bluuebunny/crossref_metadata_2025_split huggingface dataset:
UV fluorescence monitoring of the mixing of molten polymers in a batch mixer
Authors: Cassagnau P. , Melis F. , Bounor‐Legare V. 
Published: April 2004

AbstractA fluorescence monitoring device was developed to study the distributive mixing process inside the chamber of a batch mixer. A bifurcated UV‐fluorescence probe was implemented instead of the thermocouple measuring the temperature of the melt. Hydroxymethyl anthracene was used as fluorescence tracer and was preliminarily dispersed in the minor component. Furthermore, the main polymer of this study was a copolymer of ethylene and vinyl acetate (EVA). Structure development during mixing of miscible polymer blends, low viscosity ratio blends (plasticizer/polymer), and immiscible polymer blends was investigated by this method. It was shown that the mixing process of a miscible system depends on the shear rate, which governs the temperature of the melt and consequently the melting process of the solid masterbatch‐tracer at the early stages of mixing. On the other hand, the presence of a miscible component of very low viscosity, as, for example, mixing of DOP in EVA, delays the onset of mixing. This lubricant effect was shown to be due to the fact that DOP migrates to the wall of the chamber rather than inside the polymer, though it is well miscible with the EVA phase. The study of immiscible polymers, as, for example, polypropylene in EVA, did not show any fundamental difference with miscible polymer blends. This observation is actually inherent to the UV‐fluorescence tracer disperesed in a masterbatch system, which allows quantification of the distributive mixing process only.
Compatibilizers based on polypropylene grafted with itaconic acid derivatives. Effect on polypropylene/polyethylene terephthalate blends
Authors: Yazdani‐Pedram M. , Vega H. , Retuert J. , Quijada R. 
Published: April 2004

AbstractNew types of compatibilizers based on functionalized polypropylene (PP) were synthesized by radical melt grafting either with monomethyl itaconate or dimethyl itaconate. The effect of these new modified PP compounds were tested as compatibilizers in PP/polyethylene terephthalate (PET) blends. Blends with compositions 15/85 and 30/70 by weight of PP and PET were prepared in a single‐screw extruder. Morphology of the compatibilized blends revealed a very fine and uniform dispersion of the PP phase as compared with that of noncompatibilized blends of the same composition, leading to improved adhesion between the two phases. Whereas dimethyl itaconate derived agent showed less activity, the monomethyl itaconate parent compound showed an increase of the impact resistance of PET in PP/PET blend. This was attributed to the hydrophilic nature of the monomethyl itaconate part of this compatibilizer. The tensile strength of PET in noncompatibilized blends gradually decreases as the PP content increases, while blends containing functionalized PP exhibited higher values.
Tyrosine imprinted polymer beads with different functional monomers via seed swelling and suspension polymerization
Authors: Zhang Liyong , Cheng Guoxiang , Fu Cong , Liu Xiaohang 
Published: April 2004

AbstractMolecularly imprinted polymers (MIPs) in bead form were prepared by seed swelling and suspension polymerization with trimethylolpropane trimethacrylate (TRIM) as crosslinker and tyrosine as template. The appearance of the beads was found to be greatly influenced by the concentration of polyvinyl alcohol (PVA) used as dispersant and the ratio of water to TRIM (W/T) during polymerization. When W/T was 46:1 (V/V) and the concentration of PVA‐water solution was 4.6 (%m/m), the result was more desirable size distribution with fewer misshapen beads. A series of imprinted polymers with methacrylic acid (MAA), acrylamide (AM), 2‐vinylpyridine (VP) and 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) as functional monomers (FM), respectively, were prepared, where the molar ratio of tyrosine, FM and TRIM was chosen as 1:16:17. The molecule adsorbing and selecting analysis of the polymers showed that although all the imprinted polymers adsorbed the templates following the rule of Langmuir and exhibited an obvious molecule selecting capability compared with their control polymers (CP), the adsorbing constant and the separating factor were much different when the functional monomers varied. AMPS worked better than the other FM in the present work with a higher value of asymptotic maximum solid phase concentration (0.282 mol/kg), adsorbing constant (198.81/mol), and a larger separating factor (1.93) when phenylalanine was used as the competitive molecule.
Rheological and viscoelastic properties of multiphase acrylic rubber/fluoroelastomer/polyacrylate blends
Authors: Kader M. Abdul , Bhowmick Anil K. 
Published: April 2004

