bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular structure, morphology, and antioxidant‐ consumption in polybutene‐1 pipes in hot‐water applications
Authors: Karlsson K. , Eriksson P‐A. , Hedenqvist M. , Ifwarson M. , Smith G. D. , Gedde U W. 
Published: May 2005

AbstractPipes of isotactic polybutene‐1 (PB) have been exposed to internal water and external air in pressure tests at 105°C. The pipes exposed to different internal pressures exhibited different failure mechanisms, referred to as stages I, II, and III. Samples taken from these pipes have been analyzed by infrared (IR) spectroscopy, wide‐angle X‐ray scattering (WAXS), size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). IR spectroscopy and WAXS confirmed that thermal oxidation of the amorphous part of the polymer accompanied the onset of stage III. Thermal oxidation led to extensive molar mass reduction and to a significant increase in mass crystallinity and melting peak temperature. Extensive and visible degradation in pipes failing according to stage III was confined to so‐called “oxidation spots.” The latter were first formed at the outer wall and propagated inwards, finally constituting approximately 50% of the wall thickness. The antioxidant concentration profiles obtained by DSC were always symmetrical and were successfully adapted to a previously developed model. It was shown that migration of the antioxidant was the dominant loss mechanism, that the diffusion coefficient was constant through the pipe wall, and that the evaporative loss to the external air was marginally greater than the loss to the internal water phase. Chemical consumption of the antioxidant was found to be negligible.
Mechanical properties of corona‐modified cellulose/polyethylene composites
Authors: Dong S. , Sapieha S. , Schreiber H. P. 
Published: May 2005

AbstractThe effect of corona treating the surfaces of components on tensile properties of wood fiber linear low‐density polyethylene composites has been investigated. Corona treatment results in a significant increase in strength properties of the composites. Yield stress increases after treatment of one or both of the composite components. Pronounced improvement in ductility has been observed for composites containing 15 to 30% of the corona modified fiber. Relevant mechanisms involved are discussed.
Dynamic simulation of propylene polymerization in continuous flow stirred tank reactors
Authors: Sarkar Priyabrata , Gupta Santosh K. 
Published: May 2005

AbstractThe dynamic operation of an ideal continuous‐flow stirred tank slurry reactor for propylene polymerization has been studied. A simple model is developed, which could be used for optimal computer control using advanced strategies. Step increases in input feed rates of propylene, solvent, and catalyst are used as the stimuli or forcing functions. It is assumed that the volume of the slurry in the reactor is maintained constant during the period. Responses of three output variables are studied, namely, monomer concentration in the liquid, volume‐fraction of solids in the exiting slurry, and average mass fraction of catalyst in the exiting macroparticles. It is found that the transients last for about five times the mean residence time of the reactor. Competing effects of changes in the diffusional resistance, number density of catalyst particles, and washout and dilution effects lead to interesting dynamic results.
Numerical and experimental investigation of three‐dimensional flow in extrusion dies
Authors: Gupta Mahesh , Jaluria Yogesh , Sernas Valentinas , Esseghir Mohamed , Kwon Tai H. 
Published: May 2005

AbstractThe univariant element, Q1 P0, and the multivariant elements, QP0 and R P0, are compared for the numerical simulation of the flow in extrusion dies. The pressure distribution obtained by using the Q1 P0 element was found to be afflicted with the checkerboard pressure mode. On the other hand, the multivariant elements, Q P0 and R P0, gave accurate and physically reasonable velocity and pressure distributions. The computed values of the pressure drop across extrusion dies matched well with the pressure drop determined experimentally.
Shear effects on thermoplastic foam nucleation
Authors: Lee Shau‐Tarng 
Published: May 2005

AbstractPolyethylene foam experiments were conducted on a twin screw foam extruder to study the process effects upon foam nucleation. The results indicate that, other than quantity of nucleators, throughput rate and die opening are important process parameters, underscoring the importance of shear in the die on nucleation. It is also found that shear effects increase as nucleator level increases. A modified cavity model shows at least qualitative agreement with experimental results. Dimensionless Capillary number, ratio of shear force to surface tension force, provides evidence that shear force rather than shear rate alone is the principal parameter affecting foam nucleation.
A macromolecular deformation model to estimate viscoelastic flow effects in polymer melts
Authors: Porter David 
Published: May 2005

