bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersed phase morphology of impact PP copolymers. Effects of blend composition as determined by TREF
Authors: Zacur Ruth , Goizueta Graciela , Capiati Numa 
Published: April 2004

AbstractPolypropylene (PP) blends, commercially known as “impact polypropylene copolymers” (IPC), are produced by a sequential gas phase polymerization process. The final product is a complex mixture of polypropylene (PP) and a range of ethylenepropylene copolymers (EPC) with different ethylene contents. In the present work, the composition of three different IPC was estimated by performing a step elution mode Analytical Temperature Rising Elution Fractionation (TREF) separation. The recovered fractions were analyzed by Differential Scanning Calorimetry (DSC), Size Exclusion Chromatography (SEC) and Fourier Transform Infrared Spectroscopy (FTIR). The morphology was examined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Amorphous EPC were isolated in an independent way in order to perform a more careful characterization. The distinct particle size and shape of the dispersed phase for different IPC was interpreted in terms of the molecular characteristics of the blend components and their compositions.
Recycling of poly(ethylene terephthalate) into closed‐cell foams
Authors: Japon Sonia , Leterrier Yves , Månson Jan‐Anders E. 
Published: April 2004

AbstractThe increase of the elongational viscosity of recycled poly(ethylene terephthalate) (PET) is investigated with the aim of producing closed‐cell foams by means of a cost‐effective reactive extrusion technique. A recycled PET grade containing controlled contamination levels of polyvinyl chloride (PVC) and poylethylene (PE) is selected, and compared with virgin bottle‐grade PET as a reference. Reactive processing with a tetrafunctional epoxy additive induces randomly branched molecules with a lower degree of branching in recycled PET than in virgin PET, as shown by a molecular structure analysis. The corresponding increase in elongational viscosity is related to foaming experiments performed using supercritical CO2 in a pressurized vessel. Observations of foam microstructures reveal that modified virgin PET forms closed‐cell structures under a large variety of foaming conditions, as opposed to unmodified virgin and recycled PET, which collapse as a result of insufficient elongational resistance. Closed‐cell foams are also obtained using modified recycled PET, providing that the temperature at which the pressure is released is lowered to 260°. Recycling of PET into closed‐cell foams is thus achieved, although the processing window is slightly reduced compared to virgin PET.
Fracture behavior of styrene‐ethylene‐propylene rubber‐toughened polypropylene
Authors: Wei G.‐X. , Sue H.‐J. 
Published: April 2004

AbstractThe morphology and fracture behavior of isotactic polypropylene toughened by styrene‐ethylene‐propylene (PP/SEP) were investigated. The SEP rubber, having an average particle size of 0.2 µm, is found to be well dispersed in the PP matrix. The fracture toughness of SEP‐modified PP is greatly improved. The toughening mechanism investigation shows that a widespread crazing zone is generated in the crack tip damage zone. An intense narrow damage band in the center of crazed zone is formed. Crazing and shear yielding are found to be the dominant toughening mechanisms in PP/SEP. The crazes are initiated only by large SEP particles in the blend. The small SEP particles (< 0.3 µm) can neither cavitate nor trigger crazing. As a result, large scale shear deformation is suppressed in this blend. These findings are consistent with the notion that the crack tip plane strain constraint has to be relieved in magnitude in order for the deviatoric stress to reach a critical value for widespread shear banding.
Isothermal and nonisothermal crystallization kinetics of nylon 10 12
Authors: Li Yongjin , Zhu Xinyuan , Yan Deyue 
Published: April 2004

AbstractThis article studied the crystallization behaviors of a newly industrialized polyamide, Nylon 10 12, under isothermal and nonisothermal conditions from the melt. A differential scanning calorimeter (DSC) was used to monitor the energetics of the crystallization process. During isothermal crystallization, relative crystallinity develops in accordance with the time dependence described by the Avrami equation with the exponent n=2.0. For nonisothermal studies, several different analysis methods were used to describe the crystallization process. The experimental results show that the Ozawa approach cannot adequately describe the nonisothermal crystallization kinetics. However, Avrami treatment for nonisothermal crystallization is able to describe the system very well. The calculated activation energy is 264.4 KJ/mol for isothermal crystallization by Arrhenius form and 235.5 KJ/mol for nonisothermal crystallization by Kissinger method.
Polymer‐polymer miscibility study for plastic gradient index optical fiber
Authors: Lee Bongsoo , Choi Won Y. , Walker James K. 
Published: April 2004

