Preparation,microstructure, and property of silicon rubber/organically modified montmorillonite nanocomposites and silicon rubber/OMMT/fumed silica ternary nanocomposites

Five different types of organically modified montmorillonites (OMMT), including Nanomor® I.30P, I.44P, I.24TL, I.34TCN, and I.31PS, were incorporated into silicone rubber (SiR), respectively, by using a melt‐blending method. The intercalation structure and spatial dispersion of OMMT in the obtained composites were characterized with wide‐angle X‐ray diffraction and transmission electron microscopy. The results revealed that the high‐polar organic intercalants or silane‐coupling agent might play the negative roles in the melt intercalation of SiR into OMMT, and the higher the initial interlayer spacing of the OMMT, the easier the intercalation. The intercalated structure in the SiR/I.44P OMMT nanocomposite has the largest interlayer spacing, and the spatial dispersion of OMMT is also the best. When OMMT loading is low (i.e., less than 10 phr), the dispersion of OMMT is poor. The dispersion of OMMT improves with increasing OMMT dosage, when the loading does not exceed 30 phr. The gas barrier property and the mechanical properties of the SiR are obviously improved by the incorporation of OMMT. The nitrogen gas permeability coefficient of the SiR nanocomposite containing 30 phr OMMT (I.44P) is lower than that of net SiR by 31%. To further improve the dispersion of OMMT in SiR, 20 phr fumed silica (FS) was added to the compound before mixing OMMT for increasing viscosity of the compound and mechanical shearing force during compounding OMMT. The resultant SiR/OMMT/FS ternary nanocomposites exhibit improved dispersion of OMMT and better gas barrier property than the binary counterparts. POLYM. COMPOS., © 2011 Society of Plastics Engineers.     

A comparative study of nanocomposites based on a recycled poly(methyl methacrylate) matrix containing several nanoclays

Nanocomposites of recycled poly(methyl methacrylate) (PMMA) and both natural (Nanomer PGV MMT), and organically modified Nanomer I44P, Nanomer I30P and Cloisite 30B montmorillonites (O‐MMT) were prepared by solution dispersion method with the use of two miscible solvents, followed by melt intercalation process in a twin‐screw miniextruder. The final product has been found to show a homogeneous structure with a uniform dispersion/intercalation of the silicate layers. The effect of MMT and O‐MMT layers on the properties of the nanocomposites was investigated and characterized by UV–vis spectroscopy, differential scanning calorimetry, atomic force microscopy, and mechanical testing. Higher contents of nanoclay in nanocomposites exhibited worse light transmittance capacity but higher tensile modulus. Properties of the samples depended not only on the clay contents (up to 10 wt%) but also on the clay type employed. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Properties of Waterborne Polyurethane/Clay Nanocomposite Adhesives

A series of waterborne polyurethane (WBPU)/clay nanocomposite dispersions using two different organically modified clays, namely Cloisite 15A and Cloisite 30B, were prepared. It was found that the properties of WBPU/clay nanocomposites were highly dependent on both the clay content and the clay surface characteristic (hydrophilic/hydrophobic). A WBPU/clay nanocomposite dispersion with a higher clay content showed a less negative zeta potential. A lower zeta potential for dispersion with Cloisite 30B compared to Cloisite 15A was observed indicating a higher stability of the dispersion. The tensile strength, Young's modulus and adhesive strength of WBPU/clay nanocomposite containing Cloisite 30B were also higher than those of nanocomposite containing Cloisite 15A. The optimum clay contents, with respect to these properties, for nanocomposites with Cloisite 15A and Cloisite 30B were found to be 2 wt% and 3 wt%, respectively.     

