- Email: [email protected]
styrene-acrylonitrile blends
Applied Clay Science 140 (2017) 112–118
Contents lists available at ScienceDirect
Applied Clay Science journal homepage: www.elsevier.com/locate/clay
Research paper
Effects of nanoclay addition on phase morphology and stability of polycarbonate/styrene-acrylonitrile blends Rafael Grande a,b,⁎, Luiz Antonio Pessan b a b
Graduate Program in Materials Science and Engineering, Federal University of São Carlos, Via Washington Luiz, Km 235, São Carlos 13565-905, SP, Brazil Department of Materials Engineering, Federal University of São Carlos, Via Washington Luiz, Km 235, São Carlos 13565-905, SP, Brazil
a r t i c l e
i n f o
Article history: Received 12 October 2016 Received in revised form 30 January 2017 Accepted 1 February 2017 Available online xxxx Keywords: Organoclay Montmorillonite Morphology Blends Extrusion
a b s t r a c t In this work, an extensive study was performed on the compatibility and morphological stability of polycarbonate/styrene-acrylonitrile (PC/SAN) blends and on the effects of nanoclay addition to these systems. PC/SAN blends of different compositions were prepared by melt extrusion and their morphologies were characterized as prepared and after annealing at high temperature to evaluate their morphological stability. The effects of nanoclay with different organic modifiers and acrylonitrile (AN) content in the SAN copolymer on the morphology of the PC/SAN blends were also evaluated. The results indicate that the nanoclay reduces the domain size of SAN phase and stabilizes the system morphology even without complete exfoliation. Organoclays particles with polar organic modifiers were preferably located inside the SAN domains, while in blends containing organoclays with nonpolar modifiers, the clay particles migrated to the interface, resulting in domain reduction and improved morphological stability. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Blending two or more polymers is an effective approach to obtain systems with properties better than the individual polymers. However, most polymer blends are thermodynamically immiscible. Polycarbonate/styrene-acrylonitrile (PC/SAN) is a typical example of an immiscible blend, which was poor mechanical properties due to high interfacial tension despite the existence of a certain degree of interaction between the components. Chaudhry et al., 1998, have demonstrated the tendency of the PC/acrylonitrile-butadiene-acrylonitrile styrene (ABS) system to phase separate. PC/ABS system is similar to PC/SAN and shows low morphological stability, restricting the practical application of this material. To achieve high-performance polymer blends, it is essential to control and stabilize the blend morphology. Compatibility of components in polymer blends is generally achieved by incorporating graft or block copolymers, which reduce the domain sizes and enhance the interfacial adhesion between the phases (Macosko et al., 1996). However, the production of these compatibilizers is usually difficult and expensive. Several recent studies have reported the compatibilizing effect of organoclay additives in immiscible polymer blends (Vo and Giannelis, 2007; Filippone et al., 2010; Moghbelli et al., 2010; Tiwari and Paul, 2011; Nazari et al., 2012; Chen et al., 2013; Labaume et al., 2013a, 2013b). The use of organoclay additives has many advantages over the ⁎ Corresponding author. E-mail address: [email protected] (R. Grande).
http://dx.doi.org/10.1016/j.clay.2017.02.001 0169-1317/© 2017 Elsevier B.V. All rights reserved.
traditional approach of adding block copolymers, such as the ready availability of clays, lower cost, and easy processability. The effect of clay platelets on the morphology of polymer blends is yet to be completely explored. When the organoclay is located in the continuous phase, the domain size of the dispersed phase is reduced because the organoclay increases the viscosity in the matrix and acts as a physical barrier, reducing the coalescence rate of the dispersed phase. To maximize this effect, it is necessary to have the clay platelets located at the interface of the system (Si et al., 2006; Hemmati et al., 2014). On the other hand, when the clay is located within the dispersed phase, it appears to increase the dispersed phase domain size (Gahleitner et al., 2006; Sinha Ray et al., 2004; Zhang et al., 2012). Thus, the present study was designed to evaluate the effects of organoclay (OC) addition on compatibility, morphology and morphological stability of PC/SAN blends. The PC/SAN system is particularly interesting because the viscosity and polarity of the system can be modified by using SAN copolymers with different AN content (Callaghan et al., 1993; Hanafy et al., 2004), which might lead to a change in the localization of the organoclays. 2. Experimental 2.1. Materials A PC resin (Lexan® 101) with a melt flow index of 7 g/10 min (300 °C/1.2 kg), purchased from SABIC, was used as the matrix. Two SAN resins (supplied by BASF), Luran 358 N and Luran 388 S with
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
113
Fig. 1. WAXD patterns of the neat organoclays Cloisite® 30B and Cloisite® 20A and the ternary (PC/SAN/organoclay) systems.
melt flow indices of 6.3 g/10 min (230 °C/3.8 kg) and 2.6 g/10 min (230 °C/3.8 kg), respectively, and AN content of 21 wt% and 28 wt%, respectively, were used. These SAN resins will hereafter be denoted (based on the AN content) as SAN21 and SAN28, respectively. Organoclays Cloisite® 20A and Cloisite® 30B were purchased from Southern Clay Products Inc. Cloisite® 30B is a natural montmorillonite with, was a cation exchange capacity near 90 meq/100 g, which was treated with methyl tallow bis-2-hydroxyethyl quaternary ammonium chloride to form a polar organoclay. Cloisite® 20A is also a natural montmorillonite, which was treated with a low-polarity dimethyl dehydrogenated tallow quaternary ammonium chloride to form a non-polar organoclay. The difference in the polarity of the clays can be expected to alter the position of the organoclay platelets in PC/SAN mixture. The location of the clay platelets might also be altered with an increase in the AN content because SAN is expected to interact more with Cloisite ®30B than with Cloisite ®20A due SAN polarity.
2.3. Annealing The specimens were annealed at 170 °C for 60 min to evaluate the morphological stability of the PC/SAN/organoclay blends. The treatment conditions are less aggressive than that normally reported in the literature (Vo and Giannelis, 2007; Triantou and Tarantili, 2014). The altered annealing conditions were necessary to avoid organoclay degradation and to prevent bubble formation in samples, which could negatively affect transmission electron microscopy (TEM) observations. 2.4. Wide angle X-ray diffraction (WAXD) X-ray analysis was carried out in reflective mode (in a Rigaku Multiflex diffractometer) with Cu-Kα rays (wavelength = 1.542 Å). The scan rate was 1°/min and the 2θ range was 1–10°. 2.5. Morphology characterization
2.2. Blend preparation All the materials were vacuum dried at 90 °C for 24 h prior to melt processing. The PC/SAN/organoclay blends were prepared in a twinscrew extruder (B & P Process Equipment Systems, model MP19, with L/D ratio = 25 mm and length = 19 mm). The temperature profile used was 185, 195, 195, 200, and 205 °C and the screw speed was set at 140 rpm. The extrudates were pelletized and then vacuum dried again for 8 h at 80 °C. The PC/SAN/organoclay pellets were molded in an injection-molding machine (Arburg 270 V) with an injection pressure of 94 MPa and a holding pressure of 60 MPa. The temperature profile used was 200, 220, 230, 230, 240 °C and the mold temperature was set at 65 °C. The specimens were prepared using an injection mold that produces samples following ASTM D256-06 standards used in Izod impact tests. The composition of the PC/SAN blend was fixed at 70/30 wt% ratio and the organoclay content was 1, 3, or 5 wt%. For comparison, PC/ SAN21 and PC/SAN28 blends without the clays were also prepared under the conditions described above.
