Morphology of high impact polypropylene particles

Morphological features of isotactic polypropylene (iPP) and high impact polypropylene (hiPP) particles produced in a multistage polymerization process were investigated by field-emission electron microscopy (FESEM) and transmission electron microscopy (TEM) techniques. Study was mainly focused on architecture of iPP particle and distribution of elastomer phase (EPR) within the preformed iPP matrix. The iPP particle is an agglomerate of many subglobules (ca. several to hundred microns in diameter), while the subglobule in turn is formed by a great deal of primary globules (ca. 100 nm in diameter). Large macropores between the subglobules and finely distributed micropores within the subglobule constitute a network of pore inside the iPP particle. Ethylene/propylene comonomers can diffuse into the macro- and micropores and copolymerize on catalyst active sites located on periphery of the pores, forming elastomer phase inside.

Surface and interface morphology of polystyrene/poly(methyl methacrylate) thin-film blends and bilayers

The surface and interface morphologies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) thin-film blends and bilayers were investigated by means of atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. Spin-coating a drop of a PS solution directly onto a PMMA bottom layer from a common solvent for both polymers yielded lateral domains that exhibited a well-defined topographical structure. Two common solvents were used in this study. The structure of the films changed progressively as the concentration of the PS solution was varied. The formation of the blend morphology could be explained by the difference in the solubility of the two polymers in the solvent and the dewetting of PS-rich domains from the PMMA-rich phase. Films of the PS/PMMA blend and bilayer were annealed at temperatures above their glass-transition temperatures for up to 70 h. All samples investigated with AFM were covered with PS droplets of various size distributions. Moreover, we investigated the evolution of the annealed PS/PMMA thin-film blend and bilayer and gave a proper explanation for the formation of a relatively complicated interface inside a larger PS droplet.

Crystal structure and morphology of phenyl-capped tetraaniline in the leucoemeraldine oxidation state

A series of crystals of phenyl-capped tetraaniline in the leucoemeraldine oxidation state were obtained at different isothermal temperatures and were observed directly under transmission electron microscope. The crystals obtained at higher temperatures exhibit more perfect structures than those obtained at lower temperatures. Both the lamella thickness and the crystal size increase with crystallization temperature. The tetraaniline is apt to form larger scale crystals under lower degree of supercooling. However, their crystal structures keep steady with the crystallization temperature. The tetramer was found to adopt a monoclinic lattice with unit cell parameter of a = 13.93 angstrom, b = 8.82 angstrom, c = 23.20 angstrom, and beta = 95.03 degrees, as determined using electron diffraction tilting method combined with wide-angle X-ray diffraction experiment.

Solvent and polymer concentration effects on the surface morphology evolution of immiscible polystyrene/poly(methyl methacrylate) blends

The effects of solvent nature on the surface topographies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend films spin-coated onto the silicon wafer were investigated. Four different solvents, such as ethylbenzene, toluene, tetrahydrofuran and dichloromethane, were chosen. They are better solvents for PS than that for PMMA. When dichloromethane, tetrahydrofuran and toluene were used, PMMA-rich phase domains protruded from the background of PS. When ethylbenzene was used, PS-rich phase domains elevated on the average height of PMMA-rich phase domains. In addition, continuous pits, networks and isolated droplets consisted of PS formed on the blend film surfaces with the decrease of polymer concentrations. The mechanism of the surface morphology evolution was discussed in detail.

Polymer concentration, shear and stretch field effects on the surface morphology evolution during the spin-coating

Polymer concentration and shear and stretch field effects on the surface morphology evolution of three different kinds of polymers (polystyrene (PS), polybutadiene (PB) and polystyrene-b-polybutadiene-b-polystyrene (SBS)) during the spin-coating were investigated by means of atomic force microscopy (AFM). For PS and SBS, continuous film, net-like structure and particle structure were observed at different concentrations. For PB, net-like structures were not observed and continuous films and radial array of droplets emerged. Moreover, we compared surface morphology transitions on different substrate locations from the center to the edge. For PS, net-like structure, broken net-like structure and irregular array of particles were observed. For SBS, net-like structure, periodically orientated string-like structure and broken-line structure appeared. But for PB, flower-like holes in the continuous film, distorted stream-like structure and irregular distributions of droplets emerged. These different transitions of surface morphologies were discussed in terms of individual material property.

