The influence of multiple modified MMT on the thermal and fire behavior of poly (lactic acid) nanocomposites

This work reported the preparation and physical properties of biodegradable nanocomposites fabricated using polylactic acid (PLA) and multiple organic modified montmorillonite (MMT). In order to improve the chemical compatibility between PLA and Na‐MMT, the surface of Na‐MMT was first organically modified by cetyl trimethyl ammonium bromide (CTAB) and resorcinol bis(diphenyl phosphate) (RDP) using ion‐exchange and adsorption technique. Both Fourier transform infrared and X‐ray diffraction (XRD) results indicated that CTAB and RDP molecules were intercalated into the galleries of MMT sheets to enlarge the interlayer spacing. Then, the PLA/MMT nanocomposites were prepared by a simple melt‐blending method. The XRD and TEM results of the nanocomposites indicated that the PLA polymer chains inserted into the galleries of co‐modified MMT (C‐MMT) and contained disorderedly intercalated layered silicate layers within a PLA matrix. The C‐MMT nanolayers were homogenously dispersed in PLA matrix, resulting in various property enhancement. The fabricated PLA/C‐MMT nanocomposites with 5.0 wt% addition showed significant enhancements (176%) in the storage modulus compared to that of neat PLA. The thermal stability and fire resistance were also remarkably improved. These improvements are probably because of both the physical barrier effect of the MMT nanosheets and charring effect of the C‐MMT. Copyright © 2015 John Wiley & Sons, Ltd.     

β-羟基丁酸与β-羟基戊酸共聚物 (PHBV)/蒙脱土纳米复合材料的结构与性能

用溶液复合法成功地制备了插层型PHBV／蒙脱土纳米复合材料。采用X射线衍射（XRD）和透射电子显微镜（TEM）研究了复合材料的结构，硅酸盐片层间距从1.8nm升至2.4nm左右。同时研究了复合材料的结晶，熔融，动态力学行为和力学性能，发现有机蒙脱土的加入，可以加快PHBV的结晶,降低熔融温度，使基体的玻璃化转变温度升高，提高了材料的力学性能，有机蒙脱土含量在3％时，其综合性能最佳。     

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.     

Layered nanoparticles modified by chain end functional PE and their nanocomposites with PE

Layered materials (MMT,LDH) were successfully modified by chain end functionalized polyethylene via an ion exchange method.The samples were characterized by using elemental analysis,Fourier transform infrared (FTIR) spectrum,X-ray diffraction (XRD),scanning electron microscopy (SEM),transmission electron microscopy (TEM) and thermogravimetric analysis (TGA).The XRD results demonstrated that MMT was successfully exfoliated with the disappearance of [001] peak.For the LDH,the peak [003] moved to a low angle and greatly weakened,indicating that LDH was successfully functionalized and completely intercalated or exfoliated.HDPE/layered nanocomposites were obtained between HDPE and different content of functional layered materials.The SEM and TEM results of nanocomposites showed the layered materials were well dispersed in the HDPE matrix,with a particle size of 100-200 nm.     

Influence of Fe‐MMT on crosslinking and thermal degradation in silicone rubber/clay nanocomposites

In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd.     

In situ intercalative polymerization of conducting polypyrrole/montmorillonite nanocomposites

Conducting polypyrrole (PPy)‐montmorillonite (MMT) clay nanocomposites have been synthesized by the in situ intercalative polymerization method. The PPy‐MMT nanocomposites are characterized by field‐emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), ultraviolet–visible (UV–vis) spectroscopy, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. XRD patterns show that after polymerization by the in situ intercalative method with ammonium persulfate and 1 M HCl, an increase in the basal spacing from 1.2 to 1.9 nm was observed, signifying that PPy is synthesized between the interlayer spaces of MMT. TEM and SEM micrographs suggest that the coexistence of intercalated MMT layers with the PPy macromolecules. FTIR reveals that there might be possible interfacial interactions present between the MMT clay and PPy matrix. The study also shows that the introduction of MMT clay results in thermal stability improvement of the PPy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2279–2285, 2008     

原位插层聚合制备聚丁二烯/蒙脱土纳米复合材料的结构与性能研究

聚合物 /粘土纳米复合材料由于具有常规复合材料所没有的结构、形态及更优异的力学、热学、阻燃、阻隔等性能 ,自 1 987由日本丰田公司首次报道了制备尼龙 6 粘土纳米复合材料以来 ,立刻引起人们的普遍关注[1～ 17] .目前报道的聚合物 /粘土纳米复合材料主要集中在以树脂为基体 ,例如 ,聚酰胺[1～ 4] 、聚苯乙烯[5～ 8] 、聚甲基丙烯酸甲酯[9,10 ] 、聚丙烯[11,12 ] 等 .制备以橡胶为基体的橡胶/粘土纳米复合材料研究较少 ,采用的方法多为通过橡胶大分子插层 ,如熔融插层法[1 3] 、溶液插层法[14 ] 、乳液法[15,16] 等 ,这些方法均存在插层…     