The SAN dispersed domains and the location of the OC in the blends were evaluated by TEM. The Izod specimens were sliced to reveal the Table 1 d-Value obtained from the XRD patterns. Neat Cloisite® 30B
d001 (Å) 18.0
PC/SAN21–1% 30B PC/SAN21–3% 30B PC/SAN21–5% 30B PC/SAN28–1% 30B PC/SAN28–3% 30B PC/SAN28–5% 30B Neat Cloisite® 20A PC/SAN21–1% 20A PC/SAN21–3% 20A PC/SAN21–5% 20A PC/SAN28–1% 20A PC/SAN28–3% 20A PC/SAN28–5% 20A
28.5 29.5 30.5 28.5 30.5 29.5 24.9 29.4 29.4 29.8 28.7 29.4 29.4
114
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Fig. 2. TEM images of a) PC/SAN21, b) PC/SAN21-1%30B, c) PC/SAN21-3%30B, and d) PC/SAN21-5%30B. The images in the top and bottom panel are from samples without and with annealing, respectively.
core of the sample perpendicular to the injection flow. Then, the cross sections were reduced to trapezoids and cryogenically ultrathinned into sections of ~ 40 nm in thickness using an ultramicrotome (Leica Ultracut equipped with a diamond knife Diatome 45°). The temperature was maintained constant at − 45 °C and the sectioning speed was 0.2 mm/s. After sectioning, the samples were placed on a copper 400 mesh grid. The grids containing the samples were then stained with RuO4 for 8 h at room temperature. The ruthenium attached preferably to the aromatic rings of the SAN monomeric units, which provided the contrast necessary for TEM analysis (carried out in a FEI Magellan model L400 microscope). 3. Results and discussion 3.1. WAXD analysis The X-ray analysis were performed only in samples before the annealing process in order to verify the effect of composition and melt processing on the d-value of Cloisite® 30B and Cloisite® 20A on PC/SAN blends.
X-ray diffraction (XRD) patterns of the neat Cloisite® 30B and the ternary systems (PC/SAN/organoclay) with different AN content, SAN21 and SAN28 are presented in Fig. 1 a) and b). The pattern acquired from the 30B clay contains a reflection at 2θ = 4.8°, corresponding to an average d-value of 18.0 Å. The d001 reflection shifts to smaller angles (2θ of 3.2°) and broadens, indicating an increase in the d-value caused by the diffusion of the polymer molecules into the clay interlayer spaces and possibly because of intercalation/exfoliation (Najafi et al., 2012; Triantou and Tarantili, 2014). Furthermore, a second reflection was observed at higher angles, near 2θ = 6.2° (d-value of 18.0 Å). This reflection is explained as a partial collapse of clay interlayer spaces. The high intensity of the reflection and its shift to higher angles is an indication of significant decomposition of the clay modifiers, which can be attributed to the processing conditions used. The detachment/thermal degradation of organic modifiers in Cloisite® 30B was expected since many other works involving others polymeric systems have shown similar results even in mild processing conditions which the d001 reflection shifting to higher angle is attributed to the degradation of the surfactant, which leads to the collapse of interlayer spaces, reducing the interlayer
Fig. 3. TEM images of a) PC/SAN28, b) PC/SAN28-1%30B, c) PC/SAN28-3%30B, and d) PC/SAN28-5%30B. Top and bottom panels show images from samples without and with annealing, respectively.
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
115
Fig. 4. TEM images of the ternary systems containing the 30B clay. a) PC/SAN21-1%, b) PC/SAN21-3%, c) PC/SAN21-5%, d) PC/SAN28-1%, e) PC/SAN28-3%, and f) PC/SAN28-5%.
distance. (López-Quintanilla et al., 2006; Cervantes-Uc et al., 2007; Chinellato et al., 2008; Valera-Zaragoza et al., 2008; Martins et al., 2009). Benali et al., 2008 showed that the Cloisite® 30B organoclay structure collapse in polyethylene/Cloisite® 30B melt intercalated at 175 °C or by simple drying at 180 °C by 2 h. The authors showed that the decrease of d-spacing from 18 to 14 Å is related with a double bound oxidation of the ammonium alkyl chain. Thus, for both the PC/SAN systems prepared with Cloisite® 30B, it can be confirmed that while a part of the clay content was intercalated, another part was thermally degraded. The Thermal degradation/detachment of organic modifiers on Cloisite® 30B could not be avoided even using mild processing conditions for PC (240 °C) which, cannot be easily processed by injection molding bellow this temperature because of its high viscosity. Additionally, the PC/SAN28/30B system appears to show a broader d001 diffraction in comparison to the PC/ SAN21/30B system, indicating better exfoliation/intercalation. Therefore, increasing the AN content in SAN may improve the interaction between the SAN molecules and the Cloisite® 30B clay modifier, facilitating diffusion into the interlayer spaces. This results will be corroborated by TEM analysis. In the XRD pattern of Cloisite® 20A, the d001 diffraction can be observed at 2θ = 3.6°, corresponding to an average d-value of 24.9 Å. In
all the compositions, the d001 value became sharper and shifted indicating the clay intercalation. Other indication of intercalation of the 20A clay in the PC/SAN21 and PC/SAN28 blends are the diffraction corresponding to d002 at 2θ–5.7°(Pluta et al., 2006). Table 1 lists the d-value obtained from the XRD patterns. Furthermore, there is no indication of thermal degradation of Cloisite® 20A. This agrees with results reported by Shah and Paul, 2006; Cui et al., 2008, which show that organic modifiers with two alkyl tails, as in Cloisite® 20A, are more stable than modifiers with just one alkyl tail (like Cloisite® 30B). 3.2. Morphology characterization 3.2.1. TEM analysis of the PC/SAN samples with Cloisite® 30B clay The TEM images in Fig. 2 PC/SAN21 and PC/SAN21/20A-organoclay samples before and after annealing are presented. As observed in Fig. 2 a1, the PC/SAN21 blend (in the absence of clay) has dispersed domains, which are distinctly elongated because of the shear flow orientation, resulting from the injection processing. The observation of long SAN domains appears to be in agreement with the results reported by Wildes et al., 1999, which indicates that the processing conditions favored coalescence in the mixture. When annealed, the PC/SAN21 blend exhibited significant changes in its morphology (Fig. 2 a2). The
Fig. 5. TEM images of a) PC/SAN21, b) PC/SAN21-1%20A, c) PC/SAN21-3%20A, and d) PC/SAN21-5%20A. Upper panel: samples without annealing. Lower panel: annealed samples.
