J Therm Anal Calorim (2013) 111:1303–1310 DOI 10.1007/s10973-012-2510-4
Thermal, rheological, and barrier properties of waterborne acrylic nanocomposite coatings based on boehmite or organo-modified montmorillonite Giulio Malucelli • Jenny Alongi • Emilia Gioffredi Massimo Lazzari
•
Received: 31 January 2012 / Accepted: 21 May 2012 / Published online: 3 July 2012 Ó Akade´miai Kiado´, Budapest, Hungary 2012
Abstract An organo-modified montmorillonite (CloisiteÒ30B) or an unmodified boehmite (DisperalÒ40) have been added to two acrylic latex dispersions (one of them UV-curable) for obtaining nanocomposite coatings. X-ray diffraction and transmission electron microscopy show a high degree of exfoliation in the nanocoatings based on montmorillonite, together with the deagglomeration of the micrometer-sized boehmite powder and the presence of single boehmite crystallites within the polymer matrix. Such morphologies are found to enhance the thermal and thermo-oxidative stability of the latexes and to significantly decrease their oxygen permeability, as well. Keywords Acrylic latexes Nanofillers Thermal stability Viscoelastic behavior Oxygen permeability
Introduction In the last 20 years, polymer nanocomposites have raised great interest in the industrial and academic research because of their dramatically improved properties: a significant enhancement of mechanical and thermo-mechanical features
G. Malucelli (&) J. Alongi E. Gioffredi Dipartimento di Scienza Applicata e Tecnologia, Politecnico di Torino, Alessandria Branch, Viale T. Michel 5, 15121 Alessandria, Italy e-mail:
[email protected] M. Lazzari Center for Research in Biological Chemistry and Molecular Materials, Campus Vida, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
and barrier properties of polymer matrices can be achieved by moving from micro- to nano-sized particles [1–4]. Among the different investigated nanocomposites, polymer–clay systems, which consist of clay layers homogeneously distributed and finely dispersed (at a nanometric level) within a polymer matrix, exhibit enhanced thermal and mechanical properties, improved barrier properties, and reduced flammability, also in the presence of very low amounts of inorganic filler (even below 5 wt%) [2, 4]. Different strategies can be employed in order to prepare such systems. One of the first approaches is the in situ intercalative polymerization, where the layered silicate is swollen by the liquid monomer, so that the polymer formation can take place in between the intercalated clay sheets [5]. In this context, the use of the UV-curing technique, which is widely employed for obtaining functional coatings, adhesives, inks, has being successfully employed to photopolymerize UV-curable acrylic resins in presence of different nanoparticles [6–8]. Some interesting examples related to the use of boehmite (c-AlO(OH)) for preparing polymer nanocomposites have been reported in the literature [9–22]. The boehmite particles are colloidal plate-like crystals with a high anisotropy: they consist of double layers of oxygen octahedrons partially filled with Al cations [13–15]. Their aqueous dispersions exhibit flow birefringence, thixotropy, and elasticity. An important advantage of boehmite nanoparticles resides in their commercial availability coupled to ‘‘tailorable’’ interfaces (either hydrophobic, hydrophilic or silane treated) that make easy their dispersion in a large number of resins [11, 12, 16–22]. The use of organo-modified montmorillonites or boehmites in waterborne acrylic coatings has not been extensively reported in the literature so far. Nobel et al. [19] investigated the effect of boehmite, montmorillonite, and
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Craymul 2717
Transmittance/a.u.
laponite particles on the morphology, rheology, and mechanical properties of waterborne acrylic dispersions. Very recently, Yılmaz et al. [23] described the rheological behavior of nanocomposite latexes based on poly(butylacrylate-co-methylmethacrylate-co-acrylamide) terpolymers, including various commercial nanoclays, obtained via in situ emulsion polymerization. In this paper, we compare the effect on the thermal and rheological behaviors of waterborne acrylic nanocoatings, as well as the permeability features, which can be achieved by homogeneously dispersing an organo-modified montmorillonite (CloisiteÒ30B) or an unmodified boehmite (DisperalÒ40) in two commercially available acrylic latexes, typical for wood applications, through a simple sonication treatment at room temperature. 5 wt% of nanofiller concentration, which is a very common content in polymer nanocomposites, has been chosen for preparing the nanocoatings. Since one of the latexes is UV-curable, it has been also possible to compare its performances with those of the non-curable and not-cured counterparts. We first investigated the morphologies of the obtained nanocoatings using X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Furthermore, the influence of the nanofillers on the viscoelastic properties of the latexes has been studied through rheological measurements, as well as their thermal stability in nitrogen and air by thermogravimetric (TG) analyses. Finally, the oxygen permeability of the coatings has been assessed and correlated with their observed morphologies.
