Design of experiments for thermo-mechanical behavior of polypropylene/high-density polyethylene/nanokaolinite clay composites

This paper deals with the preparation of nanocomposites using polypropylene (PP)/high-density polyethylene (PE) blend and low-cost nanokaolinite clay by melt compounding in a Thermo Haake Rheocord mixer. The optimization of processing parameters and nanoclay content is done using Box–Behnken design of response surface methodology. Mechanical properties are modeled in terms of processing parameters and nanoclay content and results are verified using statistical analysis. Most reports suggest that kaolinite clay is difficult to disperse in polymer matrix compared to costly montmorillonite clay. This difficulty is overcome by surface modification of nanokaolinite clay by an organic group and the effect of modification is studied using melt flow index, thermal stability and dynamic mechanical behavior. Morphological characterization is done by scanning electron microscopy and X-ray diffraction. Study shows that cheap and abundantly occurring nanokaolinite clay is an efficient reinforcing agent for PP/PE blend. Design of experiments can be effectively used to model such a system, which is influenced by a number of variables. It is also observed that surface modification of the nanoclay with an organic group leads to remarkable improvement in the thermal and mechanical properties of the blend.     

Morphology and properties of nylon 6 and high density polyethylene blends in presence of nanoclay and PE‐g‐MA

In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE‐g‐MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE‐g‐MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X‐ray diffractometer (WAXD) study. The size of phase‐separated domains decreased considerably with increasing content of nanoclay and PE‐g‐MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend–clay nanocomposites. Addition of PE‐g‐MA in the blend–clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE‐g‐MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyamide-12 layered silicate nanocomposites by melt blending

Polyamide-12/tetrasilisic fluoromica (PA12-ME100) and polyamide-12/quaternary tallow ammonium chloride modified fluoromica nanocomposites (PA12-MAE) were prepared by melt compounding. The nanocomposite morphology and clay dispersion were investigated using wide angle X-ray diffraction (XRD), scanning electron microscopy (SEM), SEM-energy dispersive X-ray analysis (SEM-EDX), transmission electron miscroscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). A predominantly intercalated morphology was observed for PA12-ME100, and a very high degree of exfoliation for PA12-MAE. HRTEM showed that the polymer crystallites lie perpendicular to the clay surface. The tensile and flexural properties of the PA12-MAE nanocomposite were significantly enhanced compared to neat polyamide-12, even with the addition of only 4 wt% nanoclay. Furthermore, the elongation at break (%) increased from 180% for polyamide-12 up to >500% for the PA12-MAE nanocomposite. In situ measurement of the heat generated in the test specimens during uniaxial tensile deformation using infra-red thermal imaging showed that the temperature of the dumbbell samples increased from room temperature (23 °C) to as high as 70 °C regardless of the strain rate used. This is considerably above the glass transition temperature (T_g) of PA12-MAE (30 °C), as measured by dynamic mechanical thermal analysis (DMTA). The mechanism of deformation is partially explained in terms of microvoid formation. The shear viscosity of the PA12-MAE nanocomposite determined by dual capillary rheometry was lower than both neat polyamide-12 and PA12-ME100. The reduction in shear viscosity of the nanocomposites was shown, from gel permeation chromatography (GPC) studies, not to originate from polymer degradation during melt blending. The coefficient of thermal expansion, decomposition temperature, and melting and crystallisation temperatures and relative crystalline content of the nanocomposite materials were measured by thermo-mechanical analysis (TMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) respectively—properties which can be related to polymer nanoclay interactions.     

Oxygen Barrier Properties of New Thermoplastic Natural Rubber Nanocomposites

Nanocomposites of linear low-density polyethylene (LLDPE)/natural rubber (NR)/liquid natural rubber (LNR) blend denoted as TPNR with montmorillonite-based organoclay (OMMT) were prepared using melt blending method. The melt blending of LLDPE/NR/LNR with a composition of 70:20:10 formed blends. For better dispersion of nanoclay in the TPNR blend, MA-PE was used as a coupling agent. The nanoclay dispersion was investigated by X-ray diffraction (XRD), and a novel method using permeability measurements data in a permeability model. The measured d-spacing data proved a good dispersion of nanoclay at low clay contents. The permeability model for flake-filled polymer was used to estimate the aspect ratio of nanoclay platelets in the blend nanocomposites. The oxygen barrier property of the TPNR blend improved about two-fold by adding only 2 wt% of organoclay. Differential scanning calorimetry showed an increase in cystallinity up to 20% suggesting an increase in spherulite growth, by the increased in melting temperature. The increase in the barrier property of the blend with the induction in crystallinity indicates the dominant role of organoclay platelets in barrier improvement. Scanning electron micrographs of tensile fracture surface of the nanocomposite, exhibited a very ductile surface indicating a good compatibility of LLDPE and NR and also, a possible contribution of nanoparticles to the deformation mechanism, such as extensive shear yielding in the polymer blend. The transmission electron micrograph, showed an intensive intercalation structure and exfoliation structure with the presence of MA-PE.     

Structural,rheological, and mechanical properties of PA6/SAN/SEBS ternary blend/organoclay nanocomposites

The aim of this study was to investigate the effect of nanoclay addition on the morphological and mechanical properties of PA6/SAN/SEBS ternary blend. Two different nanoclays with different modifiers and two different mixing sequences were used to investigate the role of thermodynamic and kinetic, respectively, in the nanoclays localization. XRD, SEM, TEM, melt rheology, tensile and Izod impact tests were used to characterize the nanocomposites. Results of characterization of nanocomposites showed that clay localization is a very influential parameter to determine the type of morphology and, consequently, mechanical properties of ternary/clay nanocomposites. It was demonstrated that presence of nanoclay in the matrix results in the increase of stiffness, while localization of nanoclay at the interface improves the toughness and tensile strength. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41969.     

Mechanical response and rheological properties of polycarbonate layered‐silicate nanocomposites

The effect of clay loading on the mechanical behavior and melt state linear viscoelastic properties of intercalated polycarbonate (PC) nanocomposites was investigated. At low frequencies, the linear dynamic oscillatory moduli data revealed diminished frequency dependence with increasing nanoclay loading. The 3.5 and 5 wt% clay nanocomposites exhibited dramatically altered relaxation behavior, from liquid‐like to pseudo‐solid–like, compared to the pure PC and the 1.5 wt% clay nanocomposite. Thermal degradation of PC resulted from the melt compounding of organo‐modified nanoclays was evident from the reduction in the glass transition temperature and molecular weight of the PC nanocomposites. These nanocomposites also exhibited a significant decrease in the extent of tensile elongation and ductility with respect to the nanoclay incorporation. A concomitant decrease in the rheological properties at high frequencies was also observed, and was consistent with the lowering of the molecular weight of PC, particularly near or above the percolation threshold of nanoclay. These nanocomposites, nevertheless, exhibited elastic‐plastic deformation in compression, regardless of nanoclay content. Polym. Eng. Sci. 44:825–837, 2004. © 2004 Society of Plastics Engineers.     

An in-situ simultaneous SAXS and WAXS survey of PEBAX® nanocomposites reinforced with organoclay and POSS during uniaxial deformation

Poly(ether-block-amide) (PEBA), commercially known as PEBAX^®, nanocomposites filled with organically modified clay (Cloisite 30B) and trisilinolphenyl-polyhedral oligomeric silsesquioxane (tsp-POSS) were prepared by a melt mixing method, respectively. The structures of the nanocomposites were investigated using differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and in-situ simultaneous small and wide angle X-ray scatterings (SAXS and WAXS) during uniaxial deformation. The FT-IR spectra showed the hydrogen bonding between the fillers and the PEBA which helped to disperse the fillers in the polymer matrix. The crystallinities and mechanical properties of the nanocomposites were improved compared to the neat polymer. Their origins were studied with an in-situ simultaneous SAXS and WAXS technique during the uniaxial deformation.     

