bluuebunny/crossref_metadata_2025_split huggingface dataset:
Styrene grafting onto a polyolefin in an internal mixer and a twin‐screw extruder: Experiment and kinetic model
Authors: Cha Jaehyug , White James L. 
Published: April 2004

AbstractThere has been relatively little effort to quantitatively understand graft copolymerizaution in either batch mixers or twin‐screw extruders. Most efforts have concentrated on grafting maleic anhydride, which does not homopolymerize. In this paper we consider grafting with styrene, which may homopolymerize as well as graft. The influence of residence time on degree of grafting in an internal mixer and a twin‐screw extruder were studied by measuring reaction yields with respect to reaction time in a mixer and along the screw axis in a twin‐screw extruder. The degree of grafting increased with initial monomer and peroxide concentration. Grafting reactions with three different peroxides were also investigated. The degree of styrene grafting in an internal mixer is slightly higher than that in a twin‐screw extruder. The rate of reaction along the screw axis in terms of residence time seems higher than for the batch mixer. The melt viscosity dropped dramatically with addition of peroxide. A kinetic scheme is proposed and the experimental results are critically compared with it.
Blends of bitumen with polymers having a styrene component
Authors: Fawcett A. H. , McNally T. 
Published: April 2004

AbstractThe properties of a 100 penetration grade bitumen are modified considerably, and in a number of ways by the addition of 10 to 40 parts per hundred (pph) of a homopolystyrene and graft, block and random copolymers of styrene with butadiene and acrylonitrile. At low temperatures some blends have a similar stiffness to or even lower stiffness than the bitumen, but generally the blends are more than one order of magnitude stiffer, even when a rubber is added. The contrasting behavior is displayed by a polystyrene and a high impact polystyrene, ∼3% to 4% of grafted rubber on the latter being sufficient to cause the enhancement, even at the 10 pph level, by two different random styrene‐butadiene copolymers, and also by blends consisting of different amounts of SBS block copolymer. Some polymers apparently trigger a Hartley inversion of the micellar structure of the asphaltene micelles. High low temperature stiffness correlates roughly with a lower Tg' as measured by the peak maximum in the E″ plots of the dynamic mechanical thermal analysis (DMTA) and by the steps in the differential scanning calorimetry (DSC) curves at temperatures below O°C. Tan δ maxima and DSC traces detected the glass transition in the continuous phase and in the dispersed phases, but none of these amorphous polymers formed a crystalline phase, though the DSC traces of the polystyrene and the SBS blends suggested that the polymer‐rich phases underwent an aging/ordering process on cooling. Our SBS blends differ in phase inversion behavior and the pattern of loss processes from others that had a smaller asphaltene component.
The design of conformal cooling channels in injection molding tooling
Authors: Xu Xiaorong , Sachs Emanuel , Allen Samuel 
Published: April 2004

AbstractSolid Freeform Fabrication technologies have demonstrated the potential to produce tooling with cooling channels, which are conformal to the molding cavity. 3D Printed tools with conformal cooling channels have demonstrated simultaneous improvements in production rate and part quality as compared with conventional production tools. Conformal cooling lines of high performance and high complexity can be created, thus presenting a challenge to the tooling designer. A systematic, modular approach to the design of conformal cooling channels is presented. Cooling is local to the surface of the tool, so the tool is divided into geometric regions and a channel system is designed for each region. Each channel system is itself modeled as composed of cooling elements, typically the region spanned by two channels. Six criteria are applied, including: a transient heat transfer condition, which dictates a maximum distance from mold surface to cooling channel; considerations of pressure and temperature drop along the flow channel; and considerations of the strength of the mold. These criteria are treated as constraints, and successful designs are sought that define windows bounded by these constraints. The methodology is demonstrated through application to a complex core and cavity for injection molding.
Comparison of structure development in quiescent crystallization, die extrusion and melt spinning of isotactic polypropylene and its compounds containing fillers and nucleating agents
Authors: Yu Yishan , White James L. 
Published: April 2004

