Formation Of Blends Research Articles

Film Formation of Latex Blends with Bimodal Particle Size Distributions: Consideration of Particle Deformability and Continuity of the Dispersed Phase

Latex dispersions having a well-controlled, bimodal particle size distribution are gaining attention because they potentially enable control of the dispersion rheology, the film formation characteristics, and the final film properties. Here we study the film formation of dispersions with a bimodal particle size distribution (large:small size ratio of ca. 6:1) and with varying concentrations of the two particle sizes. We also compare the film formation of blends containing only deformable (i.e., “soft”) particles with blends containing both soft and nondeformable (i.e., “hard”) particles. We use ellipsometry as a noninvasive tool for studying film morphology as film formation proceeds. We interpret our ellipsometry data using a physical model of the morphology based on atomic force microscopy observation. Electron microscopy of film cross sections provides information about the bulk morphology. We measure void content and surface roughness in blend films as a function of the concentration of large particle...

Polymer synthesis and processing using supercritical carbon dioxide

Carbon dioxide is a clean and versatile solvent for the synthesis and processing of a range of materials. This review focuses on recent advances in polymer synthesis and processing using liquid and supercritical CO2. The synthetic techniques discussed include homogeneous solution polymerisation, precipitation polymerisation, dispersion and emulsion polymerisation, and bulk polycondensation. The formation of porous polymers and polymer blends is also considered, and the specific advantages of CO2 in these processes are evaluated in each case. The use of CO2 as a solvent for polymer processing is reviewed from a materials perspective, with particular attention being given to the formation of polymers with well defined morphologies. The variable solvent strength associated with supercritical fluids has been utilised in areas such as polymer fractionation and polymer extraction. Plasticisation phenomena have been exploited for the impregnation and heterogeneous chemical modification of polymeric materials. The formation of microcellular polymer foams by pressure induced phase separation is considered, as is the use of CO2 for polymer particle formation, spray coating, and microlithography. The aim of the review is to highlight the wide range of opportunities available to the materials chemist through the use of carbon dioxide as an alternative solvent.

Two‐dimensional near‐infrared correlation spectroscopy studies of polymer blends I: Composition‐dependent spectral variations of blends of atactic polystyrene and poly[2,6‐dimethyl‐1,4‐phenylene ether

AbstractGeneralized two‐dimensional (2D) near‐infrared (NIR) correlation spectroscopy has been applied to study the conformational changes and molecular interactions in blends of atactic polystyrene (PS) and poly[2,6‐dimethyl‐1,4‐phenylene ether] (PPE). NIR diffuse reflectance spectra have been measured for PS, PPE and their blends of different compositions, i.e., PS/PPE=90/10, 70/30, 50/50, 30/70, 10/90. The 2D synchronous correlation analysis of these composition‐dependent NIR spectral variations separates the bands of PS from those of PPE. The 2D asynchronous analysis identifies spectral features indicative of the conformational changes or the specific interaction of PS and PPE. It can also detect “blend bands” whose origin is attributed to the formation of the polymer blends. Two “blend bands” of PS are identified at 6887 and 4836 cm−1, and three “blend bands” of PPE are observed at 5752, 5679 and 4647 cm−1. These “blend bands” are due to vibrations of the aromatic rings of PS or PPE and of the CH3 of PPE. Thus, not only the aromatic rings of PS and PPE but also the CH3 groups of PPE play important roles in the formation of the blends.

In situ formation and processing of ultra high molecular weight polyethylene blends into precursors for high strength and stiffness fibers

AbstractWe present a novel process for the manufacture of ultra high molecular weight polyethylene precursors which can be subsequently made into high‐stiffness, high‐strength fibers or films. This process combines solid‐state extrusion and an in situ constrained solvent swelling process into a single stage for precursor preparation. The precursors produced by this process are shown to be highly ductile and porous. The inclusion of a small quantity of nontoxic solvent (10 wt% mineral oil) in the process has also been shown, using DSC and SEM characterization techniques, to provide the following process advantages: (i) better interfacial cohesion, because of the enhanced chain mobility at the particle surface due to the solvating effects; (ii) improved processability; and (iii) more uniform thermal properties and morphology across the extrudates due to enhanced heat transfer.

Marginal miscibility and solvent-dependent phase behavior in solution-blended poly(vinyl methyl ether)/poly(benzyl methacrylate)

Poly(vinyl methyl ether) (PVME) and poly(benzyl methacrylate) (PBzMA) were found to be miscible using differential scanning calorimetry (DSC), optical microscopy (OM), and infrared spectroscopy (FT-IR). Solvents and casting temperatures strongly affect the kinetics of the formation of blends and lead to different phase structures of the blends. The thermal transition behavior of the PVME/PBzMA blend suggests a marginal miscibility. Various scales of molecular aggregation might exist in the blends. According to FT-IR the intermolecular interactions are weak and not specific, which is in agreement with the glass transition behavior of the blends. Additionally, this study also shows that PVME is immiscible with any other polymethacrylate, such as poly(methyl methacrylate), poly(ethyl methacrylate), poly(propyl methacrylate), poly-(phenyl methacrylate), poly(cyclohexyl methacrylate), etc.

