bluuebunny/crossref_metadata_2025_split huggingface dataset:
Equilibrium and dynamic swelling of polyacrylates
Authors: Bell Cristi L. , Peppas Nikolaos A. 
Published: April 2004

AbstractPolyacrylates were prepared by solution polymerization of partially neutralized acrylic acid at 37°C. The swelling behavior of the polyacrylates was examined using equilibrium and dynamic swelling studies. Equilibrium swelling studies in deionized water were used to determine the molecular weight between crosslinks using the Flory‐Rehner theory. The amount of crosslinking agent incorporated into the network was a function of the nominal crosslinking ratio. Dynamic swelling studies in saline solutions were used to investigate the initial swelling rate for the polyacrylates. Swelling studies of the polyacrylates in saline solutions under load were used to elucidate the degree of swelling under load, the compliance, and sample elasticity.
Residual thermal stresses in injection molded products
Authors: Zoetelief W. F. , Douven L. F. A. , Housz A. J. Ingen 
Published: April 2004

AbstractNonisothermal flow of a polymer melt in a cold mold cavity introduces stresses that are partly frozen‐in during solidification. Flow‐induced stresses cause anisotropy of mechanical, thermal, and optical properties, while the residual thermal stresses induce warpage and stress‐cracking. In this study, the influence of the holding stage on the residual thermal stress distribution is investigated. Calculations with a linear viscoelastic constitutive law are compared with experimental results obtained with the layer removal method for specimens of polystyrene (PS) and acrylonitrile butadiene‐styrene (ABS). In contrast to slabs cooled at ambient pressures, which show the well‐known tensile stresses in the core and compressive stresses at the surfaces, during the holding stage in injection molding, when extra molten polymer is added to the mold to compensate for the shrinkage, tensile stresses may develop at the surface, induced by the pressure during solidification.
Simulation of slit dies in operation including the interaction between melt pressure and die deflection
Authors: Sander R. , Pittman J. F. T. 
Published: April 2004

AbstractA simulation of slit dies in operation is described. Two‐dimensional finite element analyses are used for the pressure field in the die (based on Hele‐Shaw flow assumptions), and for the deflection of the die body resulting from this internal pressure (using Mindlin thick plate theory). These analyses are coupled in an iterative scheme, which converges to give results for the dynamic operating performance of the die. Predictions of deflections and pressure drops agree closely with experimental data. Post‐processing of primary pressure results yields the stream function, melt residence time, total melt strain, and wall shear stresses. The calculation routines are enclosed within a graphical user interface in the MS‐Windows operating environment, running on PCs, and providing a powerful and convenient computational aid for the designer and process operator.
Effect of pressure history on shrinkage and residual stresses—injection molding with constrained shrinkage
Authors: Jansen K. M. B. , Titomanlio G. 
Published: April 2004

AbstractA simple elastic model for residual stresses and shrinkage of a thin solidifying product is proposed. The model results in expressions ready to be used. It accounts for shrinkage anisotropy between in‐plane and thickness directions, caused by different constraints in deformation. The model uses local values for temperature, pressure, crystallization, and (if present) extent of reaction, which belong to the standard output of most simulation codes. It is therefore assumed to be valid also for complex shaped products.
Crystallization behavior and mechanical properties of poly(aryl ether ether ketone)/poly(ether imide) blends
Authors: Frigione Mariaenrica , Naddeo Carlo , Acierno Domenico 
Published: April 2004

AbstractCrystallinity and mechanical properties of blends with different amounts of semicrystalline poly(aryl/ ether ether ketone) (PEEK) and amorphous poly(ether imide) (PEI) polymers have been studied. The blends, prepared by melt mixing, have been investigated by differential scanning calorimeter (DSC) to analyze the miscibility between the components and the final crystalline content. Moreover, for the 20/80 PEEK/PEI blend, crystallization in dynamic and isothermal conditions has been carefully investigated in order to find proper conditions for maximum development of crystallinity. Mechanical tests (static and dynamic) have been performed to evaluate the properties of the as‐molded and crystallized blends and to compare them with those of crystalline PEEK and amorphous PEI neat resins. Finally, a few SEM observations have been performed to compare the fractured surface of the blend with those of the pure constituents.
Studies of optical haze and surface morphology of blown polyethylene films using atomic force microscopy
Authors: Smith P. F. , Chun I. , Liu G. , Dimitrievich D. , Rasburn J. , Vancso G. J. 
Published: April 2004

