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Development of nanocomposites from polymer blends: Effect of organoclay on the morphology and mechanical properties
Journal of Alloys and Compounds xxx (2013) xxx–xxx
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Development of nanocomposites from polymer blends: Effect of organoclay on the morphology and mechanical properties Tomás J.A. Mélo ⇑, Edcleide M. Araújo, Gustavo F. Brito, Pankaj Agrawal Department of Materials Engineering, Federal University of Campina Grande, Campina Grande PB 58429-900, Brazil
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Polymer blends Organoclay Nanocomposites
a b s t r a c t In this work the effect of 2.5% and 5% (wt) of organoclay on the mechanical properties and morphology of PLA/EMA-GMA blend was investigated. The nanocomposites were prepared by extrusion followed by injection molding and characterized by X-ray diffraction (XRD), mechanical properties and Scanning Electron Microscopy (SEM). The results showed that better impact strength was achieved when 2.5% (wt) of clay was added to the PLA/EMA–GMA blend. XRD results indicated that this nanocomposite presented a partially exfoliated structure. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction With the increasing demand for new materials, polymer blends emerged as an option for the synthesis of new polymers. Polymer nanocomposites, composites were the filler exhibit at least one dimension in the nanometric scale (10 9 m) emerged as an alternative for new polymers, since they exhibit better properties than those of neat polymers and conventional composites, even with small amount of filler (<10% wt) [1]. Polymer/clay nanocomposites have been of great interest, since the clay is abundant in the nature and of low cost. The montmorillonite (MMT) clay is the most used. To become compatible with most of the polymers de MMT clay needs to be organically modified by a surfactant becoming organophilic (OMMT). The clay nanometric particles may act suppressing the coalescence between the dispersed phases in the blend, thereby decreasing the dispersed phase domains size. In recent years, research with biopolymers such as Poly (lactic acid) – PLA and its nanocomposites, has attracted the attention of researchers, around the world. PLA is an aliphatic polyester produced by chemical synthesis from lactic acid obtained by the bacterial fermentation of glucose extracted from corn, a renewable source. It is a biocompatible, biodegradable and compostable thermoplastic polymer (semi-crystalline or amorphous) [2]. Balakrishnan et al. [3] investigated the morphological and thermal properties of PLA and Linear Low Density Polyethylene (LLDPE) toughened nanocomposites. They found that the Young’s and flexural modulus improved with increasing loadings of MMT. The impact strength of PLA and PLA/ MMT nanocomposite increased with the addition of LLDPE. The ⇑ Corresponding author. E-mail addresses: [email protected] (T.J.A. Mélo), [email protected]. edu.br (E.M. Araújo), [email protected] (G.F. Brito), [email protected] (P. Agrawal).
addition of MMT and LLDPE improved the thermal stability of PLA/MMT and PLA/LLDPE/OMT nanocomposites. The morphological analyses indicated that for the PLA/MMT/LLDPE system a nanocomposite with intercalated structure was formed and the clay particles were well dispersed. Fukushima et al. [4] studied the effect of the clay type and loading (5% and 10%) on the thermal and mechanical properties of PLA nanocomposites. They observed that the addition of the clays to induced the PLA crystallization by nucleation. According to the authors the highest mechanical improvements in the PLA matrix were obtained with the addition of 10% clay. In previous work [5] we investigated the combining effect of Ethylene–Methyl Acrylate–Glycidyl Methcrylate (EMA–GMA) terpolymer and organoclay on the toughening of PLA. The amount of clay used was 2.5% and 5% (wt) and the amount of EMA–GMA was kept fixed at 12.5% (wt). It was found that EMA–GMA terpolymer presented a good interaction with the CL20A organoclay, especially when the amount of clay used was 2.5% (wt) resulting in higher impact strength of PLA. The aim of this work is to investigate the effect of the organoclay on the mechanical properties and morphology of PLA/EMA–GMA/clay nanocomposites. 2. Experimental 2.1. Materials Poly (lactic acid) – PLA Ingeo 2002D, Natureworks, MFI = 4–8 g/10 min was supplied by Cargill. Ethylene–Methyl Acrylate–Glycidyl Methacrylate (EMA–GMA), MFI = 6 g/10 min, Lotader AX8900 was provided by Arkema. Cloisite 20A (CL20A) organoclay was obtained from Southern Clay Products. 2.2. Methods Before Mixing with EMA–GMA and CL20A organoclay, PLA was dried under vacuum at 80 °C for 4 h. The composites containing 2.5% and 5% (wt) of CL20A organoclay were prepared in a counter-rotating twin screw extruder attached to
0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.11.151
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151
T.J.A. Mélo et al. / Journal of Alloys and Compounds xxx (2013) xxx–xxx
Table 1 Composition of the blend and the composites. PLA (wt%)
EMA–GMA (wt%)
C20A (wt%)
PLA (neat) PLA/EMA–GMA (80/20) PLA/EMA–GMA/C20A (77.5/20/ 2.5) PLA/EMA–GMA/C20A (75/20/5)
100 80 77.5
0 20 20
0 0 2.5
75
20
5
Impact Strength (J/m)
Systems
3.0
80
2.8 2.6
60
2.4 2.2 40
1.8 a
c
b
d
Fig. 2. Impact strength and tensile modulus of PLA/EMA–GMA/C20A blend and the nanocomposites: (a) PLA; (b) PLA/EMA–GMA (80/20); (c) PLA/EMA–GMA/C20A (77.5/20/2.5); (d) PLA/EMA–GMA/C20A (75/20/5).