Spectral, thermal and electrical properties of poly(o- and m-toluidine)—PVC blends prepared by solution blending

Poly(o-toluidine) (POT) and poly(m-toluidine) (PMT) blends with polyvinylchloride (PVC) of five different compositions have been prepared by solution blending. The POT-PVC and PMT-PVC blends were prepared using THF as a solvent in which POT-HNO3, PMT-HNO3 bases and PVC are soluble. The blends have been characterized by spectral, thermal and electrical measurements. The results indicate the formation of blends at all the compositions presently studied. The thermal stability of the POT-PVC and PMT-PVC blends is higher than that of POT-HNO3 and PMT-HNO3 salts, respectively. Using the present method, POT/PMT can conveniently be blended with 30% wt/wt of PVC without significant loss in its conductivity. (C) 1998 Elsevier Science Ltd. All rights reserved.

Formation and stability of co-continuous blends with a poly(ether-ester) block copolymer around its order–disorder temperature

Co-continuous morphologies are found over a wide composition range (30–80 vol%) in blends of a polystyrene thermoplastic and a poly(ether-ester) thermoplastic elastomer when they are blended below the block copolymer's order–disorder transition (ODT). This range decreases with increasing processing temperature and becomes limited when both polymers show pseudo-plastic behaviour. Annealing of the co-continuous blends below the ODT hardly influences the phase sizes and composition range, but when annealing takes place at higher temperatures the blends show an increase of their phase domains and the composition range decreases. The condition for the formation of co-continuous morphologies, especially at low volume fractions, is the existence of stable interconnected elongated structures, that do not show breakup or retraction. Breakup and retraction experiments on poly(ether-ester) fibres embedded in a polystyrene matrix make clear that these mechanisms can be severely limited or even stopped and therefore the condition for the existence of co-continuous morphologies is fulfilled.

Assimilation and Mineral Formation during Sintering for Blends Containing Magnetite Concentrate and Hematite/Pisolite Sintering Fines.

Blends for sintering in China commonly contain domestic magnetite concentrate and imported hematite or/and pisolite sintering fines. Interactions between these ores will, no doubt, have an important impact on sintering performance and sinter quality of these blends. Studies have been carried out to look at assimilation of sintering fines and mineral formation during sintering of such blends. The results show that at given mix composition, pisolite ores are easier to be assimilated than hematite and magnetite ores while magnetite shows the least assimilation. For the same ore, the assimilation depends on melt level and ore porosity. For this reason, higher assimilation was observed for porous ores or ores with high gangue content or when an easy-fusing ore was present in the blend. Studies on mineral phase formation of blends containing magnetite, hematite and pisolite indicate that good sinter mineralogy with increasing SFCA (silico-ferrite of calcium and aluminium) content is obtained with increasing Ore E (hematite). Substitution of Ore J (pisolite) for various hematite ores did not lead to significant changes in sinter mineralogy. The only change was the reduced level of primary hematite owing to the high reactivity of Ore J.

Surface-induced structure formation of polymer blends on patterned substrates

Phase separation in bulk mixtures commonly leads to an isotropic, disordered morphology of the coexisting phases1. The presence of a surface can significantly alter the phase-separation process, however2,3. Here we show that the domains of a phase-separating mixture of polymers in a thin film can be guided into arbitrary structures by a surface with a prepatterned variation of surface energies. Such a pattern can be imposed on a surface by using printing methods for depositing microstructured molecular films4, thereby allowing for such patterns to be readily transferred to a two-component polymer film. This approach might provide a simple means for fabricating polymer-based microelectronic circuits5 or polymer resists for lithographic semiconductor processing.

Construction of Supramolecular Structures via. Hydrogen Bonds. Supramolecular Liquid-Crystalline Networks Built through Hydrogen Bonds.

Liquid-crystalline supramolecular networks have been obtained by self-assembly through the formation of hydrogen bonds. Hydrogen-bonded networks built from 4, 4'-bipyridine and polyacrylates containing a side-chain benzoic acid show smectic A phases. The complexation of poly(acrylic acid) and bis(imidazolyl) mesogenic compounds also leads to mesomorphic networks. Self-assembly of multifunctional small molecules having benzoic acids and pyridyl moieties affords H-bonded networks which exhibit nematic and smectic phases. Liquid-crystalline polymer alloys have been prepared from a thermotropic polyester containing a lateral pyridyl group and poly(4-vinylphenol). The interaction through H bonds between these polymers results in the formation of the miscible blends that show nematic phases. These networks exhibit thermoreversible phase transitions due to the dynamic nature of H bond.