AbstractAtomic force microscopy (AFM) has been used to examine the inner and outer surfaces of commercial blown polyethylene films. When this technique has been used, direct‐space images of surface lamellae have been obtained, and the surface roughness determined. The haziness of the films has been measured, both in the as‐produced state and when coated with suitable oil. Thus, both surface and bulk contributions to the apparent turbidity have been estimated. The aim of this study has been to correlate in turn the haziness, roughness, and surface morphology. Results obtained showed that the haze is related primarily to the surface roughness and can be reduced by lowering the frost line. AFM images unveiled lamellar features that were oriented predominantly in the transverse direction. The observed wide‐angle X‐ray diffraction (WAXD) intensities were consistent with an a‐axis type of orientation.
Conductivities and thermal studies of polymeric electrolytes based on poly(epichlorohydrin)/sodium salts
Authors: De Almeida Alessandra P. , Silva Glaura Goulart , De Paoli Marco‐A. 
Published: April 2004

AbstractThe halogenated polyether named Hydrin‐T® is a terpolymer constituted of epichlorohydrin‐ethylene oxide‐allyl glycidyl ether. It was studied as a polymeric electrolyte in polymer/NaX systems (X = Br−, I−, SCN−, ClO4− and B(C6H5)4−). In this work we present an investigation of the ionic conductivity (measured by impedance spectroscopy) and thermal properties (measured by differential scanning calorimetry–DSC, modulated DSC and thermogravimetry) of the polymeric electrolyte as a function of the composition in the range of 5 to 40 m/m(%) of the sodium salt. The solubility of sodium salts in the elastomer terpolymer matrix is comparable to the solubility in the best known matrix of linear semicrystalline PEO. The conductivities of the terpolymer/NaI electrolytes are higher than those of membranes prepared with other salts studied (10−5 S/cm for the former versus 10−7 to 10−6 S/cm for the latter). This system also is the most homogeneous up to 40 m/m (%) and showed the smallest increase of Tg values as a function of salt concentration [between ‐53°C for the pure polymer and ‐35°C for the 40 m/m (%) of NaI]. Modulated DSC confirmed the homogeneity of the terpolymer/NaI system showing Tg transition in a range of only 5°C. A decrease of variation of heat capacity during glass transition with the increase of salt concentration was observed.
Synthesis and characterization of photocrosslinkable poly(organophosphazene)‐bearing cinnamyloxide side groups
Authors: Choung Yun Sic , Lee Ki Ho , Lee Dong Choo 
Published: April 2004

AbstractTwo different poly(organophosphazene)s‐bearing single‐substituents (two cinnamyloxide side groups per repeating unit) and phenoxide‐co‐substituents (one phenoxide and one cinnamyloxide group per repeating unit) were prepared to study their photochemical reaction behavior. Structural formulas confirmed by the NMRs (1H, 31P) and IR were [NP(OCH2CH = CH  C6H5)2]n  (I) and [NP(OCH2CH = CH  C6H5)0.8 (O  C6H5)1.2]n  (II). Molecular characterization yielded \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {M_w {\rm s}} $\end{document} of the order of 103 kg/mol for both the polymers. The onset temperature of decomposition found by TGA was about 250°C. DSC measurements gave Tgs as 1°C for I and 3°C for II. Their photolytic crosslinking behaviors were monitored by UV spectroscopy. The single‐substituents polymer I showed a faster rate of photo reaction than the polymer II. The potential use for practical photosensitive application is considered to be greater for the polymer I.
Investigation of double bubble tubular film extrusion of polyamide 6 and film structural characteristics
Authors: Rhee Sangkeun , White James L. 
Published: April 2004

AbstractBiaxially oriented polyamide 6 films were made by double bubble tubular film extrusion. The crystalline character and biaxial orientation of the films were investigated by measuring (in plane and out of plane) birefringences, IR (infrared) spectroscopy, and wide angle X‐ray diffraction (WAXS) flat film patterns and pole figures. The samples were also examined by tensile stretching tests in different sampling directions.
Integrated numerical modeling of the blow molding process
Authors: Laroche D. , Kabanemi K. K. , Pecora L. , Diraddo R. W. 
Published: April 2004

AbstractThe numerical modeling of the extrusion blow molding of a fuel tank is considered in this work. The integrated process phases are consecutively simulated, namely, parison formation, clamping, and inflation, as well as part solidification, part deformation (warpage), and the buildup of residual stresses. The parison formation is modeled with an integral type viscoelastic constitutive equation for the sag behavior and a semi‐empirical equation for the swell behavior. A nonisothermal viscoelastic formulation is employed for the clamping and inflation simulation, since parison cooling during extrusion strongly affects the inflation behavior. Once the parison is inflated, it solidifies while in the mold and after part ejection. Warpage and residual stress development of the part are modeled with a linear viscoelastic solid model. Numerical predictions are compared with experimental results obtained on an industrial scale blow molding machine. Good agreement is observed. A process optimization based on a desired objective function, such as uniform part thickness distribution and/or minimal part weight, is performed. The integrated clamping, inflation, and cooling stages of the process are considered. The optimization is done by the systematic manipulation of the parison thickness distribution. Iterations are performed employing a gradient based updating scheme for the parison thickness programming, until the desired objective of uniform part thickness is obtained.
Interfacial tension of polypropylene/polystyrene: Degradation of polypropylene
Authors: Visscher E. J. , Willemse R. C. 
Published: April 2004

AbstractThe coefficient of the decrease of the interfacial tension of polypropylene/polystyrene with temperature is considerably higher than the value of other polymer pairs. This coefficient can be estimated by considering the change of the interaction parameters with temperature, but this approach fails for polypropylene/polystyrene, and other mechanisms are expected to play a role. In this paper it is shown that polypropylene starts to degrade at higher temperatures, leading to smaller polymer chains, which decrease the interfacial tension. Besides the change of the interaction parameters with temperature, these smaller molecules also contribute to the temperature coefficient, leading to an apparently high coefficient. The smaller molecules, however, lead to a permanent lower interfacial tension, e.g. the interfacial tension of polypropylene/polystyrene at 200°C is 4.9, 3.9, and 3.0 mN/m, if the polypropylene is first processed at 200, 250, and 300°C, respectively.
A study on the effects of chaotic mixer design and operating conditions on morphology development in immiscible polymer systems
Authors: Sau Madhusudan , Jana Sadhan C. 
Published: April 2004

AbstractSelf‐similar mixing structures, a novel feature of chaotic mixing, were generated in this study as precursor to an array of mixing microstructures, such as nested layers, elongated fibrils, droplets and their combinations in the blending of two immiscible polymers, polypropylene (PP) and polyamide‐6 (PA6). Simulations based on Newtonian flow model were used to compute Poincaré maps and stretching distribution as the tools for investigation of the effect of shear gap and chaotic mixing parameter, such as angular displacement per period (θ) of rotors, on the degree of mixing and morphology development in a batch chaotic mixing device. It was found that a value of θ = 1440° provided the conditions for fastest conversion of the PP‐phase into droplets for the same total strain. A 25% reduction in shear gap from 0.0127 m to 0.0095 m gave rise to much more uniform mixing of the components and led to faster conversion of the PP‐phase into droplets for the same value of θ and the same total strain. A very large fraction (>90%) of the droplets generated fell below the equilibrium size and were found to be much smaller than those produced by twin‐screw extrusion method. Polym. Eng. Sci. 44:407–422, 2004. © 2004 Society of Plastics Engineers.
Heat transfer behavior of melting polymers in laminar flow field
Authors: Sato Sadao , Oka Kenichiro , Murakami Akihiko 
Published: April 2004

AbstractHeat transfer coefficients were investigated by insertion of a probe into melting polymers under laminar flow at 200–240°C and a flow velocity of 0.5–2.7 mm/sec. The average heat transfer coefficients of melting polypropylene (PP) and polystyrene (PS) were found to be 160–220 W/m·°C and 180–270 W/m·°C, respectively. These coefficients show remarkable dependence on flow velocity, and the average heat transfer coefficient of PS is about 13%–23% higher than that of PP. When the flow velocity of flowing melting PP and PS exceeds about 0.078mm/sec, heat transfer by convection becomes dominant, whereas under lower flow velocities, since the equivalent conduction layer thickness δ′ in which the quiescent state without flow approaches infinity, heat transfer by conduction becomes dominant. The Prandtl number (Pr) and Nusselt number (Nu) of melting PP are 125–133 × 106 and 38.6–51.4, respectively, and those of melting PS are 63–64 × 106 and 42.3–61.3. In the case of constant flow velocity, the Peclet number (Pe) and Stanton number (St) are dependent on the specific heat of melting polymer. Polym. Eng. Sci. 44:423–432, 2004. © 2004 Society of Plastics Engineers.
Model filled polymers: The effect of particle size on the rheology of filled poly(methyl methacrylate) composites
Authors: Li Joshua Qingsong , Salovey Ronald 
Published: April 2004

AbstractThe effect of size of crosslinked monodisperse spherical polymer particles on the steady shear and dynamic rheology of filled poly(methyl methacrylate) (PMMA) composites was studied for PMMA and polystyrene (PS) particles in the range from 0.1 to 1.3 micron particle size. For PMMA matrices filled with crosslinked PS particles, reduction in filler size increases non‐Newtonian behavior. Particle size effects on the rheology of filled PMMA were much less pronounced for PMMA filler. The rate of growth of steady shear viscosity with aging time was much larger for PMMA filled with PS particles than with PMMA particles. The apparent yield stress of filled PMMA composites was estimated from Casson plots. The yield stress was negligible for PMMA filler but increased with decreasing particle size for PS filler. We suggest that PS particles are rejected by the PMMA matrix and form clusters, causing large enhancements in viscosity and moduli. Polym. Eng. Sci. 44:452–462, 2004. © 2004 Society of Plastics Engineers.
A phenomenological constitutive model for foams under large deformations
Authors: Liu Qunli , Subhash Ghatu 
Published: April 2004

AbstractA nonlinear phenomenological constitutive model applicable to structural foams subjected to large deformations is proposed. The five‐parameter model can fully capture the three fundamental features of stress‐strain response, i.e., linearity, plasticity‐like stress plateau, and densification phases, when subjected to compressive loads. Moreover, the parameters of the model can be systematically varied to capture the influence of initial density of foams that may be responsible for changes in yield stress and hardening‐like or softening‐like behavior under various confinement conditions. The model was successfully applied to capture the stress‐strain response of two structural foams of different initial densities when subjected to uniaxial compression without lateral confinement and unixial compression under rigid confinement. Polym. Eng. Sci. 44:463–473, 2004. © 2004 Society of Plastics Engineers.
Structural changes of PVC in PVC/LDPE melt‐blends: Effects of LDPE content and number of extrusions
Authors: Sombatsompop N. , Sungsanit K. , Thongpin C. 
Published: April 2004

AbstractThis paper investigates the structural changes of polyvinyl chloride (PVC) in melt‐blends of a low‐density polyethylene (LDPE) and polyvinyl chloride (PVC), and the effects of LDPE content and number of extrusion passes. These effects were examined in terms of changes in weight average molecular weight and number average molecular weight, polyene and carbonyl indices, color changes of the blend, and the variations in glass transition and decomposition temperatures. It was found that loading LDPE into PVC led to the formation of short‐chain LDPE grafted PVC (s‐LDPE‐g‐PVC) copolymers, via a macro‐radical cross‐recombination reaction, which had greater weight average molecular weight with unchanged number average molecular weight, increased decomposition temperature, lower glass transition temperature, as compared to the pure PVC sample. The dehydrochlorination reaction of PVC was suppressed by the macro‐radical cross‐recombination reaction with addition of LDPE, the effect being more pronounced at 13.0 wt% LDPE. For a given LDPE content, the macro‐radical cross‐recombination and dehydrochlorination reactions competed with one another, thus causing the increases in molecular weight average and molecular weight number up to the 4th extrusion pass. At the 5th extrusion pass, the dehydrochlorination reaction was predominant owing to a depletion of LDPE content to be grafted onto PVC molecular chains. The glass transition and decomposition temperature decreased with increasing number of extrusion passes. Polym. Eng. Sci. 44:487–495, 2004. © 2004 Society of Plastics Engineers.
Improvement of the processability of poly(ether ketone ketone) by the addition of a thermotropic liquid crystalline polymer
Authors: Son Younggon , Chun Yong Sung , Weiss R. A. 
Published: April 2004

