Polyolefin-based nanocomposite: The effect of organoclay modifier

Polypropylene (PP) nanocomposites were prepared using montmorillonite with different organic modifiers, and the effect of processing aid (EMCA and PPG) on the dispersion of the nanofillers in the PP matrix was evaluated by WAXD, TEM, DSC, TGA, DMA, and mechanical tests. The present study helps to clarify the effects of the organic modifiers of clays on the intercalation and exfoliation processes. Nanocomposites of intercalated and partially exfoliated morphology were obtained, mainly when a low amount (1:1) of PP-g-MA/MMT was used. The results of the tests on mechanical properties showed that the clays with larger d₀₀₁ (C-15A and Nanofil 5) using PPG presented a more considerable gain in impact strength. The nanocomposites using clays with smaller d₀₀₁(C-20A) presented larger modulus when compared with those of pristine PP. The heat deflection temperature, crystallization temperature, and thermal stability of the nanocomposites were improved compared to neat PP. The DMA results showed that the organoclay improved the modulus of PP, but decreased the T_g. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2519–2531, 2008     

Thermal and mechanical properties of PE/organoclay nanocomposites

Polyethylene/montmorillonite clay nanocomposites were obtained via direct melt intercalation. The clay was organically modified with four different types of quaternary ammonium salts. The objective of this work is to study the use of montmorillonite clay in the production of nanocomposites by means on rheological, mechanical and crystallization properties of nanocomposites and to compare to the properties of the matrix and PE/unmodified clay nanocomposites. In general, the tensile test showed that the yield strength and modulus of the nanocomposites are close to the pure PE. Apparently, the mixture with Dodigen salt seems to be more stable than the pure PE and PE/unmodified clay.     

Thermal behavior of Al-, AlFe- and AlCu-pillared interlayered clays

The purified bentonite parent clay, fraction ≤; 2 mm of montmorillonite type, has been pillared by various polyhydroxy cations, Al, AlFe and AlCu, using conventional pillaring methods. The thermal behavior of PILCs was investigated by combination of X-ray diffraction (XRD), thermal analysis (DTA, TG) and low temperature N2 adsorption/desorption (LTNA). Thermal stability of Al-, AlFe- and AlCu-PILC samples was estimated after isothermal pretreatment in static air on the temperatures 300, 500, 600 and 900°C. Crucial structural changes were not registered up to 600°C, but the fine changes in interlayer surrounding and porous/microporous structure being obvious at lower temperatures, depending on the nature of the second pillaring ion. AlFe-PILC showed higher thermal stability of the texture, the AlCu-PILC having lower values and lower thermal stability concerning both overall texture and micropore surface and volume. Poorer thermal stability of AlCu-PILC sample at higher temperatures was confirmed, the presence of Cu in the system contributing to complete destruction of aluminum silicate structure, by 'extracting' aluminum in stabile spinel form. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and properties of polyimide–clay hybrid

A polyimide hybrid with montmorillonite clay mineral has been synthesized from a dimethylacetamide (DMAC) solution of poly(amic acid) and a DMAC dispersion of montmorillonite intercalated with an ammonium salt of dodecylamine. Montmorillonite consists of stacked silicate sheets about 2000 Å in length, 10 Å in thickness. In this hybrid, montmorillonite is dispersed homogeneously into the polyimide matrix and oriented parallel to the film surface. Thanks to this special structure, this hybrid showed excellent gas barrier properties. Only 2 wt % addition of montmorillonite brought permeability coefficients of various gases to values less than half of those of ordinary polyimide. Furthermore, this hybrid had low thermal expansion coefficient. © 1993 John Wiley & Sons, Inc.     

Melt compounding of polylactide/organoclay: Structure and properties of nanocomposites

A Brabender mixer was used to deagglomerate and disperse organomodified montmorillonite Cloisite® 30B (3 wt %) in polylactide (PLA) matrix to obtain nanocomposite systems. The influence of compounding conditions such as blending time (6.5, 10, 20, and 30 min) and compression molding on the nanostructure of nanocomposites was investigated. Molecular weight changes of the PLA matrices induced by melt compounding were determined. Good rheological behavior of the PLA during melt blending with Cloisite® 30B was observed. Prolongation of the blending process improved homogenization of the nanocomposites with the formation of more intercalated and exfoliated structures as revealed by transmission electron microscopy (TEM) and X‐ray analysis. Some orientation of the silicate nanoplatelets induced by compression molding of the nanocomposites was revealed by TEM. It was found that an increase of dispersion degree of the silicate layers modified pronouncedly the physical properties of nanocomposites through an increase of thermal stability as revealed by the thermogravimetric analysis, a decrease of crystallizability of the PLA matrix during melt‐crystallization and upon heating from the glassy, amorphous state. Rheological properties of the nanocomposites determined during dynamic frequency sweep appeared to be very sensitive to the nanostructure evolution. Moreover, the scanning electron microscopy and light microscopy investigations showed the presence of the micron‐size inorganic contaminations in the nanocomposites originating from organoclay Cloisite® 30B. These inclusions were resistive to deagglomeration during melt processing. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3392–3405, 2006     