Film formation of latex

Latex film formation, the process by which an aqueous dispersion of polymer particles is transformed into a continuous material, has a direct bearing on the final film morphology and properties. Each of the primary stages of film formation (evaporative drying and ordering; particle deformation; and polymer interdiffusion) have been studied experimentally. Recently-developed non-invasive techniques, including direct nonradiative energy transfer, atomic force microscopy, small angle neutron scattering, environmental scanning electron microscopy, and various optical techniques have greatly enhanced the study of these stages. Even so, the exact cause (or causes) of particle deformation is still a topic of considerable debate. Several factors are experimentally known to influence latex film formation: the ambient conditions; the presence of surfactants, plasticizers and pigments; and latex particle structure. An important aim in the study of latex film formation is to understand the mechanisms by which these and other factors affect the process. New challenges lie in the study of film formation of core-shell latices, latex blends and new compositions.

Nucleation of Impact Modified Filled Polypropylene

Nucleation of polypropylene is important in determining its mechanical properties. Nucleation in polypropylene is nearly always found to be heterogeneous. Control is best achieved by addition of a nucleant. Addition of a filler can provide nucleation, as well as enhancing stiffness. Formation of blends with other polymers can change nucleation depending on the partition of the nucleant between polypropylene and the other polymer, and the nucleant activity of the interface with the other polymer. Other crystalline forms can be obtained, depending on the crystallisation conditions and additives. For instance alpha and beta forms, and transcrystallinity occur. This paper reviews the interplay of these variables on polypropylene morphology and properties.

Nucleation of Impact Modified Filled Polypropylene

Nucleation of polypropylene is important in determining its mechanical properties. Nucleation in polypropylene is nearly always found to be heterogeneous. Control is best achieved by addition of a nucleant. Addition of a filler can provide nucleation, as well as enhancing stiffness. Formation of blends with other polymers can change nucleation depending on the partition of the nucleant between polypropylene and the other polymer, and the nucleant activity of the interface with the other polymer. Other crystalline forms can be obtained, depending on the crystallisation conditions and additives. For instance alpha and beta forms, and transcrystallinity occur. This paper reviews the interplay of these variables on polypropylene morphology and properties.

Kinetics of the step-growth polymerization of epoxide in the presence of the linear polyurethane. Effect of the phase separation of components

The process of formation of polymer blends based on linear polyurethanes (PU) and hardening polyepoxide (PEp) both without and with addition of epoxy-urethane copolymer (EpUC) was studied. Correlation between the phase separation initiation time and the degree of conversion of epoxy groups was ascertained. It was shown that the process of formation of PU/PEp blends involves an extremal character of variation of the degree of conversion of epoxy groups and of the phase separation initiation time with the composition of the system. The addition of EpUC to the hardening system caused a substantial change of the phase separation initiation time and changed the physical and mechanical characteristics of the resulting material. The influence of the molecular weight of PU and various epoxy resin hardeners on the character of phase separation and other parameters of a hardening system was studied.

Composites. 2. Reinforcement of Poly(ε-caprolactone) via Lyotropic Blends of Rigid-Rod Polyesters Derived from Substituted Terephthalic Acids

Two aryloxyterephthalic acids and two 2,5-bis(alkoxy)terephthalic acids were synthesized and polycondensed with hydroquinone (HQ), methylhydroquinone (MeHQ), phenylhydroquinone (PhHQ), or 4,4‘-dihydroxybiphenyl (DHBP). Eleven out of the possible 16 polyesters were selected for the preparation of blends with commercial poly(e-caprolactone), PCL, as the matrix. The properties of blends containing 1, 2, 4, or 8 wt % of the rigid-rod polymer were studied. The optical microscopy revealed birefringence for the entire blend below the melting temperature (Tm) of the rigid-rod polymer. The lyotropic character vanished and phase separation took place above the Tm of the rigid-rod polymer. The lyotropic blends (PCL acting as a solvent) showed a significant mechanical reinforcement effect, when examined by melt rheology and stress−strain measurements. This effect depended largely on the aromatic character of the substituents. The most surprising and important finding is the formation of lyotropic blends from a rigid-...

