Effect of organoclay on the properties of maleic‐anhydride grafted polypropylene and poly(methyl methacrylate) blend

Poly(methyl methacrylate)/polypropylene (PMMA/PP) and PMMA/maleic‐anhydride grafted PP (MAPP) blends and their blend nanocomposites containing 2 wt% organoclay (Cloisite 15A, denoted C15A), prepared by a melt mixer were studied. Both X‐ray diffraction (XRD) and transmission electron microscopy (TEM) revealed exfoliated polymer blend nanocomposites. Scanning electron microscopy (SEM) studies indicated a droplet dispersion morphology for all the blends while addition of C15A into PMMA/MAPP blend resulted to a co‐continuous morphology. In fact, rheological data and thermal properties indicated that the PMMA/MAPP/C15A nanocomposite showed a better homogeneous dispersion of silicate layers than PMMA/PP/C15A nanocomposite. A Cole–Cole plot and relaxation modulus indicated a solid‐like character for PMMA/MAPP and PMMA/MAPP/C15A, while a liquid‐like behavior was noticed for PMMA/PP and PMMA/PP/C15A. The effect of an organoclay on the dynamic mechanical properties of samples was investigated using dynamic mechanical analysis (DMA) which showed a significant enhancement on the storage modulus of the PMMA/MAPP/C15A as compared to PMMA/PP/C15A . POLYM. COMPOS., 38:431–440, 2017. © 2015 Society of Plastics Engineers     

Location of a nanoclay at the interface in an immiscible poly(ε‐caprolactone)/poly(ethylene oxide) blend and its effect on the compatibility of the components

Nanocomposites based on 80/20 and 20/80 (w/w) poly(ε‐caprolactone) (PCL)/poly(ethylene oxide) (PEO) immiscible blends and organophilic layered silicates were prepared with melt extrusion. From transmission electron microscopy analysis, it was observed that the exfoliated silicate platelets were preferentially located at the interface between the two blend phases. When the blend‐based nanocomposites were prepared via a two‐step process in which the silicates were first premixed with the PEO component or with the PCL component, the silicate layers migrated from the PEO phase or PCL phase to the interface. The rheological behavior of the nanocomposites was also investigated. At low frequencies, the frequency dependence of the storage modulus changed from a liquidlike behavior for the unfilled blend to a solidlike behavior for the nanocomposites, indicating the formation of a network structure as a result of exfoliation. From the scanning electron micrographs, a monotonic decrease of the PEO domain size in the 80/20 PCL/PEO blend was observed as a function of the organophilic clay content. Therefore, a clear emulsifying effect was induced by the organophilic layered silicates in the immiscible PCL/PEO blend. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical and rheological properties of the maleated polypropylene–layered silicate nanocomposites with different morphology

Three types of maleated polypropylene–layered silicate nanocomposites with different dispersion states of layered silicate (deintercalated, intercalated, and exfoliated states) are prepared from two kinds of polypropylenes with different molecular weights, organically modified layered silicate and pristine montmorillonite to investigate the effect of the final morphology of the nanocomposite on the rheological and mechanical properties. Maleated polypropylene with high molecular weight intercalates slowly and the other with low molecular weight exfoliates fast into the organophilic layered silicates. Rheological properties such as oscillatory storage modulus, nonterminal behavior, and relative viscosity has close relationship with the dispersion state of layered silicates. The exfoliated nanocomposite shows the largest increase and the deintercalated nanocomposite shows almost no change in relative shear and complex viscosities with the clay content. The exfoliated nanocomposite shows the largest drop in complex viscosity due to shear alignment of clay layers in the shear flow. In addition, the final dispersion state of layered silicates intimately relates to the mechanical property. The dynamic storage moduli of nanocomposites show the same behavior as the relative shear and complex viscosities. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1526–1535, 2003     

Effects of different kinds of clay and different vinyl acetate content on the morphology and properties of EVA/clay nanocomposites

A series of EVA/clay nanocomposites and microcomposites have been prepared via melt-blending. Using four kinds of EVA with different vinyl acetate (VA) contents: 28, 40, 50 and 80 wt%, and four kinds of clay: three are organophilic clay (OMMT) and one unfunctionalized clay (Na-MMT), the effects of different VA content of EVA and the kinds of the clay on the morphology and properties of EVA/clay nanocomposites were systematically investigated. In previous studies, there are only two distinct nanostructures to distinguish polymer/clay nanocomposites: the intercalated and the exfoliated. But in this paper, we proposed a new nanostructure—‘the wedged’ to describe the dispersion degree of clay in nanocomposites, it means the sheets of clay were partly wedged by the chains of polymer. The wedged, the intercalated and the partially exfoliated structures of EVA/clay nanocomposites were characterized by X-ray diffraction (XRD) and by high-resolution transmission electron microscopy (HRTEM). The enhanced storage modulus of EVA/clay nanocomposites was characterized by dynamic mechanical thermal analysis (DMTA). The enhanced degree in the storage modulus of the OMMT on EVA/clay nanocomposites with the partially exfoliated and intercalated structure is much higher than that with wedged structure, and that with the higher VA content is higher than that with the lower. The thermal stabilities of EVA/clay nanocomposites were also studied by thermal gravimetric analysis (TGA).     

Artificial latex-based opals prepared by spin casting of monodispersed nano particles

Organoclay nanocomposites based on cyclic olefin copolymer (COC) with various contents of layered silicate nanoparticles were prepared via melt blending. The influence of processing conditions and nanoclay content on solid state viscoelastic and melt rheological properties as well as thermal degradation behavior was studied. The state of dispersion was investigated using X-ray diffraction technique which showed a strong dependence on composition, where an exfoliated morphology was identified in high nanoclay loading. Besides, the processing conditions, i.e., screw rotation speed and mixing time were also found to strongly influence the state of nanophase dispersion. The rheological investigations revealed a remarkable increase in storage shear modulus and complex viscosity values upon nanoclay incorporation. Furthermore, dynamic mechanical analysis gave an evidence of increasing stiffness after nanoclay was added into COC matrix; however, no detectable change in glass transition peak was brought about. The results from thermogravimetry also exhibited a rising trend in thermal stability values as nanophase organoclay was incorporated, for which the random chain scission was suggested as the prevailing mechanism based on a theoretical analysis.     

Nanoclay dispersion in a miscible blend: an assessment through rheological analysis

In this study, miscible polymer blend nanocomposite of Poly(ethylene oxide)/Poly(methyl methacrylate), (PEO/PMMA), with sodium montmorillonite (Na⁺-MMT) clay were prepared at a constant concentration of nanoparticles via different solution intercalation methods. The resultant nanocomposites possess different structure and dispersion of Na⁺-MMT clays which are assessed through a combination of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The rheology of the neat blend and two different layered silicate nanocomposites were investigated using linear viscoelastic measurements with a parallel plate rheometry at small strain amplitudes. It was found that regardless of the extent of dispersion, the storage and loss modulus increased by incorporating the nanoparticles into the matrix of PEO/PMMA. Moreover, at low frequencies the rheological response of the nanocomposite in which layered silicates benefit from a better dispersion becomes relatively invariant with frequency and represents a mediocre solid-like behavior in comparison to the nanocomposite in which the nanoparticles are intercalated or agglomerated.     

Electrical and rheological percolation in poly(vinylidene fluoride)/multi‐walled carbon nanotube nanocomposites

Nanocomposites of poly(vinylidene fluoride) (PVDF) and multi‐walled carbon nanotubes (MWCNTs) were prepared through melt blending in a batch mixer (torque rheometer equipped with a mixing chamber). The morphology, rheological behavior and electrical conductivity were investigated through transmission electron microscopy, dynamic oscillatory rheometry and the two‐probe method. The nanocomposite with 0.5 wt% MWCNT content presented a uniform dispersion through the PVDF matrix, whereas that with 1 wt% started to present a percolated network. For the nanocomposites with 2 and 5 wt% MWCNTs the formation of this nanotube network was clearly evident. The electrical percolation threshold at room temperature found for this system was about 1.2 wt% MWCNTs. The rheological percolation threshold fitted from viscosity was about 1 wt%, while the threshold fitted from storage modulus was 0.9 wt%. Thus fewer nanotubes are needed to approach the rheological percolation threshold than the electrical percolation threshold. Copyright © 2010 Society of Chemical Industry     

Polymer/silicate nanocomposites synthesized with potassium persulfate at room temperature: polymerization mechanism, characterization, and mechanical properties of the nanocomposites

Polymer/silicate nanocomposites were synthesized using potassium persulfate (KPS) in the presence of silicate and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) without exterior redox co-catalysts at a room temperature. A mechanism for the room temperature polymerization in the presence of silicate was suggested: AMPS attached on the surface of silicate layers would oxidize Fe⁺² in silicate lattice to become Fe⁺³ and the Fe⁺³ would decompose KPS to form radicals like redox co-catalysts. Poly (acrylonitrile) (PAN)/silicate nanocomposite showed an exfoliated structure, but poly (methyl methacrylate) (PMMA)/silicate nanocomposite showed an intercalated structure. Polymers recovered from the nanocomposites synthesized at a room temperature had high isotactic configurations compared to bulk polymers. The dipole–dipole interaction between monomers and silicate surface might make the lamella of monomers to form on the silicate layer surface and produced polymers with more isotactic configurations. PAN/silicate nanocomposite showed two glass transition temperatures at 113 and 151 °C. The lower temperature might be related to the molecules with low molecular weight. PMMA/silicate nanocomposite had a storage modulus of 4.47×10⁹ Pa at 40 °C.     

Nylon 6/Na-montmorillonite nanocomposites prepared by compounding Nylon 6 with Na-montmorillonite slurry

We report a novel compounding process using Na-montmorillonite water slurry for preparing novel nylon 6/Na-montmorillonite nanocomposites. In this compounding process, the Na-montmorillonite slurry was blended with melting nylon 6 using an extruder, followed by removing the water. The Na-montmorillonite silicate layers were found to be exfoliated and dispersed homogeneously at nanometer level in the nanocomposites with an electron transmission microscope. The exfoliated Na-montmorillonite silicate layers were fixed in the nylon 6 matrix almost as they were in water. The nylon 6/Na-montmorillonite nanocomposites, loaded with only 1.6 wt% clay silicate layers, exhibited high strength, high modulus, high heat distortion temperature and low gas permeability compared to neat nylon 6. The properties of the nylon 6/Na-montmorillonite nanocomposites were nearly equal to those of conventional nylon 6/clay nanocomposites prepared by dry-compounding nylon 6 and organophilic clay ion-exchanged with alkylammonium ions.     

聚丙烯基杂化材料的动态力学性能与流变行为

研究了烷基铵离子对有机蒙脱土片层在聚丙烯基杂化材料中的分散状态和聚丙烯基杂化材料的动态力学性能、熔体流变行为的影响。结果表明:烷基铵离子N 上取代基空间效应增大,有机蒙脱土片层间距随之增大;适当的空间效应将有助于有机蒙脱土片层在聚丙烯基体中的剥离分散;与基体聚丙烯相比,聚丙烯基杂化材料表现出较高的动态储能模量和损耗模量,在低频区,3种杂化材料熔体的动态剪切黏度和模量的提高幅度在1个数量级以上。     

Preparation and characterization of polymer/organosilicate nanocomposites based on unmodified LDPE

Low‐density polyethylene (LDPE)/silicate nanocomposites were prepared by the melt compounding and solution blend methods using unmodified LDPE polymer and layered silicates with different aspect ratio. X‐ray diffraction (XRD) analysis performed on composites obtained by dispersing the organosilicates in molten LDPE evidenced an exfoliated or partially exfoliated structure for the low aspect ratio silicate (laponite) in contrast to the high aspect ratio silicate (montmorillonite), which led to the formation of intercalated nanocomposites. With regard to the preparation method, the melt compounding method was more effective in forming exfoliated/highly intercalated LDPE nanocomposites compared with the solution blend method (using CCl₄ as a solvent). A gradual increase in crystallization temperatures (T_c) with increasing laponite content for LDPE‐organolaponite nanocomposites was revealed by differential scanning calorimetry (DSC) measurements. Thermogravimetric analysis and tensile measurements results indicated that thermal stability and elastic modulus increment were more prevalent for nanocomposites prepared using organomontmorillonite as filler. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Interfacially compatibilized LDPE/POE blends reinforced with nanoclay: investigation of morphology,rheology and dynamic mechanical properties

Morphological, melt rheological and dynamic mechanical properties of low-density polyethylene (LDPE)/ethylene–octene copolymer (POE)/organo-montmorillonite (OMMT) nanocomposites, prepared via melt compounding were studied. The XRD traces indicated different levels of intercalated structures for the nanocomposites. Addition of a compatibilizer (PE-g-MA) improved the intercalation process. TEM results revealed existence of clay layers in both phases but they were mainly localized in the elastomeric POE phase. Addition of 5 wt% OMMT to the LDPE/POE blend led to reduction in the size of the elastomer particles confirmed by AFM. The complex viscosity and storage modulus showed little effect of the presence of the clay when no compatibilizer was added. As the extent of exfoliation increased with addition of compatibilizer, the linear viscoelastic behavior of the composites gradually changed specially at low-frequency regions. The interfacially compatibilized nanocomposites with 5 wt% OMMT had the highest melt viscosity and modulus among all the studied nanocomposites and blends. Also, this particular composition showed the best improvement in dynamic storage modulus. The results indicated that clay dispersion and interfacial adhesion, and consequently different properties of LDPE/POE/clay nanocomposites, are greatly affected by addition of compatibilizer.     

Biodegradable PBAT/Starch Nanocomposites

Starch-based biodegradable banocomposites of poly(butylene adipate-co-terephthalate) [PBAT] and organically modified nanoclays were prepared using melt intercalation technique in Haake Torque Rheocord 9000. Two different organically modified nanoclays Cloisite C20A and Cloisite C30B at various wt% (1, 3, 5) have been used for fabrication of nanocomposites. Starch was gelatinized to prepare thermoplastic starch (TPS) for increasing the compatibility with the PBAT matrix. Subsequently, films of PBAT/TPS blends at various TPS contents (10, 20, 30, 40) wt% and PBAT/TPS Organoclay biodegradable blend nanocomposites at different wt% of nanoclays were prepared using solvent casting method. The interfacial region between the biodegradable polymer matrix and the clays were also modified with grafting of Maleic anhydride (MA) with PBAT chains, during melt blending through two stage reactive extrusion process. Mechanical tests revealed an increase in tensile modulus and elongation at break with the incorporation of 30 wt% TPS and C30B nanoclay to the tune of 44.45% and 776.9% as compared with PBAT matrix. PBAT/TPS30 wt%/C30B3wt% shows maximum tensile modulus and elongation at break due to intercalation of silicate layers resulting from similarity in the surface polarity and interactions of C30B with TPS. Morphology of PBAT/TPS30%/C30B3% biodegradable blend nanocomposite studied using WAXD and SEM indicated intercalation and improved dispersion of TPS within PBAT with incorporation of C30B. Dynamical mechanical analysis of PBAT/TPS/C30B biodegradable blend nanocomposite revealed an increase of storage modulus and glass transition temperatures of PBAT with addition of nanoclays. Further Biodegradation test also confirmed higher biodegradability of PBAT in presence of TPS and C30B.     

High-density polyethylene reinforced by low loadings of electrochemically exfoliated graphene via melt recirculation approach

The purpose of the paper is to demonstrate the effectiveness of high-aspect ratio electrochemically exfoliated graphene (EEG) as a filler in high-density polyethylene (HDPE); we use an industrially viable polymer processing technique (melt blending with melt recirculation) to ensure excellent dispersion and reinforcement at low loadings. The effects of nanofiller loading were evaluated for two different HDPE grades with two different melt flow indices (MFI) based on crystallization, tensile, and rheological properties. The findings indicate improvements in mechanical properties (tensile modulus and tensile strength) for all HDPE/EEG nanocomposite samples; however, the reinforcement was more pronounced at 0.2 wt% loading, indicating a transition from excellent dispersion at lower loadings to aggregated at higher loadings. The low and high MFI HDPE/EEG nanocomposites at 0.2 wt% EEG loading displayed an improvement of 31% and 40% in tensile modulus and 19% and 33% in tensile strength, respectively. The improved mechanical response with higher MFI nanocomposites is likely due to enhanced dispersion associated with the lower melt viscosity. Similarly, the rheological results also showed maximum increase in storage and loss modulus at a loading of 0.2 wt% EEG. In conclusion, EEG can be an effective filler if proper dispersion is achieved, which is challenging at high loadings.     

Preparation,crystallization behavior,and dynamic mechanical property of nanocomposites based on poly(vinylidene fluoride) and exfoliated graphite nanoplate

Nanocomposites based on poly(vinylidene fluoride) (PVDF) and exfoliated graphite nanoplate (xGnP) were prepared by solution precipitation method. The resulting nanocomposites were investigated with respect to their structure and properties by scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and dynamic mechanical analysis. Both SEM and TEM examinations confirmed the good dispersion of xGnP in the PVDF matrix. The nonisothermal crystallization behavior of the PVDF/xGnP nanocomposites was studied using DSC technique at various cooling rates. The results indicated that the xGnPs in nanometer size might act as nucleating agents and accelerated the overall nonisothermal crystallization process. Meanwhile, the incorporation of xGnP significantly improved the storage modulus of the PVDF/xGnP nanocomposites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Properties of bulk-polymerized thermoplastic polyurethane nanocomposites

The thermal, rheological, and mechanical properties of bulk-polymerized thermoplastic polyurethane nanocomposites of reactive and non-reactive layered silicate clay were characterized as a function of the state of dispersion of particles. True exfoliated nanocomposites were produced by mixing reactive clay particles with polymer chains carrying residual isocyanate groups. On the other hand, non-reactive clay particles yielded only intercalated composites. Most significant improvement in mechanical properties were obtained when clay particles were fully exfoliated, e.g. 110% increase in tensile modulus, 170% increase in tensile strength, 110% increase in tear strength, 120% increase in fracture toughness, and 40% increase in abrasion resistance over pristine polyurethane with 5 wt% clay. In addition, the terminal dynamic rheological data showed strong dependence on the clay content, indicating substantial hindrance to chain relaxation by tethering clay particles. The peak location and the area under the peak of hydrogen-bonded carbonyl showed two distinct zones of temperature dependence, which indicate additional hydrogen bonding between polymer chains and organic modifier of reactive clays.     

Effect of clay modification on the morphological,mechanical, and thermal properties of polyamide 6/polypropylene/montmorillonite nanocomposites

Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic montmorillonite (OMMT) were prepared by melt compounding. The sodium montmorillonite (Na‐MMT) was modified using three different types of alkyl ammonium salts, namely dodecylamine, 12‐aminolauric acid, and stearylamine. The effect of clay modification on the morphological and mechanical properties of PA6/PP nanocomposites was investigated using x‐ray diffraction (XRD), transmission electron microscopy (TEM), tensile, flexural, and impact tests. The thermal properties of PA6/PP nanocomposites were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and heat distortion temperature (HDT). XRD and TEM results indicated the formation of exfoliated structure for the PA6/PP nanocomposites prepared using stearylamine modified montmorillonite. On the other hand, a mixture of intercalated and exfoliated structures was found for the PA6/PP nanocomposites prepared using 12‐aminolauric acid and dodecylamine modified montmorillonite. Incorporation of OMMT increased the stiffness but decreased the ductility and toughness of PA6/PP blend. The PA6/PP nanocomposite containing stearylamine modified montmorillonite showed the highest tensile, flexural, and thermal properties among all nanocomposites. This could be attributed to better exfoliated structure in the PA6/PP nanocomposite containing stearylamine modified montmorillonite. The storage modulus and HDT of PA6/PP blend were increased significantly with the incorporation of both Na‐MMT and OMMT. The highest value in both storage modulus and HDT was found in the PA6/PP nanocomposite containing stearylamine modified montmorillonite due to its better exfoliated structure. POLYM. COMPOS., 31:1156–1167, 2010. © 2009 Society of Plastics Engineers     

Characteristics of polystyrene/polyethylene/clay nanocomposites prepared by ultrasound‐assisted mixing process

In this study, polymer‐clay nanocomposites of various concentrations were prepared by ultrasonically assisted polymerization and melt‐mixing processes. A sonication process using power ultrasonic waves was employed to enhance nano‐scale dispersion during melt‐mixing of polymer blends and organically modified clay. We expected enhanced breakup of layered silicate bundles and further reduction in the size of the dispersed phase, with better homogeneity compared to the different immiscible blend pairs. X‐ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the structures of the nanocomposites. The rheological behaviors of the obtained nanocomposites were measured with parallel plate rheometry. It was found that the ultrasound‐assisted process successfully generated exfoliated nanocomposites and promoted in‐situ compatibilization of the matrix comprising an immiscible pair of polymers in a blend. The resulting nanocomposite exhibited superior thermal stability and elastic modulus compared to the base polymer. Polym. Eng. Sci. 44:1198–1204, 2004. © 2004 Society of Plastics Engineers.     

Towards the synthesis of high solids content waterborne poly(methyl methacrylate-co-butyl acrylate)/montmorillonite nanocomposites

Small angle X-ray scattering of Na-montmorillonite (Na-MMT) aqueous dispersions showed that at concentrations below 1.5 wt%, clay platelets were fully dispersed with an average distance between platelets higher than 16 nm. At higher concentrations (3 wt%) platelet–platelet interaction was not negligible and SAXS measurements detected ordered stack structures composed of 2–3 platelets with an average distance of around 14–16 nm. Thus, initiating an emulsion polymerization of methyl methacrylate and butyl acrylate in an aqueous phase containing Na-MMT at concentrations below 1.5 wt% allowed the production of stable and coagulum free waterborne nanocomposites having 30 wt% solids content, with exfoliated structure. The in situ produced poly(methyl methacrylate-co-butyl acrylate)/Na-MMT nanocomposite latexes provided better mechanical, thermal and permeability properties than composites prepared by blending pristine latex with Na-MMT or the pristine copolymer synthesized in the same conditions. Furthermore, for the first time nanocomposite latexes with 45 wt% solids content and intercalated morphologies having enhanced mechanical properties were also produced by seeded semibatch emulsion polymerization. The intercalated structure was likely due to the higher clay concentration in the aqueous phase that favoured platelet–platelet interaction, increased the viscosity of the polymeric dispersion and prevented a complete exfoliation.     

Binary and ternary nanocomposites based on PVDF,PMMA, and PVDF/PMMA blends: polymorphism,thermal, and rheological properties

Binary and ternary nanocomposites based on poly(vinylidene fluoride) (PVDF), poly(methyl methacrylate) (PMMA), and PVDF/PMMA blends were successfully prepared through a melt-mixing process, using a commercial organoclay (15A) as the nanofiller. The 15A was more finely dispersed (intercalated/partially exfoliated) within the PVDF matrix compared with the PMMA matrix. A higher PVDF content in the ternary composite essentially led to a superior degree of 15A dispersion. The 15A addition induced the polar β-form PVDF crystals, whereas the presence of PMMA in ternary composites reduced the efficiency in promoting β-form formation by 15A. Adding 15A also enhanced the nucleation of PVDF, but the enhancement was inferior while PMMA was present. Conversely, the crystal growth of PVDF was retarded with the existence of 15A, and the PVDF/15A binary composite exhibited the greatest retardation. The equilibrium melting temperature (T_m°) of PVDF in the neat state and in the blends increased after 15A addition. The PVDF/15A binary composite possessed an evidently higher β-form T_m° than the α-form T_m° of neat PVDF (~20.1 °C rise). Similar effects on the individual components, 15A declined the thermal stability of PVDF but increased that of PMMA in the ternary composites. Rheological property measurements revealed that the ternary composites performed in-between that of individual PVDF/15A and PMMA/15A binary composites. A percolation of 15A (pseudo)network structure was developed in the composites, and a more elastic behavior was observed with increasing PVDF content in the composites.