the tensile modulus decreased. This was already expected, since EMA–GMA used in this work is very flexible and has lower elastic modulus (8 MPa) than PLA (3.2 GPa). The addition of 2.5% (wt) of clay to the PLA/EMA–GMA blend increased the impact strength. It is known that the clay suppress the coalescence between the dispersed phase particles decreasing their domains size by decreasing the interfacial tension between the blends phases. This decrease in the EMA–GMA domains size may be responsible for the increase in the impact strength. The tensile modulus was decreased with the addition of 2.5% (wt) of clay to the PLA/EMA–GMA blend. When the amount of clay added to the PLA/EMA–GMA was increased from 2.5% to 5% (wt) there was a decrease in the impact strength and an increase in the tensile modulus. The decrease in the impact strength may be ascribed to the formation of clay agglomerates, while the increase in the tensile modulus may be attributed to the higher amount of clay used. As observed in our previous work [5] the system containing 2.5% (wt) of C20A organoclay showed the highest impact strength. It was also observed that the increase on the amount of EMA–GMA terpolymer from 12.5% (wt) [6] to 20% decreased the impact strength of PLA/EMA–GMA and PLA/EMA– GMA/C20A systems. This may be attributed to increase in the coalescence of EMA–GMA particles with the increase in the EMA–GMA content. According to Sundararaj and Macosco [7], coalescence occurs at higher dispersed phase concentrations, resulting in larger particles domains sizes. Fig. 3 shows the SEM micrographs of the PLA/EMA–GMA blend and the nanocomposites. Fig. 3a shows the SEM micrograph of the PLA/EMA–GMA blend. This blend shows a good adhesion between
Fig. 1 shows the XRD patterns of the C20A organoclay, PLA/ EMA–GMA blend and the composites. It may be observed that the C20A organoclay (Fig. 1a) shows two characteristic diffraction peaks: one at 2h of 7.0°, corresponding to a d(002) basal spacing of 12.4 Å, and the other at 2h of 3.6°, corresponding to a d(001) basal spacing of 24.5 Å. When 2.5% (wt) of the C20A clay is added to the PLA/EMA–GMA blend only a small shoulder is observed at around 2h 4.2° indicating that a nanocomposite with an partially exfoliated structure was obtained. For the PLA/EMA–GMA/C20A composite containing 5% of C20A clay, the clay peaks were shifted towards lower 2h angles (from 7.0° and 3.6° to 4.2 and 2.6 respectively) indicating that a nanocomposite with intercalated structure was obtained. Fig. 2 shows the mechanical properties (impact strength and tensile modulus) of the PLA/EMA–GMA blend and the nanocomposites. It may be observed that the addition of the EMA–GMA terpolymer to PLA substantially increased the impact strength. This may be attributed to the reaction between the epoxy groups present in GMA with either carboxyl or hydroxyl groups present in PLA [6] forming a copolymer in situ at the interface. On the other hand,
(b)
C20A
PLA/EMA-GMA/CL20A (75/20/5)
Intensity (a.u.)
