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Final Properties (final + property)
Selected AbstractsOutstanding Ceramic Matrix Composites for High Temperature ApplicationsADVANCED ENGINEERING MATERIALS, Issue 3 2005L. Vandenbulcke Accurate deposition of boron and silicon carbides and nitrides permits to improve the oxidation resistance of self-healing matrices of multilayered composites. The uniformity and the microstructure of each layer and of their interfaces induce the final properties of these composites. Their mechanical behaviour in conditions very close to the applications in the energy, space and aeronautic domains, allows to demonstrate the breakthrough enabled by this new composite generation. [source] Cover Picture: TiO2 Nanoparticle,Photopolymer Composites for Volume Holographic Recording (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 10 2005Mater. Abstract TiO2 nanoparticle,photopolymer composites have been employed for volume holographic recording, as reported by Sánchez and co-workers on p.,1623. Photoinduced segregation of the high refractive index, grafted nanoparticles between polymer-rich areas leads to improved refractive-index modulation amplitudes with respect to the base material without nanoparticles. The cover schematically shows a holographic grating registered in this nanocomposite material. These nanocomposite materials should enable the production of holographic optical elements to efficiently control light with angle and wavelength selectivity. This could be used, for example, in liquid-crystal display technology. A new and efficient photopolymer for the recording of volume holograms is presented. The material comprises a mixture of UV-sensitive acrylates and grafted titanium dioxide nanoparticles with an average size of 4,nm. We report the formation of holographic gratings with refractive-index modulation amplitudes of up to 15.5,×,10,3,an improvement of more than a factor of four over the base material without nanoparticles,while maintaining a low level of scattering and a high transparency in the visible-wavelength range. The influence of the composition of the acrylate system on the final properties of the holographic material is also investigated and discussed. The presence of multifunctional monomers favors the compositional segregation of the different components, while the addition of monofunctional acrylate, highly compatible with the grafting of the nanoparticles, favors the dilution of these nanoparticles. [source] Advances in Biomimetic and Nanostructured Biohybrid MaterialsADVANCED MATERIALS, Issue 3 2010Eduardo Ruiz-Hitzky Abstract The rapid increase of interest in the field of biohybrid and biomimetic materials that exhibit improved structural and functional properties is attracting more and more researchers from life science, materials science, and nanoscience. Concomitant results offer valuable opportunities for applications that involve disciplines dealing with engineering, biotechnology, medicine and pharmacy, agriculture, nanotechnology, and others. In the current contribution we collect recent illustrative examples of assemblies between materials of biological origin and inorganic solids of different characteristics (texture, structure, and particle size). We introduce here a general overview on strategies for the preparation and conformation of biohybrids, the synergistic effects that determine the final properties of these materials, and their diverse applications, which cover areas as different as tissue engineering, drug delivery systems, biosensing devices, biocatalysis, green nanocomposites, etc. [source] Quantitative microstructural and texture characterization by X-ray diffraction of polycrystalline ferroelectric thin filmsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2004Jesús Ricote Texture becomes an important issue in ferroelectric materials as it greatly influences the physical properties of polycrystalline films. The use of advanced methods of analysis of the X-ray diffraction profiles, namely quantitative texture analysis or the recently developed combined approach, allows access to quantitative information on the different components of the global texture and to more accurate values of structural and microstructural parameters of both the ferroelectric film and the substrate, not available by more conventional methods of analysis. The results obtained allow important conclusions to be drawn regarding the mechanisms that lead to the development of preferred orientations in thin films and, also, the correlation between them and the ferroelectric behaviour. For example, it is observed that the inducement of a strong ,111, texture component does not mean the complete disappearance of the so-called `natural' ,100,, ,001, components, and that the ratio between the contributions to the global texture of these two components can be changed by the presence of tensile or compressive stress during crystallization of the films. The relative contributions of these texture components are also related to the final properties of the ferroelectric films. [source] The role of a novel p -phenylen-bis-maleamic acid grafted atactic polypropylene interfacial modifier in polypropylene/mica composites as evidenced by tensile propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2009J. M. García-Martínez Abstract Present work is devoted to the study of the tensile behavior of polypropylene (PP)/mica composites with improved interfacial interactions from the matrix side caused by the presence of a p -phenylen-bis-maleamic acid grafted atactic polypropylene (aPP- pPBM) as an interfacial agent. Hence, aPP- pPBM was previously obtained, in our laboratories, by reactive processing in the melt of a by-product (atactic PP) from industrial polymerization reactors. Present article is two-fold, on one hand it has been planned to evidence the so called interfacial effects caused by this novel interfacial agent (aPP- pPBM) yielding better final properties of the heterogeneous system as a whole as revealed by tensile mechanical properties, and on the other to obtain models to forecast the overall behavior of the system. For such purpose, a Box-Wilson experimental design considering the amount of mica particles and of interfacial agent as independent variables was used to obtain polynomials to forecast the behavior of the PP/Mica system in the experimental space scanned. The existence of a critical amount of aPP- pPBM to optimize mechanical properties appears to emerge. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Impact of curing temperature on microstructures and properties of isobutylene,isoprene rubber/clay nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Yong-Lai Lu Abstract In this work, the influence of curing temperature on microstructures of isobutylene,isoprene rubber/clay nanocomposites (IIRCNs) prepared by melt compounding was characterized using wide-angle X-ray diffraction and TEM. The gas barrier and tensile properties of IIRCN cured under different temperature were examined. The results reveal that high pressure, curing reactions, and reactions of amine intercalants with curing agents together play important roles on determining the final microstructures of cured IIRCNs. Changing curing temperature would dramatically alter intercalated structure, dispersion homogeneity, filler,rubber interaction strength, and crosslinking density of obtained IIRCN, resulting in great difference in final properties. Finally, some suggestions for the preparation of successful RCNs were proposed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Compatibility study of recycled poly(vinyl chloride)/styrene-acrylonitrile blendsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007David Garcia Abstract The aim of the present study is to analyze the compatibility between recycled Poly(vinyl chloride) (PVC) and styrene-acrylonitrile copolymer (SAN). With this objective recycled PVC coming from credit cards have been blended with both virgin and recycled SAN with the aim of increase the benefits of recycled PVC. The compatibility of the components will be crucial for the final properties of the material. Furthermore, the recycled nature of some of the components will determine the compatibilization capability of the blend. The degradation level in the recycled materials was determined using Fourier transform infrared spectroscopy (FTIR). The compatibility between the PVC and the SAN was studied using differential scanning calorimetry and dynamic mechanical analysis. A greater compatibility was observed in mixtures of PVC and virgin SAN than in mixtures of PVC and recycled SAN. Finally, a morphological study of the fracture surface under cryogenic conditions was carried out using scanning electron microscopy. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Dielectric properties of thermosetting material nanocompositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Newton Luiz Dias Filho Abstract The dieletric relaxation properties of thermosetting material nanocomposites based on spherosilicate nanoplatforms were studied from room temperature to 170°C, varying the frequency from 10 to 1000 KHz. Permittivity (,,), dielectric loss (,,), and activation energy (Ea) were calculated. The results of dielectric relaxation were confirmed by those of the final properties. The dielectric loss amplitude decreases with increasing ODPG content until about 70,73 wt % and slightly increases at higher ODPG content. This means that the increasing of the ODPG content in the composite samples decreases the number of pendants groups and/or increases crosslink density, causing decreased motion of organic tethers, and subsequently decreasing of the dipolar mobility. The results of apparent activation energy, fracture toughness and tensile modulus mechanical properties show the same profile with respect to ODPG content, in the sense that they exhibit maxima around 70 wt % ODPG. For the ODPG/MDA composites, this formulation of 70 wt % ODPG containing excess of amine is not composition where the highest crosslinked density is reached. This implies that the best mechanical properties and Ea are provided by some degree of chain flexibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Structure, texture and surface acidity studies of a series of mixed zinc,aluminum (60,90 molar % Al) phosphate catalystsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2001Karim Mtalsi Abstract A series of mixed zinc,aluminum phosphate (ZnAlP) catalysts containing 40,90 aluminum molar % were synthesized by a coprecipitation method and characterized by nitrogen adsorption,desorption, X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and temperature programmed desorption (TPD) of ammonia. The presence of aluminum greatly affected the surface properties of Zn3(PO4)2 by delaying the crystallization process of Zn3(PO4)2. All amorphous samples were shown to be mesoporous and they contained two types of aluminum surface hydroxyl groups and one type of phosphorus hydroxyl group, as shown by DRIFT spectra. The specific surface area and the acidity of ZnAlP increased on increasing the aluminum content. On the