Morphology, structure and properties of a poly(1-butene)/montmorillonite nanocomposite

A specifically formulated nanocomposite based on isotactic poly(1-butene) (PB) and montmorillonite was studied, by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light optical microscopy, investigating the polymorphism of the polymer, and examining the interaction between PB and the silicate. Montmorillonite was found to disrupt the ordered morphology of the polymer, determining a dramatic increase in the rate of the II→I phase transition. Interaction between polymer and clay was studied by TEM and SAXS also under a quantitative point of view. A significant enhancement of physical-mechanical properties was observed, even though exfoliation did not occur, but just a slight intercalation and a reduction in the size of tactoids.     

The effect of crystallization on the structure and morphology of polypropylene/clay nanocomposites

The effect of crystallization on the structure and morphology of maleic anhydride grafted polypropylene (PP‐MA)/clay (montmorillonite) nanocomposites (PPCNs) is presented. Wide‐angle X‐ray diffraction (WAXD) measurements of PPCNs crystallized at different temperatures show that the extent of intercalation increases with the crystallization temperature. The enhancement of intercalation occurs with lower clay content PPCNs, and maximum intercalation takes place for 4 wt% clay content. The mechanism of intercalation has been proposed through crystallization. Excess γ‐form of the crystallite of PP‐MA appears in presence of clay, possibly because of the confinement of the polymer chain between the clay particles. WAXD data also reveals that d‐spacing increases gradually with clay content. The decrease of spherulitic size is observed with increasing clay content, which indicates that clay particles act as nucleating agents. Lamellar textures have been explored by using small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM), which exhibit that both the lamellar thickness and long period of the PPCNs are higher than those of PP‐MA.     

Uniaxial compression and stretching deformation of an i-PP/EPDM/organoclay nanocomposite

In this study, the morphology and rheological properties of nanocomposites prepared by melt mixing of isotactic polypropylene (i-PP), ethylene-propylene-diene terpolymer rubber (EPDM), and Cloisite 15A organoclay, were investigated at rest and under of uniaxial compression and stretching deformations at room temperature. Transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) experiments revealed that intercalation took place between the clay and the blend. The lamellar long period (L) of the polymeric structure determined by small-angle X-ray scattering (SAXS) was found to increase upon the addition of nanoclay, which also resulted in variations in the angle of rotation (?) between the polymer and clay lamellae. The intercalated nanoclay improved the storage and loss modulus of the resulting materials in the melt state significantly, as determined from oscillatory rheology analyses. Finally, we verified that the uniaxial plane deformation caused by compression of the nanocomposites contributed to the reduction of crystalline domains in the blend, while the crystallinity remained almost constant in the case of uniaxial stretching deformation.     

Supramolecular structure of the solid-state complexes of polyacrylamide and dodecylbenzenesulfonic acid

The solid-state complexes of a flexible polymer, polyacrylamide (PAA), and an amphiphilic surfactant, dodecylbenzenesulfonic acid (DBSA), have been investigated. Complexation between PAA and DBSA occurred via proton transfer from DBSA to the carbonyl group in PAA, giving rise to a “supramolecular comb-like polymer” with ionic bonding. The mesomorphic phase in the complexes was identified by the birefringent patterns under polarized optical microscopy. Wide angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) revealed that the complexes microphase separated into a lamellar morphology consisting of alternating polar and nonpolar layers with the long period of ca. 3 nm. As the composition x (the average number of DBSA molecules bound with a PAA repeating unit) ≥ 0.7, the SAXS profiles were characterized by a major scattering peak associated with the flat lamellar structure. Multiple scattering peaks were observed at lower degree of complexation (x ≤ 0.6), which were ascribed to the formation of undulated lamellae that organized into a macrolattice with the diffraction patterns observable by SAXS. Preliminary assignments of the lattice planes suggested that the lobes of the undulated lamellae organized into body centered cubic (bcc) or simple cubic (sc) types of unit cell. The glass transition temperature of the polar layers in PAA(DBSA) complexes increased with increasing degree of complexation owing to the stiffening of polymer chains. Complexation with DBSA also enhanced the thermal stability of PAA, where the thermal decomposition temperature can be raised by as much as 35 °C.     