G. Malucelli et al.
Craymul 2711
4000 3600 3200 2800 2400 2000 1600 1200 800
Wavenumber/cm–1 Fig. 1 FT-IR spectra of the latexes investigated
(Brunsbu¨ttel, Germany). The eventual photocuring process of Craymul 2717 was carried out in the presence of 2-hydroxy-2-methyl-1-phenyl-propan-1-one (DarocurÒ1173, from CibaÒ Specialty Chemical Inc.), as photoinitiator. Hereinafter, the different acrylic coatings will be coded as XXXX-YYY, where XXXX and YYY indicate the type of acrylic latex and nanoparticle used, respectively; furthermore, in the case of Craymul 2717, the presence of UV in the code means that the latex has been subjected to the UV-curing process. As an example, 2717UV-BOE indicates a UV-cured coating based on 2717 latex and containing 5 wt% boehmite. Preparation of the nanocomposite coatings
Experimental Materials Two commercially available acrylic latexes, typical for wood applications, namely CraymulÒ2711 and CraymulÒ2717, were kindly supplied by Cray Valley S.r.l., Italy. Their solid content is 40 and 43 wt%, respectively. The FT-IR spectra of the latexes are plotted in Fig. 1: the typical signals of acrylic esters (1700 (s; m(CO)), 1242 (m, m(COC)), 2940, 2860, 1450 and 1380 cm-1 (m, m(CH) stretching and bending) are observed; furthermore, Craymul 2717, the photocurable latex, shows the presence of acrylic unsaturations at ca. 1630 cm-1 Two commercially available nanofillers were chosen for obtaining the nanocomposite coatings, i.e., an organomodified montmorillonite (CloisiteÒ30B, hereinafter C30B) and an unmodified boehmite (DisperalÒ40, hereinafter BOE). The former was purchased by Southern Clay Product Inc. (USA) and contains a methyl, tallow, bis(2hydroxyethyl) quaternary ammonium as compatibilizer. The latter is an unmodified c-AlO(OH), supplied by Sasol
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The acrylic latexes, added with 5 wt% nanofillers (with respect to the solid content of the latex), were subjected to mechanical stirring for 1 h and subsequently ultrasonicated at room temperature for 4 h with an Elmasonic S60H Instr. The stability of the liquid dispersions was monitored by visual inspection up to 4 days after the sonication process: no sedimentation of the nanofillers was observed in any case. This behavior was further confirmed by TEM, as it will be described later. Furthermore, the systems based on the photocurable latex (2717) were either used as prepared or added with 4 wt% of the photoinitiator (with respect to the solid content of the latex) and subjected to the UVcuring process. The photochemical curing was performed by using a medium vapor pressure Hg UV-lamp (Helios Italquartz, Italy): to this aim, three non-consecutive 10 s exposures were applied. The radiation intensity on the surface of the sample was 32 mW cm-2; the irradiation was carried out under nitrogen atmosphere (gas flow: 20 cm3 min-1) in order to prevent oxygen inhibition phenomena. Films having a thickness of ca. 900 lm for thermal and morphological characterizations were obtained by pouring
Thermal, rheological, and barrier properties
the liquid dispersions into Al capsules: the film forming was carried out in an oven at 50 °C for ca. 12 h. Thinner films for permeability tests having 20 lm average thickness were prepared by coating the liquid dispersions onto 12 lm corona-treated PET films (3 M), employing a 50 lm wire wound applicator. For the subsequent film forming, the coated PET substrates were kept at room temperature for 5 h. Characterization techniques FT-IR spectra of the latexes were recorded at room temperature in the range 4,000–600 cm-1 (64 scans, 4 cm-1 resolution, silicon wafers), using a Frontier FT-IR/FIR spectrophotometer (Waltham, Massachusetts, USA). XRD analyses were performed on the coatings by using a Philips PW1830 powder X-ray diffractometer using Cu˚ , 40 kV, 20 mA), 0.05° Ka X-ray source (k = 1.540562 A step size, and 20 s integration time. The interlayer distance (d) was calculated using Bragg’s law. Specimens for TEM characterizations were prepared using a Leica ULTRACUT UCT ultramicrotome equipped with a cryo-chamber operating at -100 °C. Sections with a nominal thickness of 60 nm were cut with a Diatome diamond knife and collected onto formvar-coated copper grids. TEM images were analyzed in a series of at least 10 images per sample. Even though the total area covered by such number of images is too small to carry high statistical significance, in this case they were sufficient to get qualitative conclusions. Differential scanning calorimetry (DSC) was performed using a QA1000 apparatus (TA Instrument Inc., Waters LLC). Three successive scans were performed as follows: First scan: heating up (-30/180 °C at 20 °C min-1) and isothermal step at 180 °C for 3 min. Second scan: cooling down (180/-30 °C at 10 °C min-1) and isothermal step at -30 °C for 3 min. Third scan: heating up (same conditions as in the first scan). A TA instruments Q500 thermo-balance provided with an alumina pan was used for TG analyses. The measurements were conducted in nitrogen or air atmosphere (gas flow: 60 cm3 min-1) between 50 and 800 °C with a heating rate of 10 °C min-1. The experimental error was ±0.5 % by weight. The data collected were Tonset5 % (of mass loss), Tmax (maximum rate of mass loss, derivative curve, DTG), and final residue (at 600 °C). The rheological measurements were carried out on a strain-controlled rheometer (ARES, TA Instruments Inc., Waters LLC) with a torque transducer range of 0.2–2,000 gf cm using a 25 mm parallel plate geometry. The rheometer was equipped with a convection oven in nitrogen
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atmosphere to avoid oxidative degradation of the samples. The usual sample characterization was performed at 100 °C versus time (frequency: 1 rad/s; strain: 0.1 %), strain (frequency: 1 rad/s), and frequency (strain: 0.1 %) sweep tests. Finally, the barrier properties toward oxygen were evaluated by a MultiPerm permeometer (ExtraSolution, Pisa, Italy). The analyses were carried out at pO2 = 1.4805 atm, 25 °C, and 0 % R.H. The pure latexes and their nanocomposite coatings (average thickness: 20 lm) were coated on 12-lm corona-treated PET films used as standard substrates. At least three tests for each sample were performed in order to get significant and reproducible data.
Results and discussion Morphological characterization XRD patterns have been acquired for all the formulations under investigation. The typical peaks of neat C30B (0 1 0) plane, 2h = 4.83° corresponding to an interlayer distance of 1.83 nm, and BOE (0 2 0) plane, 2h = 14.55° corresponding to an interlayer distance of 0.61 nm, have been observed and found in agreement with the literature data previously published [8, 14]. When C30B is added to the resins, irrespective of the type of the system investigated (non-curable, UV-curable or UV-cured), the intensity of the characteristic peak is reduced and a slight shift of the position toward lower angles is found (Table 1). These data suggest that intercalated structures are formed in the three series of samples. In addition, the UV-curing reaction seems to have a negligible effect on the change of the interlamellar distance in comparison with the uncured counterpart (1.92 vs. 1.94 nm, respectively). As expected, in the case of boehmite-containing nanocomposites, the peak corresponding to (0 2 0) plane of the 40 nm crystallites is not affected by the formation of the dispersions, while the presence of diffraction peak with a very low intensity seems to indicate the deagglomeration of the micrometersized boehmite powder and the formation of single highly disordered crystallites. In order to check and confirm such hypothesis, TEM observations have been performed, aiming to directly and qualitatively visualize the state of the silicate layers and of boehmite nanoparticles. Typical images (see representative examples in Fig. 2a–d) show that both nanoparticles are homogeneously distributed and finely dispersed in all of the acrylic matrices. In particular, the analysis of at least ten independent TEM images at low magnification of C30B nanocomposites
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Thermal properties
Table 1 XRD data Code
2h
C30B
4.83
BOE
14.55
2711-C30B
4.59
2711-BOE
14.59
2717-C30B
4.59
2717-BOE
14.63
2717UV-C30B
4.56
2717UV-BOE
14.63
d001/nm
d020/nm
1.83
–
–
0.61
1.92
–
–
0.61
1.92
–
–
0.62
1.94
–
–
0.61
showed that a limited number of stacked intercalated silicate layers (responsible for the weak XRD reflection) are present, whereas a majority of highly exfoliated morphologies could be noticed (Fig. 2a, b). The partly exfoliated morphology, the formation of which is favored by the interactions between the carbonyl groups of the polymer and the hydroxyethyl groups of C30B, has been related to the nanofiller size inhomogeneity. Large layers form stacked structures whereas smaller layers easily exfoliate [24]. On the other hand, the sonication of BOE powder in the presence of any acrylic latex is sufficient to deagglomerate the nanofiller down to sizes in the range of 100–400 nm (Fig. 2c, d). Indeed, the interactions between the polar surface of crystallites and polar groups of the polymers favor an almost complete and random dispersion of the filler into the two latexes, which is still maintained upon UV-curing for the systems based on Craymul 2717.
Fig. 2 TEM magnifications of 2717 and 2717UV-based nanocoatings containing C30B (a, b) and BOE (c, d)
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DSC measurements have been carried out in order to evaluate the effect of the fillers on the thermal properties of the coatings. Table 2 collects the Tg values of the systems investigated, calculated on the second heating scan. First of all, it is noteworthy that 2711-based coatings have lower Tg values with respect to uncured 2717. Furthermore, for these former systems, the presence of nanofillers induces a significant increase of the Tg, thus indicating that the inorganic phase can partially hinder the mobility of the surrounding polymer chains. Referring to uncured 2717 systems, the obtained Tg values result higher than 2711 counterparts. In addition, the nanofillers do not seem to affect the mobility of the polymer chains: indeed, the Tg of 2717 latex does not change after the addition of the nanofillers. On the other hand, the UV-curing process is responsible for the significant increase of the Tg values of the obtained network (compare 2717 with 2717UV, Table 2). In addition, the crosslinking density of the UV-cured network is not affected by the presence of the nanofillers, since the Tg variation between 2717UV and its UV-cured nanocomposites is negligible. The thermal and thermo-oxidative stability of the coatings under study has been investigated by TG analyses performed in inert (nitrogen) and oxidative (air) atmospheres. In general, 2717 and 2717UV show a mass loss at ca. 150 °C both in nitrogen and air. Furthermore, the presence of C30B and BOE increases the thermal stability of these
Thermal, rheological, and barrier properties
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Table 2 Glass transition temperatures (Tg) and permeability of the coatings
Table 3 TG data in nitrogen and air Formulation
3
Tonset5 %/ °C
Tamax1/ °C
Tamax2/ °C
Residue at 600/%
Formulation
Tg by DSCa/°C
O2 permeability/cm mm/day atm
2711
17
0.353
2711
294
400
–
6.4
2711-C30B
23
0.307
2711-C30B
300
400
–
9.0
2711-BOE 2717
23 67
0.344 0.350
2711-BOE
304
402
–
9.5
2717
273
406/418
–
7.6
2717-C30B
68
0.287
2717-C30B
298
403/417
–
9.4
2717-BOE
68
0.318
2717UV
82
0.295
2717-BOE 2717UV
293 206
396/411 401/418
– –
12.7 7.2
2717UV-C30B
78
0.217
410
–
9.0
79
0.247
2717UVC30B
271
2717UV-BOE
2717UV-BOE
278
395/407/ 419
–
9.5
2711
288
335/373
494
5.7
2711-C30B
289
380
490
9.0
2711-BOE 2717
290 268
381 369/404
482 499
9.4 3.4
Nitrogen
a
From second heating scan
Air
Mass/%
(a)
100
2717UV 2717UV-5C30B 2717UV-5BOE
50
0 Mass loss rate/%/°C
200
400
600
125 100 75 50 25
384/416
496
10.0
287
370/409
492
10.7
2717UV
201
368/415
495
4.1
2717UVC30B
251
384/415
514
11.5
2717UV-BOE
264
384/416
495/544
10.7
From derivative curves
0 400
600
T/°C
(b) 100 Mass/%
286
2717-BOE
a
200
2717UV 2717UV-5C30B 2717UV-5BOE
50
0 Mass loss rate/%/°C
2717-C30B
200
400
600
200
400
600
100 50
respect to the neat counterparts, as confirmed by the Tonset5 % collected in Table 3. Therefore, C30B and BOE act as a physical barrier to heat or air transfer/diffusion toward the polymer, thus protecting the polymer efficiently. As an example, the Tonset5 % of 2717UV gains even *70 and 50 °C in nitrogen and air, respectively. Similar findings have been already observed in high-density polyethylene/boehmite systems by Khumalo et al. [25]. Finally, in air, the nanoparticles are able to favor the carbonization step, as observable in the Tmax2 shift and in the final residues at 600 °C (Table 3, last two columns). Rheological properties
0
T/°C
Fig. 3 TG and DTG curves of 2717UV systems in nitrogen (a) and air (b)
latexes in both atmospheres in terms of degradation delay. The TG and DTG curves show similar degradation steps (as shown in Fig. 3a and b, respectively, for 2717UV): the thermal and thermo-oxidative degradation occurs at higher temperatures in the presence of both nanofillers with
As far as the rheological behavior of the systems is considered, we first performed some preliminary tests in order to verify the thermal stability of the samples versus time at the selected conditions of strain and temperature (time sweep tests). The most relevant result refers to the instability of 2717 latex: in the adopted experimental conditions, this system evolves as a function of time (i.e. G0 continuously increases), probably because of the occurrence of crosslinking phenomena.
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Barrier properties Table 2 collects the permeability values of the neat latexes and of their nanocomposites toward oxygen. The obtained
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G´, G ˝/Pa
(a)
105
104
G´ 2717 G´ 2717-BOE G´ 2717-C30B G ˝ 2717 G ˝ 2717-BOE G ˝ 2717-C30B
103
102 10–1
100
101
102
ω /rad/s
(b)
G´, G ˝/Pa
105
104
G´ 2717UV G´ 2717UV-BOE G´ 2717UV-C30B G ˝ 2717UV G ˝ 2717UV-BOE G ˝ 2717UV-C30B
103 10–1
100
101
102
ω /rad/s
(c)
2717UV 2717UV-5C30B 2717UV-5BOE
106
105
η */Pas
In addition, strain sweep tests have been carried out in order to point out the linear viscoelastic region and measure the critical strain values. On the basis of these strain sweep tests, frequency sweep tests have been performed in the linear region, aiming to assess the nanoparticle influence on the viscoelastic properties of the latexes. Neat systems show a typical rubber-like behavior: indeed, in the selected frequency region, storage modulus (G0 ) is nearly constant and is higher than loss modulus (G00 ). In the presence of the nanofillers, an increase of moduli can be found, whereas the shape of the curves does not change. Indeed, fillers act as a reinforcement, thus increasing the moduli values of the latexes; however, the interactions between polymer chains and particles or between particles are probably weak, so that the shape of G0 ’ and G00 curves is unchanged (Fig. 4a, b). Referring to the non-curable latex (i.e., 2711), both nanoparticles do not significantly affect the storage and loss moduli. On the contrary, these values are remarkably increased for the 2717 system in the presence of both nanofillers, as shown in Fig. 4a. As far as 2717UV is concerned, the nanoparticles slightly influence its viscoelastic behavior, further enhancing the storage modulus of this latex (Fig. 4b). As predictable, the presence of nanofillers increases the complex viscosity (g*) of all samples within the experimental error; nevertheless, the typical pseudo-plastic behavior of these systems is still maintained, as revealed by the trend of the complex viscosity as a function of x (see Fig. 4c for 2717UV). Pursuing the present research, we exploited the complex viscosity curves for assessing the viscoelastic parameters of the systems under study [26]. To this aim, the slope of the regression line, which was used for interpolating viscosity data, together with its intercept on the y axis (g*) have been calculated: the former gives an indication of a non-Newtonian behavior of the material, the latter represents the resistance to flow. These data are plotted in Fig. 5a and b as fluidity and flow index, respectively. Fluidity values are strongly affected by the nanofillers for 2717 and 2717UV systems, whereas their changes are almost negligible for 2711 (Fig. 5a); in addition, the effect of BOE is much more pronounced than that of C30B. On the contrary, the flow index remains nearly constant (within the experimental error), irrespective of the nanoparticle addition (Fig. 5b). In conclusion, the presence of the fillers does not modify the non-Newtonian behavior of the coatings probably because of the poor interactions between particles and polymer chains.
G. Malucelli et al.
104
103 10–1
100
101
102
ω /rad/s Fig. 4 G0 and G00 versus x for 2717 sample (curve a) and g* versus x for 2717UV sample (curves b, c)
data show that the dispersion of the nanofillers in the polymer matrices improves the barrier properties of the latexes. In particular, the lowest oxygen permeability values are achieved for the UV-cured coatings containing C30B, which exhibit the highest degree of exfoliation, as already confirmed by TEM. In particular, Table 2 shows that O2 permeability decreases of about 15 % when neat
Thermal, rheological, and barrier properties
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The thermal stability in nitrogen and air of such coatings, evaluated by TG analyses, has been significantly improved by the presence of the nanofillers, irrespective of the used type. Finally, the oxygen permeability of the nanocoatings has been found to strongly decrease, especially in the presence of montmorillonite mainly because of its high aspect ratio morphology.
200000
Fluidity index 150000 100000 50000
B
E
30
V5 U
U 17
17
References
27
27
C
U
V5
17 27
BO
V
B 30
E
C -5
27
27
17
17
-5
BO
17
B
27
30 C
-5 11
27
27
11
-5
27
BO
E
11
0
0.3
Flow index 0.2
0.1
. V.. U
17 27
17
U
V5
BO
E
V U
B
17 27 27
30
E C -5 17 27
17
-5
BO
17 27
C -5
11
27
B 30
E BO 27
27
11
-5
27
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0
Fig. 5 Fluidity (a) and flow index (b) for the systems investigated
2717 is exposed to UV light, due to the crosslinking; on the other hand, as far as C30B is concerned, a further O2 permeability decrease of about 26 % with respect to the neat UV-cured coating is achieved. This result can be mainly attributed to the increase of tortuosity of the diffusion path, which is related both to the degree of dispersion of the clay nanoplatelets and to their high aspect ratio [27]. Indeed, the presence of BOE nanoparticles seems to be less effective in lowering the O2 permeability of the nanocoating, mainly because of their lower aspect ratio with respect to cloisite (4.5 vs. 200–1000, respectively).
Conclusions In this paper, the effect of the presence of an organomodified phyllosilicate (CloisiteÒ30B) or an unmodified boehmite (DisperalÒ40) on the thermal and rheological behaviors of two commercially available waterborne acrylic latexes has been investigated. The homogeneous distribution of the nanofillers within the latexes has been achieved by means of a simple sonication method, which gave rise to very stable dispersions. XRD measurements and TEM have pointed out the occurrence of intercalation/exfoliation phenomena and of deagglomeration for montmorillonite- and boehmite-filled nanocoatings, respectively.
1. Utracki LA, Sepehr M, Boccaleri E. Synthetic layered nanoparticles for polymeric nanocomposites (PNCs). Polym Adv Technol. 2007;18:1–37. 2. Utracki LA. Clay-containing polymeric nanocomposites, vol. 1–2. Shawbury: Smithers Rapra Technology Ltd; 2004. 3. Ray SS, Okamoto M. Polymer/layered silicate nanocomposites: a review from preparation to processing. Prog Polym Sci. 2003;28: 1539–641. 4. Pinnavaia TJ, Beall GW. Polymer–clay nanocomposites. New York: Wiley; 2001. 5. Lan T, Pinnavaia TJ. Clay reinforced epoxy nanocomposites. Chem Mater. 1994;6:2216–9. 6. Peila R, Malucelli G, Priola A. Preparation and characterization of UV-cured acrylic nanocomposites based on modified organophilic montmorillonites. J Therm Anal Calorim. 2009;97:839–44. 7. Sangermano M, Lak N, Malucelli G, Samakande A, Sanderson RD. UV-curing and characterization of polymer-clay nanocoatings by dispersion of acrylate-functionalized organoclays. Prog Org Coat. 2008;61:89–94. 8. Esposito Corcione C, Frigione M, Maffezzoli A, Malucelli G. Photo—DSC and real time—FTIR kinetic investigation on epoxy UV-curable systems containing o-boehmites. Eur Polym J. 2008; 44:2010–23. 9. Glaser HR, Wilkes GL. Polymer modified mixed metal alkoxide– metal acetyl acetonate sol–gel materials. Polym Bull. 1989;22: 527–32. 10. Suzuki F, Onozato K, Kurokawa Y. A formation of compatible poly(vinyl alcohol)/alumina gel composite and its properties. J Appl Polym Sci. 1990;39:371–81. 11. Ahmad Z, Sarwar MI, Krug H, Schmidt H. Preparation and properties of composites of Kevlar-nomex copolymer and boehmite. Angew Makromol Chem. 1997;248:139–51. 12. Esposito Corcione C, Frigione M. UV-cured polymer-boehmite nanocomposite as protective coating for wood elements. Prog Org Coat. December 2011. doi:10.1016/j.porgcoat.2011.06.024. 13. Streller RC, Thomann R, Torno O, Mu¨lhaupt R. Isotactic poly(propylene) nanocomposites based upon boehmite nanofillers. Macromol Mater Eng. 2008;3:218–27. 14. Tettenhorst RT, Corbato CE. Comparison of experimental and calculated X-ray powder diffraction data for boehmite. Clays Clay Miner. 1988;36:181–3. 15. Bocchini S, Morlat Therias S, Gardette JL, Camino G. Influence of nanodispersed boehmite on polypropylene photooxidation. Polym Degrad Stab. 2007;92:1847–56. 16. Siengchin S, Karger-Kocsis J, Psarras GC, Thomann R. Polyurethane latex/water dispersible boehmite alumina nanocomposites: thermal, mechanical and dielectrical properties. J Appl Polym Sci. 2008;110:1613–23. 17. Gatos KG, Martinez Alcazar JG, Psarras GC, Thomann R, Karger-Kocsis J. Polyurethane latex/water dispersible boehmite
123
1310
18.
19.
20.
21.
22.
alumina nanocomposites: Thermal, mechanical and dielectrical properties. Compos Sci Technol. 2007;67:157–67. Florjanczyk Z, Debowski M, Wolak A, Malesa M, Pecha J. Dispersions of organically modified boehmite particles and a carboxylated styrene-butadiene latix: a simple way to nanocomposites. J Appl Polym Sci. 2007;105:80–8. Nobel ML, Picken SJ, Mendes E. Waterborne nanocomposite resins for automotive coating applications. Prog Org Coat. 2007;58:96–104. ¨ zdilek C, Mendes E, Picken SJ. Nematic phase formation of O boehmite in polyamide-6 nanocomposites. Polymer. 2006;47: 2189–97. ¨ zdilek C, Kazimierczak K, Van Der Beek D, Picken SJ. PrepO aration and properties of polyamide-6-boehmite nanocomposites. Polymer. 2004;45:5207–14. Kloprogge JT, Ruan HD, Frost RL. Thermal decomposition of bauxite minerals: infrared emission spectroscopy of gibbsite, boehmite and diaspore. J Mater Sci. 2002;37:1121–9.
123
G. Malucelli et al. 23. Yılmaz O, Cheaburu CN, Gu¨lu¨mser G, Vasile C. Rheological behaviour of acrylate/montmorillonite nanocomposite latexes and their application in leather finishing as binders. Prog Org Coat. 2011;70:52–8. 24. Ray SS, Bousmina M. Poly(butylene sucinate-co-adipate)/montmorillonite nanocomposites: effect of organic modifier miscibility on structure, properties, and viscoelasticity. Polymer. 2005;46:12430–9. 25. Khumalo VK, Karger-Kocsis J, Thomann R. Polyethylene/synthetic boehmite alumina nanocomposites: structure, thermal and rheological properties. eXPRESS. Polym Lett. 2010;4:264–74. 26. Macosko C. Rheology: principles, measurements and applications. Poughkeepsie: Wiley; 1994. 27. Choudalakis G, Gotsis A. Permeability of polymer/clay nanocomposites: a review. Eur Polym J. 2009;45:967–84.