other hand, a great difference in the texture and the concentration of surface acid sites was found by changing the precipitating agent and calcination temperature. Thus these factors also play an important role in the final properties of these catalysts. © 2001 Society of Chemical Industry [source] Modeling and inferential control of the batch acetylation of celluloseAICHE JOURNAL, Issue 6 2006Anshul Dubey Abstract The batch acetylation of cellulose involves two main stages, acetylation followed by hydrolysis. Mathematical models were constructed for these processes using reaction parameters obtained from earlier publications. The two models were then combined, along with a model predicting the cellulose feedstock moisture content. The overall temperature profiles as well as the final degree of acetylation and polymerization were shown to match the data obtained from a commercial process. From the results of the model and the observations made in a typical process, it has been established that this process is highly sensitive to disturbances in the input streams that can result in unacceptable final properties of the batch. Because the exact disturbance occurring in a batch cannot be identified and measured, inferential control is used to formulate an intrabatch control strategy. Support vector regression is used to make predictions on the final properties of the batch. These predictions, along with the model of the hydrolysis stage, are used to estimate the inputs that, when applied during hydrolysis, can counter the disturbances caused during the acetylation stage. Simulations show that this hydrolysis control strategy can improve the average batch properties of cellulose acetate required for subsequent processing. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Transition from microemulsion to emulsion polymerization: Mechanism and final propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2004Kevin D. Hermanson Abstract Microemulsion and emulsion polymerization can have some similarities in starting conditions and polymerization mechanisms, but the resulting latices are unalike in particle size and molecular weight. Here we show that polymerizations can be formulated that display the characteristics often separately associated with microemulsion or emulsion polymerization. Kinetic modeling and particle size measurements show that emulsion polymerizations with initial concentrations close to the microemulsion,emulsion phase boundary demonstrate relatively fast consumption of monomer droplets and produce smaller particles. Because of their high surfactant concentrations, none of the emulsion polymerizations examined demonstrate the classical Smith,Ewart kinetics usually associated with emulsion polymerization. Instead these emulsion polymerizations have a long period of particle nucleation that subsides only after the disappearance of monomer droplets. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5253,5261, 2004 [source] Thermodynamic Studies on the AlN Sintering Powders Treated With Phosphate SpeciesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2007Susana Maria Olhero The processing of aluminum nitride (AlN) ceramics in aqueous media requires the use of a surface layer to protect the surface of the particles against hydrolysis. This surface layer might influence the densification, affecting the reactions between AlN and sintering additives. The present paper describes a thermodynamic and experimental approach to evaluate the effects of a phosphate-based protecting surface layer on the densification of AlN in the presence of YF3,CaF2 as sintering aids, and to predict the densification behavior during sintering using thermodynamic assessments. Based on thermodynamic calculations and the measured weight loss of the samples during heating to sintering temperature, the chemical reactions occurring during firing were proposed. The proposed reactions were related to the experimental results as well as the final properties of the AlN samples, namely, thermal conductivity, microstructure, secondary phases, and density. [source] Study of two different cold restructuring processes using two different qualities of hake (Merluccius capensis) muscle, with addition of microbial transglutaminaseJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2009Helena M Moreno Abstract BACKGROUND: Microbial transglutaminase (MTGase) can improve the mechanical and functional properties of restructured fish products without the need of thermal gelation. The present study seeks to determine whether, for different setting times, MTGase activity in restructured hake muscle made with pieces or with homogenised muscle can be affected by the quality of the protein in the raw materials. RESULTS: As regards mechanical properties, samples of both qualities subjected to the two different processes attained a suitable consistency after setting for 24 h at 5 °C. The quality of the protein in the sample is important when pieces are used for restructuring, but not when sample is homogenised. Also, there were strong correlations between residual MTGase activity up to 12 h and mechanical properties and electrophoretic band density. Water binding capacity (WBC) was not significantly altered by MTGase addition. CONCLUSION: The experimental combination of 10 g kg,1 of MTGase, 15 g kg,1 of sodium chloride and 7.5 g kg,1 of sodium caseinate was suitable for the production of minimally processed raw restructured fish products made with two different qualities of fish protein and two different restructuring processes. In the restructured