Morphological,rheological and thermal studies in melt processed compatibilized PA6/ABS/clay nanocomposites

Multicomponent compatibilized blends of polyamide 6 (PA6) and styrene-butadiene-acrylonitrile (ABS) with co-continuous morphology are among commercial alloys with an interesting combination of properties. To further enhance the properties different amounts of nanoclay were incorporated into these blends through a one step melt mixing process. The effect of nanoclay addition on rheological, thermal stability, crystallization and morphological properties of the nanocomposites were investigated and compared with those of the neat blends. The nanoscale dispersion of the clay layers in the blends were confirmed through X-ray diffraction and transmission electron microscopy methods. Rheological investigation indicated an increased viscosity and melt elasticity for the nanocomposite systems. The viscosity of nanocomposites followed a shear thinning flow behavior and decreased with increasing shear rates. The changes in the rheological properties were accompanied by refinement of the co-continuous morphology. For thermal degradation under N₂ atmosphere, the onset and maximum of degradation temperatures for the nanocomposites were as high as the neat blends, while significant improvement in thermal stability (about 60 °C by 3 wt% clay addition) was observed in the air environment. In addition agglomerated clay particles did not significantly affect thermal stability of the polymer matrix. Non-isothermal crystallization results indicated that the clay layers had a retarding effect on the crystal growth rate and facilitated the formation of α crystalline form. In addition no nucleation effect was observed during the crystallization process due to incorporation of nanoclay into the blends.     

Effect of clay content and clay/surfactant on the mechanical, thermal and barrier properties of polystyrene/organoclay nanocomposites

In the present paper, three ammonium salts namely, tetraethylammonium bromide (TEAB), tetrabutylammonium bromide (TBAB), and cetyltrimethylammonium bromide (CTAB) were employed to prepare organoclay by cation exchange process. Polystyrene (PS) /clay nanocomposites were prepared by melt blending using commercial nanoclay and organoclays prepared using above mentioned salts. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis indicated that the modified clays were intercalated and/or exfoliated into the polystyrene matrix to a higher extent than the commercial nanoclay. Further, amongst the modified organoclays, TBAB modified clay showed maximum intercalation of clay layers and also exfoliation to some extent into the polystyrene matrix. TEM micrograph exhibited that TBAB modified clay had the best nanoscale dispersion with clay platelet thickness of ∼6–7 nm only. The mechanical properties of the nanocomposites such as tensile, flexural and izod impact strength were measured and analyzed in relation to their morphology. We observed a significant improvement in the mechanical properties of polystyrene/clay nanocomposites prepared with modified clays as compared to commercial organoclay, which followed the order as; PS/TBAB system > PS/CTAB system > PS/TEAB system. Thermogravimetric analysis (TGA) demonstrated that T₁₀, T₅₀ and Tmax were more in case of polystyrene nanocomposites prepared using modified organoclays than nanoclay [nanolin DK4] and maximum being in the case of PS/CTAB system. The results of Differential Scanning Calorimetry (DSC) confirmed that the glass transition temperature of all the nanocomposites was higher as compared to neat polystyrene. The nanocomposites having 2% of TBAB modified clay showed better oxygen barrier performance as compared to polystyrene.     

Dynamics of migration and phase selective localization of nanoclay in HNBR/ENR blends

The phase specific selective localization and dynamics of migration of nanoclay in hydrogenated acrylonitrile butadiene rubber (HNBR)/epoxidized natural rubber (ENR) blend systems is investigated. The phase specific dispersion of clay particles is monitored through measuring the online measured electrical conductance (OMEC) during mixing by means of a sensor system installed inside the chamber of an internal mixer. The results of different characterization techniques, such as atomic force microscopy, transmission electron microscopy, and small angle X‐ray scattering have been used to understand and interpret the OMEC behaviors of nanoclay‐filled rubber compounds individually (HNBR and ENR) and their blend systems. The observed online conductance is ionic in nature that arises due to the release of surfactant molecules from the clay galleries. It is observed that the OMEC behavior depends mainly on two factors: the localization of nanoclay in specific phase of the blend system and on the gradual development of blend morphology. The OMEC behavior and the supported data from the microscopic methods, clearly reveal the migration of organoclay from the ENR to HNBR phase during the mixing process, particularly localizing near the interface of the blend. Further, the localization of organoclay is also evaluated by applying the surface tension measurements based model, which also predicts the favorable localization of organoclay in HNBR phase of the blend. The work clearly suggests the OMEC method to be a powerful online tool to monitor and control the nanoclay dispersion and localization in rubber based nanocomposites during the melt mixing process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44074.     