AbstractDynamic viscoelastic properties and dynamic mechanical properties of blends of acrylate rubber (ACM), fluoroelastomer and polyacrylate plastics have been investigated with a rheometer (ARES RDA III) at a frequency (ω) range of 0.1 to 100 rad.s−1. The analysis of thermorheological properties revealed that the dynamic moduli and dynamic viscosity of blends varied with the composition of the ACM/FKM blend and the level and type of polyfunctional acrylates. The blends showed negative deviation of the dynamic viscosity additive rule. Higher polyfunctional acrylates induced phase separations and showed temperature dependency. It was found that the data of the blends did not follow the Cole‐Cole plot of miscibility and the plot of log G′‐log G″ of the blend showed composition dependency. The dynamic mechanical analysis exhibited lower tan δ values for blends containing higher functional acrylates. Stress relaxation measurements showed longer periods of relaxation for all blends.
Effects of molecular weight and molecular structure of low profile additives on the properties of bulk molding compound (BMC)
Authors: Ma Chen‐chi M. , Hsieh Chung‐ting , Kuan Hsu‐chiang , Tsai Tsao‐yang , Yu Shih‐wen 
Published: April 2004

AbstractThe effects of molecular weight and molecular structure of styrene(St)‐based and vinyl acetate(VAc)‐based low‐profile additive (LPA) on the curing kinetics and compatibility of unsaturated polyester (UP)/LPA system and linear shrinkage, water absorption rate, surface gloss and pigmentability of bulk molding compound (BMC) were investigated. Results show that the curing reaction rate decreases with an increase of the molecular weight of LPA due to the chain entanglement effect. The plasticizing effect of LPA on the (UP) network was reduced with an increase of the molecular weight of LPA. Water absorption of BMC increases as the molecular weight of LPA increases, implying that more microvoids were formed inside the BMC, resulting a lower linear shrinkage rate, and worse pigmentability. However, good shrinkage control LPA does not necessarily lead to a smoother surface and better surface gloss. Furthermore, modified LPAs possess better compatibility with UP, the final curing conversion of UP is elevated, and both better shrinkage control and surface properties are also observed.
Ternary composites based on PP‐EPDM blends reinforced with flax fibers. Part I: Processing and thermal behavior
Authors: López‐manchado M. A. , Biagiotti J. , Arroyo M. , Kenny J. M. 
Published: April 2004

AbstractThe simultaneous effect of the incorporation of flax fibers and terpolymer ethylene‐propylene diene rubber (EPDM) on the properties of ternary composites with a PP matrix is investigated in this study. In order to evaluate the effects of the matrix composition and fiber percentage on the properties of the composite, an experimental design based on a Doehlert Uniform Net was employed. First, the processing conditions of these ternary composites were analyzed through a rheological study, where a noticeable increase of the viscosity upon the incorporation of the fiber and elastomer was observed. Then, the thermal behavior of the composites was studied with dynamic mechanical analysis (DMA) and differential scanning calorimetry (DSC). The results indicate a strong nucleation ability of the elastomer, showing a considerable increase of the rate of crystallization. These results concur with those obtained with an optical microscope, where it was observed that a higher number of active nuclei were formed in the presence of the elastomer. A previous characterization of the flax fibers used in this study has been also carried out by measuring the length and diameter distribution as well as the mechanical and thermal properties.
Ternary composites based on PP‐EPDM blends reinforced with flax fibers. Part II: Mechanical properties/morphology relationship
Authors: Biagiotti J. , López‐manchado M. A. , Arroyo M. , Kenny J. M. 
Published: April 2004

