bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anisotropy in injection‐molded ethylene‐propylene‐diene rubbers. Part I
Authors: Lavebratt Håkan , Stenberg Bengt 
Published: December 2004

AbstractAnisotropy and molecular orientation are well‐known phenomena in the field of thermoplastics. In the case of rubber materials only a few studies have described anisotropy. Injection molding has been shown to give rise to higher anisotropy than compression molding. The anisotropy in the rubber material is assumed to be due to molecular orientation and is strengthened by carbon black. In order to understand the mechanism of anisotropy in rubber materials, an extensive study has been performed. In this paper, results from two injection‐molded ethylene‐propylene‐diene (EPDM) rubbers, compounded both with and without carbon black, are presented. The polymers had different molecular weight distributions and the compounds were injected into center‐gated 1‐ and 4‐mm‐thick disks. The properties measured in different directions were mechanical, dynamic mechanical, and swelling. These measurements show that anisotropy can be a very important factor to take into account. The origin of anisotropy is presumably the molecular orientation which arises during the filling of the mold with the rubber melt.
Anisotropy in injection‐molded ethylene‐propylene‐diene rubbers. Part II: Disks delaminated by a water‐jet cutting technique
Authors: Lavebratt Håkan , Stenberg Bengt 
Published: December 2004

AbstractAnisotropy and molecular orientation are well known phenomena in the field of thermoplastics, but only a few studies have described anisotropy in rubber materials. It has been shown that injection molding gives rise to a higher degree of anisotropy than compression molding. The anisotropy in the rubber material was strengthened by carbon black and is presumably due to molecular orientation. This paper describes the anisotropy of injection‐molded ethylene‐propylene‐diene rubbers. The two polymers had different molecular weight distributions and thus different rheological properties. The compounds were injected into center‐gated 4mm thick disks. The disks were subsequently split into three layers using a water‐jet cutting technique. Measurement of mechanical and swelling properties in the different layers and directions showed that the anisotropy varied through the thickness of the disk. By X‐ray scattering it was shown that rubber molecules had a preferred direction and thus, that the anisotropy was probably predominantly due to molecular orientation created during the mold filling.
Water sorption in a novel liquid crystalline epoxy resin
Authors: Carfagna C. , Amendola E. , Giamberini M. , Mensitieri G. , Del Nobile M. A. , Filippov A. G. 
Published: December 2004

AbstractWater sorption tests have been carried out for a novel epoxy resin having liquid crystalline character. The sorption isotherm. Relative to the expoxy resin cured in the nematic phase, does not indicate any substantial difference from the resin cured in the isotropic state. This is an indication that, as far as this class of thermosets is considered, the liquid crystalline order does not affect mechanism and equilibrium values of water uptake.
Melting behavior and thermal properties of high density polythylene
Authors: Woo M. W. , Wong P. , Tang Y. , Triacca V. , Gloor P. E. , Hrymak A. N. , Hamielec A. E. 
Published: December 2004

AbstractThermal diffusivity of high density polyethylene (HDPE) was studied over a wide range of temperatures (25 to 200°C) by melting powdered HDPE in a cylindrical mold at several pressures (101.3 to 5065 KPa gage) and recording the temperature profiles at several radial positions. The energy equation was solved numerically for cylindrical geometry. The thermal diffusivity of HDPE was fit as a function of temperature, porosity, and pressure.
Some relationships for the orientational drawing of polymers
Authors: Vlasov S. V. , Kuleznev V. N. 
Published: December 2004

AbstractThe orientational drawing of films from different thermoplastics has been studied. The value of the activation energy of drawing in the regions of forced elasticity (necking), high elasticity, and viscous flow (ΔE1, ΔE2, ΔE3) has been found to vary directly with the activation energy for viscous flow of the melt (ΔEη). Here ΔE1 < ΔE2 < ΔE3 = ΔEη. Thus Δ Eη characterizes the potential of thermoplastics for orientational drawing under different deformation conditions, since it reflects simultaneously both the intermolecular interaction level and chain flexibility. For maximum chain orientation, the calculated values for the change in the entropy are close to that of the entropy change during crystallization (melting) of the same polymer. The deformation of polymer may be described as a deformation of an entanglement network from the standpoint of classic elasticity theory. Some parameters for an entanglement network were calculated from the results of the drawing experiments. The density of the entanglement network (DEN) depend on the polymer composition: For flexible‐chain polymers the DEN is less, for rigid‐chain polymers (with coiled chains) it is higher. The DEN affects the maximum (prebreak) drawing ratio: The greater the DEN, the smaller the ratio to which a film can be drawn. At high orientation, the tensile strength of different polymer films tend to be similar, if drawing is not accompanied by crazing.
Block copolyetherester. Part 3: Preparation of block copolyetheresters by a terephthalic acid process in the presence of salts
Authors: Chang Shinn‐Jen , Chang Feng‐Chih , Tsai Hong‐Bing 
Published: December 2004

