, the images indicated agglomeration of Ag2O particles at 10 wt% loading. The thermal stability of the nanocomposite films increased with Ag2O content. The tensile strength and elongation of the composite films were found to be higher than those of PBAT and increased with Ag2O content up to 7 wt%. The PBAT‐based nanocomposite films showed the lower oxygen and water vapor permeability when compared to the PBAT film. Antimicrobial studies were performed against two food pathogenic bacteria, namely, Klebsiella
Funding information Centre for Research, Anna University, Grant/ Award Number: CR/ACRF/2013‐10
pneumonia and Staphylococcus aureus. KEY W ORDS
Ag2O nanoparticles, antimicrobial activity, barrier properties, nanocomposites
1
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I N T RO D U CT I O N
component, have been used in the formulation of dental resin composites,5 ion exchange fibers,6 and in coatings of medical devices.7
Poly (butylene adipate‐co‐terephthalate) (PBAT) biomaterial consumes
The possible use of silver nanoparticles as antibacterial agent has,
several properties as a bio‐plastic, such as low cost, low density, high
therefore, been investigated as a means arresting increasing resistance
thermal stability, and degradable. Therefore, it is widely used in many
bacteria.8
applications, especially in food packaging. In composite flexible pack-
Use of different types of nanomaterials like copper, zinc,9
aging materials, PBAT film is used mainly as the packed and the seal
titanium,10 magnesium,11 gold,12 alginate,13 silica,14 and silver has
layer. This means that PBAT materials should not only have a high
increased and proved the most effective as they have good antimicro-
degree of mechanical toughness and barrier properties but also per-
bial efficacy against a wide variety of bacteria, viruses, and other
form better in food safety. Nanocomposite is a multiphase solid mate-
microorganisms. Poly (butylene adipate‐co‐terephthalate) is an ali-
rial system that is formed by the combination of two or more
phatic‐aromatic copolyester based on the monomers 1, 4‐butanediol,
components that include polymers and nanomaterials. Over the past
adipic acid, and terephthalic acid. Figure 1 shows the chemical struc-
decade, interest in biopolymer‐based nanocomposites has increased
ture of PBAT. It is a fully biodegradable polymer,15 and it is resistant
because of the biodegradability and improved physical, mechanical,
to water showing good potential in its application for packaging films,
1-3
In addition, remarkable antimicrobial
compost bags, and agricultural films.16 The thermal and mechano-
functions showed by certain nanocomposites have expanded the
chemical properties of PBAT/octadecylamine–modified montmorillon-
application of nanocomposite films in various applications in the area
ite nanocomposites have been studied.17 These results illustrated the
of biomedicals and food packaging sectors. It is well known that silver
property enhancement of PBAT nanocomposites prepared by a melt
ions and silver‐based compounds are highly reactive towards microor-
blending technique using montmorillonite (MMT). Cloisite 20A,
ganisms4 showing strong biocide effects against many species of bac-
Cloisite 30B, and Bentonite 10B nanoclays.18 The antimicrobial prop-
teria including Escherichia coli. Thus, silver ions, as an antibacterial
erty of such nanocomposites makes it a versatile material in packaging
and antimicrobial properties.
Polym Adv Technol. 2017;1–8.
wileyonlinelibrary.com/journal/pat
Copyright © 2017 John Wiley & Sons, Ltd.
1
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VENKATESAN
ET AL.
TABLE 1
Abbreviations of the newly prepared different types of PBAT/Ag2O nanocomposites S No.