Investigation of the morphology of polypropylene − nanoclay nanocomposites

The morphology development in polypropylene ? nanoclay composites with different weight percentages of nanoclay additives was studied using a combination of wide‐angle X‐ray diffraction, small‐angle X‐ray scattering (SAXS), polarized optical microscopy and transmission electron microscopy. SAXS studies showed an increase in long period with increase in additive weight percentage. Thermal analysis showed that even if the clay platelets are not completely exfoliated they can act as effective nucleating agents. Studies indicated that the ultimate morphology formation is influenced by both the thermodynamics of mixing and crystallization and spherulite formation. During spherulite growth, unenclosed clay platelets were excluded at the spherulite boundaries. From the observed results, a schematic model of morphology formation in polypropylene ? nanoclay composites is proposed. © 2013 Society of Chemical Industry     

Structure,morphology, and biodegradability of poly(ε‐caprolactone)‐based nanocomposites

Biodegradable polycaprolactone/organoclay nanocomposites were prepared by solvent casting, using different amounts of filler and matrices differing by average molecular weight. Intercalated nanocomposites were obtained. The nanocomposites were characterized by wide‐angle X‐ray diffraction (WAXD) and small‐angle X‐ray scattering (SAXS) methods. Negligible variations in the degree of crystallinity were detected by WAXD. The thickness of crystalline lamellae, measured by SAXS, increased in low molecular weight polymer nanocomposites with increasing clay amount; this effect was weakened in matrices with high molecular weight. Differential scanning calorimetry showed an inhibiting effect of clay on crystallization. The composites' ductility was largely increased, whereas stiffness was retained. After biodegradation in compost, in all samples, the degree of crystallinity was increased, meaning that the less ordered portion of the sample was preferentially degraded. Clay slowed down the biodegradation rate, coherently with the observed increase in the lamellar thickness due to the filler. This may offer a strategy for tuning the biodegradability by calibrating their semicrystalline framework. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.     

硫化方法对橡胶/黏土纳米复合材料黏土片层分散状态的影响

通过熔体插层法以及常压硫化法制备了橡胶/黏土纳米复合材料,并与模压硫化法制备的复合材料进行了对比,研究了硫化方法对橡胶/黏土纳米复合材料微观分散状态的影响。结果表明:采用熔体插层法制备的橡胶/黏土混合物,其受限状态的橡胶大分子链在高温、高压条件下,在黏土片层之间处于一种热力学不稳定状态;模压处理会对橡胶/黏土混合物的分散状态产生不利影响。透射电子显微镜和X光衍射分析表明,采用模压硫化、常压硫化得到的丁基橡胶或丁苯橡胶/黏土纳米复合材料中黏土片层的微观分散状态不同;排除压力的影响,常压硫化有利于提高橡胶/黏土纳米复合材料中黏土片层的分散程度。     

Nanostructure morphology and dynamic rheological properties of nanocomposites based on thermoplastic polyurethane and organically modified montmorillonite

Thermoplastic polyurethane (TPU) nanocomposites based on organophilic-layered silicates were prepared via melt blending. Wide angle X-ray diffraction (WAXD) and transmission electron microscope (TEM) were employed to investigate the state and mechanism of exfoliation of the layered silicate within TPU matrix. The TPU nanocomposites were found to have a partially exfoliated morphology at lower clay loading, whereas the morphology changed to an intercalated nanostructure at higher clay loadings. The effect of the state of dispersion of organoclay on rheological properties of the nanocomposites were carried out by rubber process analyzer (RPA), which exhibited more pronounced shear thinning behavior, and increased storage and loss modulus with the increase in organoclay content. The pseudo-plastic like behavior was observed due to change in liquid-like to solid-like behavior of nanoclay-filled systems.     

流动场下含β成核剂的玻璃纤维增强聚丙烯复合材料结构与性能研究

采用普通注射成型和动态保压注射成型分别制备了不同玻璃纤维（GF）含量和β成核剂含量的等规聚丙烯（iPP）复合材料,测试了复合材料的力学性能,并采用二维广角X射线衍射、扫描电子显微镜和二维小角X射线散射研究了复合材料的iPP分子链取向、GF取向及结晶性能。结果表明,在动态保压注射成型条件下,GF含量为30 %（质量分数,下同）、β成核剂含量为0.2 %时,复合材料具有最优异的综合性能,拉伸强度为58.52 MPa,冲击强度为9.26 kJ/m2,这是由于在流动场下含GF与β成核剂的复合材料形成了"皮刚芯韧"类竹子的仿生结构。     