116
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Fig. 6. TEM images of a) PC/SAN28, b) PC/SAN28-1%20A, c) PC/SAN28-3%20A, and d) PC/SAN28-5%20A. Top panel: samples without annealing. Bottom panel: annealed samples.
energy provided by annealing was sufficient to begin coalescence and shrinkage in the dispersed SAN phase. This effect was less significant than that that observed by Chaudhry et al., 1998, probably because of the use of lower annealing temperatures and the absence of an elastomeric phase in the present work. The addition of clay in the mixture leads to a rupture in the previously elongated reducing dispersed domains making the compatibilizing effect of clay evident. With increase in the clay content, the dispersed domains tend to become larger after annealing (Fig. 2 b2, c2, and d2). One possible explanation for this effect is the presence of agglomerates of clay, especially in systems with 3 and 5 wt%, which exhibits low dispersion of Cloisite® 30B. The increase in the AN content in the SAN results in slightly larger dispersed domains in the binary PC/SAN28 blend (Fig. 3 a1 and a2). This effect is expected because of the higher viscosity resulting from the higher AN content in SAN28. With increase in the 30B clay content (Fig. 3 b1, c1, and d1), the morphology changed from co-continuous to a typical well-dispersed phase in a continuous matrix, which is indicative of the compatibilizing effect of the clay. Similar to the SAN system with a low AN content, annealing leads to an increase in the dispersed (Fig. 3 c2 and d2) domains. Thus, Cloisite® 30B reduced the domain size of the dispersed phase and increased the thermal stability of the
morphology, however it did not entirely prevent coalescence PC/ SAN21 system. The location of the clay platelets in PC/SAN blend can be evaluated in Fig. 4. Cloisite® 30B is preferentially located in the dispersed phase and at the interphase of the PC/SAN21 and PC/SAN28 systems. This effect can be attributed to the good interaction between the nitrile groups in the dispersed phase, rich with SAN, and the hydroxyl groups in the clay modifiers. The presence of larger clay particles in PC/SAN21 (Fig. 4 b and c) in comparison to PC/SAN28 (Fig. 4 d, e) indicates that an increase in the AN content in the SAN copolymer may improve the intercalation/exfoliation of Cloisite® 30B clay platelets due to the better interaction of SAN28 that has higher polarity. Cloisite® 30B appear to interact preferentially with just one component of the blend (SAN) in both cases, even so the compatibility and morphology improvement were observed. This result is in agreement with the theoretical predictions reported by Lipatov, 2002. 3.2.2. TEM analysis of the PC/SAN samples with Cloisite® 20A clay The compatibilizing effect in systems containing Cloisite® 20A clay is even more evident due to reduction of the dispersed phase even more effective (Fig. 5). Addition of 1 wt% Cloisite® 20A (Fig. 5 b1) was
Fig. 7. TEM images of ternary systems containing the 20A clay a) PC/SAN21-1%, b) PC/SAN21-3%, c) PC/SAN21-5%, d) PC/SAN28-1%, e) PC/SAN28-3%, and f) PC/SAN28-5%.
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
sufficient to disrupt the fibrils observed in the neat blends (Fig. 5 a1), resulting in the formation of a dispersed morphology. After annealing (Fig. 5 b2), the dispersed phase particle size reduced and rounded particles with better homogeneity were obtained. This is a strong indicator of the clay particles inhibiting coalescence. With increase in the Cloisite® 20A content to 3 wt% (Fig. 5 c1 and c2), the previously observed compatibility enhancement persisted; however, the dispersed phase became more irregular. These results suggest that once the clay enters the dispersed phase, it increases the viscosity and reduces the mobility of the SAN molecules, causing shape irregularity in the dispersed particles, as shown in Fig. 5 c1 and d1. In contrast to the neat PC/SAN21 blends (Fig. 5 a1 and a2), blends containing 5 wt% clay (Fig. 5 d1) showed almost no morphological changes after annealing (d2), revealing high morphological stability. Similar to the PC/SAN21 blends, Cloisite® 20A was effective as an effective compatibilizer and morphological stabilizer for PC/SAN28 in all compositions (Fig. 6). However, the higher polarity in SAN28, resulted in a rough morphology with larger dispersed phase particles in comparison to those observed in the PC/SAN21/20A system. The increase in the AN content caused a stronger interaction between the SAN and the clay, as discussed in Section 3.2.1, which might lead to the localization of the clay in the interior of the SAN particles, as observed in Fig. 7. Furthermore, an increase in the dispersed domain size in the blends containing SAN28 is also related to a higher viscosity in comparison to SAN21 systems in which it was difficult to break the dispersed particles during the melt processing. The preferential location of Cloisite® 20A clay particles was in the interphase of the blend (Fig. 7), with is the ideal condition for the compatibilizing effect. In this case, the clay particles, in addition to reducing the interfacial tension, also act as a physical barrier, shielding the dispersed phase, preventing coalescence. This effect is highlighted in Fig. 7 b and c by dotted lines. The location of clay particles at the blend interphase, especially in lower clay contents (Fig.7 a, b) and in SAN21 indicate a balance between the interaction of nitrile groups and carbonyl groups in SAN21 and PC groups respectively, by the Cloisite® 20A particles with lower polarity, that lead to the accumulation of the clay particles at the interphase. In samples with 3 and 5 wt% Cloisite® 20A (Fig. 7 b, c, e, f), clay particles were present in the interphase and within the SAN21 phase. One possible explanation is that samples with 1 wt% Cloisite® 20A, the particles of clay tend to accumulate at the PC/SAN21 interphase. With increase in the clay content, the interphase became saturated with clay particles. Thus, when these particles compete for the interphase, they push the particles into the SAN phase. Consequently, by increasing the nitrile group content in SAN28 (Fig. 7 d, e, and f), the balance between the interaction forces is modified in favor of the SAN phase, as observed in the PC/SAN system with 30B previously. 4. Conclusions In this work, was demonstrated that the compatibility and morphological stability of PC/SAN blends can be strongly enhanced by the addition of OC. The final morphology of the blend depends on the location of the organo-clay platelets, which can be altered by the OC modifier type and the AN content in the SAN copolymer. When Cloisite® 30B modified with polar groups is used, the clay platelets are chiefly located in the dispersed SAN phase. Increasing the AN content in the SAN copolymer leads to a more favorable interaction between the clay particles and SAN, resulting in better intercalation/exfoliation. Even when the OC interacts preferentially with just one phase, reduction in the dispersed phase and increase in morphological stability are observed. However, the alkyl ammonium on Cloisite® 30B modifiers showed strong oxidation due to high processing temperature of the PC causing the collapse of the clay structure. On the other hand, better compatibility and morphological stability were obtained in the PC/ SAN21/20A system were clay particles were located mainly at the
117