FIGURE
1 Chemical structure of poly (butylene adipate‐co‐ terephthalate) [Colour figure can be viewed at wileyonlinelibrary.com]
Nanocomposite Films
Abbreviation
1
PBAT/Ag2O (0 wt%)
PA‐0
2
PBAT/Ag2O (1 wt%)
PA‐1
3
PBAT/Ag2O (3 wt%)
PA‐3 PA‐5
4
PBAT/Ag2O (5 wt%)
applications. The nanocomposites containing certain organically
5
PBAT/Ag2O (7 wt%)
PA‐7
modified nanoclay offer strong antimicrobial function against both
6
PBAT/Ag2O (10 wt%)
PA‐10
gram‐positive and gram‐negative bacteria.19 In that, the presence of quaternary ammonium groups present in the organically modified clays
Abbreviations: Ag2O, silver oxide; PBAT, poly (butylene adipate‐co‐ terephthalate).
is responsible for the antimicrobial function of nanocomposite films. These nanocomposite films with enhanced mechanical and gas barrier
approximately 0.08‐ to 0.1‐mm thickness was obtained for all the
properties have a high potential for being used as food packaging
wt% of polymer films. For quick understanding, the prepared different
materials. The PBAT/polyvinyl alcohol–blended SiO2 nanocomposites
types of nanocomposite films and their abbreviation used in the entire
show good antimicrobial activity against E coli and Staphylococcus
manuscript are given in Table 1.
20
aureus.
In this article, the report shows the structural, mechanical, barrier, and antimicrobial properties of PBAT/silver oxide (Ag2O) nanocom-
2.4
Materials characterization
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posite film. The silver oxide nanoparticles (Ag2O NPs) were synthe-
2.4.1
sized by chemical reduction method, and then the nanocomposite
Fourier‐transform infrared (FT‐IR) spectrum of the film samples was
film was made by introducing Ag2O NPs into the PBAT by solution
measured using an FT‐IR spectroscopy (Perkin Elmer spectropho-
casting method. The morphology, mechanical, thermal, barrier, and
tometer RX1) operated at a resolution of 4 cm−1. Film samples
antimicrobial activity of the prepared PBAT nanofilms were studied
were cut into rectangular shape (2 × 2 cm) and directly placed on
to find its suitability for food packaging applications.
|
Fourier‐transform infrared spectra analysis
the ray‐exposing stage. The spectrum was recorded at wavenumber of 400 to 4000 cm−1.
2 2.1
EXPERIMENTAL METHODS
|
|
Materials
2.4.2
|
X‐ray diffraction analysis
The crystal structures of the Ag2O NPs and nanocomposite film were studied by X‐ray diffraction (XRD) (Rigaku, MiniFlex 120 II‐C). Sam-
The PBAT was used as received from BASF Ltd, Japan. Trisodium cit-
ples were prepared by placing rectangular shape of each film
rate and silver nitrate were obtained from SRL, India. The test strains
(2 × 2 cm) on a glass slide, and the spectra were recorded using
Klebsiella pneumoniae, ATCC‐13883, and S aureus, ATCC‐6538, were
Cu‐Kα radiation. The size of the nanoparticles was calculated through
procured from IMTECH, Chandigarh. All chemicals and solvents were
the Scherer's equation.
obtained from SRL, India. Kλ BCosθ ¼ Kλ=β cosθ
dXRD ¼
2.2
|
dXRD
Preparation of silver oxide nanoparticles
The Ag2O NPs were prepared by sodium citrate reduction of AgNO3.21 After the addition of trisodium citrate (1% w/v) into AgNO3 solution, a dark brown precipitate was obtained. The precipitates were filtered
where d, K, λ, β, and θ are the average crystallite (nm), constant factor, X‐ray wavelength, full width at half height, and scattering angle, respectively.
and rinsed with distilled water, and the precipitate was heated in a tubular furnace at 200°C for 1 hour to obtain the Ag2O nanoparticles.