AbstractThe elastic deformation of polymer macromolecules in a shear field is used as the basis for quantitative predictions of viscoelastic flow effects in a polymer melt. Non‐Newtonian viscosity, capillary end correction factor, maximum die swell, and die swell profile of a polymer melt are predicted by the model. All these effects can be reduced to generic master curves, which are independent of polymer type. Macromolecular deformation also influences the brittle failure strength of a processed polymer glass. The model gives simple and accurate estimates of practically important processing effects, and uses fitting parameters with the clear physical identity of viscoelastic constants, which follow well established trends with respect to changes in polymer composition or processing conditions.
Measurement and correlation of liquid‐liquid equilibria for polystyrene‐cyclopentane and polystyrene‐cyclopentane‐cyclohexane systems
Authors: Iwai Yoshio , Shigematsu Yuji , Furuya Takeshi , Fukuda Hiroyasu , Arai Yasuhiko 
Published: May 2005

AbstractLiquid‐liquid equilibrium data for the polystyrene‐cyclopentane binary system and the polystyrene‐cyclopentane‐cyclohexane ternary system were measured by observing the cloud points at the temperature range in which the systems showed their lower critical solution temperature. The experimental liquid‐liquid equilibria were correlated successfully by the UNIFAC‐FV model with adjustable parameters.
Study of dielectric relaxation of an epoxide oligomer by a direct current transient method
Authors: Koike Tsuneo 
Published: May 2005

AbstractDielectric α‐relaxation of a bisphenol‐A type epoxide oligomer has been investigated in the vicinity of the glass transition temperature (Tg) by the direct current (DC) transient method. The logarithm of the DC transient current for the oligomer was well approximated by the third order function of the logarithm of time. The complex dielectric constant was calculated through the Fourier transformation of that approximation function according to Simpson's integration rule in a frequency range of 10−5 − 1 Hz. At the temperature around the Tg (45°C), the dielectric α‐relaxation process of the oligomer was found to be governed by the Havriliak‐Negami equation. The relationship between the DC conductivity (σ) and the dielectric relaxation time (τ), σ·τm = const, is valid near and above the Tg of the oligomer. The DC transient current method combined with the DC conduction and the dielectric bridge measurements is considered to be a practical tool for analyzing the dielectric α‐relaxation process of the epoxide oligomer over a wide frequency and temperature range.
The leveling of thermosetting waterborne coatings. Part I: Observation of leveling process
Authors: Kojima Shunji , Moriga Toshinori , Takenouchi Ken 
Published: May 2005

AbstractA modified observation system for the leveling process of a coated fluid is proposed, and the observation results are presented and compared with previous results. For the thermosetting waterborne coatings, the theory of Orchard, et al., and ones based on it are not applicable and fail to give even a qualitative description. The theory of Overdiep was found to be reasonable. However, it was insufficient to predict the leveling performances of coatings without experimentation. Qualitatively, the original theory suggests the possibility of the reappearance of surface ripples, in other words, the occurrence of the negative amplitude in the surface ripples during the course of leveling, although little data were presented regarding the phenomenon. It was found here that added co‐solvent plays an important role on the leveling rate and also the occurrence and the control of the negative amplitude of the surface ripples. These are thought to relate closely to the volatility of the co‐solvent and the composition of the solvent residue in the coated film during the leveling process.
Transport studies in poly(methyl methacryalate‐g‐urethane)
Authors: Sreenivasan K. 
Published: May 2005

AbstractTransport studies of two organic liquids, toluene and n‐hexane, have been performed in polyurethane and poly (methyl methacrylate‐g‐urethane). A high degree of selectivity in the permeation of these two liquids has been achieved by MMA grafting. A near perfect separation has been realized by grafting of MMA to 28%.
Temperature dependence of the nucleation effect of sorbitol derivatives on polypropylene crystallization
Authors: Kim C. Y. , Kim Y. C. , Kim S. C. 
Published: May 2005