products made with pieces, the protein quality significantly affected final properties, but in finely homogenised product the protein quality was less important. Copyright © 2009 Society of Chemical Industry [source] Synthesis and Structure,Efficiency Relations of 1,3,5-Benzenetrisamides as Nucleating Agents and Clarifiers for Isotactic Poly(propylene),MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2010Frank Abraham Abstract This paper presents the synthesis and properties of 1,3,5-benzenetrisamides with a particular focus on structure-efficiency relationships of nucleation and optical property enhancement of isotactic poly(propylene) (i -PP). A family of twenty 1,3,5-benzenetrisamide derivatives was synthesized, in which the direction of the amide linkage between the core and the peripheral substituents, as well as their length (C-3 to C-6) and flexibility were systematically varied. Dissolution- and recrystallization temperatures of the additives in the polymer melt, the crystallization temperature of i -PP, and the optical properties clarity and haze were determined in the additive concentration range from 200 to 2,500,ppm. Within the reported series of compounds, few exhibited very good nucleating and clarification abilities, only one with outstanding characteristics, whereas other, very closely related derivatives were found to be incapable to nucleate or clarify i -PP, although, intriguingly, most are structural isomers. We conclude that it is the particular chemical structure of the additive that determines its crystallization/self-assembly process, and, therewith, the structure of the heterogeneous nuclei, and at a higher hierarchical level the morphology of the poly(propylene) solid state and its final properties; and, hence, that a predictive understanding is still elusive. [source] Processability and Properties of Re-Graded, Photo-Oxidized Post-Consumer Greenhouse FilmsMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Francesco Paolo La Mantia Abstract Summary: The recycling of post-consumer plastics leads, in general, to secondary materials having properties worse than those of the reclaimed material and certainly worse than those of the same virgin polymer. This is because of the degradation undergone by the objects during their use and because of the thermo-mechanical degradation undergone during the reprocessing operations. The change of the molecular architecture is responsible for this worsening of properties. The use of stabilizing systems can slow the degradation during the melt processing but cannot give any improvement of the final properties of the material. In order to enhance the properties of the recycled plastics, some rebuilding of the molecular structure is necessary. The use of suitable additives can enlarge the molecular weight distribution or can create branching and cross-linking during the melt processing of the photo-oxidized PE. The processability in film blowing and the mechanical properties of these secondary materials are reported in this work. The rheological behavior, the filmability and most of the mechanical properties of the secondary PE with the rebuilt molecular structure are better than those of the post-consumer material and similar to those of the virgin polymer. TS in the machine and in the transverse direction for all the samples extruded at 50 rpm. [source] Empirical Modeling of Butyl Acrylate/Vinyl Acetate/Acrylic Acid Emulsion-Based Pressure-Sensitive AdhesivesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2004Renata Jovanovic Abstract Summary: Butyl acrylate/vinyl acetate/acrylic acid (BA/VAc/AA) emulsion latexes were produced in a semi-batch mode. The objective was to generate polymers with properties favoring their application as pressure-sensitive adhesives. The influence of the individual monomer concentrations on final properties such as glass transition temperature (Tg), peel strength, shear strength and tack was investigated. To obtain the maximum amount of information in a reasonable number of runs, a constrained three-component mixture design was used to define the experimental conditions. Latexes were coated onto a polyethylene terephthalate carrier and dried. Different empirical models (e.g. linear, quadratic and cubic mixture models) governing the individual properties (i.e. Tg, peel adhesion, shear resistance and tack) were developed and evaluated. In the given experimental region, no single model was found to fit all of the responses (i.e. the final properties). However, in all models the most significant factor affecting the final properties was the AA concentration, followed by the VAc concentration. Shear strength contour lines over the investigated region. [source] Synthesis and Characterization of Ethylene/Propylene Copolymers in the Whole Composition RangeMACROMOLECULAR SYMPOSIA, Issue 1 2007Ma. Joaquina Caballero Abstract Summary: The incorporation of comonomer molecules in the backbone of a homopolymer can influence the final properties of the material, decreasing its crystallinity and the melting and glass transition temperatures, and increasing its impact resistance and transparency. In the present work, ten ethylene/propylene copolymers have been synthesized using a supported metallocene catalytic system covering the whole composition range. Any desired composition was obtained by controlling the feed composition during the reaction. These synthesized copolymers have been characterized by different techniques in order to study the effect of the comonomer incorporation onto their final properties. When the comonomer content