AbstractGradient index (GRIN) materials have many applications in optical fiber communication, imaging and optical instruments. Almost all GRIN optical fiber or lenses are made of glass, which has limitations due to poor flexibility, difficulty in processing and high price. Therefore, polymers are being investigated to produce a GRIN material that solves the problems of GRIN glass. In this study, the optical transmittance and refractive indices of three kinds of miscible copolymers of Methyl Methacrylate/Benzyl Methacrylate, Methyl Methacrylate/Trifluoro‐ethyl Methacrylate and Benzyl Methacrylate/Trifluoro‐ethyl Methacrylate were examined.
Melting mechanism of a starved‐fed single‐screw extruder for calcium carbonate filled polyethylene
Authors: Thompson M. R. , Donoian G. , Christiano J. P. 
Published: April 2004

AbstractA study of starved‐fed single screw extrusion was initiated to understand the relation between its distinctive melting mechanism and the improved mixing capabilities attained during compounding of a calcium carbonate filler into HDPE. Experiments were carried out in a 63.5 mm single screw extruder, examining the effect of degree of starvation on a conventional and barrier feed screw. Interest was focused on the mixing/melting mechanism of starved‐fed solids‐conveying as it affects the size and number of filler agglomerates observed in the extrudate. The melting performance of both feed screws was examined using pressure and temperature measurements down the screw length as well as direct inspection of the polymer in the screw channel via rapid screw cooling. Both screws showed improved mixing quality with increased starvation.
The weldability of polypropylene strapping tape
Authors: Oliveira M. J. , Hemsley D. A. 
Published: April 2004

AbstractPolypropylene strapping tape, produced with different draw ratios and types of surface embossing, was welded with a standard semi‐automatic strapping machine. The effect of the welding temperature, surface profile of the sealing tool and the tape properties (draw ratio and embossing pattern) on the microstructure and the joint strength was studied. A near optimal temperature range was identified. The draw ratio of the tape was found to influence the weld efficiency.
Chemical and physical blowing agents in structural polyurethane foams: Simulation and characterization
Authors: Modesti M. , Adriani V. , Simioni F. 
Published: April 2004

AbstractPhysical blowing agents such as n‐pentane and methyl formate and, for comparison, chemical blowing agents such as water were used to prepare structural polyurethane rigid foams of different densities by reaction injection molding. Experimental runs were carried out with formulations based on oligomeric isocyanate and a mixture of polyether polyols. The constitutive equations for the vaporization rate of the two blowing agents and the polymerization kinetics data are reported. Experimental results were compared with the prediction of a simplified theoretical model, and they showed a satisfactory agreement in terms of temperatures and density profile. All the specimens were characterized by physical‐mechanical properties such as hardness, impact strength, flexural strength and elastic modulus and the results were reported in function of the densities. The best mechanical performance were obtained with the physical blowing agents, due to a better density distribution profile and a thicker skin layer.
The crystallization kinetics of polyamide 66 in non‐isothermal and isothermal conditions: Effect of nucleating agent and pressure
Authors: Won J. C. , Fulchiron R. , Douillard A. , Chabert B. , Varlet J. , Chomier D. 
Published: April 2004