Nylon‐6 nanocomposites,study of the influence of the nanofiller nature on morphology and material properties

In this article we investigated the influence of various nanofilllers' aspect ratio, chemical nature, and organic modification on some selected nylon‐6 properties, such as crystallinity, thermal and mechanical resistance, and fire behavior. Materials were prepared by twin‐screw extrusion and characterized by means of scanning and transmission electron microscopy, X‐ray diffraction, thermogravimetric analysis, tensile tests, and cone calorimeter. Fillers characteristics were found to influence at different extents the material final properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1935–1948, 2009     

Influence concentration of modifying agent on properties of natural rubber/organoclay nanocomposites

Sodium-montmorillonite (Na-MMT) nanoclay was modified with different concentrations of octadecylamine organic modifying agent at 0.5, 1.0 and 1.5 times the CEC of Na-MMT. Influence of concentration of modifying agent on properties of the organoclays and natural rubber/organoclay nanocomposites was investigated. It was found that the optimum concentration of modifying agent was 1.5 times the CEC of Na-MMT. That is, at this concentration, larger d-spacing of organoclay particles and higher degree of clay dispersion in natural rubber matrix were observed. Larger interlayer d-spacing also caused enhancement of the mechanical properties of the NR/organoclay nanocomposites. Additionally, the NR/organoclay nanocomposites with higher concentration of modifying agent exhibited faster curing reaction with higher crosslink density. Furthermore, the organoclays with larger d-spacing and higher degree of dispersion in the natural rubber matrix exhibited enhancement of the mechanical and dynamic properties and thermal stability of natural rubber/organoclay nanocomposites.     

Modified montmorillonite combined with intumescent flame retardants on the flame retardancy and thermal stability properties of unsaturated polyester resins

Modified montmorillonite‐containing phytic acid (PA‐MMT) has been prepared by acid treatment and then introduced into unsaturated polyester resin (UPR) with an intumescent flame retardant (IFRs). The flame retardancy and thermal degradation of UPR/IFRs/PA‐MMT were evaluated by a limiting oxygen index (LOI) test, a vertical burning test (UL‐94), a thermogravimetric analysis (TGA), and a cone calorimeter test (CCT). Besides, the mechanical properties were studied by a universal testing machine. The LOI value of UPR/IFRs/PA‐MMT composites was increased to 29.2%. The CCT results indicated that the incorporation of PA‐MMT and IFRs significantly improved the combustion behavior of UPR. The results of the mechanical properties indicated that 1.5 wt% loading of PA‐MMT in UPR/IFRs showed the highest improvement in flexural strength and tensile strength. The flame‐retardant mechanism of PA‐MMT/IFRs was examined and discussed based on the results of combustion behavior and char analysis.     

The rheological and colloidal properties of bentonite dispersions in the presence of organic compounds III. The effect of alcohols on the coagulation of sodium montmorillonite

The critical coagulation concentration,c _K, of sodium chloride for sodium montmorillonite dispersed in water (solid content 0.025 percent) is 8 mmol/L. It remains virtually constant (7.5–8.5 mmol/L) in water-rich alcohol mixtures (below 50% (v/v) methanol and 40% ethanol and propanol). At higher alcohol contents thec _K decreases to 3.6 mmol/L (70 percent methanol), 1.2 mmol/L (70 percent ethanol), and 0.8 mmol/L (60 percent propanol). In the presence of 10^–4 M sodium diphosphate thec _K in water rises to 195 mmol/L. In contrast to the behavior in the absence of diphosphate, even small amounts of alcohol reduce the critical coagulation concentration. In 70% methanol thec _K is 7.5 mmol/L, in 70 percent ethanol 2.5 mmol/L and in 60% propanol 5 mmol/L. The main mechanism is coagulation by contacts between negatively charged edges and faces.At high alcohol contents montmorillonite-alcohol complexes (interlayer solvates) are formed and the colloidal dispersions become unstable even in the absence of salt. Transition from the state with diffuse ionic layers into the quasi-crystalline structure of the interlayer solvates is also evident from the sediment volume which changes with the alcohol content. Maxima are observed which are indicative of band-type structures as intermediate states between the colloidally dispersed particles with repulsive interaction and the discrete particles of the montmorillonite-alcohol complexes.     