改性粘土制备粘土/POE纳米复合材料的力学性能研究

研究粘土的种类以及用量对所制得的粘土/聚烯烃弹性体(POE)纳米复合材料力学性能的影响。结果表明,在添加相同粘土份数下,与I.30P有机粘土以及十六烷基三甲基溴化铵(CTAB)改性有机粘土相比,I.44P有机粘土制备的粘土/POE纳米复合材料的各向力学性能最佳;随着粘土用量(10份以内)的增加,粘土/POE纳米复合材料的各项力学性能也在不断增强。     

Effect of electric field on polymer/clay nanocomposites depending on the affinities between the polymer and clay

Applying an electric field is an efficient way to fabricate polymer/clay nanocomposites. It helps to achieve a good dispersion of nanoclays which improves the performance of the polymeric system. In this study, the effect of an alternating current (A.C.) electric field was investigated on clay exfoliation with various combinations of polymer/clay nanocomposites. Three different types of organoclays (Cloisite 10A, 20A, 30B) were introduced in polypropylene (PP) and poly(lactic acid) (PLA) matrices. Their rheological properties showed that the A.C. electric field was effective in enhancing the dispersion of organoclays in both the PP/clay and PLA/clay composites. The efficiency of the A.C. field varied depending on the combination of polymer and clay nanoparticles. In the case of PP, the best combination was PP/C20A followed by PP/C10A and PP/C30B. In contrast, PLA/clay showed an opposite trend. This difference arises from the different affinities between the polymers and the functional groups of the clays. The Hansen solubility parameter was introduced to quantify the affinities between the polymer and clay. The electric field was more effective for polymer/clay combinations that had less difference in the Hansen solubility parameter. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43582.     

硅橡胶/有机改性蒙脱土纳米复合材料的性能研究

用熔体插层法制备甲基乙烯基硅橡胶(MVQ)/有机改性蒙脱土(OMMT)纳米复合材料并研究其微观结构和性能。结果表明:OMMT改性剂疏水性从优到劣的顺序为I.44P,I.30P,Bengel434,I.44P和I.30P在MVQ中的分散性优于Bengel434;MVQ/OMMT纳米复合材料的物理性能和热稳定性从优到劣的顺序为MVQ/I.44P,MVQ/I.30P,MVQ/Bengel434纳米复合材料;添加40份I.44P的MVQ/I.44P纳米复合材料的100%定伸应力、拉伸强度和撕裂强度比纯胶有较大提高。     

Morphology and properties of polymer/organoclay nanocomposites based on poly(ethylene terephthalate) and sulfopolyester blends

Poly(ethylene terephthalate) (PET) nanocomposite films containing two different organoclays, Cloisite 30B^® (C30B) and Nanomer I.28E^® (N28E), were prepared by melt blending. In order to increase the gallery spacing of the clay particles, a sulfopolyester (PET ionomer or PETi) was added to the nanocomposites via a master‐batch approach. The morphological, thermal and gas barrier characteristics of the nanocomposite films were studied using several characterization techniques such as scanning electron microscopy, transmission electron microscopy, X‐ray diffraction, differential scanning calorimetry, dynamic mechanical analysis, rheometry and oxygen permeability. PET and PETi were found to form immiscible polymer blends and the nanoparticles were preferentially located in the PETi dispersed phase. A better dispersion of clay was obtained for nanocomposites containing N28E with PETi. On the contrary, for nanocomposites containing C30B and PETi, the number of tactoids increased and the clay distribution and dispersion became worse than for C30B alone. Overall, the best properties were obtained for the PET/C30B nanocomposite without PETi. Higher crystallinity was found for all nanocomposite films in comparison to that of neat PET. © 2012 Society of Chemical Industry     

Supercritical carbon dioxide (scCO2) dispersion of poly(ethylene terephthalate)/clay nanocomposites: Structural,mechanical, thermal,and barrier properties