Morphology and chain mobility of reactive blend nanocomposites of PP‐EVA/Clay

Polypropylene (PP)‐ethylene vinyl acetate (EVA)/clay nanocomposites were prepared via reactive blending using dicumyl peroxide (DCP) as an initiator with the goal of enhancing the interaction between both phases and modified nanoclay. The effect of the reactive blending and clay incorporation strategies (direct and masterbatch) on the blend and nanostructure morphology, and chain mobility of nanocomposites were studied. The chemical analysis showed the chemical bonding of PP‐EVA, which helped to enhance the interaction in the nanocomposites. The nanocomposites obtained from the direct clay strategy presented a co‐continuous morphology of bordering intercalated and agglomerated nanoclay sheets, while the nanocomposites obtained from the masterbatch strategy showed that blend morphology change from droplet to co‐continuous with the increase of EVA concentration, with intercalated/exfoliated nanoclay sheets located in the EVA domains and at the interface. The dynamic mechanical and creep‐recovery results showed different behavior for the both strategies in terms of chain mobility and relaxation. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40897.     

Studies on mechanical behavior high impact polystyrene/vinyl clay nanocomposites: Comparison between in situ polymerization and melt mixing

A comparative study on various synthesis methods like melt mixing (MM) and in situ polymerization (ISP) of high impact polystyrene/vinyl clay nanocomposites (HIPS/VNCs) is attempted here. In ISP, nanocomposites were prepared by mixing vinyl clay (VC) and poly butadiene rubber (PBR) in styrene with the initiator, azo bis isobutyronitryle. Melt compounding was conducted in two ways–commercial melt mixed blend where Commercial HIPS was mixed with VC and in situ melt mixed blend, where, nanocomposites were prepared by mixing polystyrene, PBR, and VC. The effect of dispersion of the nanoclay on the morphology and material properties of HIPS/VNCs was compared for all the methods, and it is found that the product obtained by ISP gives better properties when compared with MM. Moreover, the dispersion of the clay in the matrix is greater by in situ method, which is evident from X‐ray diffraction pattern and scanning electron microscopic analysis. Statistical analysis of ISP was carried out by design expert software version 8.0.7.1. Modeling and Optimization of the mechanical properties were done by using central composite design of response surface methodology. POLYM. COMPOS., 38:68–76, 2017. © 2015 Society of Plastics Engineers     

Morphology,Rheological Properties,and Crystallization Behavior of Polypropylene/Clay Nanocomposites

Polypropylene/clay nanocomposites (PP/I.44P, PPCNs) were prepared in a twin-screw extruder using maleic anhydride grafted polypropylene (MAPP) as a compatibilizer. The intercalation of polypropylene into nanoclay particles was studied using X-ray diffraction. Rheological properties of the nanocomposites were investigated using a rheometer. The enhanced complex viscosity at low frequency regime indicated that the melt elasticity and melt strength of the nanocomposites were improved by adding nanoclay. The non-isothermal crystallization behavior of the nanocomposites was studied using differential scanning calorimetry (DSC) at various cooling rates and was analyzed with the Avrami method. It was found that the nanoclay acted as a heterogeneous nucleating agent resulted in higher crystallization temperature and higher crystallization rate than neat PP. Polarized optical microscopy revealed that the spherulites in the nanocomposites were finer than in the neat system.     

Nonisothermal crystallization behavior of melt‐intercalated polyethylene‐clay nanocomposites

The influence of nanoclay particles on the nonisothermal crystallization behavior of intercalated polyethylene (PE) prepared by melt‐compounding was investigated. It is observed that the crystallization peak temperature (T_p) of PE/clay nanocomposites is slightly but consistently higher than the neat PE at various cooling rates. The half‐time (t_0.5) for crystallization decreased with increase in clay content, implying the nucleating role of nanoclay particles. The nonisothermal crystallization data are analyzed using the approach of Avrami (Polymer 1971, 12, 150), Ozawa (Polym Eng Sci 1997, 37, 443), and Mo and coworkers (J Res Natl Bur Stand 1956, 57, 217), and the validity of the different kinetic models to the nonisothermal crystallization process of PE/clay nanocomposites is discussed. The approach developed by Mo and coworkers successfully explains the nonisothermal crystallization behavior of PE and PE/clay nanocomposites. The activation energy for nonisothermal crystallization of neat PE and PE/clay nanocomposites is determined using the Kissinger (J Res Natl Bur Stand 1956, 57, 217) method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3809–3818, 2006     