Effect of pullulan/poly(vinyl alcohol) blend system on the montmorillonite structure with property characterization of electrospun pullulan/poly(vinyl alcohol)/montmorillonite nanofibers

Nanofibers of the composite of pullulan (PULL), poly(vinyl alcohol) (PVA), and montmorillonite clay (MMT) were prepared using electrospinning method in aqueous solutions. Pullulan is an interesting natural polymer for many of its merits and good properties. Because of biocompatibility and non-toxicity of PVA, it could be used in numerous fields. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray diffraction (XRD), and thermal gravimetric analysis (TGA) were done to characterize the PULL/PVA/MMT nanofibers morphology and properties. XRD patterns and FTIR data demonstrated that there were good interactions between PULL and PVA caused by possibly hydrogen bonds. Moreover, XRD data and TEM images indicated that intercalated and exfoliated MMT nanoplatelets can be obtained within the PULL/PVA/MMT nanofibers depending on the PULL/PVA blend ratios. Furthermore, the thermal stability and mechanical property (tensile strength) of PULL/PVA/MMT nanofibers could be enhanced more by exfoliated MMT nanoplatelets than intercalated structures of that nanoplatelets.     

Investigation of Structural,Rheological and Thermal Properties of PMMA/ONi-Al LDH Nanocomposites Synthesized via Solvent Blending Method: Effect of LDH Loading

This article addresses the synthesis of organically tailored Ni-Al layered double hydroxide(ONi-Al LDH) and its use in the fabrication of exfoliated poly(methyl methacrylate)(PMMA) nanocomposites. The pristine Ni-Al LDH was initially synthesized by co-precipitation method and subsequently modified using sodium dodecyl sulfate to obtain ONi-Al LDH. Nanocomposites of PMMA containing various amounts of modified Ni-Al LDH(3 wt%?7 wt%) were synthesized via solvent blending method to investigate the influence of LDH content on the properties of PMMA matrix. Several characterization methods such as X-ray diffraction(XRD), transmission electron microscopy(TEM), Fourier transform infrared spectroscopy(FTIR), rheological analysis, differential scanning calorimetry(DSC) and thermo gravimetric analysis(TGA), were employed to examine the structural, viscoelastic and thermal properties of PMMA/OLDH nanocomposites. The results of XRD and TEM examination confirm the formation of partially exfoliated PMMA/OLDH nanocomposites. The FTIR results elucidate that the characteristic bands for both pure PMMA and modified LDH are present in the spectra of PMMA/OLDH nanocomposites. Rheological analyses were carried out to examine the adhesion between polymer matrix and fillers present in the nanocomposite sample. The TGA data indicate that the PMMA nanocomposites exhibit higher thermal stability when compared to pure PMMA. The thermal decomposition temperature of PMMA/OLDH nanocomposites increases by 28 K compared to that of pure PMMA at 15% weight loss as a point of reference. In comparison with pure PMMA, the PMMA nanocomposite containing 7 wt% LDH demonstrates improved glass transition temperature(Tg) of around 3 K. The activation energy(Ea), reaction orders(n) and reaction mechanism of thermal degradation of PMMA/OLDH nanocomposites were evaluated using different kinetic models. Water uptake capacity of the PMMA/OLDH nanocomposites is less than that of the pure PMMA.     

Structure Characterization and Thermal Properties of PMMA／Montmorillonite Nanocomposites via Emulsion Polymerization

Montmorillonite(MMT) modified with sodium silicate can change the arrangement of its layers fromedge-face and edge-edge to face-face. With the fine dispersion of the modified MMT in water, the cation-ex-change reaction was carried out with cetyltrimethyl ammonium bromide (CTAB) to obtain organo-montmoril-lonite (OMMT). As OMMT was uniformly dispersed in methyl methacrylate (MMA) monomer, PMMA/OMMT nanocomposites were formed via a common emulsion polymerization. The products were extractedwith hot acetone and characterized by FTIR, molecular weight, X-ray diffraction(XRD), transmission elec-tron microscopy(TEM), DSC and TGA. These results show that most of the OMMT layers have been exfo-liated, while the thermal stability is increased obviously. By means of FTIR spectral analysis, the ratios ofthe macromolecular radicals‘ termination of disproportionation patterns to combination are increased with theaddition of OMMT. This result further confirms the increase of the thermal degradation temperatures andglass transition temperatures of the PMMA/OMMT nanocomposites.     