AbstractThe mechanical properties and morphology of ternary composites based on PP‐EPDM blends reinforced with natural flax fibers are analyzed. In order to evaluate the simultaneous effect of the incorporation of both and fibers, an experimental design based on a Doehlert Uniform Net has been employed. The tensile, flexural and impact behaviors of the composites are investigated, and the results show that flax fibers behave as an effective reinforcing agent in these systems. In fact, a considerable increase in the studied properties in the presence of the fibers was observed. It is interesting to note that the reinforcing effect is more noticeable as the EPDM content in the blend increases. Morphological studies by scanning electron microscopy (SEM) were also carried out.
Barrier properties of injection molded blends of liquid crystalline polyesters (Vectra) and high‐density polyethylene
Authors: Flodberg G. , Hedenqvist M. S. , Gedde U. W. 
Published: April 2004

AbstractBlends of an extrusion‐grade high‐density polyethylene and two liquid crystalline copolyesters (LCP; Vectra A950 and Vectra RD501) were prepared by melt mixing and injection molding, and the morphologies and oxygen permeabilities of the blends were assessed. Scanning electron microscopy revealed that the LCP was present in the blends as mixed oriented bands and small spheres at low LCP contents (4–9 vol%), whereas blends with more than 18 vol% LCP showed LCP lamellae of macroscopic lateral size (mm). Scanning electron microscopy revealed a two‐dimensional continuity of the LCP domains in the disc plane due to radial shear deformation and circumferential stretching of the melt leaving the central gate of the disc‐shaped cavity. The oxygen permeability, diffusivity and solubility decreased with increasing LCP content of the blends. The decrease in permeability with respect to polyethylene was significant (46%–55%) already at 9 vol% LCP. At 27 vol% LCP, the decrease with respect to polyethylene, was 92% for the Vectra A950 blend and 98% for the Vectra RD501 blend. These blends showed a greater decrease in diffusivity (86%–92%) than in solubility (39%–76%) with respect to polyethylene, which showed the very pronounced effect of the LCP lamellae on the geometrical impedance factor. Microvoids were present in all the blends despite the use of a very high injection pressure (180 MPa) but their impact on the oxygen permeability was negligible for the Vectra RD501 blends and relatively small for the Vectra A950 blends.
A method to control the dispersion of carbon black in an immiscible polymer blend
Authors: Feng Jiyun , Chan Chi‐ming , Li Jian‐xiong 
Published: April 2004

AbstractThe dispersion of carbon black (CB) in an immiscible polymer blend of poly‐(methyl methacrylate) (PMMA) and polypropylene (PP) was studied as the viscosity of PMMA increased. It was found that the dispersion of carbon black was strongly influenced by the viscosity of PMMA. The CB was dispersed in the PMMA phase when the viscosities of PMMA and PP are comparable, as predicted by Sumita's model. As the viscosity of PMMA increases, the CB was found to be located at the interface between the PMMA and PP phases. On further increase in the viscosity of PMMA, the CB was found to be dispersed in the PP phase. In addition, the CB dispersion in the PP/PMMA blends can significantly influence the positive temperature coefficient (PTC) intensity of the blends.
Effects of strain and temperature on the electrical properties of carbon black‐filled alternating copolymer of ethylene‐tetrafluoroethylene composites
Authors: Feng Jiyun , Chan Chi‐ming 
Published: April 2004

AbstractCarbon black (CB)‐filled alternating copolymers of ethylene‐tetrafluoroethylene (ETFE) composites were prepared by the melt‐mixing method. The effects of strain and temperature on the electrical resistivity of the composites were elucidated in detail. Our results indicated that the CB content and CB particle size are the two main factors that influence the electrical resistance of the composites when they are subjected to strain. The large particle size CB‐filled ETFE composites with a low CB content show a significant increase in electrical resistivity as a function of strain. A linear relationship between the logarithm of the electrical resistivity of the composites and strain was observed, indicating that tunneling conduction plays an important role when the composites are subjected to strain. The tensile testing results indicated that the CB‐filled ETFE composites have reasonably good tensile properties.
Investigation of fracture properties of epoxy at low temperatures
Authors: Zhang Z. , Evans D. 
Published: April 2004