interphase of the blend proving that clay since located at the interphase, reduces interfacial tension between the components and act as a physical barrier, shielding the dispersed phase from coalescence during the melt processing. Acknowledgments R. Grande thanks the Coordination for the Improvement of Higher Education Personnel (CAPES), FAPESP (2015/07744-0) and Brazilian National Council for Scientific and Technological Development (CNPq) (309425/2013-1) for financial support. References Benali, S., Peeterbroeck, S., Larrieu, J., Laffineur, F., Pireaux, J.-J., Alexandre, M., Dubois, P., 2008. Study of interlayer spacing collapse during polymer/clay nanocomposite melt intercalation. J. Nanosci. Nanotechnol. 8:1707–1713. http://dx.doi.org/10.1166/jnn. 2008.020. Callaghan, T.A., Takakuwa, K., Paul, D.R., Padwa, A.R., 1993. Polycarbonate-SAN copolymer interaction. Polymer (Guildf). 34:3796–3808. http://dx.doi.org/10.1016/00323861(93)90503-3. Cervantes-Uc, J.M., Cauich-Rodríguez, J.V., Vázquez-Torres, H., Garfias-Mesías, L.F., Paul, D.R., 2007. Thermal degradation of commercially available organoclays studied by TGA–FTIR. Thermochim. Acta 457:92–102. http://dx.doi.org/10.1016/j.tca.2007.03. 008. Chaudhry, B.I., Hage, E., Pessan, L.A., 1998. Effects of processing conditions on the phase morphology of PC/ABS polymer blends. J. Appl. Polym. Sci. 67:1605–1613. http:// dx.doi.org/10.1002/(SICI)1097-4628(19980228)67:9b1605::AID-APP12N3.0.CO;2-T. Chen, J., Chen, J., Chen, H., Yang, J., Chen, C., Wang, Y., 2013. Effect of compatibilizer and clay on morphology and fracture resistance of immiscible high density polyethylene/polyamide 6 blend. Compos. Part B Eng. 54:422–430. http://dx.doi.org/10.1016/ j.compositesb.2013.06.014. Chinellato, A.C., Vidotti, S.E., Hu, G.-H., Pessan, L.A., 2008. An acrylic acid modified polypropylene as a compatibilizing agent for the intercalation/exfoliation of an organically modified montmorillonite in polypropylene. J. Polym. Sci. B Polym. Phys. 46: 1811–1819. http://dx.doi.org/10.1002/polb.21514. Cui, L., Khramov, D.M., Bielawski, C.W., Hunter, D.L., Yoon, P.J., Paul, D.R., 2008. Effect of organoclay purity and degradation on nanocomposite performance, part 1: surfactant degradation. Polymer (Guildf). 49:3751–3761. http://dx.doi.org/10.1016/j.polymer. 2008.06.029. Filippone, G., Dintcheva, N.T., La Mantia, F.P., Acierno, D., 2010. Using organoclay to promote morphology refinement and co-continuity in high-density polyethylene/polyamide 6 blends – effect of filler content and polymer matrix composition. Polymer (Guildf). 51:3956–3965. http://dx.doi.org/10.1016/j.polymer.2010.06.044. Gahleitner, M., Kretzschmar, B., Pospiech, D., Ingolic, E., Reichelt, N., Bernreitner, K., 2006. Morphology and mechanical properties of polypropylene/polyamide 6 nanocomposites prepared by a two-step melt-compounding process. J. Appl. Polym. Sci. 100: 283–291. http://dx.doi.org/10.1002/app.23102. Hanafy, G.M., Madbouly, S.A., Ougizawa, T., Inoue, T., 2004. Effects of AN-contents and shear flow on the miscibility of PC/SAN blends. Polymer (Guildf). 45:6879–6887. http://dx.doi.org/10.1016/j.polymer.2004.08.014. Hemmati, F., Garmabi, H., Modarress, H., 2014. Effects of organoclay on the compatibility and interfacial phenomena of PE/EVA blends with UCST phase behavior. Polym. Compos. 35:2329–2342. http://dx.doi.org/10.1002/pc.22898. Labaume, I., Huitric, J., Médéric, P., Aubry, T., 2013a. Structural and rheological properties of different polyamide/polyethylene blends filled with clay nanoparticles: a comparative study. Polymer (Guildf). 54:3671–3679. http://dx.doi.org/10.1016/j.polymer. 2013.05.020. Labaume, I., Médéric, P., Huitric, J., Aubry, T., 2013b. Comparative study of interphase viscoelastic properties in polyethylene/polyamide blends compatibilized with clay nanoparticles or with a graft copolymer. J. Rheol. N. Y. 57:377. http://dx.doi.org/10. 1122/1.4774322. Lipatov, Y., 2002. Polymer blends and interpenetrating polymer networks at the interface with solids. Prog. Polym. Sci. 27:1721–1801. http://dx.doi.org/10.1016/S00796700(02)00021-7. López-Quintanilla, M.L., Sánchez-Valdés, S., Ramos de Valle, L.F., Medellín-Rodríguez, F.J., 2006. Effect of some compatibilizing agents on clay dispersion of polypropyleneclay nanocomposites. J. Appl. Polym. Sci. 100:4748–4756. http://dx.doi.org/10.1002/ app.23262. Macosko, C.W., Guégan, P., Khandpur, A.K., Nakayama, A., Marechal, P., Inoue, T., 1996. Compatibilizers for melt blending: premade block copolymers †. Macromolecules 29:5590–5598. http://dx.doi.org/10.1021/ma9602482. Martins, C.G., Larocca, N.M., Paul, D.R., Pessan, L.A., 2009. Nanocomposites formed from polypropylene/EVA blends. Polymer (Guildf). 50:1743–1754. http://dx.doi.org/10. 1016/j.polymer.2009.01.059. Moghbelli, E., Sue, H.-J., Jain, S., 2010. Stabilization and control of phase morphology of PA/SAN blends via incorporation of exfoliated clay. Polymer (Guildf). 51: 4231–4237. http://dx.doi.org/10.1016/j.polymer.2010.05.025. Najafi, N., Heuzey, M.C., Carreau, P.J., 2012. Polylactide (PLA)-clay nanocomposites prepared by melt compounding in the presence of a chain extender. Compos. Sci. Technol. 72:608–615. http://dx.doi.org/10.1016/j.compscitech.2012.01.005.
118
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Nazari, T., Garmabi, H., Arefazar, A., 2012. Effect of clay modification on the morphology and the mechanical/physical properties of ABS/PMMA blends. J. Appl. Polym. Sci. 126:1637–1649. http://dx.doi.org/10.1002/app.36953. Pluta, M., Paul, M.-A., Alexandre, M., Dubois, P., 2006. Plasticized polylactide/clay nanocomposites. I. The role of filler content and its surface organo-modification on the physico-chemical properties. J. Polym. Sci. B Polym. Phys. 44:299–311. http://dx.doi. org/10.1002/polb.20694. Shah, R.K., Paul, D.R., 2006. Organoclay degradation in melt processed polyethylene nanocomposites. Polymer (Guildf). 47:4075–4084. http://dx.doi.org/10.1016/j.polymer. 2006.02.031. Si, M., Araki, T., Ade, H., Kilcoyne, A.L.D., Fisher, R., Sokolov, J.C., Rafailovich, M.H., 2006. Compatibilizing bulk polymer blends by using organoclays. Macromolecules 39: 4793–4801. http://dx.doi.org/10.1021/ma060125+. Sinha Ray, S., Pouliot, S., Bousmina, M., Utracki, L.A., 2004. Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends. Polymer (Guildf). 45:8403–8413. http://dx.doi.org/10.1016/j. polymer.2004.10.009. Tiwari, R.R., Paul, D.R., 2011. Effect of organoclay on the morphology, phase stability and mechanical properties of polypropylene/polystyrene blends. Polymer (Guildf). 52: 1141–1154. http://dx.doi.org/10.1016/j.polymer.2011.01.019.
Triantou, M.I., Tarantili, P.A., 2014. Studies on morphology and thermomechanical performance of ABS/PC/organoclay hybrids. Polym. Compos. 35:1395–1407. http://dx.doi. org/10.1002/pc.22792. Valera-Zaragoza, M., Ramírez-Vargas, E., Medellín-Rodríguez, F.J., 2008. Preparation and morphological evolution of heterophasic PP-EP/EVA/organoclay nanocomposites: effect of the nanoclay organic modifier. J. Appl. Polym. Sci. 108:1986–1994. http://dx. doi.org/10.1002/app.27858. Vo, L.T., Giannelis, E.P., 2007. Compatibilizing poly(vinylidene fluoride)/nylon-6 blends with nanoclay. Macromolecules 40:8271–8276. http://dx.doi.org/10.1021/ ma071508q. Wildes, G., Keskkula, H., Paul, D., 1999. Coalescence in PC/SAN blends: effect of reactive compatibilization and matrix phase viscosity. Polymer (Guildf). 40:5609–5621. http://dx.doi.org/10.1016/S0032-3861(98)00776-9. Zhang, M., Lin, B., Sundararaj, U., 2012. Effects of processing sequence on clay dispersion, phase morphology, and thermal and rheological behaviors of PA6-HDPE-clay nanocomposites. J. Appl. Polym. Sci. 125:E714–E724. http://dx.doi.org/10.1002/app.36692.
