bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of processing conditions and reactive compatibilizer on the morphology of injection molded modified poly(phenylene oxide)/polyamide‐6 blends
Authors: Son Younggon , Ahn Kyung Hyun , Char Kookheon 
Published: April 2004

AbstractThe effect of injection molding conditions and reactive compatibilization on the morphology of maleic anhydryde‐modified poly(phenylene oxide)/polyamide‐6 blends was investigated. The injection flow rate primarily influenced the position of the subskin layer, and the injection temperature affected the aspect ratio of the dispersed phase. A reduction of the sue of the dispersed phase occured during the converging flow in the barrel‐to‐sprue zone. The reactive compatibilization reduced the flow induced deformation, the coalescence and the breakup of particles and improved the dispersion of the minor phase.
Blends of a bottle grade polyethylene terephthalate copolymer and a liquid crystalline polymer. Part I: Injection molding morphology and rheological properties
Authors: Da Silva L. , Bretas R. E. S. 
Published: April 2004

AbstractBlends of a bottle grade polyethylene terephthalate copolymer (PET) with a liquid crystalline polymer (LCP) were prepared by injection molding. The thermal transitions, the morphology and the rheological properties of the pure components and of the blends were measured by dynamic mechanical analysis (DMTA), scanning electron microscopy (SEM) and capillary and parallel plates rheometry, respectively. The blends displayed only one Tg; the B60 and B80 compositions showed the highest LCP β‐transition, which has been correlated to good barrier properties. In all the blends a “skin‐core” type morphology was observed; the core region had two phases while the skin region showed only one fibrillar phase. The viscosity measurements gave an indication that the interface was strong, probably due to transterifications reactions that occurred during the tests. On creep recovery, the increasing addition of the LCP to the PET increased the blends elastic recovery. On stress growth, the highest stress overshoot was displayed by the pure LCP; this polymer actually presented two overshoots that were also observed in some of the blends at high shear rates.
Effect of catalyst residues on the chain structure and properties of a Phillips type polyethylen
Authors: Epacher Edina , Kröhnke Christoph , Pukánszky Béla 
Published: April 2004

AbstractA large number of high‐density polyethylene (HDPE) powder samples produced by Phillips technology were taken from an industrial polymerization reactor and their catalyst residue content was determined by X‐ray fluorescence spectroscopy. The chemical structure of the powder was characterized by diffuse reflectance infrared spectroscopy (DRIFT), while the functional group content of samples processed in the presence and absence of a phenolic antioxidant was determined by Fourier transform infrared spectroscopy (FTIR). The melt flow index (MFI) of all processed samples was measured. Oxygen induction time (OIT) measurements were carried out to characterize the oxidative stability of 15 selected stabilized samples. The results indicate that the distribution of both the amount of chromium‐based catalyst residues and their composition are very heterogeneous in the produced polymer. With increasing catalyst residue content, the concentration of double bonds increases in the samples extruded with or without stabilizer. Viscosity was not influenced by catalyst residues, while discoloration increased slightly with increasing catalyst residue content. The stability of the processed polymer also depends on the concentration of double bonds and on other factors. Since other components of the catalyst, including the SiO2 support, also take part in the reactions occurring during processing, chromium content is not the sole, and perhaps not even the decisive, factor determining the properties and especially the stability of HDPE produced by a Phillips catalyst.
Interface in mechanically fastened polymer joint, studied by contact electrical resistance measurement
Authors: Luo Xiangcheng , Chung D. D. L. 
Published: April 2004

AbstractA polymer‐polymer joint obtained by mechanical fastening at a compressive stress of 5% (or less) of the 1% offset yield strength of the polymer (nylon‐6) was found to exhibit irreversible decrease in the contact electrical resistance upon repeated fastening (loading) and unfastening (unloading). The decrease occurred after up to 10 cycles of fastening and unfastening, although the decrease diminished with cycling. It is primarily due to local plastic deformation of the matrix. Moreover, the stress required for the resistance to reach its minimum in a cycle decreased with cycling, owing to softening of the matrix.
A preliminary investigation of conductive immiscible polymer blends as sensor materials
Authors: Srivastava S. , Tchoudakov R. , Narkis M. 
Published: April 2004