AbstractThe temperature dependence of the nucleation effect of three sorbitol derivatives on the crystallization of isotactic polypropylene (iPP) was studied by means of isothermal crystallization kinetic analysis. Isothermal crystallization thermograms obtained by differential scanning calorimetry (DSC) were analyzed based on the Avrami equation. The Avrami analysis for the nucleated iPP was carried out with DSC data collected to 35% relative crystallinity, and the rate constants were corrected assuming the heterogeneous nucleation and three dimensional growth of iPP spherulites. A semi‐empirical equation for the radial growth rate of iPP spherulites was given as a function of temperature and was used to determine the number of effective nuclei at different temperatures. The number of effective nuclei in the nucleated samples was estimated to be 3 × 102 ∽ 105 times larger than that in the neat iPP. The logarithmic numbers of the effective nuclei decreased linearly with decreasing degree of supercooling in the range of crystallization temperatures tested. The temperature dependence of the effect of the nucleating agents on iPP crystallization was given quantitatively in terms of the deactivation factor defined as a fraction of the particles that are active at a particular temperature but inert at the temperature one degree higher. The nucleation activity and its temperature dependence are considered to be cooperative effects of many factors, including the dispersion and the physical or chemical nature of the agent as well as the interaction between the agent and the polymer. It is suggested that the temperature dependence of the effect of a nucleating agent should be treated as a characteristic of a given polymer/ nucleating agent mixture.
Manufacture of films displaying liquid‐crystalline structure
Authors: Gul′ V. E. , Sdobnikova O. A. , Peshehonova A. L. , Samoilova L. G. , Khanchech O. A. , Suvorova A. I. 
Published: May 2005

AbstractReported is an attempt to attain orientation of macromolecules during extrusion of films of cellulose derivatives that led to the liquid‐crystalline state of a polymer and resulted in enhanced film strength.
Process rheometers for molten plastics: A survey of existing technology
Authors: Dealy John M. , Broadhead Taras O. 
Published: May 2005

AbstractThere are many operations in the plastics industry where it is useful to be able to monitor the rheological properties of a melt as it is being processed. Such operations include polymerization, blending, compounding, and reactive extrusion. The design of such instruments poses major challenges, as there is a conflict between the need for rapid sample renewal and the desire for measurement accuracy. In‐line types, which are installed directly in the process flow, have a rapid response but must operate in an environment where temperature, pressure, and flow rate fluctuate in response to process upsets. On‐line types, which make use of a side stream and gear pump to feed the rheometer, allow for more freedom in the design of the rheometer but have an inherent signal delay due to the time required for melt to reach the rheometer. A variety of rheological sensors have been described in the patent and research literature, each with its unique advantages and disadvantages, and some of these are finding increased use in the plastics industry to improve product quality and process efficiency.
The mechanism of skin‐core morphology formation in extrudates of polycarbonate/liquid crystalline polymer blends
Authors: Beery D. , Kenig S. , Siegmann A. , Narkis M. 
Published: May 2005

AbstractThe mechanism of skin/core morphology development and LCP (liquid crystalline polymer) fibril formation in polycarbonate/LCP blends was studied. A certain minimum concentration of the LCP phase must be present for the formation of continuous LCP fibrils in the extrudates. A skin‐core morphology characterizes the PC/LCP extrudates. Short LCP fibrils are formed in the capillary converging entrance section, through the elongation of LCP domains and their coalescence. Continuous fibrils were formed in the skin of extrudates emerging from cylindrical capillaries, through the coalescence of the short fibrils, provided the shear stresses are high enough and the LCP viscosity is equal or lower than that of PC. Increasing capillary length enhances the LCP lateral migration and fibrils formation. The high interfacial tension stabilizes the LCP fibrils. In the core region the short fibrils recoil or breakup, resulting in spherical or elongated droplets. Long and continuous fibrils cannot be formed in a zero length capillary, even at high flow rates.
Solid state extrusion of vinylidene fluoride (VF2)/vinylidene trifluoride (VF3) copolymers. II: Structure development
Authors: Lee J. S. , Cakmak M. 
Published: May 2005