Influence of the degree of grafting on the morphology and mechanical properties of blends of poly(butylene terephthalate) and glycidyl methacrylate grafted poly(ethylene-co-propylene) (EPR)

Poly(ethylene-co-propylene) (EPR) was functionalized to varying degrees with glycidyl methacrylate (GMA) by melt grafting processes. The EPR-graft-GMA elastomers were used to toughen poly(butylene terephthalate) (PBT). Results showed that the grafting degree strongly influenced the morphology and mechanical properties of PBT/EPR-graft-GMA blends. Compatibilization reactions between the carboxyl and/or hydroxyl of PBT and epoxy groups of EPR-graft-GMA induced smaller dispersed phase sizes and uniform dispersed phase distributions. However, higher degrees of grafting (>1.3) and dispersed phase contents (>10 wt%) led to higher viscosities and severe crosslinking reactions in PBT/EPR-graft-GMA blends, resulting in larger dispersed domains of PBT blends. Consistent with the change in morphology, the impact strength of the PBT blends increased with the increase in EPR-graft-GMA degrees of grafting for the same dispersion phase content when the degree of grafting was below 1.8. However, PBT/EPR-graft-GMA1.8 displayed much lower impact strength in the ductile region than a comparable PBT/EPR-graft-GMA1.3 blend (1.3 indicates degree of grafting).

Influence of rubber content in ABS in wide range on the mechanical properties and morphology of PC/ABS blends with different composition

A series of acrylonitrile-butadiene-styrene (ABS) with different rubber content were prepared by diluting ABS grafting copolymer containing 60% rubber with a styrene-acrylonitrile copolymer. ABS prepared were blended with bisphenol-A-polycarbonate (PC) at the ratio of 70/30, 50/50, and 30/70 to prepare PC/ABS blends. Influence of rubber content in ABS on the properties of ABS and PC/ABS blends were investigated. PC/ABS blends with different compositions got good toughness when the rubber in ABS increased to the level that ABS itself got good toughness. The tensile properties and processability of PC/ABS blends decreased with the increase of the total rubber content introduced into the blends. ABS with the rubber content of 30 wt% is most suitable to be used to prepare PC/ABS blends. The rubber content in ABS affected the viscosity of ABS, and subsequently the viscosity ratio of PC to ABS. As a result, the morphology of PC/ABS blends varied. The increase of rubber content in ABS results in finer structure of PC/ABS blends.

Reactive blending of modified polypropylene and polyamide 12: Effects of compatibilizer content on crystallization and blend morphology

The crystallization behavior and morphology of nonreactive and reactive melt-mixed blends of polypropylene (PP) and polyamide (PA12; as the dispersed phase) were investigated. It Was found that the crystallization behavior and the size of the PA12 particles were dependent on the content of the compatibilizer (maleic anhydride-modified polypropylene) because an in situ reaction occurred between the maleic anhydride groups of the compatibilizer and the amide end groups of PA12. When the amount of compatibilizer was more than 4%, the PA12 did not crystallize at temperatures typical for bulk crystallization. These finely dispersed PA12 particles crystallized co-incidently with the 1313 phase. The changes in domain size with compatibilizer content were consistent with Wu's theory. These investigations showed that crystallization of the dispersed phase Could not be explained solely by the size of the dispersion. The interfacial tension between the polymeric components in the blends may yield information on the fractionation of crystallization.