is low, the behaviour of the copolymer is similar to that of the corresponding homopolymer. Nevertheless, if the comonomer content increases, the copolymer becomes more amorphous (low crystallization temperature and soft XRD signals) and easily deformable, reaching a behaviour close to that corresponding to an elastomeric material. In order to corroborate these results the samples have been characterized by TREF and GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more than 80% of ethylene are semicrystalline, with elution temperatures typical of this kind of polymers. Molecular weights are higher for homopolymers and they decrease as the comonomer concentration increases, whereas the polydispersity index keeps almost constant at the expected value for this kind of samples. [source] Reactive processing of syndiotactic polystyrene with an epoxy/amine solvent systemMACROMOLECULAR SYMPOSIA, Issue 1 2003Jaap Schut Abstract Syndiotactic polystyrene (sPS) is a new semi-crystalline thermoplastic which is believed to fill the price-performance gap between engineering and commodity plastics. In order to reduce the high processing temperature of sPS (>290°C), an epoxy-amine model system was used as a reactive solvent. Such a processing aid can be used to achieve a 50 to 500 fold lowering of the melt viscosity. When initially homogeneous solutions of sPS in a stoechiometric epoxy-amine mixture are thermally cured, Reaction Induced Phase Separation (RIPS) takes place, leading to phase separated thermoplastic-thermoset polymer blends. We focus our study on low (wt% sPS < 20%) and high concentration blends (wt% sPS > 60%) prepared by two processing techniques (mechanical stirring in a laboratory reactor or internal mixer/ reactive extrusion respectively). These blends have different potential interests. Low concentration blends (sPS domains in an epoxy-amine matrix) are prepared to create new, tunable blend morphologies by choosing the nature of the phase separation process, i.e. either crystallisation followed by polymerization or polymerization followed crystallisation. High concentration blends (sPS matrix containing dispersed epoxy-amine particles after RIPS) are prepared to facilitate the extrusion of sPS. In this case, the epoxy amine model system served as a reactive solvent. The time to the onset of RIPS is in the order of 7-9 min for low concentration blends, while it increases to 20-45 min for high concentration samples, as the reaction rates are substantially slowed down due to lower epoxy and amine concentrations. During the curing reaction the melting temperature of sPS in the reactive solvent mixture evolves back from a depressed value to the level of pure sPS. This indicates a change in the composition of the sPS phase, caused by (complete) phase separation upon reaction. We conclude that our epoxy amine system is suited for reactive processing of sPS, where final properties depend strongly on composition and processing conditions. [source] A comprehensive set of simulations studying the influence of gas expulsion on star cluster evolutionMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007H. Baumgardt ABSTRACT We have carried out a large set of N -body simulations studying the effect of residual-gas expulsion on the survival rate, and final properties of star clusters. We have varied the star formation efficiency (SFE), gas expulsion time-scale and strength of the external tidal field, obtaining a three-dimensional grid of models which can be used to predict the evolution of individual star clusters or whole star cluster systems by interpolating between our runs. The complete data of these simulations are made available on the internet. Our simulations show that cluster sizes, bound mass fraction and velocity profile are strongly influenced by the details of the gas expulsion. Although star clusters can survive SFEs as low as 10 per cent if the tidal field is weak and the gas is removed only slowly, our simulations indicate that most star clusters are destroyed or suffer dramatic loss of stars during the gas removal phase. Surviving clusters have typically expanded by a factor of 3 or 4 due to gas removal, implying that star clusters formed more concentrated than as we see them today. Maximum expansion factors seen in our runs are around 10. If gas is removed on time-scales smaller than the initial crossing time, star clusters acquire strongly radially anisotropic velocity dispersions outside their half-mass radii. Observed velocity profiles of star clusters can therefore be used as a constraint on the physics of cluster formation. [source] Reactive extrusion of poly(ethylene terephthalate),(ethylene/methyl acrylate/glycidyl methacrylate),organoclay nanocompositesPOLYMER COMPOSITES, Issue 2 2007Elif Alyamac This study was conducted to investigate the effects of component concentrations and addition order of the components on the final properties of ternary nanocomposites composed of poly(ethylene terephthalate), organoclay, and an ethylene,methyl acrylate,glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET. In this context, first, the optimum amount of the impact modifier was determined by melt compounding binary PET-terpolymer blends in a corotating twin-screw extruder. The amount of the impact modifier (5 wt%) resulting in the highest Young's modulus and moderate elongation at break was selected owing to its balanced mechanical properties. Thereafter, by using 5 wt% terpolymer content, the effects of organically modified clay concentration and addition order of the components on the properties of