Contents lists available at ScienceDirect
Applied Clay Science journal homepage: www.elsevier.com/locate/clay
Research paper
Effects of nanoclay addition on phase morphology and stability of polycarbonate/styrene-acrylonitrile blends Rafael Grande a,b,⁎, Luiz Antonio Pessan b a b
Graduate Program in Materials Science and Engineering, Federal University of São Carlos, Via Washington Luiz, Km 235, São Carlos 13565-905, SP, Brazil Department of Materials Engineering, Federal University of São Carlos, Via Washington Luiz, Km 235, São Carlos 13565-905, SP, Brazil
a r t i c l e
i n f o
Article history: Received 12 October 2016 Received in revised form 30 January 2017 Accepted 1 February 2017 Available online xxxx Keywords: Organoclay Montmorillonite Morphology Blends Extrusion
a b s t r a c t In this work, an extensive study was performed on the compatibility and morphological stability of polycarbonate/styrene-acrylonitrile (PC/SAN) blends and on the effects of nanoclay addition to these systems. PC/SAN blends of different compositions were prepared by melt extrusion and their morphologies were characterized as prepared and after annealing at high temperature to evaluate their morphological stability. The effects of nanoclay with different organic modifiers and acrylonitrile (AN) content in the SAN copolymer on the morphology of the PC/SAN blends were also evaluated. The results indicate that the nanoclay reduces the domain size of SAN phase and stabilizes the system morphology even without complete exfoliation. Organoclays particles with polar organic modifiers were preferably located inside the SAN domains, while in blends containing organoclays with nonpolar modifiers, the clay particles migrated to the interface, resulting in domain reduction and improved morphological stability. © 2017 Elsevier B.V. All rights reserved.
1. Introduction Blending two or more polymers is an effective approach to obtain systems with properties better than the individual polymers. However, most polymer blends are thermodynamically immiscible. Polycarbonate/styrene-acrylonitrile (PC/SAN) is a typical example of an immiscible blend, which was poor mechanical properties due to high interfacial tension despite the existence of a certain degree of interaction between the components. Chaudhry et al., 1998, have demonstrated the tendency of the PC/acrylonitrile-butadiene-acrylonitrile styrene (ABS) system to phase separate. PC/ABS system is similar to PC/SAN and shows low morphological stability, restricting the practical application of this material. To achieve high-performance polymer blends, it is essential to control and stabilize the blend morphology. Compatibility of components in polymer blends is generally achieved by incorporating graft or block copolymers, which reduce the domain sizes and enhance the interfacial adhesion between the phases (Macosko et al., 1996). However, the production of these compatibilizers is usually difficult and expensive. Several recent studies have reported the compatibilizing effect of organoclay additives in immiscible polymer blends (Vo and Giannelis, 2007; Filippone et al., 2010; Moghbelli et al., 2010; Tiwari and Paul, 2011; Nazari et al., 2012; Chen et al., 2013; Labaume et al., 2013a, 2013b). The use of organoclay additives has many advantages over the ⁎ Corresponding author. E-mail address: [email protected] (R. Grande).
http://dx.doi.org/10.1016/j.clay.2017.02.001 0169-1317/© 2017 Elsevier B.V. All rights reserved.
traditional approach of adding block copolymers, such as the ready availability of clays, lower cost, and easy processability. The effect of clay platelets on the morphology of polymer blends is yet to be completely explored. When the organoclay is located in the continuous phase, the domain size of the dispersed phase is reduced because the organoclay increases the viscosity in the matrix and acts as a physical barrier, reducing the coalescence rate of the dispersed phase. To maximize this effect, it is necessary to have the clay platelets located at the interface of the system (Si et al., 2006; Hemmati et al., 2014). On the other hand, when the clay is located within the dispersed phase, it appears to increase the dispersed phase domain size (Gahleitner et al., 2006; Sinha Ray et al., 2004; Zhang et al., 2012). Thus, the present study was designed to evaluate the effects of organoclay (OC) addition on compatibility, morphology and morphological stability of PC/SAN blends. The PC/SAN system is particularly interesting because the viscosity and polarity of the system can be modified by using SAN copolymers with different AN content (Callaghan et al., 1993; Hanafy et al., 2004), which might lead to a change in the localization of the organoclays. 2. Experimental 2.1. Materials A PC resin (Lexan® 101) with a melt flow index of 7 g/10 min (300 °C/1.2 kg), purchased from SABIC, was used as the matrix. Two SAN resins (supplied by BASF), Luran 358 N and Luran 388 S with
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
113
Fig. 1. WAXD patterns of the neat organoclays Cloisite® 30B and Cloisite® 20A and the ternary (PC/SAN/organoclay) systems.
melt flow indices of 6.3 g/10 min (230 °C/3.8 kg) and 2.6 g/10 min (230 °C/3.8 kg), respectively, and AN content of 21 wt% and 28 wt%, respectively, were used. These SAN resins will hereafter be denoted (based on the AN content) as SAN21 and SAN28, respectively. Organoclays Cloisite® 20A and Cloisite® 30B were purchased from Southern Clay Products Inc. Cloisite® 30B is a natural montmorillonite with, was a cation exchange capacity near 90 meq/100 g, which was treated with methyl tallow bis-2-hydroxyethyl quaternary ammonium chloride to form a polar organoclay. Cloisite® 20A is also a natural montmorillonite, which was treated with a low-polarity dimethyl dehydrogenated tallow quaternary ammonium chloride to form a non-polar organoclay. The difference in the polarity of the clays can be expected to alter the position of the organoclay platelets in PC/SAN mixture. The location of the clay platelets might also be altered with an increase in the AN content because SAN is expected to interact more with Cloisite ®30B than with Cloisite ®20A due SAN polarity.
2.3. Annealing The specimens were annealed at 170 °C for 60 min to evaluate the morphological stability of the PC/SAN/organoclay blends. The treatment conditions are less aggressive than that normally reported in the literature (Vo and Giannelis, 2007; Triantou and Tarantili, 2014). The altered annealing conditions were necessary to avoid organoclay degradation and to prevent bubble formation in samples, which could negatively affect transmission electron microscopy (TEM) observations. 2.4. Wide angle X-ray diffraction (WAXD) X-ray analysis was carried out in reflective mode (in a Rigaku Multiflex diffractometer) with Cu-Kα rays (wavelength = 1.542 Å). The scan rate was 1°/min and the 2θ range was 1–10°. 2.5. Morphology characterization
2.2. Blend preparation All the materials were vacuum dried at 90 °C for 24 h prior to melt processing. The PC/SAN/organoclay blends were prepared in a twinscrew extruder (B & P Process Equipment Systems, model MP19, with L/D ratio = 25 mm and length = 19 mm). The temperature profile used was 185, 195, 195, 200, and 205 °C and the screw speed was set at 140 rpm. The extrudates were pelletized and then vacuum dried again for 8 h at 80 °C. The PC/SAN/organoclay pellets were molded in an injection-molding machine (Arburg 270 V) with an injection pressure of 94 MPa and a holding pressure of 60 MPa. The temperature profile used was 200, 220, 230, 230, 240 °C and the mold temperature was set at 65 °C. The specimens were prepared using an injection mold that produces samples following ASTM D256-06 standards used in Izod impact tests. The composition of the PC/SAN blend was fixed at 70/30 wt% ratio and the organoclay content was 1, 3, or 5 wt%. For comparison, PC/ SAN21 and PC/SAN28 blends without the clays were also prepared under the conditions described above.
