Chlorinated polyethylene nanocomposites using PCL/clay nanohybrid masterbatches

Exfoliated nanocomposites were prepared by dispersion of poly(ε-caprolactone) (PCL) grafted montmorillonite nanohybrids used as masterbatches in chlorinated polyethylene (CPE). The PCL-grafted clay nanohybrids with high inorganic content were synthesized by in situ intercalative polymerization of ε-caprolactone between silicate layers organo-modified by alkylammonium cations bearing two hydroxyl functions. The polymerization was initiated by tin alcoholate species derived from the exchange reaction of tin(II) bis(2-ethylhexanoate) with the hydroxyl groups borne by the ammonium cations that organomodified the clay. These highly filled PCL nanocomposites (25 wt% in inorganics) were dispersed as masterbatches in commercial chlorinated polyethylene by melt blending. CPE-based nanocomposites containing 3-5 wt% of inorganics have been prepared. The formation of exfoliated nanocomposites was assessed both by wide-angle X-ray diffraction and transmission electron microscopy. The thermal and thermo-mechanical properties were studied as a function of the filler content, by differential scanning calorimetry and dynamic mechanical analysis, respectively. The mechanical properties were also assessed by tensile tests. The Young’s modulus of CPE is increased by a decade when a PCL-grafted clay masterbatch is exfoliated to reach 5 wt% of clay in the resulting nanocomposite. The influence of PCL-grafting on the properties of these nanocomposites was investigated by comparison with materials obtained with ungrafted-PCL.     

Chlorinated polyethylene/layered silicate nanocomposites: Poly(ε-caprolactone)-based “masterbatch” approach

Chlorinated polyethylene (CPE)/organophilic-montmorillonite (Cloisite^®30B (CL30B)) nanocomposites have been prepared by melt intercalation using (poly(ε-caprolactone), (PCL)) as CPE/clay compatibilizer. Actually, a high clay content masterbatch-based on PCL was first produced and then dispersed by melt blending within CPE. CPE/CL30B nanocomposites was also prepared by direct blending of CPE with CL30B for sake of comparison. All the composites were characterized by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The thermal stability of the nanocomposites was analyzed by thermogravimetric analysis (TGA) while the mechanical properties were assessed by tensile testing. When using low molecular mass PCL chains as compatibilizer, the nanocomposites displayed a rather intercalated structure but their ultimate properties remained unchanged whereas with high molecular weight PCL chains, clay delamination was favoured and led to an increase of both thermal and mechanical properties of the resulting nanocomposites.     

Structure and mechanical properties of poly(l-lactide)/layered silicate nanocomposites

Poly(ε-caprolactone) (PCL) masterbatches with the intercalated and the exfoliated morphology were prepared by ring opening polymerization of ε-caprolactone in the presence of organomodified montmorillonite (MMT) Cloisite 30B. Poly(l-lactide) (PLLA) nanocomposites with Cloisite 30B or PCL masterbatches were prepared by melt blending. The effects of the silicate type, MMT content and the nanocomposite morphology on thermal and mechanical properties of PLLA nanocomposites were examined. The montmorillonite particles in PLLA/Cloisite 30B and PLLA/intercalated masterbatch nanocomposites were intercalated. In contrary to expectations, the exfoliated silicate layers of exfoliated masterbatch were not transferred into the PLLA matrix. Due to a low miscibility of PCL and PLLA, MMT remained in the phase-separated masterbatch domains. The stress-strain characteristics of PLLA nanocomposites, Young modulus E, yield stress σ_y and yield strain ε_y, decreased with increasing MMT concentration, which is associated with the increase in PCL content. The expected stiffening effect of MMT was low due to a low aspect ratio of its particles and was obscured by both plastifying effects of PCL and low PLLA crystallinity. Interestingly, in contrast to the neat PLLA, ductility was enhanced in all PLLA/Cloisite 30B materials and in PLLA/masterbatch nanocomposites with low MMT concentrations.     