Morphology and melt rheology of nylon 11/clay nanocomposites

Nylon 11 (PA11)/clay nanocomposites have been prepared by melt-blending, followed by melt-extrusion through a capillary. Transmission electron n-Licroscopy shows that the exfoliated clay morphology is dominant for low nanofiller content, while the intercalated one is prevailing for high filler loading. Melt rheological properties of PA11 nanocomposites have been studied in both linear and nonlinear viscoelastic response regions. In the linear regime, the nanocomposites exhibit much higher storage modulus (G') and loss modulus (G") values than neat PAIL The values of G' and G" increase steadily with clay loading at low concentrations, while the G' and G" for the sample with 5 wt % clay show an inverse dependence and lie between the modulus values of the samples with 1 and 2 wt % of clay. This is attributed to the alignment/orientation of nanoclay platelets in the intercalated nanocomposite induced by capillary extrusion. In the nonlinear regime, the nanocomposites show increased shear viscosities when compared with the neat resin. The dependence of the shear viscosity on clay loading has analogous trend to that of G' and G".

Morphology and structures of self-assembled symmetric poly(di-n-alkylsilanes)

The self-assembly of poly(di-n-butylsilane) (PDBS) and poly(di-n-hexylsilane) (PDHS) on the surfaces of amorphous carbon and highly oriented pyrolytic graphite (HOPG) have been investigated, respectively. The morphology and structures of these self-assembled thin films were studied by using atomic force microscopy, transmission electronic microscopy, and wide-angle X-ray diffraction. In the case of weak van der Waals interactions between absorbed molecules and substrate, i.e., on amorphous carbon, the self-assembly process was driven by absorbate-absorbate intermolecular interactions. For PDBS with weak absorbate-absorbate intermolecular interactions, the thin film showed organization lacking any measurable preferred orientation on the surface of amorphous carbon. While for PDHS with rigid backbone and strong intermolecular interactions, flat-on lamellae with silicon backbones perpendicular to the surface of amorphous carbon were formed. However, in the case of strong van der Waals interactions between absorbed molecules and substrate, i.e., on HOPG, the self-assembly process was tailored by the balance of absorbate-absorbate intermolecular interactions and molecule-substrate interactions. Both PDHS and PDBS thin films grew into edge-on lamellae on the surface of HOPG, which aligned according to a Mold symmetry.

Morphology control and luminescence properties of YAG : Eu phosphors prepared by spray pyrolysis

Starting from nitrate aqueous solutions with citric acid and polyethylene glycol (PEG) as additives, Y3Al5O12:Eu (YAG:Eu) phosphors were prepared by a two-step spray pyrolysis (SP) method. The obtained YAG:Eu phosphor particles have spherical shape, submicron size and smooth surface. The effects of process conditions of the spray pyrolysis on the crystallinity, morphology and luminescence properties of phosphor particles were investigated. The emission intensity of the phosphors increased with increasing of sintering temperature and solution concentration due to the increase of the crystallinity and particles size, respectively. Adequate amount of PEG was necessary for obtaining spherical particles, and the optimum emission intensity could be obtained when the concentration of PEG was 0.10 g/ml in the precursor solution. Compared with the YAG:Eu phosphor prepared by citrate-gel (CG) method with non-spherical morphology, spherical YAG:Eu phosphor particles showed a higher emission intensity.

Surface morphology control of immiscible polymer-blend thin films

The effects of the molecular weights (molecular weight of polystyrene, M-w,M-PS, varying from 2.9 to 129 k) on the surface morphologies of spin-coated and annealed polystyrene/poly (methyl methacrylate) (PS/PMMA = 50/50, w/w) blend films were investigated by atomic force microscopy and X-ray photoelectron spectroscopy. For the spin-coated films, when the M-w,M-PS varied from 2.9 to 129 k, three different kinds of surface morphologies (a nanophase-separated morphology, a PMMA cellular or network-like morphology whose meshes filled with PS, a sea-island like morphology) were observed and their formation mechanisms are discussed, respectively. Upon annealing, two different morphology-evolution processes were observed. It is found that a upper PS-rich phase layer is formed when M-w,M-PS < 4 k, and this behavior is mainly attributed to the low interfacial tension between PS and PMMA component. When M-w,M-PS > 4 k, the PS-rich phase forms droplets on top of the PMMA-rich phase layer which wets the SiOx substrate. These results indicate that the surface morphology of the polymer blend films can be controlled by the polymer molecular weight and annealing conditions.