AbstractThe work of fracture of a number of epoxide resins has been measured at room temperature, 77K, and 4.2K, using a three‐point‐bending method with deeply notched specimens. Various types of yield behavior were noted, and the results and observations have been used to classify resins as brittle or semi‐flexible at room temperature and to record the presence of plasticity even at lower temperatures. For semi‐flexible resins at room temperature, the geometry dependent elastic/plastic contribution to the work of fracture is discussed. This work indicates how the work of fracture and the glass transition temperatures of the resin may be used to guide developments of resins for low temperature applications and possibly to derive a numerical term as a ‘Cracking Index.’ These results were used to explain the observed thermal shock resistance of these materials. A scanning electron microscope (SEM) and optical microscopy were used to investigate the fracture surfaces associated with the different types of yield and fracture behavior. The fracture surface microstructure has been used to explain the observed mechanical behavior, including the existence of plastic deformation in some resins at 77K. The results are of help in understanding the process of crack initiation, growth, and the crack tip deformation processes in epoxide resins.
Numerical simulation of film casting using an updated lagrangian finite element algorithm
Authors: Smith Spencer , Stolle Dieter 
Published: April 2004

AbstractThis paper presents a new numerical algorithm for 2D nonisothermal time‐stepping simulations of a nonlinear viscoelastic cast film process. A significant contribution of the algorithm is that an updated Lagrangian description of motion is employed, as opposed to the more conventional Eulerian description generally used for continuous polymer processing simulations. Furthermore, use is made of a Perzynatype constitutive equation, which is different from what is usually employed for molten polymers. The constitutive equation accommodates viscoelasticity, extensional thinning/thickening, and strain‐hardening. This new numerical algorithm can find the steady‐state film properties, and it can predict the onset of instability by observing draw resonance. The critical draw ratio is determined from the response problem, which means that the mathematical complications of the more common linear stability analysis are avoided. In terms of the stability of the film, it was observed that stability is decreased by extensional thinning, strain‐hardening, and higher relaxation times, and stability is increased by higher heat transfer coefficients and higher ratios of air‐gap length to die width.
Synthesis and characterization of ethylene vinyl‐acetate/polyaniline blends prepared by emulsion polymerization technique
Authors: Jeevananda T. , Siddaramaiah  
Published: April 2004

AbstractA series of ethylene vinyl acetate‐polyaniline (98/02, 95/05, 93/07, … … 50/50) (EVA‐PAni) blends were prepared by the emulsion polymerization technique and made into sheets by the compression molding at 150°C. These sheets were characterized by electrical, physico‐mechanical, thermal, X‐ray and morphological studies. All electrical properties of EVA‐(PAni)TSA blends increased with an increase in PAni content. The conductivity, dielectric constant and tan δ values increased from 1.34 × 10−14 to 2.89 × 10−2 S/cm, from 2.113 to 19.845, from 0.094 to 4.789. Tensile strength increased with an increase in PAni content up to 7% and drastically decreased above 15%, while the percentage elongation at break decreased with an increase in PAni content. TGA studies revealed that the thermal stability of PAni improved after blending with EVA. EVA‐PAni blends were found stable up to 110°C. X‐ray diffractograms of EVA‐PAni blend showed an intense peak at 26° (2θ), reflecting the influence of EVA crystallinity. Scanning electron micrographs confirmed the two‐phase morphology of the system.
Development of renewable resource–based cellulose acetate bioplastic: Effect of process engineering on the performance of cellulosic plastics
Authors: Mohanty A. K. , Wibowo A. , Misra M. , Drzal L. T. 
Published: April 2004