Preparation of highly exfoliated epoxy/clay nanocomposites by clay grafted with liquid crystalline epoxy

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved by intercalating liquid crystalline epoxy into clay intragallery as well as using a so-called ‘solution compounding’ process. In this process, clay modified was first treated with trichloromethane to form organoclay-trichloromethane suspension followed by liquid crystalline epoxy modification. The liquid crystalline epoxy grafted clay was then mixed extensively with epoxy to form epoxy/nanoclay composites. The mechanism of exfoliation was explored by monitoring the change of morphology of organoclay during each stage of processing with X-ray diffraction (XRD). The liquid crystalline epoxy grafted clay synthesised was characterised by fourier transform infrared spectroscopy (FT-IR) and polarising optical microscopy (POM). The clay platelets uniformly dispersed and highly exfoliated in the whole epoxy matrix were observed using transmission electron microscopy (TEM) and FT-IR imaging system. The epoxy nanocomposites were fabricated by incorporating different liquid crystalline epoxy grafted clay loading. The results revealed that the incorporation of liquid crystalline epoxy grafted clay resulted in a significant improvement in glass transition temperature (Tg) derived from dynamic mechanical analysis (DMA) and thermal stability measured by thermogravimetric analysis (TGA).     

Motional heterogeneity of intercalated species in modified clays and poly(epsilon-caprolactone)/clay nanocomposites

Modified laponites and synthetic saponites are used as precursors for the preparation of poly(epsilon-caprolactone) (PCL)/clay nanocomposites. The structure and dynamics of species intercalated in the modified clays and the corresponding nanocomposites are characterized by X-ray diffraction and magic-angle spinning NMR. The influence of the headgroup, the hydrocarbon chain length, and the loading of the surfactant on the nanocomposite formation are discussed. The yield of PCL intercalation is related to the probability of direct polymer-clay interactions and to the size of the clay platelets. Relaxation times in the laboratory and rotating frames that allow characterization of fast and slow molecular dynamics in these systems are discussed, showing a motional heterogeneity of the intercalated species.     

Synthesis of polylactide/clay nanocomposites by in situ intercalative polymerization in supercritical carbon dioxide

Polylactide (PLA)/clay nanocomposites have been prepared by in situ ring-opening polymerization in supercritical carbon dioxide. Depending on the type of organoclay used, polylactide chains can be grafted onto the clay surface, leading to an exfoliated morphology. Nanocomposites with high clay contents (30-50 wt.%), called masterbatches, have also been successfully prepared and were recovered as fine powders thanks to the unique properties of the supercritical fluid. Dilution of these masterbatches into commercial l-polylactide by melt blending has led to essentially exfoliated nanocomposites containing 3 wt.% of clay. The mechanical properties of these materials have been assessed by flexion and impact tests. Significant improvements of stiffness and toughness have been observed for the PLA/clay nanocomposites compared to the pure matrix, together with improved impact resistance.     

Biodegradable polyester nanocomposites: The effect of structure on mechanical and degradation behavior

The study describes the effect of the layered silicate content and its dispersion on the mechanical behavior of poly(ε-caprolactone) (PCL) nanocomposites and their corresponding changes during the degradation in a phosphate buffer at 37 °C. Two nanocomposite systems were compared: intercalated and exfoliated nanocomposites. They were prepared by melt-compounding of a high-molecular-weight PCL with in situ polymerized silicate masterbatches or an organophilized montmorillonite. It has been shown that Young modulus increases with the increasing silicate content and at the same time, the highest increase in the modulus is observed for the exfoliated system. The stiffness enhancement is predominantly caused by the dispersed inorganic phase but also supported by the contribution of the low-molecular-weight PCL fraction, which comes from the masterbatch, to the total degree of crystallinity. In contrast, the increase in the yield stress is driven mainly by the present low-molecular-weight PCL fraction with higher crystallinity. The degradation behavior reflects both the presence of the layered silicate as well as the low-molecular-weight PCL fraction. Their presence accelerates the degradation in the phosphate buffer at 37 °C.     