2.4.3
|
Scanning electron microscopy
Scanning electron microscopy (SEM) analysis was performed to
2.3 | Preparation of PBAT/Ag2O nanocomposite films
observe the microstructure of the film samples. A small piece of
The polymer used in this study was previously dried at 60°C for
a SEM (S‐4800, Hitachi Co, Ltd, Japan) with an accelerating voltage
24 hours before use. A total of 2.0 g of PBAT polymer were dissolved
of 5.0 kV.
film was mounted on a SEM specimen holder and analyzed using
in 100 mL of chloroform with constant magnetic stirring until the clear solution was obtained. Instantaneously, the prepared Ag2O NPs of the
2.4.4
following wt% (1, 3, 5, 7, and 10) were dispersed in the polymer solu-
The morphology of Ag2O NPs and nanocomposite film was exam-
tion. The solution was cast into a petri dish and dried in an oven for
ined by transmission electron microscopy (TEM) using a micro-
48 hours at 40°C. Finally, the resulting films were dried under vacuum
scope TECNAI‐G2 (model T‐30), operated at an accelerating
for 48 hours to obtain the nanocomposites. A homogeneous film of
voltage of 300 kV.
|
Transmission electron microscopy
VENKATESAN
2.4.5
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3
ET AL.
Thermogravimetric analysis
3
RESULTS AND DISCUSSION
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The thermal stability evaluation was performed using a thermogravimetric analyzer model QA 50 (TA Instruments). The samples were heated from 25°C to 700°C at the rate 10°C min−1 under nitrogen atmosphere (50 mL min−1).
3.1
|
Fourier‐transform infrared spectra analysis
The characterization of the prepared Ag2O NPs was analyzed using FT‐ IR. Absorbance bands at 3441, 1658, 1535, and 1400 cm−1 were indicative of the stretching vibrations of primary and secondary amines
2.4.6
|
Mechanical properties
(Figure 2). The result revealed that the capping ligand of the Ag2O NPs may be an aromatic compound or amines. The absorption peak at
The mechanical properties of PBAT and nanocomposite films, viz, tensile strength and percentage elongation, have been done. The tests for measurement of these mechanical properties were done using Universal Testing Machine (UTM, H10KS, Tinius Olsen, UK), as noted earlier. As per ASTM D‐882‐02 standard test method, specimen films of PBAT and PBAT/TiO2 nanocomposite with dimensions 100 mm × 25 mm × 0.085 mm have been used at a speed of 500 mm min−1. The gauge length of each film was maintained at 50 mm. The tensile strength is expressed in MPa.
1040 cm−1 represents the Ag–O; this bond was confirmed the Ag2O NPs. The evaluation of antibiotic resistance of pathogenic fungi has stimulated the search for effective antifungal agent from alternative sources. Many studies have shown the antimicrobial effects of Ag2O NPs. Figure 3 shows the FT‐IR of the PBAT with different loadings of Ag2O nanoparticles. The FT‐IR was performed to study the effects of functional groups in the Ag2O NPs with respect to potential interactions with the polymer components. The FT‐IR spectra show a strong absorbance peak at around 1714 cm−1, which may be due to the vibration of carbonyl group, C=O. The C=O stretching slightly shifted to
2.4.7
|
Oxygen transmission rate
The oxygen transmission rate of the PBAT and nanocomposite films was calculated by oxygen permeability tester (Noselab ats, Italia) at 25°C under the condition of 0% relative humidity at 1 atm by the standard of ASTM D‐3985. The measurements were taken at 3 times at different places of the film, and the average value was calculated. All specimens were conditioned at ambient conditions.
2.4.8
|
Water vapor transmission rate
The ASTM E‐987 standard method was used to determine water vapor permeability (WVP). The samples were kept at 25°C and 50% RH in a conditioned chamber for 2 hours. The weight loss of each cup was considered to be equal to the water transferred through the film and adsorbed by the desiccant. Weight loss from
FIGURE 2
Fourier‐transform infrared spectra of the synthesized silver oxide nanoparticles (Ag2O NPs) [Colour figure can be viewed at wileyonlinelibrary.com]
each cup was measured as a function of time for 12 hours. The WVP was calculated by WVP ¼ WVTR × x=Δp where WVTR is the water vapor transmission rate (g m−2 per 24 h) through the film, x is the film thickness (m), and Δp is the partial water vapor pressure difference.