The SAN dispersed domains and the location of the OC in the blends were evaluated by TEM. The Izod specimens were sliced to reveal the Table 1 d-Value obtained from the XRD patterns. Neat Cloisite® 30B
d001 (Å) 18.0
PC/SAN21–1% 30B PC/SAN21–3% 30B PC/SAN21–5% 30B PC/SAN28–1% 30B PC/SAN28–3% 30B PC/SAN28–5% 30B Neat Cloisite® 20A PC/SAN21–1% 20A PC/SAN21–3% 20A PC/SAN21–5% 20A PC/SAN28–1% 20A PC/SAN28–3% 20A PC/SAN28–5% 20A
28.5 29.5 30.5 28.5 30.5 29.5 24.9 29.4 29.4 29.8 28.7 29.4 29.4
114
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Fig. 2. TEM images of a) PC/SAN21, b) PC/SAN21-1%30B, c) PC/SAN21-3%30B, and d) PC/SAN21-5%30B. The images in the top and bottom panel are from samples without and with annealing, respectively.
core of the sample perpendicular to the injection flow. Then, the cross sections were reduced to trapezoids and cryogenically ultrathinned into sections of ~ 40 nm in thickness using an ultramicrotome (Leica Ultracut equipped with a diamond knife Diatome 45°). The temperature was maintained constant at − 45 °C and the sectioning speed was 0.2 mm/s. After sectioning, the samples were placed on a copper 400 mesh grid. The grids containing the samples were then stained with RuO4 for 8 h at room temperature. The ruthenium attached preferably to the aromatic rings of the SAN monomeric units, which provided the contrast necessary for TEM analysis (carried out in a FEI Magellan model L400 microscope). 3. Results and discussion 3.1. WAXD analysis The X-ray analysis were performed only in samples before the annealing process in order to verify the effect of composition and melt processing on the d-value of Cloisite® 30B and Cloisite® 20A on PC/SAN blends.
X-ray diffraction (XRD) patterns of the neat Cloisite® 30B and the ternary systems (PC/SAN/organoclay) with different AN content, SAN21 and SAN28 are presented in Fig. 1 a) and b). The pattern acquired from the 30B clay contains a reflection at 2θ = 4.8°, corresponding to an average d-value of 18.0 Å. The d001 reflection shifts to smaller angles (2θ of 3.2°) and broadens, indicating an increase in the d-value caused by the diffusion of the polymer molecules into the clay interlayer spaces and possibly because of intercalation/exfoliation (Najafi et al., 2012; Triantou and Tarantili, 2014). Furthermore, a second reflection was observed at higher angles, near 2θ = 6.2° (d-value of 18.0 Å). This reflection is explained as a partial collapse of clay interlayer spaces. The high intensity of the reflection and its shift to higher angles is an indication of significant decomposition of the clay modifiers, which can be attributed to the processing conditions used. The detachment/thermal degradation of organic modifiers in Cloisite® 30B was expected since many other works involving others polymeric systems have shown similar results even in mild processing conditions which the d001 reflection shifting to higher angle is attributed to the degradation of the surfactant, which leads to the collapse of interlayer spaces, reducing the interlayer
Fig. 3. TEM images of a) PC/SAN28, b) PC/SAN28-1%30B, c) PC/SAN28-3%30B, and d) PC/SAN28-5%30B. Top and bottom panels show images from samples without and with annealing, respectively.
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
115
Fig. 4. TEM images of the ternary systems containing the 30B clay. a) PC/SAN21-1%, b) PC/SAN21-3%, c) PC/SAN21-5%, d) PC/SAN28-1%, e) PC/SAN28-3%, and f) PC/SAN28-5%.
distance. (López-Quintanilla et al., 2006; Cervantes-Uc et al., 2007; Chinellato et al., 2008; Valera-Zaragoza et al., 2008; Martins et al., 2009). Benali et al., 2008 showed that the Cloisite® 30B organoclay structure collapse in polyethylene/Cloisite® 30B melt intercalated at 175 °C or by simple drying at 180 °C by 2 h. The authors showed that the decrease of d-spacing from 18 to 14 Å is related with a double bound oxidation of the ammonium alkyl chain. Thus, for both the PC/SAN systems prepared with Cloisite® 30B, it can be confirmed that while a part of the clay content was intercalated, another part was thermally degraded. The Thermal degradation/detachment of organic modifiers on Cloisite® 30B could not be avoided even using mild processing conditions for PC (240 °C) which, cannot be easily processed by injection molding bellow this temperature because of its high viscosity. Additionally, the PC/SAN28/30B system appears to show a broader d001 diffraction in comparison to the PC/ SAN21/30B system, indicating better exfoliation/intercalation. Therefore, increasing the AN content in SAN may improve the interaction between the SAN molecules and the Cloisite® 30B clay modifier, facilitating diffusion into the interlayer spaces. This results will be corroborated by TEM analysis. In the XRD pattern of Cloisite® 20A, the d001 diffraction can be observed at 2θ = 3.6°, corresponding to an average d-value of 24.9 Å. In
all the compositions, the d001 value became sharper and shifted indicating the clay intercalation. Other indication of intercalation of the 20A clay in the PC/SAN21 and PC/SAN28 blends are the diffraction corresponding to d002 at 2θ–5.7°(Pluta et al., 2006). Table 1 lists the d-value obtained from the XRD patterns. Furthermore, there is no indication of thermal degradation of Cloisite® 20A. This agrees with results reported by Shah and Paul, 2006; Cui et al., 2008, which show that organic modifiers with two alkyl tails, as in Cloisite® 20A, are more stable than modifiers with just one alkyl tail (like Cloisite® 30B). 3.2. Morphology characterization 3.2.1. TEM analysis of the PC/SAN samples with Cloisite® 30B clay The TEM images in Fig. 2 PC/SAN21 and PC/SAN21/20A-organoclay samples before and after annealing are presented. As observed in Fig. 2 a1, the PC/SAN21 blend (in the absence of clay) has dispersed domains, which are distinctly elongated because of the shear flow orientation, resulting from the injection processing. The observation of long SAN domains appears to be in agreement with the results reported by Wildes et al., 1999, which indicates that the processing conditions favored coalescence in the mixture. When annealed, the PC/SAN21 blend exhibited significant changes in its morphology (Fig. 2 a2). The
Fig. 5. TEM images of a) PC/SAN21, b) PC/SAN21-1%20A, c) PC/SAN21-3%20A, and d) PC/SAN21-5%20A. Upper panel: samples without annealing. Lower panel: annealed samples.
116
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Fig. 6. TEM images of a) PC/SAN28, b) PC/SAN28-1%20A, c) PC/SAN28-3%20A, and d) PC/SAN28-5%20A. Top panel: samples without annealing. Bottom panel: annealed samples.