AbstractThis paper discusses the feasibility of the application of conductive immiscible polymer blends as sensor materials for detection of organic liquid solvents. Immiscible polymer blends of polypropylene (PP), nylon 6 (Ny6) and carbon black (CB) have been used to produce a series of electrically conductive filaments by a capillary rheometer process. In these immiscible blends, PP serves as a semi‐crystalline matrix and Ny6 as the semi‐crystalline dispersed phase. The enhancement of conductivity in these blends is due to the attraction of CB to Ny6 and localization of CB particles at the PP/Ny6 interface, giving rise to conductive networks. The dc electrical resistivity of extruded filaments, produced at different shear levels, is found to be sensitive to various organic liquid solvents. The shear rate at which the filaments are produced has an important effect on the PP/Ny6/CB filament's sensitivity. The compositions studied were close to the double‐percolation structure believed to perform best as sensor materials. In addition, it seems that the PP/Ny6 interface plays a major role in the sensing process. Liquid contact/drying cycling of the filaments indicates stabilization of the sensitivity change making the sensing process reversible.
Mechanical properties and interfacial interaction of CaCO3 filled HDPE compatibilized with HDPE functionalized by ultraviolet irradiation
Authors: Lei Jingxin , Zhou Rong 
Published: April 2004

AbstractThe mechanical properties of CaCO3 filled high density polyethylene (HDPE) compatibilized with ultraviolet (UV) irradiated HDPE (uHDPE) were studied and the interfacial interactions between CaCO3 and the polymers were evaluated by SEM, the Molau test, and ESCA. UV irradiation in air introduces the following functional groups on HDPE: >COOH, >CO, OOH and OH. The concentration of these groups increases with irradiation time. The addition of a small amount (<10% by wt) of uHDPE to the HDPE/CaCO3 improves the tensile and impact strength. For example, the addition of 3% HDPE irradiated for 500 hours (u500HDPE) increases the tensile and impact strength of HDPE/CaCO3 from 16.7 MPa and 210 J/m to 25.2 MPa and 430 J/m, respectively. Chemical reactions between uHDPE and CaCO3 promote interactions between HDPE and CaCO3. The morphology of the compatibilized compound is nearly homogenous, and no CaCO3 sediment was observed in a hot xylene solution of HDPE/u500HDPE/CaCO3 when the content of u500HDPE exceeded 30% (wt).
Silane grafting and moisture crosslinking of polypropylene
Authors: Beltraán M. , Mijangos C. 
Published: April 2004

AbstractPeroxide initiated vinylsilane grafting of polypropylene in an intensive mixer, and the subsequent water crosslinking process were studied. Different concentrations of vinyl trimethoxysilane and dicumyl peroxide were used. The materials obtained after mixing in the rheocord were hot pressed at 190°C. The melt viscosity of the obtained sheets, the melting enthalpy and melting temperature (DSC, differential scanning calorimetry), the mechanical properties and the thermal decomposition behavior (TG, thermogravimetric analysis) were studied. No evidence of grafting during the rheocord processing was observed. Nevertheless, for the hot pressed sheets with concentrations higher than 4 phr of vinyl silane an important increase in the melt viscosity was observed. This increase agrees with the change observed in the mechanical properties, which show a maximum for the water crosslinked samples containing 4 phr of vinyl silane. The modulus increases by 39% at 90°C and 33% at 130°C, while the tensile strength rises by ∼22% at both temperatures. The silane grafted water crosslinked samples show a more stable thermal behavior than both the silane grafted samples and the unmodified polypropylene.
Influence of rheological properties on the sagging of polypropylene and abs sheet for thermoforming applications
Authors: Lau H. C. , Bhattacharya S. N. , Field G. J. 
Published: April 2004