AbstractThe influences of fillers and nucleating agents on crystalline structure and stress induced crystallization of isotactic polypropylene were studied under a range of cooling and processing conditions, including die extrusion and melt spinning. Continuous cooling transformation curves were determined for polypropylene and various polypropylene filler compounds. The influence of spinline stress on crystallization was studied. The experiments reveal that under quiescent conditions, the kinetics and crystalline forms produced by the crystallization of polypropylene are dominated by nucleating fillers and impurities. The crystalline orientation‐spinline stress relationship, on the other hand, was found to be the same for polypropylene and its compounds. At high uniaxial stresses, kinetics and orientation development are dominated by homogeneous orientation crystallization.
Molecular characterization and rheological properties of modified poly(ethylene terephthalate) obtained by reactive extrusion
Authors: Nguyen Quoc Tuan , Japon Sonia , Luciani André , Leterrier Yves , Månson Jan‐Anders E. 
Published: April 2004

AbstractThe use of a tetrafunctional epoxy‐based additive to modify the molecular structure of poly(ethylene terephthalate) (PET) was investigated with the aim of producing PET foams by an extrusion process. The molecular structure analysis and shear and elongation rheological characterization showed that branched PET is obtained for 0.2, 0.3 and 0.4 wt% of a tetrafunctional epoxy additive. Gel permeation chromatography (GPC) analysis led to the conclusion that a randomly branched structure is obtained, the structure being independent of the modifier concentration. The evolution of shear and extensional behavior as a function of molecular weight (Mw), degree of branching, and molecular weight distribution (MWD) were studied, and it is shown that an increase in the degree of branching and Mw and the broadening of the MWD induce an increase in Newtonian viscosity, relaxation time, flow activation energy and transient extensional viscosity, while the shear thinning onset and the Hencky strain at the fiber break decrease markedly.
Visualization and microscopic modeling of phase inversion during compounding
Authors: Ratnagiri R. , Scott C. E. 
Published: April 2004

AbstractA detailed description of the sequence of deformation steps leading to phase inversion during compounding in a low‐viscosity‐ratio co‐polyester/polyethylene blend is presented. Visualization using a glass window and sampling of the blend at different mixing times enabled identification of the intermediate morphologies of the major component en route to phase inversion. Based on these observations, a theoretical model is developed to predict the time to phase inversion. The model incorporates a simplified flow‐field approximation and the calculation of strain imparted to the major component domains. A strain‐based criterion for phase inversion is then proposed, which, in conjunction with the model, yields an explicit expression for the time to phase inversion during compounding, tP.I.. The model predictions are seen to be in good agreement with the increase of tP.I., on scaleup between two mixing bowls. The correct functional dependence of tP.I. on the nominal maximum‐shear‐rate is predicted. Using combination of pure drag and planar extensional flow, the model predictions are shown to be consistent with the observed dependence of tP.I. on the volume fraction of the minor component and the blend viscosity ratio.
Nonlinear viscoelastic and viscoplastic response of glassy polymers
Authors: Spathis G. , Kontou E. 
Published: April 2004

AbstractThe main features of inelastic mechanical behavior of glassy state were studied theoretically and experimentally in terms of tensile stress‐strain and tensile creep experiments. A theoretical treatment introduced in earlier work, which takes into account the viscoelastic path at small strains and the viscoplastic one at higher stresses, proved to be capable of describing the main aspects of mechanical response of glassy polymers, i.e. nonlinear viscoelasticity during creep procedure, and yield stress, yield strain, strain softening and rate effect in a constant crosshead speed test.
Membrane inflation of polymeric materials: Experiments and finite element simulations
Authors: Li Yong , Nemes James A. , Derdouri A. A. 
Published: April 2004