AbstractThe crystallization kinetics of virgin and nucleated polyamide 66 was investigated in non‐isothermal and isothermal conditions, by use of DSC and high pressure dilatometry. In non‐isothermal conditions, at atmospheric pressure, the results were first analyzed using the Ozawa equation, leading to an Avrami exponent of 4 in the case of the virgin grade and 2.1 for the nucleated polyamide. However, experimental and calculated kinetics showed a difference in the ending part of the crystallization, likely due to a large secondary crystallization phenomenon. Thus, the relative crystallinities were normalized to extract the primary crystallization from the whole signal and analyzed using the Douillard/Kim equation. In isothermal conditions, at atmospheric pressure, the Avrami exponents were similar to the values obtained in non‐isothermal conditions for both virgin and nucleated grades. Furthermore, the crystallization under pressure was examined in terms of crystallization supercooling. In non‐isothermal conditions, the crystallization supercooling (ΔTc) increases when the cooling rate increases, but it is not affected by the pressure since the crystallization temperature increase is due to the equilibrium melting temperature rise. In isothermal conditions, the supercooling (ΔT) rises according to the increase of the pressure for the same crystallization temperature.
Thermoplastic apparent interpenetrating polymer networks of polyurethane and styrene/acrylic acid copolymer obtained by melt mixing. Structure‐property relationships
Authors: Vatalis A. S. , Delides C. G. , Grigoryeva O. P. , Sergeeva L. M. , Brovko A. A. , Zimich O. N. , Shtompel V. I. , Georgoussis G. , Pissis P. 
Published: April 2004

AbstractThermoplastic apparent interpenetrating polymer networks (thermoplastic‐AIPNs) were prepared at several compositions by melting and pressing of crystallizable polyurethane (CPU), based on butylene adipate glycol (BAG), and styrene/acrylic acid random copolymer (S/AA). Structure‐property relationships in the thermoplastic‐AIPNs were investigated by means of wide‐angle and small‐angle X‐ray scattering (WAXS, SAXS), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), thermally stimulated depolarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS) and several physico‐mechanical characterization techniques. The results obtained by the various techniques were critically compared to each other. They suggest that the two components show weak affinity to each other and that the thermoplastic‐AIPNs can be classified into two groups with high and low contents of CPU, showing essentially the behavior of CPU and S/AA, respectively. However, deviations from additivity and significant changes for several properties on addition of small amounts of either of the components suggest partial miscibility. Most of the results are explained by physical interactions of COOH‐groups of AA in S/AA with the ester groups of the flexible CPU blocks, which promote microphase separation in both the CPU and the S/AA components.
The production of a new partially biodegradable starch plastic by reactive extrusion
Authors: De Graaf R. A. , Janssen L. P. B. M. 
Published: April 2004

AbstractThe grafting of polystyrene onto dissolved starch in a twin screw extruder has been studied. This copolymerization was initiated using the thermal initiators benzoyl peroxide and K2S2O8. As end product a mixture containing polystyrene‐grafted starch, homopolymer of polystyrene and starch was obtained. Parameters like screw rotation rate, fully filled length of the extruder, wall temperature and throughput have been varied in order to obtain information about their influence on conversion, graft percentages and molecular weight of the materials formed. To increase the amount of graft points, maleic acid anhydride (MAH) was added resulting in an increased grafting of polystyrene onto starch. Graft percentages of 60% could be achieved. The total conversion of styrene could be controlled by adjusting extruder parameters like barrel temperature, fully filled length and initiator type. Conversions of 95% were found. Molecular weights of the polystyrene formed could be controlled by adding a chain transfer agent (dodecylmercaptan) to the styrene phase. In this way the molecular weight (Mn) of the styrenic part could be varied from 20,000 to 140,000. The experiments with the chain transfer agent showed that the grafting of polystyrene onto starch is a process occurring at the interface between the dissolved starch and the styrene phase.
Percolation phenomena in carbon black–filled polymeric concrete
Authors: Rejón L. , Rosas‐Zavala A. , Porcayo‐Calderon J. , Castaño V. M. 
Published: April 2004

AbstractPercolation in carbon black‐filled polymeric concrete, is discussed based on the measured changes in electrical conductivity and morphology of the composite at different concentrations of carbon black. The percolation threshold ranged between 6 and 7 wt% (based on resin weight) of carbon black. Above this concentration, the filler particles formed agglomerates in contact with each other, suggesting that the conduction process is nearly ohmic in nature. A power law predicted by percolation theory described the behavior of the conductivity as a function of carbon black content. Microscopic analysis showed the presence of a continuous structure formed by the polyester resin and carbon black, in which silica particles were embedded.
Comparative study of continuous‐power and pulsed‐power microwave curing of epoxy resins
Authors: Fu Bao , Hawley Martin C. 
Published: April 2004

AbstractThree epoxy reaction systems, diglycidyl ether of bisphenol A (DGEBA) with curing agents meta phenylene diamine (mPDA), diaminodiphenyl methane (DDM), and diaminodiphenyl sulfone (DDS), were cured with both pulsed‐power and continuous‐power microwave curing systems. Isothermal curing was conducted at three different temperatures for each reaction system with both pulsed‐power and continuous‐power microwave curing systems. Extent of cure was measured with Fourier Transform Infrared Spectroscopy (FTIR). The temperature characteristics, incident and reflected power patterns, and the reaction rates were compared between the two curing approaches. The incident power and reflected power of both curing processes were observed to reveal reaction status. Continuous‐power microwave curing produced noticeably higher reaction rates than pulsed‐power microwave curing.
The vibration welding of polycarbonate/acrylonitrile‐butadiene‐styrene blends to themselves and to other resins and blends
Authors: Stokes Vijay K. 
Published: April 2004

AbstractThe weldabilities of two commercial blends of polycarbonate (PC) and acrylonitrile‐butadiene‐styrene (ABS) to themselves and to several other resins and blends are assessed through 120 Hz vibration welds of 6.35‐ and 3.2‐mm‐thick specimens. While the thicker specimens of both blends have relative weld strengths of 83%, the thinner specimens in one of the grades have a lower relative weld strength of 73%. Welds of thicker specimens of both grades to PC have relative strengths of 85%. Again, welds of thinner specimens of one of the grades to PC have a lower relative strengths of 68%. Welds of the thinner specimens of this grade with ABS have relative strengths of 85%. Welds of this material with poly(butylene terephthalate) (PBT), a PC/PBT blend, modified poly(phenylene oxide), and a poly(phenylene oxide)/polyamide blend, have relative weld strengths of 45%, 26%, 76%, and 20%, respectively.
Physical properties of isobutylene based block copolymers
Authors: Tse M. F. , Wang H.‐C. , Shaffer T. D. , McElrath K. O. , Modi M. A. , Krishnamoorti R. 
Published: April 2004

AbstractPhysical, mechanical and thermal properties of a new class of isobutylene based model block copolymers are studied and contrasted with those of traditional thermoplastic elastomers based on polydienes and saturated polydienes (polyolefins) such as Kraton (or Vector) and Kraton G block copolymers. Melt state rheological and dynamic mechanical measurements confirm that thermodynamic interactions between polystyrene (S) and polyisobutylene (iB) or poly‐p‐tert‐butylstyrene (tbS) and iB are comparable to, if not larger than, those between S and polybutadiene (B) or S and ethylene/butene‐1 copolymer (EB). Physical properties for the S‐iB‐S and tbS‐iB‐tbS block copolymers, particularly the injection‐moldability and cut‐growth characteristics, are found to be considerably different from those found for the S‐B‐S and S‐EB‐S systems. We attribute this behavior to the longer entanglement chain length of iB compared with those for B and EB.
Elastomeric joint performance of PVC, VC, and FRC Pipes
Authors: Lu J. P. , Burn L. S. , Whittle A. J. 
Published: April 2004

AbstractFor rubber ring joints to resist plant root penetration in drier countries, it has been reported and promulgated into some national standards that a sufficiently high contact pressure between the rubber and the pipe must be maintained. The evaluation of the appropriate interfacial pressure to be used has been under discussion for some time and different values have been stated in different standards. This matter has been the subject of considerable controversy, and decisions on the interface pressure used will affect the performance and ease of insertion of a rubber ring joint. This paper reports and discusses previous and current research on root penetration past elastomeric joints, the existing test requirements of elastomeric pipe joints for resisting root penetration given in standards, and the inconsistencies in performance requirements across the different pipe material types. The initial interface sealing pressures for commonly used PVC. VC and FRC joints were assessed and these are discussed in light of the accelerated root intrusion tests performed in Black Hill Flora Centre in Adelaide, South Australia.
Three‐dimensional simulation of thermoforming process and its comparison with experiments
Authors: Nam Gi Joon , Lee Jae Wook , Ahn Kyung Hyun 
Published: April 2004

AbstractThree‐dimensional solid element analysis and the membrane approximated analysis employing the hyperelastic material model have been developed for the simulation of the thermoforming process. For the free inflation test of a rectangular sheet, these two analyses showed the same behavior when the sheet thickness was thin, and they deviated more and more as the sheet thickness increased. In this research, we made a guideline for the accuracy range of sheet thickness for the membrane analysis to be applied. The simulations were performed for both vacuum forming and the plug‐assisted forming process. To compare the simulation results with experiments, laboratory scale thermoforming experiments were performed with acrylonitrile‐butadiene‐styrene (ABS). The material parameters of the hyperelastic model were obtained by uni‐directional hot tensile tests, and the thickness distributions obtained from experiments corresponded well with the numerical results. Non‐isothermal analysis that took into account the sheet, temperature distribution measured directly from the experiments was also performed. It was found that the non‐isothermal analysis greatly improved the predictability of the numerical simulation, and it is important to take into account the sheet temperature distribution for a more reliable simulation of the thermoforming process.
Morphological and mechanical properties of polypropylene [PP]/poly(ethylene vinyl acetate) [EVA] blends. I. Homopolymer PP/EVA systems
Authors: Ramírez‐Vargas E. , Navarro‐Rodríguez D. , Huerta‐Martínez B. M. , Medellín‐rodríguez F. J. , Lin J. S. 
Published: April 2004

AbstractMorphological and mechanical properties of polypropylene [PP]/poly(ethylene vinyl acetate) [EVA] blends have been studied. Infrared results using thin films first indicated a transition toward compatibility between both components at concentrations above 40% EVA. The transition was verified with different experimental techniques and it was associated to morphological changes and mechanical properties. The PP/EVA blends were mechanically evaluated in terms of impact and tensile strength to determine the influence of blending on the performance properties of these materials. Agreement was found between the transition and the enhancement of both elongation at break and impact strength.
Novel strategies for novolak resin fractionation: Consequences for advanced photoresist applications
Authors: Narasimhan Balaji , Wanat Stanley F. , Rahman M. Dalil 
Published: April 2004

AbstractThe importance of well‐characterized novolak resins in the manufacture of high performance photoresists is paramount. Two novel fractionation methods for novolaks synthesized by solution condensation are reported in this paper. Solid resin solutions in methanol and ethyl lactate were fractionated by ultracentrifugation and liquid‐liquid centrifugation (using water and hexane as non‐solvents). The techniques resulted in high yield, low‐polydispersity (high Mw) resins that exhibited superior dissolution rates and lithographic performance when compared to resins obtained by conventional isolation techniques. The effects of solvent/non‐solvent ratio, temperature, and centrifuge rpm on resist performance were evaluated. It was found that at sufficiently high rpm and at 25°C, the Mw and the polydispersity of the fractionated resin increases and the dissolution rate decreases as the solvent/non‐solvent ratio decreases, Slow dissolution rates and improved lithographic performance characteristics in experimental i‐line formulations were obtained for resin solutions fractionated by liquid‐liquid centrifugation using a 1/2 ratio of ethyl lactate (and/or methanol) to hexane. Scaling laws between dissolution rate and polymer molecular weight were derived and the data seem to support reptation‐type diffusion. The use of appropriate process manipulation in order to precisely control resin properties and to design novel resins is discussed.
A laboratory spiral disk extruder for flow visualization
Authors: Maffettone Pier Luca , Grizzuti Nino 
Published: April 2004

AbstractA laboratory spiral‐disk extruder for the study of gas entrainment phenomena is presented. The rotating plate is transparent, thus allowing for the direct observation of the steady liquid‐gas interface when operating under starve‐fed conditions. The extruder flow is modeled with the conventional single screw extruder approach. This leads to a simple working equation for the spiral screw, which is formally identical to the classical screw equation for standard extruders. The model is validated by comparing the predictions with experimental data taken in both closed and open die configurations.