AbstractThe isothermal sagging resistance of different grades of conventional and a high melt strength (HMS) PP has been correlated with the rheological characteristics of the polymers, such as dynamic shear properties, melt strength, and zero shear viscosity. A thermoforming grade of acrylonitrile‐butadiene‐styrene (ABS) was used as a reference material. At 190°C, ABS had the highest viscosity and elastic modulus in the frequency range measured, showing that this polymer is highly elastic. HMS PP had a greater shear thinning behavior than conventional PP because of its broader molecular weight distribution. The tan δ of the polymers showed that conventional PP had a higher tendency to flow than HMS PP and ABS when heated above 172°C. This was confirmed with sagging experiments performed in an air circulating oven, where the rate of sagging decreased as the melt strength and the zero shear viscosity of the polymer increased.
Molar mass of poly (ethylene terephthalate) (PET) during ultimate uniaxial drawing
Authors: Göschel Ulrich , Cools Paul J. C. H. 
Published: April 2004

AbstractThe changes of the average molar mass Mw, Mn, Mz, and molar mass distributions during multistep uniaxial drawing of poly(ethylene terephthalate) (PET) to achieve ultimate mechanical properties have been studied in detail by means of size exclusion chromatography (SEC) with triple detection: concentration, viscosimetry, and light scattering, using HFIP as solvent. An increase in molar mass of PET due to post‐polycondensation and/or transesterfication during drawing at a high temperature of 160 to 230°C was found. Moreover, drawing leads to crystallization and large orientation in the amorphous phase, which results in lower molecular mobility and prevents a further growth in chain length. Crazing under extreme drawing conditions occurs and affects a decrease in molar mass.
The effects of dual‐orifice air‐ring design on blown film cooling
Authors: Sidiropoulos V. , Vlachopoulos J. 
Published: April 2004

AbstractNumerical simulations of turbulent air flows tangentially impinging on blown film bubbles have been carried out. The cooling air is assumed to originate from a dualorifice adjustable air‐ring. The streamline patterns and heat fluxes are determined through a finite volume numerical technique for modeling of turbulent air flow. It is shown that cooling efficiency is critically sensitive to the air‐ring design as minor modifications cause large variations in cooling performance. Additionally, for a given design, the operational setup of the air ring is equally critical to the cooling performance. It is explained that the large influence observed on heat transfer rates is primarily due to the Coanda effect, which forces air jets to attach themselves to surfaces.
Surface tension of polyethylene used in thermal coating
Authors: Demarquette Nicole Raymonde , Da Silva Fabio Teodoro , Brandi Sergio Duarte , Gouvêa Douglas 
Published: April 2004

AbstractIn this work the surface tension of a polyethylene used in thermal coating, identified as a mixture of low density polyethylene (LDPE) and stearic acid, was measured as a function of temperature for temperatures ranging from 120°C to 150°C using a pendant drop apparatus. The values were compared to the surface tension of the pure components (low density polyethylene and stearic acid). It was shown that the surface tension of the mixture is higher than the surface tension of the pure components (more than 25%). Surface analysis by Electron Spectroscopy for Chemical Analysis (E.S.C.A.) of the polyethylene used in thermal coating before and after surface tension measurement was conducted; the experimental results showed that the oxygen and the carbon present at the surface of both the powder and the drop were involved in COH and COOH bonds (for oxygen) and in CC and CO bonds (for carbon). It was shown that there is an increase of COOH and a decrease of COH bonds at the surface when the polymer is heated. It was also shown that there is an increase of C bounded to O at the surface of the drop and consequently a decrease of CC bonds. The decrease of COH was attributed to the drying of the polymer during heating and the decrease of CC was attributed to the coalescence of the polymer particles during pendant drop fomation.
Binary blends of metallocene polyethylene with conventional polyolefins: Rheological and morphological properties
Authors: Kwag Hanjin , Rana Dipak , Cho Kyucheol , Rhee Jangweon , Woo Taewoo , Lee Byung H. , Choe Soonja 
Published: April 2004