AbstractThe block copolyetheresters with hard segments of poly(butylene terephthalate) and soft segments of poly(tetramethylene ether) were prepared by a terephthalic acid (TPA) process in the presence of some salts. The preparations of a block copolyetherester under various conditions were first studied in a 1 L stainless steel reactor to find the best method. Then, the preparations of four block copolyetheresters were run in a pilot plant comprising a 200 L polyesterification reactor and a 200 L polymerization reactor under the suitable condition. The presence of some salts reduced the formation of tetrahydrofuran (THF), and also reduced the total reaction time in the pilot plant. The thermal properties and various mechanical properties of the block copolytheresters prepared by the pilot plant were investigated to evaluate the feasibility of this method.
Review of stabilization of polyolefin insulated conductors. Part II: Characteristics of good stabilizers and methods of evaluation
Authors: Hendrickson L. , Connole Kent B. 
Published: December 2004

AbstractIn a previous paper, the theory of polylefin stabilization and the major factors contributing to degradation were discussed. This paper reviews the methods of test employed to date, the characteristics of a good stabilization system, and the experimental work we propose to use to study the problem. The characteristics of a stabilizer which are reviewed are: color, melt temperature, solubility, resistance to extraction, migration, phase state, structural arrangement, energy considerations, and thermodynamic potential. The methods of test reviewed include: pedestal testing, oven aging, oxygen uptake, testing under stress, melt flow testing, thermal analysis by DSC, thermal analysis by TGA, color change, torque rheometry, and aged elongation. Our approach will be to quantify the effects of antioxidant, metal deactivator, and blowing agent on stability by doing differential scanning calorimetry (DSC); to study fracture surfaces with scanning electron microscopy (SEM) to study diffusion rate of the stabilizer and reaction rate of the degradation process; and to use dynamic mechanical analysis (DMA) to measure the change in loss modulus with aging.
A simple approach to determining three‐dimensional screw characteristics in the metering zone of extrusion processes using a total shape factor
Authors: Kim S. J. , Kwon T. H. 
Published: December 2004

AbstractIt is of great importance in designing extruders to predict the screw characteristics, that is, the throughput in terms of the screw speed and the pressure gradient along the down‐channel direction. The screw characteristics depend on the extruder geometry, the operating conditions, and material properties of non‐Newtonian fluids. This paper suggests a simple approach to determining the screw characteristics for a three‐dimensional flow in a channel with a finite aspect ratio (ratio of a width to a depth, W/H) by introducing a Total Shape Factor (Ft) to correct a two‐dimensional flow analysis for a channel with an infinite aspect ratio. In the present study, the Total Shape Factor (Ft) was defined as a ratio of a net flow rate obtained by the three‐dimensional analysis to that by the two‐dimensional analysis. In the proposed approach, the quantity, ∂Ft/∂(H/W), which turns out to be almost constant, offers important information for understanding the effects of the flights. Threfore, ∂Ft/∂(H/W) is extensively reported in this paper in terms of several dimensionless parameters. This simple approach with such a database will be very useful for extruder designers to predict screw characteristics.
A constitutive theory for rigid polyurethane foam
Authors: Neilsen M. K. , Krieg R. D. , Schreyer H. L. 
Published: December 2004

AbstractRigid, closed‐cell, polyurethane foam consists of interconnected polyurethane plates that form cells. When this foam is compressed, it exhibits an initial elastic regime, which is followed by a plateau regime in which the load required to compress the foam remains nearly constant. In the plateau regime, cell walls are damaged and large permanent volume changes are generated. As additional load is applied, cell walls are compressed against neighboring cell walls, and the stiffness of the foam increases and approaches a value equal to that of solid poyurethane. When the foam is loaded in tension, the cell walls are damaged and the foam fractures. A constitutive theory for rigid polyurethane foam has been developed. This theory is based on a decomposition of the foam in two parts: a skeleton and a nonlinear elastic continuum in parallel. The skeleton accounts for the foam behavior in the elastic and plateau regimes and is described using a coupled plasticity with continuum damage theory. The nonlinear elastic continuum accounts for the lock‐up of the foam due to internal gas pressure and cell wall interactions. This new constitutive theory has been implemented in both static and dynamic finite element codes. Numerical simulations performed using the new constitutive theory are presented.
Effect of NOx environments and stress on degradation of mechanical properties of Kevlar 49 and nylon 6
Authors: Perry M. C. , Vail M. A. , Devries K. L. 
Published: December 2004