energy provided by annealing was sufficient to begin coalescence and shrinkage in the dispersed SAN phase. This effect was less significant than that that observed by Chaudhry et al., 1998, probably because of the use of lower annealing temperatures and the absence of an elastomeric phase in the present work. The addition of clay in the mixture leads to a rupture in the previously elongated reducing dispersed domains making the compatibilizing effect of clay evident. With increase in the clay content, the dispersed domains tend to become larger after annealing (Fig. 2 b2, c2, and d2). One possible explanation for this effect is the presence of agglomerates of clay, especially in systems with 3 and 5 wt%, which exhibits low dispersion of Cloisite® 30B. The increase in the AN content in the SAN results in slightly larger dispersed domains in the binary PC/SAN28 blend (Fig. 3 a1 and a2). This effect is expected because of the higher viscosity resulting from the higher AN content in SAN28. With increase in the 30B clay content (Fig. 3 b1, c1, and d1), the morphology changed from co-continuous to a typical well-dispersed phase in a continuous matrix, which is indicative of the compatibilizing effect of the clay. Similar to the SAN system with a low AN content, annealing leads to an increase in the dispersed (Fig. 3 c2 and d2) domains. Thus, Cloisite® 30B reduced the domain size of the dispersed phase and increased the thermal stability of the
morphology, however it did not entirely prevent coalescence PC/ SAN21 system. The location of the clay platelets in PC/SAN blend can be evaluated in Fig. 4. Cloisite® 30B is preferentially located in the dispersed phase and at the interphase of the PC/SAN21 and PC/SAN28 systems. This effect can be attributed to the good interaction between the nitrile groups in the dispersed phase, rich with SAN, and the hydroxyl groups in the clay modifiers. The presence of larger clay particles in PC/SAN21 (Fig. 4 b and c) in comparison to PC/SAN28 (Fig. 4 d, e) indicates that an increase in the AN content in the SAN copolymer may improve the intercalation/exfoliation of Cloisite® 30B clay platelets due to the better interaction of SAN28 that has higher polarity. Cloisite® 30B appear to interact preferentially with just one component of the blend (SAN) in both cases, even so the compatibility and morphology improvement were observed. This result is in agreement with the theoretical predictions reported by Lipatov, 2002. 3.2.2. TEM analysis of the PC/SAN samples with Cloisite® 20A clay The compatibilizing effect in systems containing Cloisite® 20A clay is even more evident due to reduction of the dispersed phase even more effective (Fig. 5). Addition of 1 wt% Cloisite® 20A (Fig. 5 b1) was
Fig. 7. TEM images of ternary systems containing the 20A clay a) PC/SAN21-1%, b) PC/SAN21-3%, c) PC/SAN21-5%, d) PC/SAN28-1%, e) PC/SAN28-3%, and f) PC/SAN28-5%.
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
sufficient to disrupt the fibrils observed in the neat blends (Fig. 5 a1), resulting in the formation of a dispersed morphology. After annealing (Fig. 5 b2), the dispersed phase particle size reduced and rounded particles with better homogeneity were obtained. This is a strong indicator of the clay particles inhibiting coalescence. With increase in the Cloisite® 20A content to 3 wt% (Fig. 5 c1 and c2), the previously observed compatibility enhancement persisted; however, the dispersed phase became more irregular. These results suggest that once the clay enters the dispersed phase, it increases the viscosity and reduces the mobility of the SAN molecules, causing shape irregularity in the dispersed particles, as shown in Fig. 5 c1 and d1. In contrast to the neat PC/SAN21 blends (Fig. 5 a1 and a2), blends containing 5 wt% clay (Fig. 5 d1) showed almost no morphological changes after annealing (d2), revealing high morphological stability. Similar to the PC/SAN21 blends, Cloisite® 20A was effective as an effective compatibilizer and morphological stabilizer for PC/SAN28 in all compositions (Fig. 6). However, the higher polarity in SAN28, resulted in a rough morphology with larger dispersed phase particles in comparison to those observed in the PC/SAN21/20A system. The increase in the AN content caused a stronger interaction between the SAN and the clay, as discussed in Section 3.2.1, which might lead to the localization of the clay in the interior of the SAN particles, as observed in Fig. 7. Furthermore, an increase in the dispersed domain size in the blends containing SAN28 is also related to a higher viscosity in comparison to SAN21 systems in which it was difficult to break the dispersed particles during the melt processing. The preferential location of Cloisite® 20A clay particles was in the interphase of the blend (Fig. 7), with is the ideal condition for the compatibilizing effect. In this case, the clay particles, in addition to reducing the interfacial tension, also act as a physical barrier, shielding the dispersed phase, preventing coalescence. This effect is highlighted in Fig. 7 b and c by dotted lines. The location of clay particles at the blend interphase, especially in lower clay contents (Fig.7 a, b) and in SAN21 indicate a balance between the interaction of nitrile groups and carbonyl groups in SAN21 and PC groups respectively, by the Cloisite® 20A particles with lower polarity, that lead to the accumulation of the clay particles at the interphase. In samples with 3 and 5 wt% Cloisite® 20A (Fig. 7 b, c, e, f), clay particles were present in the interphase and within the SAN21 phase. One possible explanation is that samples with 1 wt% Cloisite® 20A, the particles of clay tend to accumulate at the PC/SAN21 interphase. With increase in the clay content, the interphase became saturated with clay particles. Thus, when these particles compete for the interphase, they push the particles into the SAN phase. Consequently, by increasing the nitrile group content in SAN28 (Fig. 7 d, e, and f), the balance between the interaction forces is modified in favor of the SAN phase, as observed in the PC/SAN system with 30B previously. 4. Conclusions In this work, was demonstrated that the compatibility and morphological stability of PC/SAN blends can be strongly enhanced by the addition of OC. The final morphology of the blend depends on the location of the organo-clay platelets, which can be altered by the OC modifier type and the AN content in the SAN copolymer. When Cloisite® 30B modified with polar groups is used, the clay platelets are chiefly located in the dispersed SAN phase. Increasing the AN content in the SAN copolymer leads to a more favorable interaction between the clay particles and SAN, resulting in better intercalation/exfoliation. Even when the OC interacts preferentially with just one phase, reduction in the dispersed phase and increase in morphological stability are observed. However, the alkyl ammonium on Cloisite® 30B modifiers showed strong oxidation due to high processing temperature of the PC causing the collapse of the clay structure. On the other hand, better compatibility and morphological stability were obtained in the PC/ SAN21/20A system were clay particles were located mainly at the
117