AbstractThe rheology and morphology of four sets of binary blends of polyethylene synthesized with metallocene catalysis (metallocene polyethylene: MCPE) with polyolefins prepared using Ziegler‐Natta catalysts have been investigated. The blend systems are MCPE with high density polyethylene (MCPE‐HDPE), polypropylene (MCPE‐PP), poly(propylene‐co‐ethylene) (MCPE‐CoPP), and poly(propylene‐co‐ethylene‐co‐1‐butylene) (MCPE‐TerPP). Cole‐Cole plots [storage melt viscosity (η′) versus loss melt viscosity (η″)], plots of the dynamic storage modulus (G′) versus the dynamic loss modulus (G″), and plots of the log melt viscosity (η*, η′, and η″) versus blend compositions were constructed. The morphology of the blends after microtoming and etching was studied. The phase morphology of MCPE‐HDPE appeared homogeneous, whereas the other three blends were heterogeneous. Rheological and morphological investigations indicated that the MCPE‐HDPE blend was miscible, but the other three blends were immiscible in the melt as well as in the solid state. These observations can be rationalized in terms of the similarity of the chemical structures of the polyolefins.
The effect of kevlar fiber reinforcement on the curing, thermal, and dynamic‐mechanical properties of an epoxy/anhydride system
Authors: Antón J. J. Suay , Pradas M. Monleóan , Ribelles J. L. Gómez 
Published: April 2004

AbstractCuring, thermal, and dynamic‐mechanical relaxational behavior of an epoxy/‐anhydride resin and a Kevlar‐fiber/epoxy composite were compared. Reinforcement by Kevlar fibers had a catalytic effect on the curing reaction. Reinforced formulations produced higher extents of reaction than neat formulations at the same curing time. Curing kinetics was also studied by means of DSC heating scans. When the Kevlar content increased, the heat flow curves and the exothermic peak temperature shifted significantly to lower temperatures. The glass transition temperature of the matrix also decreased as the Kevlar content increased. Postcuring reduced the differences between the neat and reinforced formulations. Loss tangent and storage modulus versus frequency master curves were obtained from isothermal dynamic‐mechanical measurements. The effect of fiber addition on the main dynamic‐mechanical relaxation was analyzed with a simple mechanical model.
Rotational molding of plastics: Comparison of simulation and experimental results for an axisymmetric mold
Authors: Olson L. G. , Crawford R. , Kearns M. , Geiger N. 
Published: April 2004

AbstractWe present a validation study comparing the mold wall temperature estimates from an axisymmetric thermal finite element simulation of the rotational molding process with temperature data obtained during experiments conducted on industrial‐grade rotational molding equipment. The finite element model simulates the heat transfer processes involved in rotational molding through the end of powder deposition, and uses an Arbitrary Lagrangian Eulerian technique to track the growing molten plastic layer. The experiments were conducted with nine different operating conditions on a single axisymmetric mold shape. The simulation results for mold wall temperature agreed well with the experimental data under all of the conditions tested.
An investigation of the friction and wear behaviors of polyphenylene sulfide filled with solid lubricants
Authors: Yu Laigui , Yang Shengrong , Liu Weimin , Xue Qunji 
Published: April 2004

AbstractComposites of polyphenylene sulfide (PPS) filled with solid lubricant particles of graphite (C), molybdenum disulfide (MoS2), and polytetrafluoroethylene (PTFE) were prepared by compression molding. The size of the solid lubricant particles was 3‐;5 µm. The friction and wear behaviors of the composites were examined with a pinon‐disk test rig. The worn composite pin surfaces and the transfer films formed on the counterface were analyzed with scanning electron microscopy. An X‐ray photo‐electron spectroscope (XPS) was used to characterize the chemical states of the elements in the transfer film. It has been found that graphite and PTFE as the fillers increase the wear resistance of PPS considerably, while MoS2 as the filler decreases the wear resistance of PPS greatly. The fillers promote the decomposition of PPS and generate compounds, which accounts for the changes in the wear resistance of the composites.
On‐line NIR sensing of CO2 concentration for polymer extrusion foaming processes
Authors: Nagata Takefumi , Tanigaki Masataka , Ohshima Masahiro 
Published: April 2004

AbstractAn on‐line sensor using near infrared (NIR) spectroscopy is developed for monitoring CO2 concentration in polymeric extrusion foaming processes. NIR absorption spectra are acquired by a probe installed at the foaming extruder die. The calibration curve relating the absorbance spectrum at 2019 nm to the dissolved gas concentration is derived so as to infer dissolved CO2 gas concentration on‐line from measured NIR spectra. Experimental results show the developed on‐line NIR sensor can successfully estimate dissolved CO2 concentration in the molten polymer and illustrate that the developed NIR sensing technique is among the more promising methods for quality control of polymeric extrusion foaming processes.
Novel variations in the microstructure of the auxetic microporous ultra‐high molecular weight polyethylene. Part 1: Processing and microstructure
Authors: Webber R. S. , Alderson K. L. , Evans K. E. 
Published: April 2004