Alignment and orientational proliferation of HEX cylinders in a polystyrene-block-polyisoprene-block-polystyrene copolymer in the presence of clay

We investigated the effect of an anisotropic silicate layer on the alignment and orientational proliferation of hexagonally packed cylinder microdomains of a block copolymer in the presence of a clay by using synchrotron small angle X-ray scattering (SAXS), rheology, and transmission electron microscopy (TEM). The block copolymer employed in this study was polystyrene-block-polyisoprene-block-polystyrene copolymer (SIS). The degree of intercalation of the clay in the presence of SIS was examined by wide angle X-ray diffraction (WAXD).Almost all of the HEX cylinders in neat SIS are aligned toward the flow direction after large amplitude oscillatory shearing is applied to the specimens. However, some tactoids in nanocomposites are not aligned, although most tactoids are also aligned to the flow direction. Due to HEX cylinders near tactoids, which are not aligned to the flow direction, the orientational factor of HEX cylinders in SIS/clay nanocomposites is smaller than that of neat SIS. However, once HEX cylinders in SIS/clay nanocomposites are degenerated after experiencing body-centered cubic microdomains, the decrease in the orientational factor from original aligned HEX is smaller compared with neat SIS.     

Effects of clay on the morphology of poly(acrylonitrile-butadiene-styrene) and polypropylene nanocomposites

The effects of clay on the morphology of the poly(acrylonitrile-butadiene-styrene) (ABS)/polypropylene (PP) nanocomposites were investigated. From the studies of wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) analysis of the ABS/PP (70/30) nanocomposites with clay, it was observed that most of the clay existed in the ABS matrix because of the good affinity between the ABS and clay which contained benzyl group. From the studies of the scanning electron microscopy (SEM) analysis, the size of the PP droplet decreased with clay from 16.7 to 5.6 μm when the clay was added up to 4.0 phr. When the clay content was increased, the droplet of the dispersed phase (PP) was shown to elongated structure. The elongated structure could be explained by the decrease of the viscosity ratio of the PP and continuous phase (ABS) with clay, which corresponded to the increase of the viscosity of the continuous phase (ABS/clay). From the results of the SEM, TEM, and WAXD analysis, it is suggested that the increase of the viscosity of the continuous phase (ABS/clay) is mainly due to the location of clay in the ABS matrix. POLYM. ENG. SCI., 47:1671–1677, 2007. © 2007 Society of Plastics Engineers     

A SAXS–WAXD study on the mesomorphic-α transition of isotactic polypropylene

The smectic-α transition of iPP was studied by wide angle X-ray diffraction (WAXD) and small angle X-ray scattering (SAXS). WAXD and SAXS patterns were taken at different temperatures during the transition. Two different approaches were taken in the analysis of SAXS data: the correlation function and a fitting method based on theoretical distribution models. Up to 80°C just smectic phase was observed, whereas beyond that temperature α lamellae appeared and the two populations of lamellae were found to coexist in the sample. The new α phase population stemmed from within the preexistent smectic stacks, according to a lamellar insertion model. α lamellae thickened to a larger extent than the smectic phase, that just underwent thermal expansion. Results were consistent with a mechanism of transformation involving a rearrangement of the chains without a melting-recrystallization process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

The quantitative analysis of nano-clay dispersion in polymer nanocomposites by small angle X-ray scattering combined with electron microscopy

The main objective of this work is to propose a new approach for the quantitative analysis of the degree of dispersion of clay particles in the polymer matrix by small angle X-ray scattering (SAXS) combined with electron microscopy. Due to the low temperature processibility and good thermal stability, poly[(butylene succinate)-co-adipate] (PBSA) was chosen as a model polymer matrix for this study. The nanocomposites of PBSA with four different weight percentages of organically modified montmorillonite (OMMT) loadings were prepared via melt-blending method. The dispersed structure of the clay particles in the PBSA matrix was studied by SAXS. Results show that the clay particles are nicely dispersed in the case of all nanocomposites. However, with a systematic increase in clay loading, the dispersed clay structure of the nanocomposites changes from a highly delaminated to a flocculated and then to a stacked intercalated one. The probability of finding neighboring clay particles in the PBSA matrix as well as their thickness was calculated using the Generalized Indirect Fourier Transformation technique developed by Glatter and the modified Caillé theory proposed by Zhang. The morphology of the nanocomposites was also extensively studied by scanning transmission electron microscopy (STEM). In the case of all nanocomposites, SAXS results were in good agreement with STEM observations. Finally, a correlation between the predicted morphology of nanocomposites and their melt-state rheological properties is reported.     