AbstractCopolymers of vinylidene fluoride (VF2) and vinyltrifluoride (VF3) exhibit Curie transition temperatures well below their melting points. Above these endothermic transitions, they soften and this behavior helps in their solid state extrudability. In this paper, the effects of extrusion speed, temperature, and draw ratio on structure development in 60/40 and 72/28 VF2/VF3 copolymer compositions are presented. With the increase of extrusion draw ratio the Curie transition temperature of the extrudates decreased and melting temperature increased. This behavior suggested that the chains in the crystalline regions contain higher levels of conformational defects while overall crystallinity is increased. Unoriented polymers were optically opaque and extrudates were found to be transparent as a result of breakdown on the superstructural level which decreases the scattering effects in the visible wavelength range. The micro beam WAXS studies on the samples taken from the entrance of the dies revealed that the unoriented core is surrounded by alternating unoriented and oriented layers close to the core. The remainder of the skin layers are found to be oriented with local symmetry axes and main chain orientation being parallel to the die wall surface. The regions that are found to be oriented were also found to be optically translucent and unoriented regions were optically opaque. This structure turns uniformly transparent–and thus oriented‒as the polymer enters the die. The existence of layered structure suggests that highly localized yielding occurs during early states of deformation at the converging entrance region of the die. Examination of the radial structural variation in extrudates with micro beam X‐ray diffraction technique revealed that the local symmetry axes are tilted away from the extrusion direction and this tilt angle reduces at the sample macro‐symmetry axis at the core of the samples. This indicated that the tilted structure developed at the converging entrance region is partially preserved through the die. While the orientation of local symmetry axes varies from skin to core in the extrudates, the orientation of chains with respect to these local symmetry axes remains relatively unaffected.
The reactive modification of polyethylene. I: The effect of low initiator concentrations on molecular properties
Authors: Suwanda D. , Balks S. T. 
Published: May 2005

AbstractCommercial samples of high density, linear low density, and low density polyethylene were modified by injection of low concentrations of free radical initiator during extrusion. Molecular properties monitored included molecular weight distribution, degree of unsaturation, and branching. When the polyethylene teed to this reactive extrusion process had similar values of Mw, but varying polydispersity, degree of branching and degree of unsaturation, the magnitude of the change in molecular weight distribution was found to be in the following order: HDPE 1 > LDPE2 > LLDPE. In general, terminal vinyls enhanced molecular weight increase, and branching promoted degradation. However, for a second high density polyethylene sample with Mw = 154,000 (rather than the previous sample's Mw of 85,600), the change in molecular weight distribution was small and located at the lower molecular weight end. This work provided data for the kinetic model development detailed in Part II.
Processing/performance relationships considering voids in structural reaction injection molding
Authors: McGeehan John A. , Gillespie John W. , Hulway Joseph A. 
Published: May 2005

AbstractThe causes of void content and its resulting effect on the material properties of structural reaction injection molded (SRIM) composites were investigated. Plaques were molded under different combinations of five two‐level factors, and the resulting effect of each factor on void content was determined. The geometry of the glass reinforcement had the largest effect, as woven mats caused double the void content of random mats. Evacuating the mold cavity proved to greatly reduce void content as well. Varying the injection rate and shot size had little effect. Material property testing was conducted on groups of specimens with similar void content. Tension testing revealed no decrease in strength with increasing void content. One million cycles of tension‐tension fatigue at 20% of the ultimate strength caused no decrease in strength at any void content, while fatigue at 30% caused premature failure. Impact testing showed that only very high void contents had a substantial effect on performance. Environmental conditioning showed moisture absorption proportional to void content and furthermore significantly reduced the residual tensile strength after a single thermal cycle to 0°C. These results suggest that void content in conjunction with a weak interface may have been responsible for limiting material properties.
Acrylic acid containing copolymers as reactive compatibilitzers for toughening nylon 6
Authors: Lu M. , Keskkula H. , Paul D. R. 
Published: May 2005