PLA/EMA-GMA/CL20A (77.5/20/2.5)
PLA/EMA-GMA (80/20)
12.4
2
4
6
2θ (degrees)
PLA
8
3.2
20
3. Results and discussion
24.5
Impact Strength Tensile Modulus
2.0
a Haake System 90 torque rheometer. The thermal profile from hopper to die was 160:180:180:180:180 °C. Neat PLA and the PLA/EMA–GMA blend were prepared under the same processing conditions. The composition of the blend and the composites is shown in Table 1. Samples for tensile and Izod impact strength tests were Injection molded at 180 °C using a Fluidmec H30/40 Injector. The mold temperature was 20 ± 2 °C. The degree of dispersion (intercalation and/or exfoliation) of the clay in the PLA/ EMA–GMA blend was evaluated by X-ray Diffraction (XRD) using a Shimadzu XRD-6000 X-ray diffractometer (Cu Ka, k = 0.1542 nm). Tensile tests were carried out, according to ASTM D638 under room temperature, using a Shimadzu AG IS 100 kN universal testing machine, at crosshead speed of 50 mm/min. Izod impact strength tests were performed, according to ASTM D256, in notched samples using a pendulum of 2.75 J. The fracture surfaces of the samples subjected to the impact strength tests were coated with gold and the morphology was analyzed by Scanning Electron Microscopy (SEM) using a Shimadzu SSX-550 Super Scan Scanning Electronic Microscope.
(a)
3.4
100
Tensile Modulus (GPa)
2
10
5
10
15
20
25
2θ (degrees)
Fig. 1. XRD patterns: (a) C20A organoclay; (b) PLA/EMA–GMA blend and the nanocomposites.
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151
30
T.J.A. Mélo et al. / Journal of Alloys and Compounds xxx (2013) xxx–xxx
3
Fig. 3. SEM micrographs of the blend and the nanocomposites: (a) PLA/EMA–GMA (80/20); (b) PLA/EMA–GMA/C20A (77.5/20/2.5); (c) PLA/EMA–GMA/C20A (75/20/5).
the PLA and EMA–GMA phases. As discussed earlier, the epoxy groups of EMA–GMA react with either carboxyl or hydroxyl groups of PLA forming a copolymer in situ at the interface resulting in good impact strength as observed in Fig. 2. However large EMA–GMA particles are still observed. It may be observed that the addition of 2.5% (wt) of C20A organoclay to the PLA/EMA–GMA (Fig. 3b) blend substantially decreased the EMA–GMA particles domain size thereby improving the impact strength as observed in Fig. 2. When the amount of clay added to the PLA/EMA–GMA blend was increased from 2.5% to 5% (Fig. 3c) some clay agglomerates may be observed. These agglomerates may be responsible for the decrease in the impact strength (Fig. 2). 4. Conclusions The aim of this work was to investigate the effect of the organoclay on the mechanical properties and morphology of PLA/EMA– GMA blend. The nanocomposites containing 2.5% and 5% (wt) of C20A organoclay were characterized by XRD, mechanical properties and SEM. XRD results showed that the PLA/EMA–GMA/C20A nanocomposite containing 2.5% of organoclay presented a partially exfoliated structure while the nanocomposite containing 5% of organoclay presented an intercalated structure. The better impact
strength was achieved when 2.5% of organoclay was added to the PLA/EMA–GMA blend. The addition of the organoclay to the PLA/ EMA–GMA blend substantially decreased the EMA–GMA domains size. Acknowledgements The authors thank Arkema for providing EMA–GMA terpolymer and CAPES and CNPq for the financial support. References [1] T. Kashiwagi, R.H. Harris Jr., X. Zhang, R.M. Briber, B.H. Cipriano, S.R. Haghawan, W.H. Awad, J.R. Shields, Polymer 45 (2004) 881–891. [2] R.M. Rasal, A.V. Janorkar, D.E. Hirt, Prog. Polym. Sci. 35 (2010) 338–356. [3] H. Balakrishnan, A. Hassan, M.U. Wahit, A.A. Yussuf, S.B.A. Razak, Mater. Des. 31 (2010) 3289–3298. [4] K. Fukushima, D. Tabuani, M. Arena, M. Gennari, G. Camino, Reac. Func. Polym. 73 (2013) 540–549. [5] G.F. Brito, P. Agrawal, E.M. Araújo, T.J.A. Mélo, Combining effect of ethylene/ methyl acrylate/glycidyl methacrylate terpolymer and organoclay on the toughening of poly (lactic acid), Polym. Eng. Sci. DOI 10.1002/pen.23739, 2013. (in press). [6] G.F. Brito, P. Agrawal, E.M. Araújo, T.J.A. Mélo, Polímeros 22 (2012) 427–429. [7] U. Sundararaj, C.W. Macosko, Macromolecules 28 (1995) 2647–2657.