AbstractA high‐speed optical measurement system, which is capable of measuring transient surface shape, is used in the polymer membrane inflation experiments. The accurate measurement data, which is an array of points, with known Cartesian coordinates and with respect to a fixed coordinate system, provides a source for further bubble shape analysis. Inflation pressure is correlated with each bubble shape measurement. The measured results reveal the importance of the thermal warpage and temperature gradient in the bubble inflation tests. Potential errors in the material parameter calculation, which are caused by assuming uniform temperature and zero thermal warpage, are pointed out. Consequently, a finite element analysis has been carried out to simulate the membrane inflation with/without thermal warpage and the temperature gradient. The material parameters obtained considering the thermal warpage and temperature gradient yield improved agreement with the experimental data. Although in this paper the measurement data is mainly used for the determination of the material parameters in the bubble inflation tests, they are also a source of validating other computer‐aided simulations as well as in the study of the thermal shrinkage of polymer products.
The vibration and hot‐tool welding of polyamides
Authors: Stokes Vijay K. 
Published: April 2004

AbstractThe weldabilities of polyamide 6 (PA‐6), polyamide 6,6 (PA‐6,6), 33 wt% glass‐filled PA‐6,6 (33‐GF‐PA‐6,6), and amorphous polyamide (PA‐A) are assessed through 120 Hz vibration welds. Weld strengths equal to those of the base resins can easily be obtained in vibration welds of both undried and dried PA‐6 and PA‐6,6. Relative weld strengths in the range of 54–57% are demonstrated for 120 Hz welds of 33‐GF‐PA‐6.6. Relative weld strengths in the range of 90–97% are demonstrated for dried PA‐A. The highest relative weld strengths obtained in hot‐tool welds of undried and dried PA‐6,6 are only 57% and 54% respectively.
Review: Recycling of nylon from carpet waste
Authors: Mihut Corina , Captain Dinyar K. , Gadala‐Maria Francis , Amiridis Michael D. 
Published: April 2004

AbstractLarge amounts of post‐consumer carpet are discarded every year. Most of this waste is currently landfilled, while a small percentage is incinerated. The face carpet fibers, consisting primarily of nylon 6 and nylon 6,6, represent the majority component in the carpet waste. Recent financial incentives and environmental constraints have motivated the industrial sector to develop recycling strategies for these fibers. Depolymerization into their constituent monomers is the most complex recycling route, but at the same time it produces the most valuable product. A second alternative involves the use of solvents for the extraction of carpet fiber components in their polymeric form. Finally, a third recycling option yields thermoplastic mixtures by melt blending the carpet waste. The recent literature on the recycling of nylon from carpet waste is reviewed in this paper. The paper also includes a section focusing on the current state of carpet recycling at the Industrial level.
A review on interface modification and characterization of natural fiber reinforced plastic composites
Authors: George Jayamol , Sreekala M. S. , Thomas Sabu 
Published: April 2004

AbstractAn Important aspect with respect to optimal mechanical performance of fiber reinforced composites in general and durability in particular is the optimization of the interfacial bond between fiber and polymer matrix. The quality of the fiber‐matrix interface is significant for the application of natural fibers as reinforcement for plastics. Since the fibers and matrices are chemically different, strong adhesion at their interfaces is needed for an effective transfer of stress and bond distribution throughout an Interface. A good compatibilization between cellulose fibers and non‐polar matrices is achieved from polymeric chains that will favor entanglements and interdiffiusion with the matrix. This article gives a critical review on the physical and chemical treatment methods that improve the fiber‐matrix adhesion and their characterization methods.
Measuring Tg in ultra‐thin polymer films with an excimer fluorescence technique
Authors: White C. C. , Migler K. B. , Wu W. L. 
Published: April 2004

AbstractAn excimer fluorescence technique has been applied to the measurement of Tg of ultra‐thin polystyrene films. This technique utilizes an excimer‐forming molecule with fluorescent emission in two wavelength bands. The intensity ratio of these bands is a sensitive measure of local viscosity. This technique has been applied to five polystyrene films in the thickness range of 25 nm to 200 nm supported on quartz substrates. The observed Tg for the five ultra‐thin polymer films was similar to the bulk Tg with no observed dependence upon thickness. Additionally, the Tg determined for each film did not show any dependence upon thermal history.
Rheology of blends of a thermotropic liquid crystalline polymer with polyphenylene sulfide
Authors: Han Minsoo , Kim Woo Nyon , Giles David W. 
Published: April 2004