AbstractRecent publications have detailed how auxetic (negative Poisson's ratio) polymers have been fabricated by a novel thermal processing route consisting of three welldefined stages—compaction, sintering and extrusion. In this paper, the compaction stage of the processing route is omitted and the effects of this on the structural integrity, microstructure and Poisson's ratios of the extrudates examined. The effects of varying the processing parameters of the sintering and extrusion stages are studied so that a set of conditions that produce a highly fibrillar auxetic material with sufficient structural integrity to allow mechanical properties to be evaluated can be defined. Poisson's ratios as low as −4 have been obtained.
Polymerization of anilinium/DBSA in the presence of clay particles: Catalysis and encapsulation
Authors: Segal E. , Aviel O. , Narkis M. 
Published: April 2004

AbstractThis paper describes polymerization of anilinium‐DBSA complex to PANI‐DBSA (DBSA doped polyaniline) in an aqueous dispersion in the presence of mica or talc clays. It is found that the clay presence significantly accelerates the polymerization kinetics by metal ions, such as Fe+2 ions, present in the clays. Polymerization occurs preferentially on the clay particles' surface, causing their encapsulation with PANI‐DBSA shells. Further coating with PANI‐DBSA takes place on the already coated particles with thin PANI‐DBSA shells by an autoacceleration effect of anilinium‐DBSA polymerization by PANI. It is suggested that the catalytic/autoacceleration effect dominating in the coating process of clay particles with PANI‐DBSA can be extended to other particle/coating systems, which are already under investigation.
Friction welding of similar and dissimilar materials: PMMA and PVC
Authors: Lin C. B. , Wu Li Cheng 
Published: April 2004

AbstractThe effects of spin friction pressure and time on the friction welding between parts of the same material and different materials are discussed. The heat‐affected zone is divided into three regions: the plasticized region (Zpl), the partly plasticized region (Zpd), and the undeformed region (Zud). The tensile fracture morphology has three sections: the non‐plasticized central section (Fud), the plasticized peripheral section (Fpl), and the partly plasticized section between Fud and Fpl (Fpd). Friction pressure (spinning timing): 0.784 Mpa (6 seconds), 0.981 MPa (8 seconds and 10 seconds) in PMMA‐PMMA welding, 0.588 Mpa (10 seconds) in PVC‐PVC welding, and 15.7 MPa (15 seconds) in PMMA‐PVC welding attains better bonding strength, because these parts have larger Fpd and Fpl regions, which have no Fud in the central part.
Polyethylene compounds containing mineral fillers modified by acid coatings. 1: Characterization and processing
Authors: Haworth B. , Raymond C. L. , Sutherland I. 
Published: April 2004

AbstractResearch has been carried out to determine the effect of filler coatings on the processing properties of medium density polyethylene (MDPE) modified by an ultrafine grade of flame‐retardant magnesium hydroxide (Mg(OH)2) filler. Selected filler coatings were acid‐group terminated and were of varying aliphatic chain length. The filler dry‐coating process has been optimized by characterizing the reaction between Mg(OH)2 filler surface and the acid group, using spectroscopic techniques including Fourier transform infrared (FTIR) and X‐ray photoelectron spectroscopy (XPS). Using immersion calorimetry, the interactions between the fillers and the polyolefin matrix were shown to decrease on the addition of a fatty‐acid coating. Compounding torque and specific energy data relate to filler dispersion; qualitative analysis has demonstrated how the coatings provide a reduction in both size and number of particle agglomerates. MDPE compound processability was assessed by capillary rheometry; wall slip was evident in compounds containing uncoated Mg(OH)2 filler. Consequently, the development of molecular orientation of the polymer during injection mold filling, quantified by a reversion analysis, is modified by the effects of filler coating chain length and addition level, an effect that has important implications to link the mechanical properties of MDPE‐Mg(OH)2 composites to processing history.