Dispersed poly(ethylene terephthalate) (PET)/clay nanocomposites can lead to materials with superior barrier and mechanical properties. PET/clay nanocomposites were prepared by melting extrusion of PET with as‐received or supercritical carbon dioxide (scCO₂) predispersed Cloisite^® 30B (30B). The predispersion of 30B was assessed by WAXD, SEM, and TGA, and results indicated that scCO₂ processing could predisperse 30B and the surface modification of the clay was preserved after processing. The structure of PET/30B nanocomposites was investigated by WAXD and TEM confirming that PET has penetrated into the clays inter‐galleries and the predispersed clays lead to improved interfacial interaction and homogenous clay dispersion. Both tensile strength and Young's modulus were improved by 12.1% and 24.9% respectively, as incorporating of 3 wt % of scCO₂ processed clay. Differential scanning calorimetry (DSC) results indicated that clay particles served as nucleation agent could increase the crystallinity whereas had no impact on melting process. In addition, with the addition of 1 wt % of predispersed clay, a significant reduction of oxygen permeation (～33%) was achieved at 23 °C and the maximum reduction (44%) was achieved by adding 3 wt % processed clay. Moreover, we confirmed the effect of temperature on the permeation of PET/30B nanocomposites depended both on the Arrhenius behavior of the organic phases and tortuous path effects, where improved clay dispersion resulted in a higher effective activation energy. Moreover, the transparency of PET matrix was preserved for all nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44779.     

Effect of solvent on the properties of thermoplastic polyurethane/clay nanocomposites prepared by solution mixing

Effect of different solvents on the clay dispersion and the final properties of the thermoplastic polyurethanes (TPUs)/clay nanocomposites prepared via solution mixing was studied. The polyether‐ and polyester‐based TPUs were used along with organically modified clays (C30B, C25A, and C15A) and the pristine montmorillonite (PM). Dimethylacetamide (DMAc) and tetrahydrofuran (THF) were used as solvents for solution mixing. Nanocomposites containing C30B prepared from DMAc solution showed the better clay dispersion than the ones from THF solution, while THF gave the better dispersion of clays for nanocomposites containing C15A. Morphologies of the nanocomposites were observed to be determined not only by the state of clay dispersion in different solvents but also by the interaction between the polymer and the specific clay. Affinity between solvents and clays becomes important when there is no specific interaction between the clay and the polymer of interest, or when the interaction between the two is rather weak. The compatibility between clays and polymers becomes dominating if there exists a specific interaction between the two. FTIR analysis was conducted to study the interactions involved in the nanocomposites. Dynamic mechanical properties measurement was also carried out to see the effect of solvents. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Phase separation behavior and morphologies of PMMA/poly(styrene‐co‐acrylonitrile)/clay nanocomposites prepared by solution mixing

Nanocomposites of blends of PMMA and poly(styrene‐co‐acrylonitrile) (SAN) with natural (PM) or organically modified montmorillonite clays (Cloisite 30B, 25A, and 15A) were prepared by solution mixing and the effect of clay on the phase separation behavior along with morphologies of nanocomposites was investigated. Nanocomposites containing clay C30B prepared from methyl ethyl ketone showed the noticeable decrease in the cloud points. None of the other nanocomposites showed the increase in the cloud point. Location of clay particles in the phase separated matrix is observed to be different depending on the type of clays and solvents. The lowest cloud point of nanocomposites containing C30B may arise from the good dispersion of C30B where Clay C30B may act as the nucleating agent inducing phase separation. Dynamic mechanical and thermal analyses support above observations. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Role of polymer-clay interactions and nano-clay dispersion on the viscoelastic response of supercritical CO2 dispersed polyvinylmethylether (PVME)-Clay nanocomposites