Structure and morphology development during deformation of propylene based ethylene-propylene copolymer and its blends with isotactic polypropylene

The structure and morphology development during the deformation of metallocene based ethylene-propylene copolymers with dominant propylene moiety (C3 M-EP) and its isotactic polypropylene (M-iPP) blends were investigated by simultaneous small-angle X-ray scattering (SAXS) and wide-angle X-ray diffraction (WAXD) using synchrotron radiation, high temperature tensile testing and differential scanning calorimetry (DSC). X-ray results showed that the structure and morphology in the blends of M-iPP/C3 M-EP are dictated by the M-iPP component. During stretching at room temperatures, both pure M-iPP and polymer blends exhibited the same transition from the α-form crystal to the mesophase. However, the α-form was found to be unchanged during the deformation of C3 M-EP copolymer, which indicated that the effect of local stress on the crystal domain in pure copolymer was too small to induce the phase transition. Although the DSC results showed that the blends in their isotropic state were immiscible with each other, the mechanical properties of the blends at high temperature (70 °C) indicated that they follow the conventional rule of mixing.     

On the determination of platinum particle size in carbon-supported platinum electrocatalysts for fuel cell applications

Using a conventional laboratory diffractometer, small angle X-ray scattering (SAXS) was used to determine the average platinum particle size in samples of carbon with a range of platinum loadings. The results obtained were compared with those obtained from wide-angle X-ray diffraction (WAXS) studies. SAXS was more effective than WAXS for determining the average platinum particle size in samples where the grains were so small that the resultant diffraction peaks in the WAXS profiles were too broad to accurately determine the peak width for use in the Scherrer equation.     

Combined effect of shear and fibrous fillers on orientation-induced crystallization in discontinuous aramid fiber/isotactic polypropylene composites

The shear-induced crystallization behavior in isotactic polypropylene (iPP) composite melt containing short aramid fibers was investigated by means of WAXD (wide-angle X-ray diffraction) and SAXS (small-angle X-ray scattering) techniques using synchrotron radiation. The study was carried out in a post-shear isothermal crystallization mode at temperatures of 140-160 °C. Parameters pertaining to the crystallization morphology and kinetics were analyzed, including total crystallinity, orientated crystalline and amorphous fractions, dimensions of the formed shish-kebab structure, as well as induction time and rate of crystallization. The individual contributions of shear and fibers were evaluated and the combined effect was compared. The results clearly indicated that the effect is synergistic rather than additive.     

Ethylene Vinyl Acetate and Polycaprolactone–Organoclay Nanocomposite: Thermal,Mechanical and Morphological Properties

Organoclay of the type Cloisite^® 20A (C-20A) with two structurally different but semicrystalline polymer matrices was studied. Polycaprolactone (PCL), a linear, biodegradable polymer, and ethylene vinyl acetate (EVA), a branched copolymer, were chosen to prepare polymer clay nanocomposites via the melt-blending method. The results show that the structure of a polymer matrix plays a significant role towards compatibilization with the silicate layers of the clay. Scanning electron microscopy and X-ray diffraction analyses revealed an exfoliated-intercalated mixed morphology for the PCL matrix. However, for the EVA matrix, silicate layers agglomerated to form tactoids and resulted primarily in an intercalated morphology. Fourier transform infrared spectroscopy was used to determine the nature of the interactions between the polymer and the filler. The thermal properties were investigated using thermogravimetric analysis and indicated that, with an increase in clay loading, the thermal stability was reduced for both matrices. Tensile tests suggested that Young’s modulus improved for the EVA matrix with an increase in clay dosage whereas for PCL the modulus was found to be highest for 8% clay loading.     