Self-compatibilization of polymer blends via concentrated emulsions

A novel approach to the formation and compatibilization of polymeric blends is suggested, namely the self-compatibilization via concentrated emulsions. In this method, two concentrated emulsions are prepared from different monomers and subjected to partial polymerization; at least one concentrated emulsion contains also some di-vinyl-terminated macro-monomers. A blend is formed by mixing the partially polymerized latexes and subjecting the mixture to complete polymerization. Some AB networks, with the macro-monomers as chains A and the homo- and co-polymers generated from the other monomers as chains B, are formed, which ensure the self-compatibilization of the resulting blend. Blends of styrene-co-methyl methacrylate and poly (vinyl acetate) were prepared and investigated as a model system.

Avaliação da competição intergenotipica em misturas de cultivares de soja

Para avaliar os efeitos da competição intergenotípica em misturas de cultivares de soja - Glycine max (L.) Merrill - foi conduzido um experimento em Capão do Leão, RS, no ano agrícola de 1989/90. Os tratamentos foram os estandes puros de IAS 5, Ivorá, Bragg, BR 8 - Pelotas e Ivaí e as combinações de Bragg com os demais cultivares, nas proporções de 20, 35, 50, 65 e 80%. O delineamento experimental foi o látice parcialmente balanceado 5x5, com quatro repetições. A competição intergenotípica foi quantificada pela variação percentual = 100 (PM - PEP)/ PEP, onde PM é a média do caráter em mistura e PEP é a média do caráter em estande puro. As misturas produziram, em média, 3,8% mais que a média dos componentes em estande puro. Duas misturas, IAS 5 + Bragg e BR 8-Pelotas + Bragg, proporcionaram acréscimos no rendimento em todas as proporções de misturas. Concluiu-se que a competição intergenotípica pode ser utilizada no melhoramento da soja, visando a obtenção de misturas com rendimento e desempenho superior. Respostas diferenciadas à competição intergenotípica foram observadas em diferentes misturas e proporções e, proporção e características contrastantes entre os cultivares como capacidade de ramificação, altura de planta, ciclo de maturação e período de florescimento devem ser consideradas para a formação de misturas superiores.

THE FORMATION OF INTERPENETRATING POLYMER BLENDS

Formation of the thermoplastic blends of co-continuous morpholology has been discussed, the dynamic character of this process being stressed. Interpenetrating polymer blends represent the intermediate stage of a multicomponent polymer system during dispersive mixing. The time for reaching such a state of heterogeneity and its stability depend on the viscoelastic characteristics of the component polymers , their ratio in ablend, interfacial tension and mixing parameters. The role of particular factors influencing the formation of interpenetrating polymer blends has been presented for the LPDE/PS system. Because of the dynamic character of the evolution of polymer blend morphology upon mixing, the processing history specifications should accompany every morphology presentation

Pattern Formations in Unstable Network: Model for Cross-Linked Polymer Chains

We propose a model of an unstable chain network to study the pattern formation of cross-linked polymer blends in the thermodynamically unstable state. When the instability is triggered by a small number of point triggers, target patterns emerge. As time proceeds each concentric ring separates into several parts, but the overall image of the target pattern is maintained. Such patterns are frozen-in.

Transformation of lignin-related compounds with laccase in organic solvents

The extracellular laccase (benzenediol: oxygen oxidoreductase, EC 1.10.3.2) of Trametes versicolor was isolated from culture medium and immobilized by entrapment of the enzyme in a solvent-resistant hydrophilic matrix like Sepharose-CL-6B. The gel-enzyme association has been shown to be stable in water containing organic solvents. The efficiency of the immobilized laccase in different organic solvents was comparable with the activity shown in a buffered aqueous system. The immobilized laccase in organic solvents showed a good stability and a high tolerance to elevated temperatures. Water-insoluble organosolv lignin (OL), dissolved in dioxane/water, was readily converted by immobilized laccase from Trametes versicolor. The transformed lignin showed an increase in phenolic groups, changes in the quantity of conjugated elements, and a significant modification of both the aliphatic and aromatic carbon moieties of the lignin molecule. The changes in the lignin molecule were analyzed by UV-, IR-spectroscopy, and 13C-NMR solid-state spectroscopy. High-performance size exclusion chromatography (HPSEC) of the lignin transformed with the laccase—Sepharose complex revealed a pronounced increase in weight-average molecular weight. Polymerization of the lignin in the organic solvent proved to be 4 times more effective than polymerization of the same compound in an aqueous system. Water-insoluble organosolv lignin as well as a variety of lignin-related aromatics, solubilized in dioxane-H 2O (7 : 3), was readily converted by laccase preparation either in batch or in continuous flow column. Reaction of laccase with the solubilized lignin generates in the reaction media reduced oxygen species able to reduce the cytochrome c. For the first time it is now possible to perform enzymatically catalyzed reactions with lignin in an organic solvent. This is a first step towards an enzymatically derivatization of lignin, the formation of polymer blends on the basis of lignin by an enzymatically catalyzed reaction.