Clay dispersion and polymer-clay interactions play a key role in producing property enhancements in nanocomposites; yet characterizing them in complex polymer-clay systems is often a challenge. Rheology can offer insights into clay dispersion and clay-polymer interactions. We have investigated the viscoelastic response for a series of supercritical CO₂ (scCO₂) processed polyvinylmethylether (PVME)/clay nanocomposites with varying polymer-clay interactions and nano-clay dispersion. PVME is used in this study because it is highly swellable in scCO₂, thereby enabling processing of PVME/clay mixtures without the presence of a co-solvent. Since PVME and natural clay are water-soluble, highly dispersed PVME-clay nanocomposites were prepared using water, followed by lyophilization in the presence of polymer. In this ‘weakly interacting’, but highly dispersed systems, with clay loadings above the percolation threshold, terminal behavior was observed in the linear viscoelastic moduli (i.e. no low frequency plateau is observed). When the nanocomposites were processed in scCO₂, with 15 wt% of 30B and I.30P, the WAXD patterns of the resultant nanocomposites were largely comparable, indicating partial dispersion, with intercalation peaks. However, the rheology of these two nanocomposites were significantly different despite similar inorganic volume loading (4 vol%). Even with less dispersion compared to the water-based system, the low-frequency moduli were significantly more enhanced, accompanied by a plateau, and a cross-over frequency shift. Neglecting the small differences in the actual clay content between these clays (4-5 vol% of inorganic matter), this suggests that rheology may be sensitive to strong interactions between the clay surfactant and the polymer. Therefore, polymer-clay interactions and clay-clay interactions may both be important in the ability to sustain a “so-called” percolated network, rather than just clay dispersion.     

Studies of organoclays with functionalized pillaring agents

A series of clay pillaring agents with amino, olefin, and epoxy groups were synthesized. These pillaring agents were used to modify montmorillonite clay by ion‐exchange reactions. TGA studies showed that organoclays with imidazolium pillaring agents have a higher thermal stability than those with ammonium groups. The d‐spacings of organoclays were not affected by the pillaring agent functional groups and were sensitive to the size of pillaring agents. The dynamic‐mechanical properties of the resulting clay/epoxy composites determined by DMA were similar. The addition of these clays to this epoxy resin enhanced the T_g value of the resulting composites and greatly enhanced the storage moduli versus the pure epoxy resin by 1.6–1.8 times at 135°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation and properties of epoxy nanocomposites. Part 2: The effect of dispersion and intercalation/exfoliation of organoclay on mechanical properties

The effect of the dispersion and intercalation/exfoliation of organoclay on the mechanical properties of epoxy nanocomposites was studied. The epoxy resin was EPON828 and the hardener was Jeffamine D‐230. The organoclay Cloisite 30B was used. Nanocomposites were prepared by different mixing devices that can generate different shear forces, such as a mechanical stirrer, a microfluidizer, and a homogenizer. The results indicate that the modulus increases almost linearly with the clay loading and also is improved with the quality of microdispersion, although the latter plays a less important role. On the other hand, only good dispersion can improve the strength, while poor dispersion results in loss of strength. The strength levels off above 4 wt% organoclay loading. It can be concluded that finer and more uniform dispersion increases the clay surface area available for interaction with the matrix and reduces stress concentration in the large aggregates that initiate the failure under stress. It is also observed that the presence of C30B does not significantly affect the glass transition (T_g) of the epoxy systems regardless of the level of clay dispersion and clay loading. Dynamic mechanic analysis (DMA) shows the positive effect of dispersion and intercalation/exfoliation on the storage modulus of epoxy nanocomposites (ENCs). POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Morphology and properties of SAN‐clay nanocomposites prepared principally by water‐assisted extrusion

An efficient extrusion process involving the injection of water while processing was used to prepare poly (styrene‐co‐acrylonitrile) (SAN)/clay nanocomposites with a high degree of nanoclay delamination. The usefulness of water‐assisted extrusion is highlighted here, in comparison with classical extrusion and roll mill processes. Cloisite® 30B (C30B), a montmorillonite clay organomodified with alkylammonium cations bearing 2‐hydroxyethyl chains, and pristine montmorillonite were melt blended with SAN (25 wt% AN) in a semi‐industrial scale extruder specially designed to allow water injection. XRD analysis, visual and TEM observations were used to evaluate the quality of clay dispersion. The relationship between the nanocomposite morphology and its mechanical and thermal properties was then investigated. The superiority of the SAN/C30B nanocomposite extruded with water has been evidenced by cone calorimetry tests and thermogravimetric measurements (TGA). These analyses showed a substantial improvement of the fire behavior and the thermal properties, while a 20% increase of the Young modulus was recorded. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Curing kinetics and mechanical properties of epoxy nanocomposites based on different organoclays