AbstractBlends of thermotropic liquid crystalline polymer (LCP) and polyphenylene sulfide (PPS) were studied over the entire composition range using Rheometrics Stress Rheometer, capillary rheometer, and differential scanning calorimeter. There is no molecular scale mixing or chemical reaction between the components, as evidenced by melting and crystallization points in the PPS phase. From the strain scaling transients test at low‐rate, LCP and the blends require approximately 60 strain units to obtain steady stale shearing results. The large recoveries in the strain recovery test, magnitude 3 to 3.3 strain unit, are likely the results of texture present in LCPs. With increasing PPS content in LCP/PPS blends, the total recovery declines. Scaling of the transient strain rate remains, but the magnitude of the transients is reduced. At low‐rate, when the LCP is added to the PPS, the pure melts have similar visosity: 500 Pa · s for LCP and 600 Pa · s for PPS, but the viscosity of the blends goes through a maximum with concentration that is nearly three times the viscosity of the individual melts. At high‐rate, a significant depression of the viscosity is observed in the PPS‐rich compositions and this may be due to the fibrous structure of the LCP at high shear rates.
Preparation and characterization of polyimide nanocomposites with different organo‐montmorillonites
Authors: Chang Jin‐Hae , Park Kwang Min , Cho Donghwan , Yang Hee Sam , Ihn Kyo Jin 
Published: April 2004

AbstractPoly(amic acid) nanocomposites were synthesized from a dimethylacetamide (DMAc) solution with two organophilic montmorillonites (organo‐MMTs). It was then heated at various temperatures under vacuum, yielding 15–20 um thick films of polyimide/organo‐MMT hybrid with different clay contents (1–8 wt%). Dodecy‐lamine (C12‐) and hexadecylamine (C16‐) were used as aliphatic alkylamines in organo‐MMT. The ultimate strength monotonically increased with increasing clay content in the polymer matrix. Maximum enhancement in the initial modulus was observed for the blends containing 2 wt% clay with two kinds of organo‐clays, and values did not alter significantly with further increases in clay content. Additions of only 2 wt% C12‐ and C16‐MMT to the polyimide were shown to cause 94%‐95% reduction in oxygen gas permeability. This is caused by the barrier properties of the clay layers dispersed in the composite. In general, C16‐MMT is more effective than C12‐MMT in increasing both the tensile property and the gas barrier in a polyimide matrix. Intercalations of the polymer chains in clay were examined through wide‐angle X‐ray diffraction (XRD) and electron microscopies (SEM and TEM).
Crystallization kinetics by differential scanning calorimetry for PCL/starch and their reinforced sisal fiber composites
Authors: Cyras Viviana P. , Vázquez Analía , Kenny José M. 
Published: April 2004

AbstractCalorimetric results obtained by differential scanning calorimetry (DSC) have been used to develop a kinetic model for the crystallization behavior of PCL/starch and their composites with sisal fibers. The model takes into account the effects of nucleation and crystal growth, and it is able to describe the isothermal and non‐isothermal conditions, especially for the low cooling rates. The effect of the sisal fiber has also been analyzed. The Avrami exponent was 2.0 for the crystallization of PCL/starch and sisal fiber reinforced composite. The activation energy of the crystallization process was 4.3 and 4.0 kJ/mol for PCL/starch and sisal composite, respectively. The induction time of the crystallization and the crystallization rate was not influenced by the presence of sisal fiber.
Thermoforming shrinkage prediction
Authors: Xu Haihong , Kazmer David O. 
Published: April 2004