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: www.elsevier.com/locate/jalcom
Development of nanocomposites from polymer blends: Effect of organoclay on the morphology and mechanical properties Tomás J.A. Mélo ⇑, Edcleide M. Araújo, Gustavo F. Brito, Pankaj Agrawal Department of Materials Engineering, Federal University of Campina Grande, Campina Grande PB 58429-900, Brazil
a r t i c l e
i n f o
Article history: Available online xxxx Keywords: Polymer blends Organoclay Nanocomposites
a b s t r a c t In this work the effect of 2.5% and 5% (wt) of organoclay on the mechanical properties and morphology of PLA/EMA-GMA blend was investigated. The nanocomposites were prepared by extrusion followed by injection molding and characterized by X-ray diffraction (XRD), mechanical properties and Scanning Electron Microscopy (SEM). The results showed that better impact strength was achieved when 2.5% (wt) of clay was added to the PLA/EMA–GMA blend. XRD results indicated that this nanocomposite presented a partially exfoliated structure. Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction With the increasing demand for new materials, polymer blends emerged as an option for the synthesis of new polymers. Polymer nanocomposites, composites were the filler exhibit at least one dimension in the nanometric scale (10 9 m) emerged as an alternative for new polymers, since they exhibit better properties than those of neat polymers and conventional composites, even with small amount of filler (<10% wt) [1]. Polymer/clay nanocomposites have been of great interest, since the clay is abundant in the nature and of low cost. The montmorillonite (MMT) clay is the most used. To become compatible with most of the polymers de MMT clay needs to be organically modified by a surfactant becoming organophilic (OMMT). The clay nanometric particles may act suppressing the coalescence between the dispersed phases in the blend, thereby decreasing the dispersed phase domains size. In recent years, research with biopolymers such as Poly (lactic acid) – PLA and its nanocomposites, has attracted the attention of researchers, around the world. PLA is an aliphatic polyester produced by chemical synthesis from lactic acid obtained by the bacterial fermentation of glucose extracted from corn, a renewable source. It is a biocompatible, biodegradable and compostable thermoplastic polymer (semi-crystalline or amorphous) [2]. Balakrishnan et al. [3] investigated the morphological and thermal properties of PLA and Linear Low Density Polyethylene (LLDPE) toughened nanocomposites. They found that the Young’s and flexural modulus improved with increasing loadings of MMT. The impact strength of PLA and PLA/ MMT nanocomposite increased with the addition of LLDPE. The ⇑ Corresponding author. E-mail addresses: [email protected] (T.J.A. Mélo), [email protected]. edu.br (E.M. Araújo), [email protected] (G.F. Brito), [email protected] (P. Agrawal).
addition of MMT and LLDPE improved the thermal stability of PLA/MMT and PLA/LLDPE/OMT nanocomposites. The morphological analyses indicated that for the PLA/MMT/LLDPE system a nanocomposite with intercalated structure was formed and the clay particles were well dispersed. Fukushima et al. [4] studied the effect of the clay type and loading (5% and 10%) on the thermal and mechanical properties of PLA nanocomposites. They observed that the addition of the clays to induced the PLA crystallization by nucleation. According to the authors the highest mechanical improvements in the PLA matrix were obtained with the addition of 10% clay. In previous work [5] we investigated the combining effect of Ethylene–Methyl Acrylate–Glycidyl Methcrylate (EMA–GMA) terpolymer and organoclay on the toughening of PLA. The amount of clay used was 2.5% and 5% (wt) and the amount of EMA–GMA was kept fixed at 12.5% (wt). It was found that EMA–GMA terpolymer presented a good interaction with the CL20A organoclay, especially when the amount of clay used was 2.5% (wt) resulting in higher impact strength of PLA. The aim of this work is to investigate the effect of the organoclay on the mechanical properties and morphology of PLA/EMA–GMA/clay nanocomposites. 2. Experimental 2.1. Materials Poly (lactic acid) – PLA Ingeo 2002D, Natureworks, MFI = 4–8 g/10 min was supplied by Cargill. Ethylene–Methyl Acrylate–Glycidyl Methacrylate (EMA–GMA), MFI = 6 g/10 min, Lotader AX8900 was provided by Arkema. Cloisite 20A (CL20A) organoclay was obtained from Southern Clay Products. 2.2. Methods Before Mixing with EMA–GMA and CL20A organoclay, PLA was dried under vacuum at 80 °C for 4 h. The composites containing 2.5% and 5% (wt) of CL20A organoclay were prepared in a counter-rotating twin screw extruder attached to
0925-8388/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jallcom.2013.11.151
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151
T.J.A. Mélo et al. / Journal of Alloys and Compounds xxx (2013) xxx–xxx
Table 1 Composition of the blend and the composites. PLA (wt%)
EMA–GMA (wt%)
C20A (wt%)
PLA (neat) PLA/EMA–GMA (80/20) PLA/EMA–GMA/C20A (77.5/20/ 2.5) PLA/EMA–GMA/C20A (75/20/5)
100 80 77.5
0 20 20
0 0 2.5
75
20
5
Impact Strength (J/m)
Systems
3.0
80
2.8 2.6
60
2.4 2.2 40
1.8 a
c
b
d
Fig. 2. Impact strength and tensile modulus of PLA/EMA–GMA/C20A blend and the nanocomposites: (a) PLA; (b) PLA/EMA–GMA (80/20); (c) PLA/EMA–GMA/C20A (77.5/20/2.5); (d) PLA/EMA–GMA/C20A (75/20/5).