The effect of different organoclays and mixing methods on the cure kinetics and properties of epoxy nanocomposites based on Epon828 and Epicure3046 was studied. The two kinds of organoclay used in this study, both based on natural montmorillonite but differing in intercalant chemistry, were I.30E (Nanomer I.30E—treated with a long‐chain primary amine intercalant) and C.30B (Cloisite 30B—treated with a quaternary ammonium intercalant, less reactive with epoxy than the primary amine). The two mixing processes used to prepare the nanocomposites were (i) a room‐temperature process, in which the clay and epoxy are mixed at room temperature, and (ii) a high‐temperature process, in which the clay and epoxy are mixed at 120°C for 1 h by means of mechanical mixing. The nanocomposites were cured at room temperature and at high temperature. The quality of dispersion and intercalation/exfoliation were analyzed by scanning electron microscopy, transmission electron microscopy, and X‐ray diffraction. The heat evolution of the epoxy resin formulation and its nanocomposite systems was measured using differential scanning calorimetry at different heating rates of 2.5, 5, 10, 15, and 20°C min^?1. The cure kinetics of these systems was modeled by means of different approaches. Kissinger and isoconversional models were used to calculate the kinetics parameters while the Avrami model was utilized to compare the cure behavior of the epoxy systems. The cure kinetics and mechanical properties were found to be influenced by the presence of nanoclay, by the type of intercalant, and by the mixing method. POLYM. ENG. SCI., 47:649–661, 2007. © 2007 Society of Plastics Engineers.     

Preparation and characterization of poly(propylene carbonate)/exfoliated graphite nanocomposite films with improved thermal stability,mechanical properties and barrier properties

Relatively high aspect ratio exfoliated graphite (EFG) particles with an average size of 7.4 µm and a nanometer sized thickness of 30–50 nm were successfully prepared by thermal treatment at 1050 °C and subsequent ultrasonication for application as a filler to improve the physical properties of eco‐friendly poly(propylene carbonate) (PPC). A series of poly(propylene carbonate)/exfoliated graphite (PPC/EFG) nanocomposite films with different EFG contents were prepared via a solution blending method. The physical properties were strongly dependent upon the chemical and morphological structures originating from the differences in EFG composition. The morphological structures, thermal properties, mechanical properties and barrier properties of the nanocomposite films were investigated as a function of the EFG content. While all of the PPC/EFG nanocomposite films exhibited good dispersion of EFG to some extent, Fourier transform infrared and SEM results revealed that solution blending did not lead to strong interactions between PPC and EFG. As a result, poor dispersion occurred in composite films with a high EFG content. By loading EFG particles, the oxygen permeabilities, moisture permeabilities and water uptake at equilibrium decreased as the EFG content increased. Compared with pure PPC, PPC/EFG nanocomposite films have enhanced molecular ordering. Specifically, the 2% PPC/EFG composite film shows greater molecular ordering than the other composite films, which results in the highest mechanical strength. In future work, the compatibility and dispersion of the PPC matrix polymer and EFG filler particles should be increased by modifying the EFG surface or introducing additives. © 2013 Society of Chemical Industry     

聚甲基乙撑碳酸酯/乙烯-乙烯醇共聚物/黏土复合材料的流变性能与阻透性能

采用熔融共混的方法制备了聚甲基乙撑碳酸酯(PPC)/黏土和PPC/乙烯-乙烯醇共聚物(EVOH)/黏土纳米复合材料,测试了复合材料的流变性能和阻氧性能,并对其微观形态进行了分析。结果表明,当基材PPC相对分子质量较高时,PPC/黏土复合材料的复数黏度、储能模量和耗能模量也较高;随着黏土和相容剂马来酸酐接枝聚乙烯（PE-g-MAH）的添加, PPC/EVOH复合材料的复数黏度和模量明显增加,PE-g-MAH的加入使PPC、EVOH和黏土之间的界面作用力增强,改善了PPC与EVOH的相容性,同时提高了PPC/EVOH复合材料的阻氧性能。     