Flame retardancy of polyamide 66 nanocomposites with thermally stable organoclay

A thermally stable imidazolium organoclay was synthesized to improve the flame retardancy performance of polyamide 66 (PA 66). To enhance flame retardancy of the PA 66/organoclay nanocomposite, the thermally stable organoclay was coated with monomethylol melamine (MMM) before melt‐compounding with PA 66. Transmission electron microscopy and X‐ray diffraction results confirmed the partial exfoliation of the organoclay in the PA 66 matrix. The use of the thermally stable organoclay did not affect the thermal stability of PA 66. The cone calorimeter results showed that the PA 66/orgnaoclay nanocomposite exhibited a greatly reduced heat release rate and a longer ignition time. However, the PA 66/organoclay binary nanocomposite had no rating in the UL‐94 vertical burning test because it did not extinguish until the entire polymer component was burnt. The PA 66 nanocomposite with 15 wt% of MMM‐coated organoclay performed better in the ignition resistance test than the PA 66/organoclay nanocomposite containing 15 wt% of melamine. Copyright © 2011 John Wiley & Sons, Ltd.     

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

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

A study on phase morphology and surface properties of polyurethane/organoclay nanocomposite

In this study, polyurethane/organically modified layered silicate (organoclay) nanocomposites were prepared through in situ polymerization in the presence of organoclay. Phase morphology of the polyurethane/organoclay nanocomposite was investigated by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The results suggest that the inter-domain repeat distance decreased with the introduction of organoclay. The organoclay has a more significant effect on the inter-domain repeat distance at a low hard segment content. Also with the increase of the hard segment, the inter-domain repeat distance and domain size increased markedly. The size of hard domain of the polyurethane was found to be in the range of 12-32 nm in this case, and it keeps nearly unchanged with the clay content. It is suggested by AFM phase imaging technique that the hard domain can self-organize further to form spherical aggregates. The introduction of clay into the polyurethane matrix resulted in the decrease in the size of the spherical aggregates from ∼800 nm to ∼500 nm, indicating clay has an important effect on the aggregation behavior of hard domains. The effect of clay on the surface energy was examined by means of AFM and goniometry techniques. The results obtained by two methods are consistent, i.e., with the increase of clay content, the surface energy decreased due to the effect of organic modifier.     

The role of organoclay and matrix type in photo-oxidation of polyolefin/clay nanocomposite films

In this paper the photo-oxidation behaviour of polyolefin/clay nanocomposite films was studied; in particular, the effect of the amount of organo-modifier and the matrix polarity on the photo-oxidation was investigated. Two different organo-modified clays and compositions of LDPE/EVA blend films were used and the photo-oxidation was followed by mechanical and spectroscopic analyses.The organoclay and matrix type strongly influence the photo-oxidative behaviour of nanocomposite films. The films filled with CL15A show a faster loss of mechanical performance and higher carbonyl formation with respect to the films filled with the CL20A. Additionally, the LDPE based nanocomposite undergoes photo-oxidation more rapidly than the EVA based one.     

Effect of the type of nanoaddition on the thermal properties of polyacrylonitrile fibres

Thermal properties of precursor polyacrylonitrile fibres containing nanoparticles of additives such as SiO₂, hydroxyapatite and montmorillonite have been examined. The thermal curves of the fibres under investigation obtained by the derivatographic method in air and DSC in a neutral gas atmosphere were interpreted from the point of view of physical and chemical changes in the fibre-forming polymer. Based on the thermogravimetric curves, the coefficients of thermal stability of the fibres were found. It has been found that the thermal stability of PAN fibres is affected by the type of nanoadditives and the value of the as-spun draw out ratio used during fibre spinning.     

The role of monomer geometry on the properties of polyolefins: A numerical study

We explore the role of monomer geometry on the structural, dynamic, and thermodynamic properties of polyolefis by employing all-atom molecular dynamic simulations. Specifically, we compare properties of atactic polyolefins in the molten state including polypropylene (aPP), a short-chain branched polymer: poy(1-hexene) (aPH), and a polymer having cyclic olefins: poly(vinyl cyclobutane) (aPVCB). We find polymers having the same chain mass and atom composition (hydrocarbon-based molecules), but having different monomer architecture differ strongly in material properties. In particular, the polymer glass transition ( $T_{\mathrm{g}}$) and bulk modulus ( $B$) show higher values for aPVCB in comparison to aPP and aPH. This increase is caused by having the carbon atoms in a cyclic structure, making aPVCB achieve higher mass and energy densities. By contrast, adding linear short side chains to polymer backbones causes a reduction in $T_{\mathrm{g}}$ and $B$, since side chains make backbones displace each other reducing their packing and thus their mass and energy densities. More broadly, our numerical results suggest that the incorporation of VCB monomers to linear polyolefins will enhance their properties, opening the possibility for designing a new set of materials.     