2.4.9
|
Antimicrobial activity
The antimicrobial activity of PBAT and PBAT/Ag2O nanocomposite films was tested by an inhibition zone as per ASTM D‐2149 standard method. Food pathogenic bacteria, K pneumonia and S aureus, were used for finding the antimicrobial activity of the films. For the qualitative measurement of antimicrobial activity, a small piece of film samples were punched to make disks (diameter = 11 mm), and the antimicrobial activity was determined using a modified agar diffusion assay. The plates were kept for 2 days after incubation at 37°C for possible clear zones.
FIGURE 3
The Fourier‐transform infrared spectrum of poly (butylene adipate‐co‐terephthalate) with 0%, 1%, 3%, 5%, 7%, and 10% (w/w) of silver oxide nanoparticles [Colour figure can be viewed at wileyonlinelibrary.com]
4
VENKATESAN
ET AL.
higher wavenumber when nanoparticles were incorporated into the PBAT polymer. This means that there is interaction between nanoparticle and C O carbonyl group. The C–O stretching also peaks at 1268 cm−1 of C–O stretching the characteristic peaks of PBAT. The absorption peak at 1040 cm−1 indicates the characteristic of Ag2O NPs. Hence, FT‐IR spectra reveal that no new peak is formed, but there is interaction between Ag2O NPs and the PBAT. The results of FT‐IR show that the formation of PBAT and its nanocomposite film consists of PBAT along with Ag2O NPs.
3.2
|
X‐ray diffraction analysis
The XRD patterns of the Ag2O NPs prepared by the chemical precipitation method at 100°C are shown in Figure 4. The diffraction peaks FIGURE 4
X‐ray diffraction patterns of the synthesized silver oxide nanoparticles
are well indexed to the Ag2O structure. The intensity of the peak increases with increased crystallinity of the Ag2O NPs. The Ag2O showed 2 characteristic peaks at 27.9° and 32.2°, which correspond to the crystal plane 110 and 111, of Ag2O nanoparticles. The diffraction peaks at 46.3°, 54.9°, and 67.4° can be indexed to 211 and 222 planes of fcc Ag2O. The size of the nanoparticles was thus determined to be about 50 ± 2 nm for Ag2O NPs synthesized at 50°C. The XRD showed the crystal structure of PBAT and PBAT/Ag2O nanocomposite films, and the XRD spectra are depicted in Figure 5. The PBAT showed 5 diffraction peaks of the crystal structure at 17.3°, 20.4°, 23.0°, and 23.9°, at 2θ value. These 5 characteristic peaks of pure PBAT were also observed for PBAT/nisin samples at the same 2θ values (Figure 5). Nevertheless, small changes in the intensity of the polymer diffraction peak were detected for the PBAT/Ag2O samples, suggesting that the peak intensity tends to decrease when Ag2O was added to PBAT matrix (5 to 10 wt% Ag2O). As the Ag2O content was increased from 0 to 10 wt%, the 2θ value of the peak increased from 17.3° to 23.9°. The XRD results indicate that the introduction of Ag2O enhanced molecular arrangement in the crystalline and structures polymer.
3.3 FIGURE
X‐ray diffract grams: poly (butylene adipate‐co‐ terephthalate) with (A) 0, (B) 1, (C) 3, (D) 5, (E) 7, and (F) 10 wt% of silver oxide nanoparticles
FIGURE 6
|
Morphological characterization
5
The surface morphology of prepared Ag2O NPs was analyzed by SEM and TEM. The SEM analysis was performed to understand
(A) Scanning electron microscopy image of synthesized silver oxide nanoparticles; transmission electron microscopy images of the synthesized silver oxide nanoparticles at (B) 50 and (C) 200 nm
VENKATESAN
5
ET AL.