Chlorophyll adsorption by alumina-pillared acid-activated clays

Clays, acid-activated to an optimum level, have been pillared with alumina to give semi-crystalline expanded materials with surface acidities, pore volumes and average pore diameters generally higher than those of the corresponding pillared materials derived from a clay matrix not previously acid-activated. The chlorophyll adsorption capacity of the pillared acid-activated materials is significantly greater than that of pillared, nonactivated clays. The procedures used in the preparation of these pillared acid-activated clays (i.e., temperature of pillaring, method of drying and calcination temperature) have a significant influence on chlorophyll adsorption capacity because they influence both the physical and the chemical properties of the final pillared material. This variation provides a useful means of relating the various properties of the pillared materials to the chlorophyll adsorption capacity. As a result, a correlation has been demonstrated between adsorption capacity and a combination of pore volume and number of strong acid sites (of strength pK_a < −1.5) present in the pillared material. Optimal adsorbents were obtained from freeze-dried samples prepared by exchange at 20°C and calcination in air at 500°C.     

Effect of organoclay structure characteristics on properties of ternary PP‐EP/EVA/nanoclay blend systems

In this study, the effect on the degree of organoclay exfoliation in polypropylene‐ethylene (PP‐EP)/Ethylene vinyl acetate (EVA)/organoclay blend system was studied while varying organoclay structural characteristics. Cloisite 6A, Cloisite 15A, Cloisite 20A, Cloisite 25A, Cloisite 30B, Cloisite 93A, and Cloisite 10A were used because they have different type of modifier. Ternary PP‐EP/EVA/organoclay system was obtained with each type of clay and results were organized to analyze the effect of type of clay chemical modification (C20A, C15A, and C6A), steric effect caused by surfactant structure (C15A and C10A), length of substitute groups on the surfactant (C20 and C25A), and surfactant polarity (C30B and C93A). Samples were characterized by: wide angle X‐ray diffraction, scanning transmission electron microscopy (STEM), dynamic mechanical analysis, and capillary rheometry. Results showed that clay galleries can be saturated with chemical modifier complicating the polymer chain intercalation into the clay galleries. Some clay modifier substituent groups could cause certain steric effect promoting less exfoliated platelets structures. Finally, longer chains in the modifier substituent group can promote a better intercalated–exfoliated structure. Among all the studied organoclays, best results were obtained in the ternary system when using C20A, which modifier has two hydrogenated tallows. In this case, interlayer spacing was increased more noticeable after ternary system was formed. This was corroborated with the obtained increase in viscosity and the intercalated–exfoliated structure observed by STEM. POLYM. COMPOS., 35:2241–2250, 2014. © 2014 Society of Plastics Engineers     

Immobilization of TiO2 nanoparticles on montmorillonite clay and its effect on the morphology of natural rubber nanocomposites

Natural rubber/organoclay/titanium dioxide nanocomposites were obtained via mechanical blending using rubber latex, organically modified montmorillonite clay (cloisite 30B) and titanium dioxide (TiO₂). Glycerol was utilized as a dispersant for the inorganic components. Scanning electron microscopy analysis shows that TiO₂ nanoparticles were deposited on the clay surface and that the clay–TiO₂ combination was homogeneously dispersed on the natural rubber. The high aspect ratio and the polar character of the clay layers allowed interactions with individual nanoparticles of TiO₂. The X-ray diffraction patterns reveal an increment of the crystalline character of the NR/C30B/TiO₂ nanocomposites as a consequence of the nanoscale dispersion of the TiO₂ particles. Infrared Spectroscopy spectra indicate compatibility between natural rubber and glycerol due to the formation of hydrogen bonds. A mechanism in particle–natural rubber compatibility, in which glycerol is involved, is proposed. However, nanoscale dispersion was largely dependent on the clay–TiO₂ interactions. This work proposes an easy method to immobilize TiO₂ nanoparticles on clay layers, which allows their dispersion in polymers. Nanocomposites obtained by this method can be used for supports of photocatalyst molecules.