Effect of Clay Types on the Mechanical,Dynamic Mechanical and Morphological Properties of Polypropylene Nanocomposites

In the present investigation Polypropylene–Maleic anhydride grafted polypropylene–organically modified MMT (PP-MAPP-OMMT) nanocomposites were prepared by melt mixing in a twin screw extruder followed by injection molding. The effect of clay chemistry and compatibilizer on the properties of the nanocomposites has been studied. Sodium montmorillonite has been organically modified using quaternary and alkyl amine intercalants. A comparative account with commercial quaternary ammonium modified clays i.e Cloisite 20A, Cloisite 15A and Cloisite 30B has been presented. Storage modulus of PP matrix also increased in the nanocomposites, indicating an increase in the stiffness of the matrix polymer with the addition of organically modified nanoclays. The morphology of the nanocomposites has been examined using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). Morphological findings revealed efficient dispersion of organically modified nanoclays within the PP matrix. MAPP compatibilized PP/Cloisite 15A nanocomposites displayed finely dispersed exfoliated nanomorphology as compared with other systems.     

Preparation,characterization, and nanostructural evolution of epoxy nanocomposites

Epoxy nanocomposites were prepared from the different organoclays with aerospace epoxy resin. A series of organoclays treated with alkylammonium chloride with different alkyl groups of different carbon chains were prepared, including SC4, SC6, SC8, SC10, SC12, SC16, SC18, and NC8, NC12, NC18. All of these organoclays, except for SC4, are very compatible with the aerospace Epon 862/curing agent W. The characterization from wide‐angle X‐ray diffraction (WAXD), small‐angle X‐ray scattering (SAXS), and transmission electron microscopy (TEM) confirms the exfoliated nanostructure. The six‐carbon chain length of the ammonium cation is enough to wet the surface of the clay gallery to make the organoclay compatible with epoxy resin. The clay with lower cation exchange capacity is more favorable for the polymer penetration inside the gallery and is dispersed better in the polymer matrix. The structural evolution of the aerospace epoxy nanocomposite was monitored by in situ SAXS. The 3% SC18/Epon 862/W, 3 and 6% SC8/Epon 862/W showed exfoliated nanostructure, while there is no exfoliation taking place for 3% S30B/Epon 862/W and 3%S25A/Epon 862/W up to 200°C. The acidity from the pendent group in SC18 and SC8 has a catalytic effect for the polymerization inside the gallery, while the organic pendent group of S30B and S25A does not. The faster reaction of the intragallery epoxy resin produced extra thermal heat inside the gallery to expand the gallery and is favorable for the migration of epoxy resin outside the gallery into the gallery where exfoliation took place. The exothermal heat of curing inside the gallery is an important factor for nanosheets exfoliation. Although exfoliation took place for both 3% SC18/Epon 862/W and 3% SC8/Epon 862/W, the detailed morphology development during the curing is different. For 3% SC8/Epon 862/W, the interplanar spacing between the layers is increased gradually, while 3% SC18/Epon 862/W experienced the disappearance of the ordered structure of the layered silicate in the beginning of the curing process and reappearance of the ordered structure of the silicate later. The glassy and rubbery moduli of the polymer‐silicate nanocomposites were found to be greater than the unmodified resin because of the high aspect ratio and high stiffness of the layered silicate filler. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2276–2287, 2003     

Effect of clay/water ratio during bentonite clay organophilization on the characteristics of the organobentonites and its polypropylene nanocomposites

A sodium bentonite (montmorillonite‐based layered silicate clay) was organically modified with cetyl trimethyl ammonium bromide (cetrimide), using different clay/water ratios—but the same clay/cetrimide ratio—to suspend the bentonite clay and perform its organophilization. Infrared spectroscopy and thermogravimetric analysis indicated the incorporation of organic modifier into the bentonite. Wide‐angle X‐ray scattering showed that the incorporation of surfactant significantly increased the interlayer spacing in the bentonite for all concentrations studied. It was found that clay/water ratio employed during the modification affects neither the amount of organic salt incorporated nor the interlayer spacing in the organobentonites, but influences its degree of structural disorder. Lower clay/water ratios resulted in a more disorderly structure, as established by the decrease of the areas under the X‐ray peaks as the clay/water ratio diminishes. The modified bentonites were melt compounded with maleic anhydride‐grafted polypropylene. X‐ray diffraction patterns of the hybrids revealed that the more disorderly organobentonites were better dispersed in the polymer matrix, indicating that, in the present system, the structure of polymer nanocomposites obtained were affected by the clay/water ratio used in organobentonite preparation. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers