bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of isotactic and syndiotactic polypropylene as matrix materials of hybrid composites
Authors: Stricker F. , Mülhaupt R. 
Published: April 2004

AbstractThe structure/property relationships and morphology of glass bead–reinforced syndiotactic and isotactic polypropylene composites containing 0 to 20 vol% thermoplastic elastomer (TPE) were studied. Polystyrene‐block‐poly(ethylene‐co‐butylene)‐block‐polystyrene (SEBS) and the corresponding block copolymer grafted with maleic anhydride (SEBS‐g‐MA) were used as the TPEs. The Young's modulus of hybrid composites based on s‐PP showed no dependence on the type of TPE used, whereas i‐PP hybrid composites containing SEBS had a higher Young's modulus than composites containing SEBS‐g‐MA. A comparison of the data with theoretical predictions of Young's modulus and tensile yield stress gave strong evidence of two different morphologies for the hybrid composites. The increasing tensile yield stress of s‐PP hybrid composites and i‐PP hybrid composites containing SEBS‐g‐MA was attributed to an interlayer formation and in‐situ encapsulation of glass beads, which resulted in core‐shell particles with improved interfacial interactions. In contrast, SEBS in hybrid composites based on i‐PP formed a separate dispersed phase. Crystallization and scanning electron microscopy studies also provided evidence of a core‐shell morphology for hybrid composites based on s‐PP. Results of lap‐shear and peel tests confirmed strong interfacial interaction between glass and SEBS‐g‐MA and between SEBS and s‐PP as well as i‐PP. Only above a critical volume fraction did the TPE provide significant improvement of the notched Izod impact strength of hybrid composites based on s‐PP or i‐PP.
Effects of polyethylenes on the morphology, barrier, and impact properties of polyethylene/modified polyamide blends
Authors: Yeh Jen‐Taut , Jyan Chau‐Fa 
Published: April 2004

AbstractAn investigation of the influence of the melt shear viscosities of polyethylenes (PE) on the morphology, barrier, and impact properties of polyethylene/modified polyamide PE/MPA bottles is reported. The melt shear viscosities of polyethylenes exhibited a significant influence on the deformation and morphology of MPAs during the blow molding of polyethylene/modified polyamide (PE/MPA) blends. Some obscure MPA laminars were observed in PE/MPA bottles as the value of melt shear viscosity ratio of MPA to PE (VR) deviated significantly from the “optimum” range. In contrast, clear and elongated laminar structures of MPAs were found as the value of VR reached the “optimum” range. Similarly, the total impact energies (Ets) and permeation barrier properties of PE/MPA samples improved with the value of VR until it reached the “optimum” range, after which value Ets and permeation barrier properties of PE/MPA samples reduced significantly with further increasing VR. Possible mechanisms accounting for these interesting behaviors are presented in this study.
Liquid‐crystallization induced reactions. Microstructure and morphology of copolyesters synthesized by transesterification of PET with some LCP monomers
Authors: Tonti Maria Silvia , Masseti Marco , Poli Giovanna , Paci Massimo , Magagnini Pierluigi , Forte Claudia , Veracini Carlo Alberto 
Published: April 2004

AbstractThe transesterification of poly(ethylene terephthalate) (PET) with a mixture of sebacic acid (S), 4,4′‐diacetoxybiphenyl (B) and 4‐acetoxybenzoic acid (H), carried out under conditions expectedly favoring the formation of a p(ET‐SBH) random copolyester, produces biphasic materials with an isotropic matrix and a highly fibrous, liquid‐crystalline dispersed phase. Spectroscopic, calorimetric, microscopic and diffractometric characterization of the fractions separated by solvent extraction has shown that the two phases consist of practically random copolyesters having different average composition. Interestingly, the degree of aromaticity of the matrix is even lower than that of PET, whereas that of the minor phase is appreciably higher than that calculated for the SBH copolyester that would be produced from the monomer mixture in the absence of PET. This unexpected result is interpreted on the basis of an enthalpy‐driven progressive diffusion of aromatic‐rich material toward the mesophase which segregates at an early stage of the polycondensation within the isotropic mixture of low molar mass oligomers initially produced by the PET acidolysis. Thus, an increasing differentiation, rather than an equilibration, of the composition of the two phases takes place. It is noteworthy that, despite the strong compositional difference, the two phases of these products show fairly good compatibility and interfacial adhesion.
Experimental study and computer simulation of the effect of spider shape on the weld‐lines in extruded plastic pipe
Authors: Huang Y. , Prentice P. 
Published: April 2004

AbstractWeld‐lines, also referred to as spider‐lines or knit‐lines, are regions in the wall of an extruded plastic pipe, running the whole length of the pipe, at which there is a change in dimension and a possible reduction in mechanical properties. Weld‐lines result from the flow of the polymer melt around the supports (spiders) that hold the metal core to the outer die assembly in an in‐line annular die. This work examines the fatigue life and the tensile strength of weld‐lines created by a conventionally shaped “torpedo” spider and four modified spider shapes. It is demonstrated that the shape of the spiders has a dramatic effect on the fatigue life of weld‐lines while having a minimal effect on the tensile strength in static loading. The experimental results show that the fatigue life of the weld‐line produced by one of the four new shaped spiders is significantly higher than that of a conventionally shaped spider. Numerical simulations of the flow field around this new and conventional spiders were carried out using the package FIDAP® based on the finite element method (FEM). The simulation results provide a good explanation for the experimental observations and show that the newly designed shape of spider can give rise to a higher relative fatigue life of the weld‐line when compared with that of the bulk material than does the conventional spider.
The effect of temperature on the observed flow‐induced structure in semidilute solutions of gently solubilized starches
Authors: Carriere C. J. , Loffredo A. R. 
Published: April 2004

AbstractThe effect of temperature on the unexpected shear‐thickening behavior exhibited by semidilute solutions of waxy maize starch during a repeated shear‐loop experiment was evaluated. Shear‐thickening behavior, characterized using power law models, was observed for waxy maize starch, but not for normal maize starch at the same concentration. The shear‐thickening region was observed for waxy maize starch at temperatures ranging from 25°C to 80°C and shear rates from 2–100 s−1 during the initial part of the shear‐loop experiment. For waxy maize starch, the power law exponent, n, was found to be 0.539 ± 0.017 in the shear‐thinning region. For normal maize starch, the value of n was found to be equal to 0.751 ± 0.015 and only shear‐thinning behavior was observed. The values of n for both waxy maize and normal maize starch were found to be temperature independent within the precision of the experimental measurements. The differences in n indicate the differences in the conformational dynamics of waxy maize and normal maize starches in solution.
The interfacial tension between a thermotropic liquid crystalline copolyester and polyethersulfone: A comparison of methods
Authors: Machiels A. G. C. , Busser R. J. , Van Dam J. , De Boer A. Posthuma 
Published: April 2004

AbstractThree dynamic methods to determine the interfacial tension between the thermotropic liquid crystalline polymer (TLCP) Vectra A900 and polyethersulfone were evaluated: (1) thread breakup, (2) fiber retraction and (3) dynamic shear rheometry. The thread breakup and retraction methods, were suitable for measuring the interfacial tension, provided that the shear thinning flow behavior of the TLCP was taken into account. The viscosity of the TLCP during breakup or retraction was estimated from steady‐shear measurements at the observed overall rate of deformation during growth of capillary instabilities or during retraction. The calculation of the interfacial tension from breakup rates of TLCP threads was improved by accounting for transient flow behavior during distortion growth using a single‐element Maxwell model. Determination of the interfacial tension by oscillatory shear measurements on TLCP/PES dispersions using the emulsion model of Palierne, was not applicable for this system. Only for dispersions containing low TLCP volume fractions (e.g. 9 vol%) was there reasonable agreement between the emulsion model and measurements. At higher volume fractions agreement was poor, possibly because of different dynamic flow behavior of the TLCP in the pure form and in blends. The interfacial tension values obtained from thread breakup and fiber retraction ranged from 4 to 6 mN/m, which demonstrate that in‐situ determination of the interfacial tension is possible for blends containing TLCPs, despite their complex flow behavior.
Chain orientation in sheared molten poly(ethylene oxide) fractions by measurement of infrared dichroism
Authors: Skytt M.‐L. , Jansson J.‐F. , Gedde U. W. 
Published: April 2004

AbstractRheo‐infrared spectroscopy was used to study the development of orientation of molten narrow molar mass fractions of poly(ethylene oxide) [molar masses between 18,000 and 120,000 g/mol] during non‐Newtonian shear flow at shear rates between 2 and 270 s−1 and temperatures between 75 and 100°C. The steady state degree of orientation [expressed as the Hermans orientation function (fss)] reached a saturation level with increasing shear rate; fss increased with increasing molar mass (M) according to fss = C1 − C2/M (C1 and C2 are coefficients; the latter depended on shear rate and temperature). The coefficient C1 (fss) for a polymer with infinite molar mass took a universal value close to 0.05 for the temperatures and shear rates used. Under large shear stresses, the relationship between stress and orientation deviated markedly from linearity. The time to establish a steady state level of orientation was proportional to M1/2. The recovery of the isotropic state after the cessation of shear could initially be described by a simple exponential relaxation law: f ∝ e, where τρ is the relaxation time. The latter showed a weak molar mass dependence according to τr ∝ M0.6 and an Arrhenius temperature dependence with an activation energy of ∼60 kJ/mol. The relaxation of the shear stress after the cessation of shear was more rapid than the recovery of the isotropic state.
In‐process control of epoxy composite by microdielectrometric analysis. Part II: On‐line real‐time dielectric measurements during a compression molding process
Authors: Stephan F. , Duteurtre X. , Fit A. 
Published: April 2004

AbstractThe curing of a fiberglass epoxy composite based on diglycidyl ether of bisphenol A (DGEBA) with dicyanodiamide (DDA) as the hardener and imidazole as the catalyst agent was analyzed using microdielectrometry. The curing behavior of thick epoxy composite parts was examined in a production environment for compression molding process. The particular focus of this paper is to present the method used to collect on‐line real‐time conversion measurements during an epoxy/fiberglass composite cure. For this purpose, temperature and ionic conductivity profiles during industrial moldings of a thick epoxy part were recorded. Corresponding conversion profiles were deducted from a previous empirically established correlation and discussed in terms of cure gradients as a function of the through‐the‐thickness location and of the cure cycle time.
Phase behavior of blends of poly(ethylene terephthalate) with liquid‐crystalline polymers
Authors: Magagnini Pierluigi , Tonti Maria S. , Masseti Marco , Paci Massimo , Minkova Lilia I. , Miteva Tsenka T. 
Published: April 2004

AbstractPoly(ethylene terephthalate) (PET) was melt blended with several liquid‐crystalline polymers (LCPs), both with and without Ti(OBu)4 catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra‐A950, Rodrun LC‐5000, Rodrun LC‐3000, and a laboratory copolyester of sebacic acid (S), 4,4′‐diacetoxybiphenyl (B), and 4‐acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by differential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET‐rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase.
Isothermal and non‐isothermal crystallization kinetics of polyethylene terephthalate: Mathematical modeling and experimental measurement
Authors: Verhoyen O. , Dupret F. , Legras R. 
Published: April 2004

AbstractResults obtained by differential scanning calorimetry have been used to develop a macro‐kinetic model for the crystallization behavior of semicrystalline polymeric materials. Our model, which takes into account the effects of induction time, final degree of crystallinity and secondary crystallization, describes both isothermal and non‐isothermal crystallization kinetics, including cold‐ and melt‐crystallization. Experimental data obtained with Polyethylene terephthalate in a wide range of thermal conditions compare well with predictions.
Fluid mechanics analysis of a two‐dimensional pultrusion die inlet
Authors: Sharma D. , McCarty T. A. , Roux J. A. , Vaughan J. G. 
Published: April 2004

AbstractFluid mechanics plays an important role in many manufacturing processes including the pultrusion of composite materials. The analysis of fluid mechanics problems generally involves determination of quantities such as pressure and velocity. During the pultrusion process, the short, tapered inlet region of the pultrusion die experiences a significant amount of fluid resin pressure rise. The quality of a pultruded product can be affected by the amount of pressure rise in the pultrusion die inlet. Void formation can be suppressed and good fiber “wet out” achieved by a sufficiently high pressure rise in the pultrusion die inlet region. In this study the change in fluid resin pressure rise as a function of die entrance geometry is investigated by developing a finite element model based on the assumptions of Darcy's law for flow in porous media. The momentum equations are combined with the continuity equation to save computational time and memory. A Galerkin weighted residual based finite element method is developed to solve the resulting equation. This model is capable of predicting the pressure rise in the tapered inlet region of the pultrusion die as well as the straight portion of the die. By varying the size of the preform plates the thickness of the fiber/resin matrix approaching the die inlet can be varied. The finite element model predicts the impact of changing the preform plate size on the fluid resin pressure rise in the pultrusion die. The effect of varying the wedge angle for a linearly tapered die inlet region is also studied using this model. The results in this work can be useful for designing a pultrusion die system.
The effect of a new type of pin mixing section on the performance of a single‐screw extruder
Authors: Yao W. G. , Takahashi K. , Koyama K. , Yamashita Y. 
Published: April 2004

AbstractThe effect of a holed‐pin mixing section on the performance of a single screw extruder was investigated and compared with a free flight and a normal pin mixing section, using a practical single‐screw extruder. The effect of axial distance between two pins in a holed‐pin mixing section on performance was also studied. Mixing ability was quantified using the statistical approach of carbon black concentration distribution in the extruded film mixed with a carbon black masterbatch. The results indicate that a free flight gives the lowest melt temperature rise, pressure drop, and driver power, but the worst mixing; a holed‐pin mixing section has better mixing ability, lower melt temperature rise, and lower driver power than a normal pin mixing section does; the value of the pressure drop of the two types of pin mixing sections is approximately identical. A longer axial distance between the two pins in a holed‐pin mixing section gives better mixing and lower melt temperature rise than a shorter one; however, when the distance is longer than a critical value, the improvement of mixing is not so outstanding; for different axial distances between two pins, no great change in pressure drop was found and the extrusion throughput has almost no great relation to the axial distance.
New process for producing an extrusion laminated film without any chemical primer—non anchor coating extrusion laminating process
Authors: Hayashida H. , Ishibashi F. , Takahata H. , Nishio T. , Gotoh Y. , Sato Y. 
Published: April 2004

AbstractA new process, the Non Anchor Coating Extrusion Laminating Process for producing an extrusion laminated film without any chemical primer, was investigated. Good adhesive properties were obtained by combining an ozone treatment of a molten polyethylene (LDPE) web and an activation treatment of the polyamide (ONy) substrate film. The adhesion mechanism induced by the new process was studied by FT‐IR, ESCA and extraction of unreacted polyamide from the laminated samples. The peel strength between the ONy and LDPE laminated films produced with this process was greater than that for laminated film made with a conventional lamination process using anchor coating agents. A model of the adhesive mechanism is proposed. Hydrogen and covalent bonds through oxygenated functional groups are responsible for the enhanced adhesion.
Transport properties of methanol in blends of a liquid crystalline copolyester and polyethersulfone
Authors: Wiberg G. , Hedenqvist M. S. , Boyd R. H. , Gedde U. W. 
Published: April 2004

AbstractData for the diffusivity and solubility of methanol in blends of polyethersulfone (PES) and a liquid crystalline copolyester (polyhydroxy‐benzoic acid (73 mol%)‐co‐hydroxy‐naphthoic acid (27 mol%)) (LCP) are reported. Samples taken from injection molded and compression molded specimens over a wide composition range were studied by gravimetry (sorption and desorption), dielectric spectroscopy, differential scanning calorimetry and scanning electron microscopy. The sorption of methanol in PES led to the formation of an ordered phase. The sorption curves were S‐shaped and they could be described by a diffusion model assuming a concentration‐dependent diffusivity and time‐dependent boundary conditions. The solubility of methanol in the blends was strictly proportional to the PES content. The zero‐concentration‐diffusivity decreased strongly with increasing LCP content and it was dependent on the morphology. Injection molding yielded samples with a fibrillar LCP phase with a greater continuity of the PES component and a high diffusivity (in relative terms). Compression molding led to samples with a more continuous LCP component even at low LCP contents and a low diffusivity.
The role of specific interactions and transreactions on the compatibility of polyester ionomers with poly(ethylene terephthalate) and nylon 6,6
Authors: Boykin Timothy L. , Moore Robert B. 
Published: April 2004

AbstractThe compatibility of polyester ionomers with polar polymers (i.e., poly(ethylene terephthalate) and nylon 6,6) is under investigation for their potential use as minor component compatibilizers. Binary blends have been prepared by both solution and melt‐mixed methods to determine the effect of melt‐processing on blend compatibility. The effect of the sulfonate group and counterion type on compatibility was evaluated by blending sulfonated and nonsulfonated forms of the amorphous polyester ionomer with both nylon 6,6 and poly(ethylene terephthalate). The melting point and phase behavior of the blends were determined by differential scanning calorimetry (DSC) and environmental scanning electron microscopy (ESEM), respectively. A comparison of the melting behavior between the melt and solution blends suggests compatibility due to specific interactions for the ionomer/nylon 6,6 blends, and transesterification for the ionomer/poly(ethylene terephthalate) blends. The phase morphology of the melt blends is consistent with the results obtained by DSC analysis.
Low‐rate dynamic contact angles on polystyrene and the determination of solid surface tensions
Authors: Kwok D. Y. , Lam C. N. C. , Li A. , Zhu K. , Wu R. , Neumann A. W. 
Published: April 2004

AbstractLow‐rate dynamic contact angles of 13 liquids on a polystyrene polymer are measured by an automated axisymmetric drop shape analysis – profile (ADSA‐P). It is found that 7 liquids yielded non‐constant contact angles, and/or dissolved the polymer on contact. From the experimental contact angles of the other 6 liquids, it is found that the liquid‐vapor surface tension times cosine of the contact angle changes smoothly with the liquid‐vapor surface tension, i.e. γlvcosθ depends only on γlv for a given solid surface (or solid surface tension). This contact angle pattern is in harmony with those from other inert and non‐inert (polar and non‐polar) surfaces (7–13, 24–26). The solid‐vapor surface tension calculated from the equation‐of‐state approach for solid‐liquid interfacial tensions (33) is found to be 29.8 mJ/m2, with a 95% confidence limit of ±0.5 mJ/m2 from the experimental contact angles of 6 liquids.
Transient elongational viscosity of LLDPE/LDPE blends and its relevance to bubble stability in the film blowing process
Authors: Micic P. , Bhattacharya S. N. , Field G. 
Published: April 2004

AbstractTransient elongational viscosity of linear low density polyethylene (LLDPE) and its blends with 10% and 20% of low density polyethylene (LDPE) was measured at two temperatures by a constant strain rate elongational rheometer. In addition, the performance of the blends in the film blowing process was assessed in terms of bubble stability at two processing temperatures. An operating window for stable bubble production was determined. The elongational viscosity measurements on blends revealed stronger strain hardening characteristics at a higher temperature of testing. These results correlate favorably with findings from a bubble stability investigation where it was found that the size of the operating window for stable bubble production increased with increasing extrusion temperature. This work seems to indicate that increasing processing temperature during the film blowing of LLDPE‐rich blends could lead to a processability improvement of these blends as far as bubble stability is concerned.