Characterization of latex-based isotactic polypropylene/clay nanocomposites

Polypropylene/clay nanocomposite (PCN) containing 1 wt% organo-modified clay was prepared by latex technology, previously successfully applied for preparation of carbon nanotubes (CNTs)/polymer composites. The level of dispersion of organoclay and the microstructure of the resulting PCNs were characterized by means of X-ray diffraction analysis, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The obtained results have demonstrated that the latex technique represents a promising method for preparation of PP/clay nanocomposites with good dispersion of exfoliated nanoclay particles. The influence of clay nanoparticles on nonisothermal crystallization of PCN was investigated by DSC. The crystallization onset temperature of the matrix rises for about 5 °C when crystallizing from the quiescent melt. Improved thermal stability of PP/nanoclay was observed as evaluated by TGA. The dynamic mechanical analysis reveals an increase in storage modulus of PP matrix in the nanocomposites for 30% over a temperature range, indicating an increase in the stiffness of the material with the addition of organically modified clay.     

Effect of functionalized polyethylenes on clay dispersion in high density polyethylene nanocomposites

The compatibilization effects provided by maleic anhydride (MA), itaconic acid (IAc), itaconic anhydride (IA), and 2-[2-(dimethylamine)-ethoxy]ethanol (DMAE) functionalized polyethylenes for forming high density polyethylene (HDPE)-based nanocomposites were studied and compared. IAc and IA were grafted into HDPE by melt mixing to obtain functionalized polyethylenes (HDPEgIAc and HDPEgIA) and amino alcohol functionalized polyethylene was prepared by reaction of commercial HDPEgMA with DMAE in the melt to form polyethylene-grafted dimethyl-amine-ethoxy-ethanol (PEgDMAE). Nanocomposites were prepared by melt processing using a twin screw extruder by blending polyethylene and these compatibilizers with a quaternary ammonium surfactant-modified montmorillonite clay (Nanomer I28E). FTIR characterization confirmed the formation of these compatibilizers and confirmed the reaction between HDPEgMA and the amino alcohol. All the compatibilized nanocomposites had better clay exfoliation compared to the uncompatibilized HDPE nanocomposites. Barrier properties, X-ray diffraction and transmission electron microscopy results showed the following order of their performance as a compatibilizer: PEgDMAE > HDPEgAI > HDPEgAcI > HDPEgMA. This behavior was attributed to the specific interactions between the anionic surface of the clay and the functionality of the compatibilizer. Samples with higher clay content showed poorer clay dispersion or intercalation which was attributed to possible clay saturation when the van der Waals attractive interactions between the clay layers become dominant when the distance between them was small enough at a certain concentration of clay. A noticeable reduction in the degree of crystallinity with the incorporation of nanoclay was observed by thermal analysis whereas the melting temperature did not change noticeably.     

Effect of nanoclay type on dyeability of polyethylene terephthalate/clay nanocomposites

Polyethylene terephthalate (PET)-based nanocomposites containing three differently modified clays were prepared by melt compounding. The influence of type of clay on disperseability, thermal, and dyeing properties of the resultant nanocomposite was investigated by various analytic techniques, namely, X-ray diffraction, optical microscopy (OPM), differential scanning calorimetry, thermal gravimetric analysis, dynamical mechanical thermal analysis, contact angle measurement (CAM), reflectance spectroscopy, and light fastness. OPM images illustrated formation of large-sized spherulites in pure PET, while only small-sized crystals appeared in PET/clay nanocomposites. Decreased glass transition temperatures for all PET/clay nanocomposites indicate that the amorphous regions of such composites become mobile at lower temperatures than those in pure PET. CAMs on the resultant PET composites demonstrated that the wettability of such composites depends on hydrophilicity of the nanoclay particles. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and crystalline morphology of biodegradable starch/clay nanocomposites

An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H₂O was investigated and the gelatinized temperature (T_gel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N₂ atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.     