AbstractThe addition of a thermotropic liquid crystalline, wholly aromatic copolyester, TLCP, improved the melt processability of poly(ether ketone ketone), PEKK. The tensile strength and modulus of the blends also improved with increasing TLCP, but the elongation at break decreased significantly. The blends were phase‐separated, but the polymers were partially miscible as evident from shifts of the glass transition temperature (Tg) of each component towards that of the other component in the blend. Similarly, the melting points (Tm) of both components were depressed by blending. When the crystallization temperature was above Tm of the TLCP, the PEKK crystallization rate in the blend was slower than for the pure material, while crystallization was faster when the temperature was below Tm of the TLCP. Polym. Eng. Sci. 44:541–547, 2004. © 2004 Society of Plastics Engineers.
Recycling PET beverage bottles and improving properties
Authors: Oromiehie Abdulrasoul , Mamizadeh Alireza 
Published: April 2004

AbstractRecycling PET from bottles has been carried out by three different extrusion methods. Under optimized processing conditions, a virgin poly(ethylene terephthalate (PET), recycled PET and a mixture of virgin and recycled PET, with and without the modifier polypropylene functionalized with maleic anhydride [PP‐graft‐MA]), were processed. Different methods were used to characterize the processed products. The results showed that the intrinsic viscosity and molecular weight decreased as the blend ratio of recycled PET was increased. This was due to thermal exposure as well as shear degradation of recycled PET. Thermal cycles of the processes used for recycling PET and its blending specimens with virgin PET show the importance of the thermal treatment in the improvement of mechanical strength and increased crystallinity. Nevertheless, the properties of the functionalized blends were improved. This behaviour is attributed to a series of chemical and physico‐chemical interactions taking place between the two components. Copyright © 2004 Society of Chemical Industry
Plausible guard effect on the active sites of heterogeneous Ziegler–Natta catalyst by coordinating monomers and growing polymer chains in the initial stage of propene polymerization
Authors: Murayama Namiko , Liu Boping , Nakatani Hisayuki , Terano Minoru 
Published: April 2004

AbstractInvestigation of propene polymerization by a modified stopped‐flow technique using TiCl4/ethylbenzoate(EB)/MgCl2 Ziegler–Natta catalyst with or without pretreating the catalyst with triethylaluminium (TEA) within an ultra‐short period (ca 1 s) was conducted to gain new understanding of the nature of active sites related to TEA in the early stage of polymerization. When the catalyst was pretreated by a cocatalyst, deactivation behaviour was clearly observed, even within an extremely short pretreatment period. In contrast, without pretreatment, the deactivation of active sites can be neglected within the polymerization period indicating that the activated Ti species might be protected from deactivation by TEA when monomer is present in the system. A plausible guard effect on the active sites by coordinating monomer and growing polymer chains in the initial stage of polymerization is proposed to account for this phenomenon. Copyright © 2004 Society of Chemical Industry
Micellization to gelation of a triblock copolymer in water: Thermoreversibility and scaling
Authors: Lau Boon Kiak , Wang Qiqiang , Sun Wei , Li Lin 
Published: April 2004

AbstractAqueous solutions of a poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer, Pluronic F108 (PEO133PPO50PEO133), ranging from 1 to 35 wt %, were studied with differential scanning microcalorimetry and rheology. The thermoreversible micellization and gelation were examined through a heating process and a subsequent cooling process at a fixed rate of 1 °C/min. The critical micellization temperature (CMT), determined by the onset temperature of the endothermic peak in the heating process, was a decreasing function of the F108 concentration. A small secondary endothermic peak appeared only when the polymer concentration was 22.5 wt % or higher, indicating that there was a sol–gel transition but that the gelation was a nearly athermic process. Upon heating, an abrupt increase was observed in both the dynamic storage modulus (G′) and dynamic loss modulus (G″) within a narrow temperature range. TG′, the temperature for the transition in G′, was a linear decreasing function of the polymer concentration and different from CMT. TG′ tended to approach CMT with an increasing F108 concentration. Beyond this transition, G′ reached a plateau, and the plateau increased in height and broadened with the polymer concentration. The value of G′ at 70 °C (G′70) could be approximately scaled with concentration c by G′70 ∝ c7.3. In addition, the definition for a gel to obey G′ > G″ was valid only when c was greater than 22.5 wt %, and this was in agreement with the secondary endothermic peak found with differential scanning calorimetry. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2014–2025, 2004