Morphology, structure, and properties of in situ compatibilized linear low-density polyethylene/polystyrene and linear low-density polyethylene/high-impact polystyrene blends

Blends of linear low-density polyethylene (LLDPE) with polystyrene (PS) and blends of LLDPE with high-impact polystyrene (HIPS) were prepared through a reactive extrusion method. For increased compatibility of the two blending components, a Lewis acid catalyst, aluminum chloride (AlCl3), was adopted to initiate the Friedel-Crafts alkylation reaction between the blending components. Spectra data from Raman spectra of the LLDPE/PS/AlCl3 blends extracted with tetrahydrofuran verified that LLDPE segments were grafted to the para position of the benzene rings of PS, and this confirmed the graft structure of the Friedel-Crafts reaction between the polyolefin and PS. Because the in situ generated LLDPE-g-PS and LLDPE-g-HIPS copolymers acted as compatibilizers in the relative blending systems, the mechanical properties of the LLDPE/PS and LLDPE/HIPS blending systems were greatly improved. For example, after compatibilization, the Izod impact strength of an LLDPE/PS blend (80/20 w/w) was increased from 88.5 to 401.6 J/m, and its elongation at break increased from 370 to 790%. For an LLDPE/HIPS (60/40 w/w) blend, its Charpy impact strength was increased from 284.2 to 495.8 kJ/m(2). Scanning electron microscopy micrographs showed that the size of the domains decreased from 4-5 to less than 1 mum, depending on the content of added AlCl3.

Morphology and thermal properties of conductive polyaniline/polyamide composite films

Polyaniline (PANI) in an emeraldine-base form, synthesized by chemical oxidation polymerization, was doped with camphor sulfonic acid (CSA). The conducting complex (PANI-CSA) and a matrix, polyamide-66, polyamide-11, or polyamide-1010, were dissolved in a mixed solvent, and the blend solution was dropped onto glass and dried for the preparation of PANI/polyamide composite films. The conductivity of the films ranged from 10(-7) to 10(0) S/cm when the weight fraction of PANI-CSA in the matrices changed from 0.01 to 0.09, and the percolation threshold was about 2 wt %. The morphology of the composite films before and after etching was studied with scanning electron microscopy, and the thermal properties of the composite films were monitored with differential scanning calorimetry. The results indicated that the morphology of the blend systems was in a globular form. The addition of PANI-CSA to the films resulted in a decrease in the melting temperature of the composite films and also affected the crystallinity of the blend systems.

Rheology and morphology of reactively compatibilized PP/PA6 blends

This work aims to use the Palierne emulsion type model to describe the relationship between the rheological response to small amplitude oscillatory deformation and morphology of polypropylene/polyamide 6 (PP/PA6) blends compatibilized with maleic anhydride grafted polypropylene (PP-g-MAH). It was found that the Palierne emulsion type model could describe very well the linear viscoelastic responses of binary uncompatibilized PP/PA6 blends and failed to describe the ternary compatibilized PP/PP-g-MAH/PA6 blends. These features could be attributed to the fact that the morphology of the ternary blends was not of the emulsion type with the PA6 particles dispersed in the PP matrix but of an emulsion-in-emulsion type, i.e., PA6 particles dispersed in the PP matrix themselves contained PP or PP-g-MAH inclusions. By consideration of PP-in-PA6 particles as pure PA6 particles, where the volume fraction of the PA6 phase was increased accordingly, the Palierne emulsion type model could work very well for a ternary blending system. Preshear at low frequencies modified the morphology of both binary and ternary blends. The particles of the dispersed phase (PA6) became more uniform. These results suggested that the Palierne emulsion type model could be used to extract information on rheological properties and interfacial tension of polymer blends from known morphology and vice versa.