Structure and morphology of HDPE-g-MA/organoclay nanocomposites: Effects of the preparation procedures

Nanocomposites comprising high density polyethylene (HDPE) or maleic anhydride-grafted HDPE (HDMA) as the host polymers and Cloisite^® 20A (20A) as the organoclay filler were prepared by melt-compounding, solution-blending and static annealing of polymer/clay powder mixtures. The dependence of their structure and morphology on the preparation conditions was studied by X-ray diffraction (XRD and SAXS), polarized optical microscopy (POM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was shown that intercalated nanocomposites based on HDPE or HDMA cannot be obtained by solution-blending, as long as solvent removal is made at room temperature. In fact, wide angle XRD patterns of solution blended composites are similar to those of mechanical blends of clay and polymer. However, as demonstrated by XRD and SAXS, fast intercalation or even complete delamination was obtained when the HDMA composites prepared from solution were annealed statically at temperatures higher than the polymer melting point. This implies that solution-blending causes efficient fragmentation of the clay agglomerates into thin tactoids (though unintercalated) homogeneously dispersed in the polymer matrix. This conclusion, supported by the finding that annealing mechanical blends of polymer and clay powders only leads to intercalated structures, was confirmed by TEM and SEM analyses. Morphology investigation revealed that, in contrast to melt-compounding, solution-blending followed by static annealing fails to produce significant orientation of clay platelets and polymer crystallites. However, repeated compression molding cycles were shown by XRD and SAXS to cause increasing levels of orientation of the platelets and the polymer matrix parallel to the sample flat surface.     

Efficient photoinduced In situ preparation of clay/poly(glycidyl methacrylate) nanocomposites using hydrogen‐donor silane

Clay/poly(glycidyl methacrylate) nanocomposites (clay/PGMA) were prepared by in situ radical photopolymerization using N,N‐dimethylaminopropyltrimethoxysilane(DMA)‐modified bentonite clay acting as hydrogen donor for benzophenone in solution. This initiating system permits to photopolymerize glycidyl methacrylate between the lamellae of the DMA‐modified clay. The approach provides exfoliated nanocomposites as judged by the measurements of X‐ray diffraction. However, a low fraction of persistent intercalated clay regions was visible by transmission electron microscopy. X‐ray photoelectron spectra analyses indicate that the nanocomposites have PGMA‐rich surface. The clay/PGMA nanocomposites can be readily dispersed in ethanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 800–808     

Effects of spacing between the exfoliated clay platelets on the crystallization behavior of polyamide‐6 in polyamide‐6/clay nanocomposites

Exfoliated polyamide‐6 (PA6)/organoclay nanocomposite films with planar‐oriented clay platelets were prepared by the simple hot pressing of melt‐extruded nanocomposite pellets. The average distance between the neighboring clay platelets was controlled by changes in the clay loading content in the nanocomposites. The effects of the clay platelet spacing on the crystallization behavior of PA6 were investigated with transmission electron microscopy and wide‐angle X‐ray diffraction. The crystal lamellae were found to be mainly perpendicular to the clay surface for the nanocomposites with large spacing between the clay sheets at low clay loading contents. This perpendicular orientation morphology was attributed to the strong interactions between the PA6 molecular chain and the clay surface. In contrast, the crystal lamellae were found to be parallel to the clay surface when the spacing between the neighboring clay platelets was less than 30 nm. It was concluded that the confinement crystallization of PA6 within the nanoscale channels formed by clay sheets resulted in this parallel orientation texture. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 284–290, 2006     

Effect of polymerically‐modified clay structure on the morphology and properties of UV‐cured polyurethane acrylate/clay nanocomposites

Polyurethane acrylate (PUA)/clay nanocomposites were prepared by UV‐curing from a series of styrene‐based polymerically‐modified clays and PUA resin. Effect of the chemical structure of the polymeric surfactants on the morphology and tensile properties of nanocomposites has been explored. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) experimental results indicated that surfactants having hydroxyl or amino groups show better dispersion and some of the clay platelets were fully exfoliated. However, the composites formed from pristine clay and other polymerically‐modified clays without hydroxyl or amino groups typically contained both tactoids and intercalated structure. The mechanical properties of PUA composites were greatly improved where the organoclays dispersed well. Thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) were carried out to examine the thermal properties of the composites. The results showed that the loading of polymerically‐modified clays do not effect the thermal stability, but increased the Tgs of PUA/clay composites. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of matrix viscosity on the extent of exfoliation in EVA/organoclay nanocomposites

The influence of matrix viscosity and polarity on ethylene‐vinyl acetate copolymer (EVA) nanocomposites was studied. Five different EVA grades, with different melt flow indexes (MFIs) and/or vinyl acetate (VA) contents, were mixed with two montmorillonite (MMT) nanoclays: pristine and modified with a polar surfactant, producing 75/25 w/w% masterbatches which were subsequently diluted in the EVA matrix to obtain 5 wt% MMT nanocomposites. Although the same VA content, WAXS results, rheological measurements and TEM analysis showed that the lower the EVA viscosity, the greater the tendency to obtain exfoliated and well dispersed nanocomposites with the organically modified clay. On the other hand, the high viscosity EVA nanocomposites showed that the (001) organoclay diffraction peak was shifted to higher values of 2θ, suggesting lamellae collapsing. TGA and FTIR measurements were used to probe the thermal degradation of organoclay; furthermore, it was not possible to identify, by the techniques used, any reaction between the VA groups and hydroxyl surfactant groups. Thus, it was inferred that the organic surfactant was removed (or ejected) from the clay galleries as a consequence of huge shear tensions developed during processing of the masterbatches/nanocomposites with high viscosity EVA matrices. Copyright © 2009 John Wiley & Sons, Ltd.     

Assessing crystalline lamellae orientation impact on the properties of semi‐crystalline polymer‐clay nanocomposites

Semi‐crystalline polymer‐clay nanocomposite properties are often considered only by their clay dispersion state. The purpose of this work is to highlight texture effects on semi crystalline polymer‐clay properties. Maleic anhydride‐grafted polyethylene nanocomposites with two different processing techniques (Blown Extrusion and Compression) were studied. The processing was shown to induce different crystalline lamellae orientation in the films but with no significant changes in the crystalline lamellae long period, degree of crystallinity, clay particle orientation morphology and dispersion. The impact of these specific textures on the nanocomposites barrier and tensile properties were reported. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1966–1975, 2008     

Studies of ABS-graft-maleic anhydride/clay nanocomposites: Morphologies, thermal stability and flammability properties

ABS-g-MAH (maleic anhydride) with different grafting degree, ABS/OMT (organo montmorillonite) and ABS-g-MAH/OMT nanocomposites were prepared via melt blending. The grafting reaction, phase morphology, clay dispersion, thermal properties, dynamic mechanical properties and flammability properties were investigated. FTIR spectra results indicate that maleic anhydride was successfully grafted onto butadiene chains of the ABS backbone in the molten state using dicumyl peroxide as the initiator and styrene as the comonomer and the relative grafting degree increased with increasing loading of MAH. TEM images show the size of the dispersed rubber domains of ABS-g-MAH increased and the dispersion is more uniform than that of neat ABS resin. XRD and TEM results show that intercalated/exfoliated structure formed in ABS-g-MAH/OMT nanocomposites and the rubber phase intercalated into clay layers distributed in both SAN phase and rubber phase. TGA results reveal the intercalated/exfoliated structure of ABS-g-MAH/OMT nanocomposites has better barrier properties and thermal stability than intercalated ones of ABS/OMT nanocomposites. The T_g of ABS-g-MAH/OMT nanocomposites was also higher than that of neat ABS/OMT nanocomposites. The results of cone measurements show that ABS-g-MAH/OMT nanocomposites exhibit significantly reduced flammability when compared to ABS/OMT nanocomposites even at the same clay content. The chars of ABS-g-MAH/OMT nanocomposites were tighter, denser, more integrated and fewer surface microcracks than ABS/OMT residues.     

Methyl methacrylate oligomerically-modified clay and its poly(methyl methacrylate) nanocomposites

A methyl methacrylate oligomerically-modified clay was used to prepare poly(methyl methacrylate) clay nanocomposites by melt blending and the effect of the clay loading level on the modified clay and corresponding nanocomposite was studied. These nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis and cone calorimetry. The results show a mixed intercalated/delaminated morphology with good nanodispersion. The compatibility between the methylacrylate-subsituted clay and poly(methyl methacrylate) (PMMA) are greatly improved compared to other oligomerically-modified clays.     

Phase behavior of modified montmorillonite– poly(ϵ‐caprolactone) nanocomposites

The thermal behavior and overall isothermal crystallization kinetics of a series of organophilic modified montmorillonite–poly(?‐caprolactone) nanocomposites were investigated. In general, the thermal behavior was influenced more by the type of dispersion than by the clay content. For nanocomposites in which silicate platelets were predominantly dispersed in the polymer matrix to give exfoliated structures, the thermal properties were improved with respect to those of neat poly(?‐caprolactone), whereas in those cases in which simply intercalated structures were attained, the thermal properties regularly decayed as the clay content increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1321–1332, 2004     

Transesterification catalysts to improve clay exfoliation in synthetic biodegradable polyester nanocomposites

We report here on the melt intercalation preparation of polymer/clay nanocomposites based on three commercial synthetic biodegradable polyesters: EastarBio Ultra, Ecoflex, and Bionolle, respectively. The montmorillonite clay addition is performed either by direct dispersion of Cloisite 30B in the polyester matrix or by dispersing a “PCL-grafted Cloisite 30B” masterbatch in the biodegradable polyesters. All obtained nanocomposites display an intercalated morphology as attested by X-ray diffraction measurements. The various analyses clearly show that the Bionolle (BIO) matrix gives the best results. Morphological characterization and mechanical properties of these nanocomposites also show that the “masterbatch route” leads to poor results as a consequence of the very low compatibility between the poly(ε-caprolactone) (PCL) of the masterbatch and the three other polyester matrices. In a second part, nanocomposites based on the BIO matrix are prepared by direct dispersion of the organo-clay in the presence of three different metal-based catalysts with the aim to promote transesterification reactions between the nanocomposite constituents. The mechanical properties and morphological characterization of these nanocomposites show that the tin-based catalyst (Sn) is the more efficient. Indeed, the effectiveness of transesterification reactions taking place between the ester functions of the BIO matrix and the hydroxyl groups of the organo-clay and the resulting “grafting” of BIO chains on the organo-clay surface are confirmed by thermogravimetric analyses performed after the extraction procedure. TEM observations show that this catalyst enhances the clay platelets exfoliation within the BIO matrix as a consequence of the transesterification reactions. Nanocomposites prepared in presence of Sn show better clay dispersion and enhanced stiffness with a 60% increase in Young’s modulus.     

Sonochemical intercalation of preformed gold nanoparticles into multilayered clays

Multilayered Na (+)-montmorillonite clays intercalated with Au nanoparticles were synthesized by direct ultrasonic impregnation of preformed gold colloid into the clay matrix. The sonicated composite product then consists of Au nanoparticles homogeneously dispersed in the clay. The resulting clay/nano-Au composite was calcined at 800 degrees C and characterized by BET surface area analysis, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared measurements. Nearly spherical-shaped gold nanoparticles, with a size of 6 +/- 0.5 nm, are located in the pores of clay calcined at 800 degrees C. Their nanocomposites are thermally stable as was shown by thermogravimetric analysis. No aggregation of the gold nanoparticles was observed during calcination. The proposed ultrasonic intercalation approach is an universal one and can be employed for synthesis of catalytically active metal-clay nanocomposites stable at high temperatures with high dispersability of the metal nanoparticles in the clay matrix.     

Characterization of HDPE /Polyamide 6/ Nanocomposites Using Scanning-and Transmission Electron Microscopy

Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed.     

A novel method for preparation of exfoliated UV-curable polymer/clay nanocomposites

The half adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate (IPDI-HEA), as a reactive organic modifier, was used to functionalize Na-montmorillonite (Na-MMT) clay. Unlike the electronic interaction in the conventional cation-exchange method, the driving force for the organic modification came from the chemical reaction between IPDI-HEA and framework hydroxyl groups on the surface of clay. With high degree of organic modification (48%), the d-spacing of clay layer was greatly enlarged to 3.32 nm, and the clay became more organophilic. After in situ photopolymerization among the IPDI-HEA grafted MMT clay, monomers and oligomers, the exfoliated polymer/clay nanocomposites were obtained. X-ray diffraction and transmission electron microscopy were used to detect the structure and morphology of the clay dispersed in the polymer matrix. Compared with the pure polymer materials, the exfoliated polymer/clay nanocomposites exhibited enhancements in mechanical and thermal properties.