the morphology of Ag2O NPs, which showed the synthesis of uniform distribution with spherical shape Ag2O nanoparticles (Figure 6A). The TEM study confirmed that the inner morphology of Ag2O nanoparticles was mainly spherical shape and size of about 50 nm (Figure 6B,C), in which the Ag2O NPs appear as narrow size distribution. The SEM was used to investigate the surface morphology of prepared nanocomposite film with reference to PBAT film and Ag2O nanoparticles. The SEM images of PBAT, Ag2O, and PBAT/ Ag2O (1, 3, 5, 7, and 10 wt%) nanocomposite film are shown in Figure 7. The PBAT/Ag2O nanocomposite film has aggregated particle structures; however, the micrographs of PBAT and Ag2O are uniform. The nanoparticles in nanocomposite film were found with almost spherical morphology. However, some of the agglomeration of nanoparticles was also found. The SEM image of 10 wt% of
FIGURE 8 Energy‐dispersive X‐ray spectral profile of poly (butylene adipate‐co‐terephthalate)/silver oxide (10 wt%) nanocomposite film [Colour figure can be viewed at wileyonlinelibrary.com]
Ag2O nanoparticles blended PBAT film shows the nonuniform distribution. The elemental composition of Ag2O was confirmed for PBAT/ 10 wt% Ag2O by energy‐dispersive X‐ray spectral analysis and is
the Ag2O concentration increased, particles of this antimicrobial substance were observed possibly because of its partial aggregation and migration to the film surface.
shown in Figure 8. From the spectral data, it was found that the appropriate concentration of Ag, O, and other components is presented in the nanocomposites.22 The above results indicate the formation of
3.4
PBAT/Ag2O nanocomposite film.
Thermogravimetric analysis results for the PBAT and PBAT/Ag2O
|
Thermal stability
The TEM images obtained from PBAT and PBAT/Ag2O films
nanocomposites in nitrogen with a heating rate of 20°C min−1 are
are depicted in Figure 9. The Ag2O formulation and its solution
shown in Figure 10, and the initial, 50%, and final degradation temper-
dispersion were also visualized by TEM. The morphology of pure
atures are shown in Table 2, to determine the thermal stability of PBAT
PBAT was homogeneous, while Ag2O NPs agglomerates were visi-
nanocomposites with different Ag2O filler content (1, 3, 5, 7, and
ble on the films containing 5, 7, or 10 wt% Ag2O (Figure 9D‐F). As
10 wt%). When the Ag2O NPs were added, the thermal degradation
FIGURE 7
Scanning electron microscopy images of the surfaces of poly (butylene adipate‐co‐terephthalate) (PBAT) and its nanocomposites: (A) PBAT, (B) 1, (C) 3, (D) 5, (E) 7, and (F) 10 wt% of silver oxide nanoparticles (Ag2O NPs) [Colour figure can be viewed at wileyonlinelibrary.com]
6
VENKATESAN
ET AL.
FIGURE 9
Transmission electron microscopy images of the surfaces of poly (butylene adipate‐co‐terephthalate) and its nanocomposites [Colour figure can be viewed at wileyonlinelibrary.com]
FIGURE 11 FIGURE 10
Stress‐strain curves of poly (butylene adipate‐co‐ terephthalate) and poly (butylene adipate‐co‐terephthalate)/silver oxide nanocomposites with 1 to 10 wt% of silver oxide [Colour figure can be viewed at wileyonlinelibrary.com]
Thermogravimetric analysis curves of poly (butylene adipate‐co‐terephthalate) and poly (butylene adipate‐co‐terephthalate)/ silver oxide nanocomposites with 1 to 10 wt% silver oxide nanoparticles [Colour figure can be viewed at wileyonlinelibrary.com]
increasing Ag2O NPs loading. Because the Ag2O possesses good ther-
temperature was shifted to a higher temperature than that obtained
PBAT matrix enhanced the thermal stability. The dispersed Ag2O
with the pure PBAT, with the shift temperature increasing with
regions in PBAT matrix improved the thermal properties of the
mal properties, the results reflect that the presence of Ag2O NPs in the
TABLE 2
Samples
Thermogravimetric analysis analysis of poly (butylene adipate‐co‐terephthalate) and its nanocomposites Initial Degradation Temperature, °C
Final Degradation Temperature, °C
50% Degradation Temperature, °C
Ash Content, %
PA‐0
319.51
412.00
405.01
8.13
PA‐1
323.29
416.25
409.34
8.01
PA‐3
326.88
420.59
413.87
7.83
PA‐5
339.30
428.90
419.33
7.41
PA‐7
342.08
435.82
421.51
7.32
PA‐10
352.19
450.10
424.90
7.03
VENKATESAN
7
ET AL.