Modified preparation of HDPE/clay nanocomposite by in situ polymerization using a metallocene catalyst

In this study, preparation of high-density polyethylene (HDPE)/clay nanocomposite by in situ polymerization of ethylene using a zirconocene catalyst (bis-(cyclopentadienyl) zirconium dichloride (Cp₂ZrCl₂)) was investigated. To obtain higher efficiency, nanoclay particles (Na-montmorillonite) were modified by ammonia (NH₃), NH₃/methylaluminoxane (MAO), NH₃/dodecylamine (DDA), and NH₃/MAO/DDA systems. The results showed that the activity of the catalyst supported on the nanoclay particles modified by NH₃/MAO (762 g_p/mmol (Zr) t [atm]) was higher than that of the one supported on the unmodified nanoclay as well as the other prepared modified nanoclay-supported catalyst systems. The catalyst activities versus MAO concentration in NH₃/MAO treatment system and versus DDA concentration in NH₃/DDA system showed a maximum. Unexpectedly, a very low catalyst activity (180 g_p/mmol(Zr) t [atm]) was obtained using NH₃/MAO/DDA system. X-ray diffraction patterns showed that the HDPE/clay nanocomposites prepared by NH₃/MAO/DDA treatment system had less intercalated structure. Fourier transform infrared (FTIR) spectroscopy confirmed that water molecules of the nanoclay particles were reduced by NH₃ modification. DSC results revealed that crystallinity of the HDPE/clay nanocomposites increased with the modification of the nanoclay particles. The maximum degree of crystallinity of 80.8% was obtained for HDPE/clay nanocomposites prepared by the nanoclay modified by NH₃. In addition, nanoclay modification with NH₃, NH₃/MAO, and NH₃/DDA systems resulted in higher thermal decomposition temperature (~30 °C higher than 480 °C of the unmodified one). Such increase was not observed for the NH₃/MAO/DDA treatment system. Dynamic mechanical analysis showed an increase in the elastic modulus of the nanocomposite samples prepared by modified nanoclay particles, as well. Meanwhile, modification of the nanoclay particles by NH₃ led to the highest elastic behavior compared to the other modification systems. It was about 4.6 GPa which was 28% higher than the elastic modulus of the nanocomposite prepared by unmodified nanoclay particles.     

Enhanced electroactive β phase in three phase PVDF/CaCO3/nanoclay composites: Effect of micro‐CaCO3 and uniaxial stretching

In this study, electroactive polar phase transformation and crystallinity of poly(vinylidene fluoride) (PVDF)‐based composites, such as PVDF/CaCO₃/nanoclay, is explored as a function of micro‐CaCO₃ fraction and draw ratio (R) of uniaxial stretching. Composites including PVDF/clay, PVDF/CaCO₃ and most importantly PVDF/CaCO₃/clay with varying fraction of micro‐CaCO₃ were extruded into homogenous and flexible cast films. Characterization via Fourier transform infrared spectroscopy, X‐ray diffraction, and differential scanning calorimetry (DSC) confirmed the presence of β phase in all the composites incorporated with micro‐CaCO₃ and nanoclay either individually (i.e., PVDF/CaCO₃ and PVDF/clay films, respectively) or together (i.e., PVDF/CaCO₃/nanoclay composites). Interestingly, a gradual but significant improvement in this electroactive phase (β phase) was obtained with successive increment in CaCO₃ content into a fixed composition of PVDF and nanoclay (PVDF/CaCO₃/clay composites). Further increment in β phase content was obtained via uniaxial stretching to different draw ratios and at a temperature of 90 °C, where for PVDF/CaCO₃/clay (especially, 100–35‐3 and 100–40‐3) samples almost no α phase was observed irrespective of R. Conversely, the crystallinity of melt extruded samples decreased gradually all the way with CaCO₃ concentration in PVDF/CaCO₃/clay composites compared to the neat PVDF while increased gradually with increasing draw ratio. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44940.