ternary nanocomposites were systematically investigated. Mechanical testing revealed that different addition orders of the materials significantly affected the mechanical properties. Among the investigated addition orders, the best sequence of component addition (PI-C) was the one in which poly(ethylene terephthalate) was first compounded with E-MA-GMA. Later, this mixture was compounded with the organoclay in the subsequent run. In X-ray diffraction analysis, extensive layer separation associated with delamination of the original clay structure occurred in PI-C and CI-P (Clay + Impact Modifier followed by PET) sequences with both 1 and 3 wt% clay contents. X-ray diffraction patterns showed that at these conditions exfoliated structures resulted as indicated by the disappearance of any peaks due to the diffraction within the consecutive clay layers. POLYM. COMPOS., 28:251,258, 2007. © Society of Plastic Engineers [source] Relative viscosity models and their application to capillary flow data of highly filled hard-metal carbide powder compoundsPOLYMER COMPOSITES, Issue 1 2005Tomas Honek The rheological behavior of highly filled polymer systems used in powder injection molding (PIM) technology strongly influences the final properties of the products. In this study, the capillary flow data of multi-component polymer binders,based on polyethylene, paraffin, ethylene-based copolymers, and polyethylene glycol,compounded with three various hard-metal carbide powders were employed. The rheology of such highly filled (up to 50 vol%) multiphase systems is necessarily a complex phenomenon characterized by strain dependent, non-Newtonian properties complicated by flow instabilities and yield. Over 15 mathematical models proposed for highly filled systems were tested, some of them calculating the maximum filler loading. Due to the complex structure of the filler (irregular shape, particle size distribution) and a multi-component character of the binder, the applicability of these models varied with the powder-binder systems studied. However, the particular values of maximum loadings are in good accordance with the predictions based on powder characteristics. Simple modification of Frankel-Acrivos model to the systems containing unimodal hard-metal carbide powders with particles of an irregular shape and broad particle size distribution gave precise agreement between experimental data and model prediction. POLYM. COMPOS., 26:29,36, 2005. © 2004 Society of Plastics Engineers. [source] Reactive extrusion of recycled bottle waste materialPOLYMER ENGINEERING & SCIENCE, Issue 4 2002R. Hettema The objective of this study is to investigate the effect of reactive processing of commingled bottle waste polymer in an extruder. A variety of peroxides and monomers were tested to assess their influence on the final mechanical properties of the product. The reactive extruded polymer blends were prepared in two types of extruders: a co-rotating twin-screw extruder and a Buss co-Kneader single-screw extruder. Blends were analyzed for mechanical and thermal properties. The effectiveness of the different monomers and peroxides was evaluated in terms of improvement in impact properties. It has been found that the toughness of the polymer blend is improved by reactive processing. Depending on the amount and type of reactants, the impact strength can be improved by 220%, with a slight reduction in the modulus compared to an unmodified physical blend. The most suitable monomers were n-butylmethacrylate (BMA), t-butylamino ethylmethacrylate (TBAEMA) and a combination of styrene/maleic anhydride (ST/MAH). The peroxide should have a short half-lifetime compared to the average residence time in the extruder. The most effective monomers have a high initial reactivity and low rate of evaporation at the processing conditions used. Changes in processing conditions in the extruder influence the reaction conditions and therefore the final properties of the blend. Results were interpreted in terms of residence time, melting profile and peroxide concentration. [source] Processing of short-fiber reinforced polypropylene.POLYMER ENGINEERING & SCIENCE, Issue 1 2000An experimental investigation of the processing of glass fiber reinforced polypropylene is presented. Final fiber orientation distribution, fiber distribution in filament sections, rheological properties, final fiber length distribution and surface morphology were analyzed. This analysis was done taking into account the quantity of fibers and their interactions and flow conditions. The final fiber orientation increased when shear rate increased and fiber concentration decreased. Moreover, inhomogeneities in fiber distribution increased as the concentration of fibers decreased. The density profile showed a significant variation with fiber concentration, but it was not dependent on the shear rate applied. The viscosity showed a linear dependence with shear rate. The average fiber length and the breadth of this distribution decreased with the increasing fiber concentration and extrusion rate. The extruded filament surface showed minor roughness when the shear rate increased or when the fiber concentration decreased. The results of this experimental characterization give useful information to determine the influence of the processing variables on the final properties of short-fiber reinforced polypropylene and constitutes the first part of a more ambitious project that also includes the development of a modeling strategy of the processing behavior for short-fiber composites. [source] | |||||||||||||||||||||||||