nanocomposites. That is, the good interaction between the PBAT and
PBAT/ZnO films increased significantly with increasing metal oxide
the Ag2O NPs induced the better thermal stability. The PBAT/Ag2O
concentration because of a possible strain‐induced alignment of the
nanocomposites are relevant to the potential use of these materials
metal particles in the polymer matrix.23 There was significant
in demanding engineering applications.
influence of the Ag2O concentration on the mechanical properties of the films. It was also observed that the tensile strength ranged from 30.60 MPa (pure PBAT) to 47.70 MPa (7 wt%) after that, the
3.5
|
Mechanical properties
tensile strength decreased because of the agglomeration of
Mechanical strength of film is described in terms of tensile strength,
nanocomposites. The decrease in the elongation might be a result
and brittle films are characterized and represented in Figure 11. The
of the restriction of mobility of polymer chains in the presence of
mechanical properties determined by tensile and elongation at break
nanoparticles. The obtained results are found in good agreement with
were also influenced by the incorporation of the Ag2O as shown in
the previous reports of Nafchi et al24 about the decrease in percent
Table 3. Generally, the tensile strength (TS) of PBAT‐based nanofilms
elongation on the addition of the nanoparticle. The effect of Ag2O
increased in the presence of Ag2O, while elongation at break slightly
addition was found to enhance as well as impair the mechanical
decreased. Previous works have reported that tensile values of
properties depending on the wt% addition of nanoparticles. In the
TABLE 3
observed by way of obtaining the nanocomposite films.
present work, the regular dispersion of Ag2O in the PBAT matrix is Mechanical properties of PBAT and PBAT/Ag2O nanocomposites Tensile Strength, MPa
Tensile Modulus, MPa
Elongation at Break, %
PA‐0
30.60
1.53
365.32
Nanocomposite materials that prevent oxygen permeation are being
PA‐1
34.76
2.26
350.09
studied for use in packaging industries. The PBAT/Ag2O nanocompos-
PA‐3
39.83
2.46
290.40
ites are the class of biodegradable material of bio origin suitable for
PA‐5
40.06
2.94
245.61
manufacturing of packaging films. The oxygen transmission rate of
PA‐7
47.70
3.50
227.60
Ag2O‐based nanocomposite PBAT films was determined, and the
PA‐10
31.42
3.63
105.38
results are shown in Table 4. The oxygen permeability ranged from
Samples
Abbreviations: Ag2O, silver oxide; PBAT, poly (butylene adipate‐co‐ terephthalate).
3.6
|
Oxygen transmission rate
1150.5 to 300.2 cc m−2 per day, depending on the driving force used and on the nanoparticle content, whereas the control recorded 1150 cc m−2 per day. The PBAT and Ag2O nanoparticles concentration influences oxygen permeability significantly. It was also observed that
TABLE 4
Barrier properties of PBAT/Ag2O nanocomposite films
the maximum reduction in oxygen permeability over the control was 76% for the Ag2O 10%. A pronounced decrease in permeability with
Oxygen Water Vapor Composition of PBAT/Ag2O Transmission Rate, Transmission Rate, Nanocomposites, wt% cc m−2 per 24 h g m−2 per 24 h
the higher driving force is observed. It reduces about 76% of its initial
100/0
1150.1 ± 3.1
132.4 ± 5.0
decreased with the increase in Ag2O percent.
99/1
962.9 ± 2.0
117.7 ± 5.2
97/3
791.3 ± 3.4
91.9 ± 4.8
95/5
640.1 ± 3.0
83.5 ± 5.0
3.7
93/7
389.7 ± 2.7
70.2 ± 5.4
The WVTR is one of the most important parameters for biodegradable
90/10
300.3 ± 2.5
57.4 ± 4.9
films. The WVTR to the pure PBAT and nanocomposites with different
Abbreviations: Ag2O, silver oxide; PBAT, poly (butylene adipate‐co‐ terephthalate).
FIGURE 12
Antimicrobial activity of different loadings of poly (butylene adipate‐co‐ terephthalate) nanocomposite films against (A) Staphylococcus aureus and (B) Klebsiella pneumonia [Colour figure can be viewed at wileyonlinelibrary.com]
value at 10% Ag2O content. It was observed that oxygen permeability
|
Water vapor transmission rate
concentrations of Ag2O is shown in Table 4. By adding the nanoparticles and increasing the film thickness, the WVTR of the film decreased.
8
VENKATESAN
ET AL.
Most of the reduction in gas penetration was observed in the Ag2O
One of the authors R.V. specially thanks to The Director, Centre for
concentration of 10%. In such treatment, the WVTR of the film
Research, Anna University, for providing funding support (Proc No.
decreased by 29%. The water vapor penetration reduction is due to
CR/ACRF/2013‐10; dated: 27.02.2013), to perform the research work.
incorporation of nanoparticles because it would result in a more complicated path for oxygen gases to penetrate. Ray et al25 reported
CONFLIC T OF IN TE RE ST
similar results for water vapor permeation after incorporation of
No conflict of interest declared.
nanoparticles. Moreover, the results of this study confirmed by increasing the Ag2O content; the WVTR shows a reduction.
RE FE RE NC ES 1. Jennifer MS, Michael D, Edward JW. Biomaterials. 2007;28:3269
3.8
|
Antimicrobial activity
As these types of nanocomposite films are the emerging in the field of packaging applications, in this context, antimicrobial property must be one of the characteristics to find its applications in food packaging. The
2. Rhim JW, Hong SI, Chang‐Sik H. LWT – Food Sci Tech. 2009;42(612): 3. Guichao L, Song Y, Wang J, et al. LWT – Food Sci Tech. 2014;57(562): 4. Na J, Chengzhen L, Shuangling Z, Xiong L, Qingjie S. LWT – Food Sci Tech. 2016;74(311):
antimicrobial activity of the films is checked against K pneumonia and
5. Herrera M, Carrion P, Baca P, Liebana J, Castillo A. Microbios. 2001;104:141
S aureus, and the results are shown in Figure 12. As evident from the
6. Nonaka T, Noda E, Kurihara S. J Appl Poly Sci. 2000;77:1077
images that the PBAT films do not show clear microbial inhibition
7. Schierholz JM, Beuth J, Pulverer G. Ame J Medi. 1999;107:101
zones,26 whereas Ag2O NPs incorporated PBAT nanocomposite films
8. Gong P, Huimin L, Xiaoxiao H, et al. Nanotechnology. 2007;18:285604
exhibit distinctive microbial inhibition zones for both the microorganisms,26 the zones of inhibition diameter of PBAT/Ag2O nanocomposites are 11.0, 12.4, 16.1, 18.2, 19.0, and 19.7 mm against K pneumonia and 11.0, 11.3, 12.0, 13.0, 13.7, and 14.0 mm against S aureus with loadings 0, 1, 3, 5, 7, and 10 wt% Ag2O nanoparticles,
9. Venkatesan R, Rajeswari N. Polym Adv Tech. 2017;28:20 10. Akbar V, Seyed MO, Afshin A, Mehdi A. LWT – Food Sci Tech. 2016;71(88): 11. De Silva RT, Mantilaka MMMGPG, Ratnayake SP, Amaratunga GAJ, Nalin de Silva KM. Carbohy Polym. 2017;157(739):
respectively. This indicates that Ag2O nanoparticles exhibit fair antimi-
12. Gu H, Ho PL, Tong E, Wang L, Xu B. Nano Lett. 2003;3:1261
crobial action against K pneumonia and S aureus.
13. Ahmad Z, Pandey R, Sharma S, Khuller GK. Ind J Chest Dis Allied Sci. 2005;48:171
4
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C O N CL U S I O N S
14. Venkatesan R, Rajeswari N. Silicon. 2016. https://doi.org/10.1007/ s12633‐015‐9402‐8
In summary, the PBAT‐based nanocomposites were prepared by solu-
15. Witt U, Einig T, Yamamoto M, Kleeberg L, Deckwer WD, Muller RJ. Chemosphere. 2001;44:289
tion casting method using Ag2O as a nanofiller. The studies of FT‐IR
16. Someya Y, Sugahara Y, Shibata M. J Appl Poly Sci. 2005;95:386
show the formation of nano polymer matrix of PBAT, and the results
17. Jung‐Hung C, Chin‐Chi C, Ming‐Chien Y. J Polym Res. 2011;18:2151
of SEM image analysis reveal the morphological nature of the prepared
18. Mohanty S, Nayak SK. Polym Compo. 2010;31:1194
films. It is found that the addition of Ag2O nanoparticles in the films
19. Rhim JW, Hong SI, Park HM, Ng PKW. J Agri and Food Chem. 2006;54:5814
improves the mechanical strength and shows good antimicrobial properties. The tensile strength of the prepared nanocomposite films was increased from 30.60 to 47.70 MPa by increasing weight percentage of nanoparticles in the film from 1 to 7 wt%. The film becomes stiff at higher loading of 10 wt% of Ag2O nanoparticles. The increase in filler loading shows good oxygen permeability from 1150 to
20. Venkatesan R, Rajeswari N, Thendral T. J Polym Mate. 2015;32:93 21. Jin Y, Sun‐Dong K. J Phy Chem B. 2003;107:12902 22. Tripathi S, Mehrotra GK, Dutta PK. Bull Mater Sci. 2011;34:29 23. Hasegawa N, Okamoto H, Kato M, Usuki A. J Appl Poly Sci. 2000;78:1918
300 cc m−2 per 24 hours and also effective antimicrobial properties.
24. Nafchi AM, Nassiri R, Sheibani S, Ariffin F, Karim AA. Carbohy Polym. 2012;96:233
Based on the results, it is found that increase in nanofiller wt%
25. Ray SS, Okamoto M. Prog Polym Sci. 2003;28:1539
improves mechanical, oxygen permeability, and antimicrobial proper-
26. Venkatesan R, Rajeswari N. Polym Adv Tech. 2017. https://doi.org/ 10.1002/pat.4042
ties but at a higher loading of PA‐10 film, becomes stiff. Hence, it is concluded that the prepared film with 7 wt% of nanofiller with PBAT can be selected as a suitable film to find application for suitable food packaging applications.
How to cite this article: Venkatesan R, Rajeswari N, Tamilselvi A. Antimicrobial, mechanical, barrier, and thermal properties of bio‐based poly (butylene adipate‐co‐terephthalate) (PBAT)/
ACKNOWLEDGEMEN TS We thank Dr K Palanivelu, Principal, Cental Institute of Plastics Engineering and Technology, India, for helping the mechanical studies.
Ag2O nanocomposite films for packaging application. Polym Adv Technol. 2017;1–8. https://doi.org/10.1002/pat.4089