AbstractMost thermoforming product development processes rely on costly and time‐consuming forming trials to determine the adequacy of the mold and process. In this paper, an analytical method is developed for shrinkage predictions on the basis of a visco‐elastic constitutive material model with initial conditions from a commercial thermoforming simulation. The theoretical analysis has been developed to accommodate different sets of materials, process conditions, and mold geometry. The shrinkage model consists of a transient thermal analysis for temperature solution; a stretching phase analysis for Inflation‐induced stress estimation; a post‐contact analysis for thermal stress and relaxation; and a post‐molding strain analysis based on stress solution. The shrinkage prediction analysis has been developed and validated with a complex geometry thermoforming application. The results indicate that the shrinkage estimates provided by the analysis were within the objective tolerances of 0.1%, as measured in terms of absolute prediction error of part dimensions.
Viscoelastic simulation of film casting process for a polymer melt
Authors: Satoh Naoki , Tomiyama Hideki , Kajiwara Toshihisa 
Published: April 2004

AbstractNumerical simulations of the film casting process were performed using a finite element method for Newtonian and viscoelasttc fluids. We simplified the governing equations by the assumption that the stress and velocity gradients in the thickness direction were negligible, and obtained the film thickness and mean value of stress and velocity components in the thickness direction as variables. Viscoelasticity was described by the Larson model with multiple relaxation times. Non‐isothermal conditions were considered by applying the time‐temperature superposition law. The simulation results for the several kinds of commercial low‐density polyethylenes wore compared to the experimental data for a laboratory‐scale process at l90°C and a commercial‐scale process at 310°C. The film width and film thickness distribution at chill roll, and the change of film width were in good agreement for the laboratory‐scale process, but the agreement for the commercial‐scale process was; not as good. In the simulation of the commercial‐scale process at high temperature, the value predicted by the use of the Viscoelasticity for the original pellet showed poor agreement owing to the change of Viscoelasticity in the process. The agreement was improved by the use of the Viscoelasticity for the processed resin, which was changed from the original one. Next, viscoelastic effects on neck‐in and edge bead phenomena were investigated. The neck‐in and edge bead phenomena were considered to be affected by both the uniaxial elongational viscosity and planar elongational viscosity.
Evaluation of the derivatives of the strain energy function with respect to strain invariants for carbon black–filled EPDM
Authors: Kakavas P. A. 
Published: April 2004

AbstractThe experimental and theoretical investigation of the mechanical properties of an ethylene‐propylene‐diene terpolymer (EPDM) elastomer reinforced with carbon black was examined. The material constants of the testing material were determined by plotting the stress‐strain experimental curve in a reduced stress versus the inverse stretch diagram. The Ogden equation was used for the strain energy function to fit uniaxial experimental stress‐strain curves. The characterization of the material was examined using the contour maps of ∂W/∂I1 and ∂W/∂I2, i.e., of the derivatives of strain energy function with respect to strain invariants I1 and I2.
NIR, DSC, and FTIR as quantitative methods for compositional analysis of blends of polymers obtained from recycled mixed plastic waste
Authors: Camacho Walker , Karlsson Sigbritt 
Published: April 2004

AbstractMethods for the determination of the composition of two binary blends in mixtures of recycled polymeric materials were analyzed and compared. Recycled polypropylene/polyethylene (PP/HDPE) and recycled poly(acryl‐butadiene‐styrene) and polypropylene(ABS/PP) were used to develop and validate the methods. Diffuse reflectance near infrared spectroscopy (NIRS) offers high sensitivity and ease of operation and a possibility to perform multivariate data analysis. In comparison, differential scanning calorimetry (DSC) and Mid‐IR, which are commonly used for this purpose require certain sample preparation and are indeed time consuming. In addition, the low sensitivity of these two methods to concentrations lower than 1% wt makes their application in quality control of recycled polymers inappropriate. NIR can be used for estimating the composition of the recyclate on‐line in only a few seconds, no sample preparation is required, and high precision is achieved. We obtained a root mean square error of prediction (RMSEP) equal to 0.21% wt in the interval from 0‐15% wt of PP in HDPE and a RMSEP equal to 0.91% wt in the interval 0‐100%. For blends of PP/ABS a RMSEP of 0.74% wt in the range 0‐100% and 0.32% wt in the range 0‐15% wt PP was calculated. Most of the variation in the spectral data with respect to the polymer blend composition for all the studied blends were explained by two principal components (PC). The optimal number of factors (PC) was determined by cross‐validation analysis.