AbstractNylon 6 has been toughened by rubber particles that were dispersed within the matrix via additives that physically interact with the elastomer phase but chemically react with the polyamide phase. To disperse a core‐shell impact modifier having a poly(methyl methacrylate) or PMMA shell, most of the work presented is based on the use of a styrene/acrylic acid copolymer containing 8 wt% acrylic acid, SAA8. SAA8 is miscible with PMMA and should located in the PMMA grafted chains of the impact modifier while chemically reacting with the nylon 6 matrix; hence, it should aid in both the dispersal and strenghtening the modifier‐matrix interface. Microscopy and mechnical properties confirm that SAA8 does function in this way but less effectively than styrene/maleic anhydride copolymers, which are also miscible with PMMA but evidently react more effectively with the polyamides. The use of ethylene/acrylic acid copolymer for dispersal of the coreshell impact modifier and a styrene/ethylene‐butene/styrene block copolymer in nylon 6 was also briefly considered. Low‐temperature toughness of the blends proved to be a much more critical test of the effectiveness of such additives than room temperature impact strenght.
Relating the heat‐of‐mixing of analog mixtures to the miscibility of hydrogen‐bonding polymers
Authors: French R. N. , Walsh J. M. , Machado J. M. 
Published: May 2005

AbstractThe prediction of polymer/polymer miscibility is addressed using analog calorimetry and molecular modeling. For each polymer, an analog compound representing one or two repeat units was chosen. Heat‐of‐mixing was measured for liquid mixtures of analog compounds and then used in a binary interaction model to predict polymer miscibility. Specifically, we have measured exothermic heats‐of‐mixing for 4‐ethyl phenol, an analog of poly(vinly phenol), with several analogs containing ether, ester, or ketone functional groups. The exothermic heat‐of‐mixing results are consistent with the observed miscibility of poly(vinyl phenol) with polymers containing these functional groups. Using interaction parametes derived from the analog calorimetry in the binary interaction model or using premixes of 4‐ethyl phenol in ethyl benzene, we correctly predict the magnitude and relative order of the fraction of vinyl phenol units in copolymers with styrene required for miscibility with poly(methyl methacrylate), polyacetal, and a polyketone. the miscibility trends for poly(vinyl phenol) blends predicted from analog calorimetry and the binary interaction model are in reasonable agreement with those predicted from the association model of Painter and Coleman, despite the different bases of the two approaches. We have used molecular modeling to complement the analog calorimetry and to assess steric effects on hydrogen‐bonding ability for models of poly(n‐butyl acrylate) and poly(t‐butyl acrylate) with phenol. The modeling results suggest that, in some cases, steric effects and the three‐dimensional structure of the polymer can significantly influence the hydrogen‐bonding ability of polymers relative to their analogs.
J‐Rcurve calculation with the normalization method for toughened polymers
Authors: Zhou Z. , Landes J. D. , Huang D. D. 
Published: May 2005

AbstractThe method of normalization is used to develop theJ‐Rcurve fracture toughness characterization for polymeric materials. This method can developJ‐Rcurves directly from load vs. displacement records without a need for an on‐line crack monitoring system. It was used previously to developJ‐Rcurves for metallic materials and is applied here for the first time to polymer materials. Single edge notched bend specimens of rubber toughened nylon 6/6 and rubber toughened amorphous nylon are used in this study. TheJ‐Rcurves from the method of normalization are compared with the results obtained from the multiple specimen method of ASTM Standard E813. The results show that the method of normalization gives reasonableJ‐Rcurves; both methods show agreement over the earlyJ‐Rcurve region. In addition theJIcvalues are determined for each method and compared. Based on this work it is suggested that the method of normalization could be used as a general test method to developJ‐Rcurves for polymeric materials.