AbstractThis paper deals with the development of a cellulose acetate biopolymer. Plasticization of this biopolymer under varying processing conditions to make it a suitable matrix polymer for bio‐composite applications was studied. In particular, cellulose acetate was plasticized with varying concentrations of an eco‐friendly triethyl citrate (TEC) plasticizer, unlike a conventional, petroleum‐derived phthalate plasticizer. Three types of processing were used to fabricate plasticized cellulose acetate parts: compression molding, extrusion followed by compression molding, and extrusion followed by injection molding. The processing mode affected the physicomechanical and thermal properties of the cellulosic plastic. Compression molded samples exhibited the highest impact strength, tending towards the impact strength of a thermoplastic olefin (TPO), while samples that were extruded and then injection molded exhibited the highest tensile strength and modulus values. Increasing the plasticizer content in the cellulosic plastic formulation improved the impact strength and strain to failure while decreasing the tensile strength and modulus values. The coefficient of thermal expansion (CTE) of the cellulose acetate increased with increasing amounts of plasticizer. Plasticized cellulose acetate was found to be processable at 170–180°C, approximately 50°C below the melting point of neat cellulose acetate.
Micromechanical behavior of impact modified poly(ethylene terephthalate)
Authors: Chapleau N. , Ajji A. 
Published: April 2004

AbstractThe micromechanical behavior of poly(ethylene terephthalate), PET, modified with a metallocene polyolefin copolymer (mPE) was investigated. Uniaxial deformation tests were performed using a tensile stage in a scanning electron microscope. This technique allowed the identification of the main deformation mechanisms that are associated with energy dissipation and toughness improvement. The poly(ethylene terephthalate) was blended with 5 wt% mPE by single‐screw extrusion. Films with thicknesses ranging from 200 to 500 μm were produced. Observation of the surfaces of the films during uniaxial deformation revealed the sequence of events leading to the full yielding of the matrix. In the early stages of deformation, the particles deform together with the matrix. As the deformation is increased, cavitation inside the particles occurs and fibrillation at the particle/matrix interface is observed, as well as the onset of shear banding. In order to study the effect of interfacial adhesion of the deformation mechanisms, the PET/mPE blends were compatibilized by grafting with glycidyl methacrylate (GMA). The reduction of the particle size was significant, which is indicative of the efficiency of GMA grafting in this type of blend. In this case, the particles were difficult to detect on the surface. Cavitation and shear banding occurred simultaneously. A similar behavior was observed in the case of oriented blends.
Effect of die temperature on the morphology of microcellular foams
Authors: Han Xiangmin , Koelling Kurt W. , Tomasko David L. , Lee L. James 
Published: April 2004

AbstractA study on the extrusion of microcellular polystyrene foams at different foaming temperatures was carried out using CO2as the foaming agent. The contraction flow in the extrusion die was simulated with FLUENT computational fluid dynamics code at two temperatures (150°C and 175°C) to predict pressure and temperature profiles in the die. The location of nucleation onset was determined based on the pressure profile and equilibrium solubility. The relative importance of pressure and temperature in determining the nucleation rate was compared using calculations based on classical homogeneous nucleation theory. Experimentally, the effects of die temperature (i.e., the foaming temperature) on the pressure profile in the die, cell size, cell density, and cell morphology were investigated at different screw rotation speeds (10 ∼ 30 rpm). Experimental results were compared with simulations to gain insight into the foaming process. Although the foaming temperature was found to be less significant than the pressure drop or the pressure dropratein deciding the cell size and cell density, it affects the cell morphology dramatically. Open and closed cell structures can be generated by changing the foaming temperature. Microcellular foams of PS (with cell sizes smaller than 10 μm and cell densities greater than 10 cells/cm3) are created experimentally when the die temperature is 160°C, the pressure drop through the die is greater than 16 MPa, and the pressure droprateis higher than 109Pa/sec.
Synthesis and characterization of new aromatic polyimides containing well‐defined conjugation units
Authors: Shin T. J. , Park H. K. , Lee S. W. , Lee B. , Oh W. , Kim J.‐S. , Baek S. , Hwang Y.‐T. , Kim H.‐C. , Ree M. 
Published: April 2004

AbstractA series of aromatic polyimides composed of well‐defined conjugation units were synthesized form 5,5′‐bis(4‐aminophenyl)‐2,2′‐bifuryl (PFDA) and 2,2′‐bis(furyl) benzidine (FurylBZ) with various dianhydrides. The synthesized polyimides emit blue to green light with a quantum yield of 7.3–14.9%, depending on the polymer backbone. In particular, PFDA‐based polymers exhibit extremely narrow photo‐luminescence. The structure, thermal stability, refractive index and dielectric properties of the polymer films were also determined.