Effect of glass cullet on thermal properties of kaolinite

Waste compromises environmental preservation as well human health in many countries. Recycling is an alternative that sometimes represents the only economical activity for a significant population in the big cities. Almost 3% of waste materials in Brazil are vitreous. Ceramic production adding waste glass is possible with advantages of costs reduction associated to decrease on firing temperatures and to the raw material itself. At present paper up to 80 mass% of waste glass was added to clay. The sintering temperature decreased linearly and the shrinkage increased with glass content, an effect more pronounced for high glass amount.     

Study on elastic modulus of crosslinked polyurethane/organoclay nanocomposites

In this paper, two polyurethane/clay nanocomposite systems with crosslinked structure were synthesized via in situ polymerization of a polyether‐ as well as a polyester‐based prepolymer with methylene‐bis‐ortho‐chloroanilline (MOCA). Two types of modified clays with different organic modifiers were used in order to see the effect of compatibility between polymer matrix and clays on elastic modulus of nanocomposites. The morphology and the dispersion of clay layers in polyurethanes have been characterized by X‐ray diffraction (XRD) and microscopic techniques. The changes of elastic modulus of nanocomposites with clay content were examined and compared with those predicted by some conventional composite models. The results showed a reasonable fitting of experimental and theoretical values only at very low clay contents. As the clay content exceeds 1.5 wt% in this system, a reduction in elastic modulus was experimentally observed due to insufficient dispersion degree of silicate layers throughout the crosslinked matrix. This behavior was not predicted with the conventional composite theories. A new model on the basis of Wu model was then developed in order to predict the reduction of elastic modulus at various clay contents in crosslinked PU matrix. This model fitted reasonably the experimental results. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and properties of polyimide-clay hybrid films

Polyimide-clay hybrid films with four different sizes of clay minerals have been synthesized to investigate the effect of the size of clay minerals to the properties of the hybrids. Hectrite, saponite, montmorillonite, and synthetic mica were used as clay minerals. Those clays consist of stacked silicate sheets about 460 Å (hectrite), 1650 Å (saponite), 2180 Å (montmorillonite), and 12300 Å (synthetic mica) in length, 10 Å in thickness. The longer the length of clay mineral was, the more effectively properties of polyimide were improved. In the case of polyimide-mica hybrid, only 2 wt % addition of synthetic mica brought permeability coefficients of water vapor to value less than one-tenth of that of ordinary unfilled polyimide, and thermal expansion coefficient was lowered at the level of 60% of the original one. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2289–2294, 1997     

Fe2O3-ZrO2层柱蒙脱石的合成和热稳定性

蒙脱石是具有2∶1层状结构的粘土矿物,酸化蒙脱石用途广泛[1]。利用较大体积多聚金属阳离子与蒙脱石进行离子交换并把蒙脱石层撑开,可以得到复合材料—层柱蒙脱石(ＰＩＬＭ),它具有二维的层柱结构,其孔径比一般的分子筛大。其孔径还可以根据蒙脱石离子交换当量和交换阳离子的体积大小加以控制。它具有良好的热稳定性和酸性,并且合成方法简单。蒙脱石和膨润土在我国分布广泛,储量大。因此ＰＩＬＭ在载体、吸附剂及较大分子转化催化剂等方面具有较好的应用前景。传统的层柱蒙脱石是由单组分多聚金属阳离子与蒙脱石进行交联而合成的,本文在…     

Combined effects of clay modifications and compatibilizers on the formation and physical properties of melt‐mixed polypropylene/clay nanocomposites

The melt mixing technique was used to prepare various polypropylene (PP)‐based (nano)composites. Two commercial organoclays (denoted 20A and 30B) served as the fillers for the PP matrix, and two different maleated (so‐called) compatibilizers (denoted PP‐MA and SMA) were employed as the third component. The results from X‐ray diffraction (XRD) and transmission electron microscope (TEM) experiments revealed that 190 °C was an adequate temperature for preparing the nanocomposites. Nanocomposites were achieved only if specific pairs of organoclay and compatibilizer were simultaneously incorporated in the PP matrix. For example, PP/20A(5 wt %)/PP‐MA(10 wt %) and PP/30B(5 wt %)/SMA(5 wt %) composites exhibited nanoscaled dispersion of 20A or 30B in the PP matrix. Differential scanning calorimetry (DSC) results indicated that the organoclays served as nucleation agents for the PP matrix. Generally, their nucleation effectiveness increased with the addition of compatibilizers. The thermal stability enhancement of PP after adding 20A was confirmed with thermogravimetric analysis (TGA). The enhancement became more evident as a suitable compatibilizer was further added. However, for the 30B‐included composites, thermal stability enhancement was not evident. The dynamic mechanical properties (i.e., storage modulus and loss modulus) of PP increased as the nanocomposites were formed; the properties increment corresponded to the organoclay dispersion status in the matrix. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4139–4150, 2004