Preparation and characterization of rigid poly(vinyl chloride)/MMT nanocomposites. II. XRD,morphological and mechanical characteristics

A Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na⁺‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na⁺‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006     

Influence of gamma irradiation on high density polyethylene/ethylene‐vinyl acetate/clay nanocomposites

The study of high density polyethylene (HDPE)/ethylene‐vinyl acetate (EVA)/and organically‐modified montmorillonite (OMT) nanocomposites prepared by melt intercalation followed by exposure to gamma‐rays have been carried out. The morphology and properties of the nanocomposites were studied using X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and cone calorimetry. The purpose of the study focuses on the influence of gamma irradiation on the morphology, thermal stability and flammability properties of the nanocomposites. XRD studies and TEM images verified that the ordered intercalated nanomorphology of the nanocomposites was not disturbed by gamma irradiation. TGA data showed that the nano‐dispersion of clay throughout the polymer inhibited the irradiation degradation of HDPE/EVA blend, which led to the nanocomposites exhibiting superior irradiation‐resistant properties than that of the pure blend. Cone calorimetry results indicated that the improvement in heat release rate (HRR) for irradiated HDPE/EVA blend was suppressed efficiently when clay was present. Increasing clay loading from 2 to 10% was beneficial by improving the flammability properties of the nanocomposites, but promoted a rapid increase in the sub‐peak HRR at high irradiation dose level. Copyright © 2004 John Wiley & Sons, Ltd.     

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

In this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na⁺‐MMT nanocomposites are decreased with increasing the amount of Na⁺‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na⁺‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005     

Synthesis,characterization, and mechanical properties evaluation of thermally stable apophyllite vinyl ester nanocomposites

The objective of this study is to prepare layered organosilicates with enhanced thermal stability that can be used to formulate high‐temperature polymer nanocomposites. Fourier transform infrared (FTIR) spectroscopy, wide‐angle X‐ray diffraction (WAXD), and thermal gravimetric analysis (TGA) characterization results of the modified silicates indicate that the organic pendant group has been chemically grafted on to the backbone of layered silicate and the organically modified apophyllite is thermally stable up to approximately 430°C. The organically modified apophyllite was mixed along with vinyl ester resin and styrene diluent in a sonic dismembrator and the mixture cured to form a nanocomposite specimen. Transmission electron microscopy (TEM) results of the nanocomposites showed mixed morphology with predominant fraction of organosilicates exhibiting an intercalated structure. Tapping mode atomic force microscopy (TMAFM) observation of the nanocomposite showed striated layered silicates dispersed in the resin matrix. The nanocomposites formulated with organosilicates containing reactive terminal pendant group were found to have a higher tensile strain than the nanocomposites formulated with organosilicates containing inert pendant group. Copyright © 2007 John Wiley & Sons, Ltd.     

Morphological structures of poly(vinylidene fluoride)/montmorillonite nanocomposites

Poly(vinylidene fluoride) (PVDF)/montmorillonite (MMT) nanocomposites were prepared by melt blen- ding a kind of organically modified montmorillonite with PVDF. The morphological structures of the nanocomposites were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and differential scanning calorimetry (DSC). The re- sults indicate that organically modified montmorillonites are in the form of intercalation, exfoliation, and fragments in the PVDF matrix. For the composites, the (001) peak position of MMT was found to shift to a lower angle in XRD patterns, and some MMT fragments could be observed under TEM. MMT loading was favorable to producing the piezoelectric β phase in the PVDF matrix and caused internal stress in α crystals. At the same time, the crystallinity and spherulite size of PVDF decreased with the MMT content. MMT induced β phase is stable even at high temperatures (160℃). For these changes in morphological structures, some possible explanations were proposed based on the experimental re- sults.     