the tensile modulus decreased. This was already expected, since EMA–GMA used in this work is very flexible and has lower elastic modulus (8 MPa) than PLA (3.2 GPa). The addition of 2.5% (wt) of clay to the PLA/EMA–GMA blend increased the impact strength. It is known that the clay suppress the coalescence between the dispersed phase particles decreasing their domains size by decreasing the interfacial tension between the blends phases. This decrease in the EMA–GMA domains size may be responsible for the increase in the impact strength. The tensile modulus was decreased with the addition of 2.5% (wt) of clay to the PLA/EMA–GMA blend. When the amount of clay added to the PLA/EMA–GMA was increased from 2.5% to 5% (wt) there was a decrease in the impact strength and an increase in the tensile modulus. The decrease in the impact strength may be ascribed to the formation of clay agglomerates, while the increase in the tensile modulus may be attributed to the higher amount of clay used. As observed in our previous work [5] the system containing 2.5% (wt) of C20A organoclay showed the highest impact strength. It was also observed that the increase on the amount of EMA–GMA terpolymer from 12.5% (wt) [6] to 20% decreased the impact strength of PLA/EMA–GMA and PLA/EMA– GMA/C20A systems. This may be attributed to increase in the coalescence of EMA–GMA particles with the increase in the EMA–GMA content. According to Sundararaj and Macosco [7], coalescence occurs at higher dispersed phase concentrations, resulting in larger particles domains sizes. Fig. 3 shows the SEM micrographs of the PLA/EMA–GMA blend and the nanocomposites. Fig. 3a shows the SEM micrograph of the PLA/EMA–GMA blend. This blend shows a good adhesion between
Fig. 1 shows the XRD patterns of the C20A organoclay, PLA/ EMA–GMA blend and the composites. It may be observed that the C20A organoclay (Fig. 1a) shows two characteristic diffraction peaks: one at 2h of 7.0°, corresponding to a d(002) basal spacing of 12.4 Å, and the other at 2h of 3.6°, corresponding to a d(001) basal spacing of 24.5 Å. When 2.5% (wt) of the C20A clay is added to the PLA/EMA–GMA blend only a small shoulder is observed at around 2h 4.2° indicating that a nanocomposite with an partially exfoliated structure was obtained. For the PLA/EMA–GMA/C20A composite containing 5% of C20A clay, the clay peaks were shifted towards lower 2h angles (from 7.0° and 3.6° to 4.2 and 2.6 respectively) indicating that a nanocomposite with intercalated structure was obtained. Fig. 2 shows the mechanical properties (impact strength and tensile modulus) of the PLA/EMA–GMA blend and the nanocomposites. It may be observed that the addition of the EMA–GMA terpolymer to PLA substantially increased the impact strength. This may be attributed to the reaction between the epoxy groups present in GMA with either carboxyl or hydroxyl groups present in PLA [6] forming a copolymer in situ at the interface. On the other hand,
(b)
C20A
PLA/EMA-GMA/CL20A (75/20/5)
Intensity (a.u.)