interphase of the blend proving that clay since located at the interphase, reduces interfacial tension between the components and act as a physical barrier, shielding the dispersed phase from coalescence during the melt processing. Acknowledgments R. Grande thanks the Coordination for the Improvement of Higher Education Personnel (CAPES), FAPESP (2015/07744-0) and Brazilian National Council for Scientific and Technological Development (CNPq) (309425/2013-1) for financial support. References Benali, S., Peeterbroeck, S., Larrieu, J., Laffineur, F., Pireaux, J.-J., Alexandre, M., Dubois, P., 2008. Study of interlayer spacing collapse during polymer/clay nanocomposite melt intercalation. J. Nanosci. Nanotechnol. 8:1707–1713. http://dx.doi.org/10.1166/jnn. 2008.020. Callaghan, T.A., Takakuwa, K., Paul, D.R., Padwa, A.R., 1993. Polycarbonate-SAN copolymer interaction. Polymer (Guildf). 34:3796–3808. http://dx.doi.org/10.1016/00323861(93)90503-3. Cervantes-Uc, J.M., Cauich-Rodríguez, J.V., Vázquez-Torres, H., Garfias-Mesías, L.F., Paul, D.R., 2007. Thermal degradation of commercially available organoclays studied by TGA–FTIR. Thermochim. Acta 457:92–102. http://dx.doi.org/10.1016/j.tca.2007.03. 008. Chaudhry, B.I., Hage, E., Pessan, L.A., 1998. Effects of processing conditions on the phase morphology of PC/ABS polymer blends. J. Appl. Polym. Sci. 67:1605–1613. http:// dx.doi.org/10.1002/(SICI)1097-4628(19980228)67:9b1605::AID-APP12N3.0.CO;2-T. Chen, J., Chen, J., Chen, H., Yang, J., Chen, C., Wang, Y., 2013. Effect of compatibilizer and clay on morphology and fracture resistance of immiscible high density polyethylene/polyamide 6 blend. Compos. Part B Eng. 54:422–430. http://dx.doi.org/10.1016/ j.compositesb.2013.06.014. Chinellato, A.C., Vidotti, S.E., Hu, G.-H., Pessan, L.A., 2008. An acrylic acid modified polypropylene as a compatibilizing agent for the intercalation/exfoliation of an organically modified montmorillonite in polypropylene. J. Polym. Sci. B Polym. Phys. 46: 1811–1819. http://dx.doi.org/10.1002/polb.21514. Cui, L., Khramov, D.M., Bielawski, C.W., Hunter, D.L., Yoon, P.J., Paul, D.R., 2008. Effect of organoclay purity and degradation on nanocomposite performance, part 1: surfactant degradation. Polymer (Guildf). 49:3751–3761. http://dx.doi.org/10.1016/j.polymer. 2008.06.029. Filippone, G., Dintcheva, N.T., La Mantia, F.P., Acierno, D., 2010. Using organoclay to promote morphology refinement and co-continuity in high-density polyethylene/polyamide 6 blends – effect of filler content and polymer matrix composition. Polymer (Guildf). 51:3956–3965. http://dx.doi.org/10.1016/j.polymer.2010.06.044. Gahleitner, M., Kretzschmar, B., Pospiech, D., Ingolic, E., Reichelt, N., Bernreitner, K., 2006. Morphology and mechanical properties of polypropylene/polyamide 6 nanocomposites prepared by a two-step melt-compounding process. J. Appl. Polym. Sci. 100: 283–291. http://dx.doi.org/10.1002/app.23102. Hanafy, G.M., Madbouly, S.A., Ougizawa, T., Inoue, T., 2004. Effects of AN-contents and shear flow on the miscibility of PC/SAN blends. Polymer (Guildf). 45:6879–6887. http://dx.doi.org/10.1016/j.polymer.2004.08.014. Hemmati, F., Garmabi, H., Modarress, H., 2014. Effects of organoclay on the compatibility and interfacial phenomena of PE/EVA blends with UCST phase behavior. Polym. Compos. 35:2329–2342. http://dx.doi.org/10.1002/pc.22898. Labaume, I., Huitric, J., Médéric, P., Aubry, T., 2013a. Structural and rheological properties of different polyamide/polyethylene blends filled with clay nanoparticles: a comparative study. Polymer (Guildf). 54:3671–3679. http://dx.doi.org/10.1016/j.polymer. 2013.05.020. Labaume, I., Médéric, P., Huitric, J., Aubry, T., 2013b. Comparative study of interphase viscoelastic properties in polyethylene/polyamide blends compatibilized with clay nanoparticles or with a graft copolymer. J. Rheol. N. Y. 57:377. http://dx.doi.org/10. 1122/1.4774322. Lipatov, Y., 2002. Polymer blends and interpenetrating polymer networks at the interface with solids. Prog. Polym. Sci. 27:1721–1801. http://dx.doi.org/10.1016/S00796700(02)00021-7. López-Quintanilla, M.L., Sánchez-Valdés, S., Ramos de Valle, L.F., Medellín-Rodríguez, F.J., 2006. Effect of some compatibilizing agents on clay dispersion of polypropyleneclay nanocomposites. J. Appl. Polym. Sci. 100:4748–4756. http://dx.doi.org/10.1002/ app.23262. Macosko, C.W., Guégan, P., Khandpur, A.K., Nakayama, A., Marechal, P., Inoue, T., 1996. Compatibilizers for melt blending: premade block copolymers †. Macromolecules 29:5590–5598. http://dx.doi.org/10.1021/ma9602482. Martins, C.G., Larocca, N.M., Paul, D.R., Pessan, L.A., 2009. Nanocomposites formed from polypropylene/EVA blends. Polymer (Guildf). 50:1743–1754. http://dx.doi.org/10. 1016/j.polymer.2009.01.059. Moghbelli, E., Sue, H.-J., Jain, S., 2010. Stabilization and control of phase morphology of PA/SAN blends via incorporation of exfoliated clay. Polymer (Guildf). 51: 4231–4237. http://dx.doi.org/10.1016/j.polymer.2010.05.025. Najafi, N., Heuzey, M.C., Carreau, P.J., 2012. Polylactide (PLA)-clay nanocomposites prepared by melt compounding in the presence of a chain extender. Compos. Sci. Technol. 72:608–615. http://dx.doi.org/10.1016/j.compscitech.2012.01.005.
118
R. Grande, L.A. PessanApplied Clay Science 140 (2017) 112–118
Nazari, T., Garmabi, H., Arefazar, A., 2012. Effect of clay modification on the morphology and the mechanical/physical properties of ABS/PMMA blends. J. Appl. Polym. Sci. 126:1637–1649. http://dx.doi.org/10.1002/app.36953. Pluta, M., Paul, M.-A., Alexandre, M., Dubois, P., 2006. Plasticized polylactide/clay nanocomposites. I. The role of filler content and its surface organo-modification on the physico-chemical properties. J. Polym. Sci. B Polym. Phys. 44:299–311. http://dx.doi. org/10.1002/polb.20694. Shah, R.K., Paul, D.R., 2006. Organoclay degradation in melt processed polyethylene nanocomposites. Polymer (Guildf). 47:4075–4084. http://dx.doi.org/10.1016/j.polymer. 2006.02.031. Si, M., Araki, T., Ade, H., Kilcoyne, A.L.D., Fisher, R., Sokolov, J.C., Rafailovich, M.H., 2006. Compatibilizing bulk polymer blends by using organoclays. Macromolecules 39: 4793–4801. http://dx.doi.org/10.1021/ma060125+. Sinha Ray, S., Pouliot, S., Bousmina, M., Utracki, L.A., 2004. Role of organically modified layered silicate as an active interfacial modifier in immiscible polystyrene/polypropylene blends. Polymer (Guildf). 45:8403–8413. http://dx.doi.org/10.1016/j. polymer.2004.10.009. Tiwari, R.R., Paul, D.R., 2011. Effect of organoclay on the morphology, phase stability and mechanical properties of polypropylene/polystyrene blends. Polymer (Guildf). 52: 1141–1154. http://dx.doi.org/10.1016/j.polymer.2011.01.019.
Triantou, M.I., Tarantili, P.A., 2014. Studies on morphology and thermomechanical performance of ABS/PC/organoclay hybrids. Polym. Compos. 35:1395–1407. http://dx.doi. org/10.1002/pc.22792. Valera-Zaragoza, M., Ramírez-Vargas, E., Medellín-Rodríguez, F.J., 2008. Preparation and morphological evolution of heterophasic PP-EP/EVA/organoclay nanocomposites: effect of the nanoclay organic modifier. J. Appl. Polym. Sci. 108:1986–1994. http://dx. doi.org/10.1002/app.27858. Vo, L.T., Giannelis, E.P., 2007. Compatibilizing poly(vinylidene fluoride)/nylon-6 blends with nanoclay. Macromolecules 40:8271–8276. http://dx.doi.org/10.1021/ ma071508q. Wildes, G., Keskkula, H., Paul, D., 1999. Coalescence in PC/SAN blends: effect of reactive compatibilization and matrix phase viscosity. Polymer (Guildf). 40:5609–5621. http://dx.doi.org/10.1016/S0032-3861(98)00776-9. Zhang, M., Lin, B., Sundararaj, U., 2012. Effects of processing sequence on clay dispersion, phase morphology, and thermal and rheological behaviors of PA6-HDPE-clay nanocomposites. J. Appl. Polym. Sci. 125:E714–E724. http://dx.doi.org/10.1002/app.36692.