聚苯胺/离子液体/蒙脱土纳米复合材料的制备及其导电性能研究

采用1-羧甲基-3-甲基咪唑氯化盐离子液体对钠化蒙脱土进行插层改性,然后用苯胺的盐酸溶液进行二次插层,以过硫酸铵为氧化剂,盐酸溶液为掺杂剂,使进入离子液体/蒙脱土(CMMIm/MMT)层间的苯胺(An)发生氧化聚合反应,制备了一种具有良好导电性的聚苯胺/离子液体/蒙脱土复合材料(PANI/CMMIm/MMT).用红外光谱、X-射线衍射,热重分析和DSC对样品进行了表征.结果表明当离子液体/蒙脱土用量为7.5%、盐酸浓度为1mol/L、过硫酸铵与苯胺的摩尔比为1∶1、0℃下反应6h时制备的PANI/CMMIm/MMT纳米复合材料电导率最高,达到了0.3S/cm,是相同条件下聚苯胺/钠化蒙脱土纳米复合材料电导率的2.5倍,聚苯胺的7.5倍.     

Morphology study of layered silicate/chitosan nanohybrids

Modification of clay with biopolymers has been of high interest in recent years. These new materials may be used for drug delivery systems and as biomaterials due to their high biocompatible properties and because they have the advantage of being biodegradable. The modification of montmorillonite (MMT) with chitosan was done in solution, at ratio 1:2 and at room temperature, or at stages of high temperature, and subjected to a microwave treatment. The influence of pH was observed upon the intercalation process.The obtained materials were characterized through X‐ray diffraction (XRD), thermogravimetrical analyses (TGA), Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Using such a mixed treatment, the basal distance of modified MMT increased up to 3.6 nm. The results show the intercalation of chitosan between the layers of MMT and obtaining of intercalated and partial exfoliated nanocomposites. Copyright © 2011 John Wiley & Sons, Ltd.     

Kinetic study of the thermal degradation of PS/MMT nanocomposites preparedwith imidazolium surfactants

Styrene and montmorillonite organically modified with imidazolium surfactants (MMT) at various alkyl chain lengths (C₁₂, C₁₆ and C₁₈) were used to prepare the corresponding PS/MMT/C₁₂, PS/MMT/C₁₆ and PS/MMT/C₁₈ nanocomposites by in situ polymerization. XRD and TEM analyses evidenced the formation of both intercalated and exfoliated structures. The glass transition temperatures (T _g) of nanocomposites, as well as that of neat PS, were obtained by DSC measurements. The thermal degradations were carried out in the scanning mode, in both inert and oxidative environments, and the initial temperatures of decomposition (T _i) and the apparent activation energies of degradation (E _a) were determined. Due to an oxidative degradation mechanism, the T _i and E _a values in air atmosphere were lower than those under nitrogen. The results indicated that nanocomposites are more thermally stable than polystyrene, and suggested an increasing degree of exfoliation as a function of alkyl chain length of surfactant, associated with enhancing thermal stability.     

Significantly enhanced electromagnetic interference shielding effectiveness of montmorillonite nanoclay and copper oxide nanoparticles based polyvinylchloride nanocomposites

In the present study, montmorillonite (MMT) nanoclay and copper oxide (CuO) nanoparticles (NPs) reinforced polyvinylchloride (PVC) based flexible nanocomposite films were prepared via solvent casting technique. Using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (SEM) and thermo-gravimetric analysis (TGA), the structural, morphological and thermal properties of PVC/MMT/CuO nanocomposite films with various loadings of CuO NPs and MMT were investigated. These studies suggested that by the addition of dual nanofillers in the polymer matrix some structural modifications occurred owing to the homogenous dispersion of MMT and CuO NPs within the PVC matrix. The TGA results reveal that the addition of CuO NPs and MMT considerably improved the thermal stability of the nanocomposites. The EMI shielding effectiveness (SE) of nanocomposites was examined in the X-band (8–12 GHz) and Ku-band (12–18 GHz) frequency regions. The EMI SE values were found to be −30 dB (X-band) and −35 dB (Ku-band) for nanocomposites containing 0.3 wt% of CuO NPs and 4.7 wt% of MMT respectively while the shielding was found to be absorption dominant. These results emphasize that PVC/MMT/CuO nanocomposite films can be used as a potential EMI shielding material.     

Insertion of Polypyrrole Chains into Montmorillonite Galleries by a Solvent‐Free Mechanochemical Route

Summary: Non‐ionic pyrrole was directly intercalated into unmodified montmorillonite (MMT) and organically modified MMT galleries by adsorption, and subsequently polymerized within the interlamellar spaces by a mechanochemical route under solvent‐free conditions. XRD analysis revealed the successful intercalation of pyrrole into unmodified MMT and organically modified MMT clay galleries by mechanochemical grinding. After in situ polymerization, the XRD and FT‐IR analyses confirmed the insertion of polypyrrole chains between both MMT galleries.

X‐ray powder diffraction patterns of (A) pyrrole‐intercalated MMT and (B) pyrrole‐intercalated C18‐MMT.