PLA/EMA-GMA/CL20A (77.5/20/2.5)
PLA/EMA-GMA (80/20)
12.4
2
4
6
2θ (degrees)
PLA
8
3.2
20
3. Results and discussion
24.5
Impact Strength Tensile Modulus
2.0
a Haake System 90 torque rheometer. The thermal profile from hopper to die was 160:180:180:180:180 °C. Neat PLA and the PLA/EMA–GMA blend were prepared under the same processing conditions. The composition of the blend and the composites is shown in Table 1. Samples for tensile and Izod impact strength tests were Injection molded at 180 °C using a Fluidmec H30/40 Injector. The mold temperature was 20 ± 2 °C. The degree of dispersion (intercalation and/or exfoliation) of the clay in the PLA/ EMA–GMA blend was evaluated by X-ray Diffraction (XRD) using a Shimadzu XRD-6000 X-ray diffractometer (Cu Ka, k = 0.1542 nm). Tensile tests were carried out, according to ASTM D638 under room temperature, using a Shimadzu AG IS 100 kN universal testing machine, at crosshead speed of 50 mm/min. Izod impact strength tests were performed, according to ASTM D256, in notched samples using a pendulum of 2.75 J. The fracture surfaces of the samples subjected to the impact strength tests were coated with gold and the morphology was analyzed by Scanning Electron Microscopy (SEM) using a Shimadzu SSX-550 Super Scan Scanning Electronic Microscope.
(a)
3.4
100
Tensile Modulus (GPa)
2
10
5
10
15
20
25
2θ (degrees)
Fig. 1. XRD patterns: (a) C20A organoclay; (b) PLA/EMA–GMA blend and the nanocomposites.
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151
30
T.J.A. Mélo et al. / Journal of Alloys and Compounds xxx (2013) xxx–xxx
3
Fig. 3. SEM micrographs of the blend and the nanocomposites: (a) PLA/EMA–GMA (80/20); (b) PLA/EMA–GMA/C20A (77.5/20/2.5); (c) PLA/EMA–GMA/C20A (75/20/5).
the PLA and EMA–GMA phases. As discussed earlier, the epoxy groups of EMA–GMA react with either carboxyl or hydroxyl groups of PLA forming a copolymer in situ at the interface resulting in good impact strength as observed in Fig. 2. However large EMA–GMA particles are still observed. It may be observed that the addition of 2.5% (wt) of C20A organoclay to the PLA/EMA–GMA (Fig. 3b) blend substantially decreased the EMA–GMA particles domain size thereby improving the impact strength as observed in Fig. 2. When the amount of clay added to the PLA/EMA–GMA blend was increased from 2.5% to 5% (Fig. 3c) some clay agglomerates may be observed. These agglomerates may be responsible for the decrease in the impact strength (Fig. 2). 4. Conclusions The aim of this work was to investigate the effect of the organoclay on the mechanical properties and morphology of PLA/EMA– GMA blend. The nanocomposites containing 2.5% and 5% (wt) of C20A organoclay were characterized by XRD, mechanical properties and SEM. XRD results showed that the PLA/EMA–GMA/C20A nanocomposite containing 2.5% of organoclay presented a partially exfoliated structure while the nanocomposite containing 5% of organoclay presented an intercalated structure. The better impact
strength was achieved when 2.5% of organoclay was added to the PLA/EMA–GMA blend. The addition of the organoclay to the PLA/ EMA–GMA blend substantially decreased the EMA–GMA domains size. Acknowledgements The authors thank Arkema for providing EMA–GMA terpolymer and CAPES and CNPq for the financial support. References [1] T. Kashiwagi, R.H. Harris Jr., X. Zhang, R.M. Briber, B.H. Cipriano, S.R. Haghawan, W.H. Awad, J.R. Shields, Polymer 45 (2004) 881–891. [2] R.M. Rasal, A.V. Janorkar, D.E. Hirt, Prog. Polym. Sci. 35 (2010) 338–356. [3] H. Balakrishnan, A. Hassan, M.U. Wahit, A.A. Yussuf, S.B.A. Razak, Mater. Des. 31 (2010) 3289–3298. [4] K. Fukushima, D. Tabuani, M. Arena, M. Gennari, G. Camino, Reac. Func. Polym. 73 (2013) 540–549. [5] G.F. Brito, P. Agrawal, E.M. Araújo, T.J.A. Mélo, Combining effect of ethylene/ methyl acrylate/glycidyl methacrylate terpolymer and organoclay on the toughening of poly (lactic acid), Polym. Eng. Sci. DOI 10.1002/pen.23739, 2013. (in press). [6] G.F. Brito, P. Agrawal, E.M. Araújo, T.J.A. Mélo, Polímeros 22 (2012) 427–429. [7] U. Sundararaj, C.W. Macosko, Macromolecules 28 (1995) 2647–2657.
Please cite this article in press as: T.J.A. Mélo et al., J. Alloys Comp. (2013), http://dx.doi.org/10.1016/j.jallcom.2013.11.151