AbstractMechanical and chemical mechanisms may act synergistically to degrade the mechanical properties of polymers. This synergism should be considered during design of components for sustained loads in hostile environments. If these polymers are to be used as load‐bearing structural elements in automobile and industrial environments, they are likely to be simultaneously exposed to such environments and stress. These studies explore the deleterious effects of gaseous pollutants (e.g. NOx in air) and mechanical stress on polymers. This research included studies on nylon‐6 and composites of nylon‐6 yarns embedded in a bis‐A‐phenolic resin with an amine curing agent, as well as single fibers and yarns of poly(p‐phenylene terephthalamide) (DuPont Kevlar 49) as bare fibers and also embedded in an epoxy matrix. The protective effect of embedding fibers in the epoxy matrix was demonstrated. NOx concentrations were varied between 0 and 1.5%. The sustained loads during exposure were in the range of 50 to 80 percent of the ultimate stress short term load carrying capability of the fibers. Exposure times varied from several minutes to months. Electron spin resonance spectroscopy (ESR) is used in these studies to explore the kinetics of bond rupture and how they relate to the environmental and stress loading histories in nylon. Kevlar 49 degradation studies were conducted by measuring times required for sample failure in NOx concentrations at various stress levels. Preliminary studies on the single fibers indicate a stress‐NOx synergism over the range of stresses (48 and 77% of ultimate) and 0.1 and 1.5% gas concentrations. Yarn samples exhibited this synergism over a wide range of stresses (40 to 80% of ultimate). Bare yarn degradation was accelerated by NOx concentrations in air as low as 0.1%. We view these effects as having practical technological significance since these lower NOx concentrations approach the level of emissions from exhaust from older model automobiles.
The relationship between structure and deformation behavior of sulfone polymers
Authors: Chiu Hsien‐Tang , Hwung Dao‐Shinn 
Published: December 2004

AbstractThe deformation of three types of sulfone polymers—polysulfone (PSF), poly(ether sulfone) (PESF), and polyarylsulfone (PASF)—was performed with a mechanical testing system (MTS). The result and samples were studied using a transmission electron microscope (TEM), a dynamic mechanical analyzer (DMA), and a dielectric thermal analyzer (DETA). Stripes on TEM micrographs for small deformations increase with the fracture toughness (GIc). The activation energy (Ea) of the α‐transition was determined from DETA. The results show that both Ea and TEM micrographs can be used to qualitatively estimate the order of GIc of sulfone polymers. An energy model was proposed to explain this phenomenon.
Coefficients of dynamic friction as a function of temperature, pressure, and velocity for several polyethylene resins
Authors: Spalding Mark A. , Hyun Kun S. 
Published: December 2004

AbstractThe coefficient of dynamic friction is often the controlling factor for solids conveying, pressure generation, and thermal decomposition of a resin in the feed section of a single‐screw plasticating extruder. The coefficients of friction are, however, very poorly understood, and the interpretation of the measurements are complicated by the dissipation of frictional energy at the sliding interface. A new instrument was recently built to help understand dynamic friction, and a numerical technique was developed to estimate the interface temperture. Coefficients of dynamic friction for several polyethylene resins are presented in this paper as a function of the surface temperature, pressure, and velocity. The relationship of the data with respect to the extrusion process is discussed.
Rheology and thermal properties of liquid crystalline copolyester and poly(ethylene 2,6‐naphthalate) blends
Authors: Kim Bong Shik , Jang Sang Hee 
Published: December 2004

AbstractBlends of a poly(ethylene 2,6‐naphthalate) (PEN) and a liquid crystalline copolyester (LCP), poly(benzoate‐naphthoate) were prepared in a twin‐screw extruder. Specimens for thermal properties were investigated by means of an instron capillary rheometer (ICR) and scanning electron microscopy (SEM). The blend viscosity showed a minimum at 10 wt% of LCP and increased with increasing LCP content above 10 wt% of LCP. Above 50% of LCP and at higher shear rate, phase inversion occured and the blend morphology was fibrous and similar to pure LCP. The ultimate fibrillar structure of LCP phase appeared to be closely related to the extrusion temperature. By employing a suitable deformation history, the LCP phase may be elongated and oriented such that a microfibrillar morphology can be retained in the solid state. Thermal properties of the LCP/PEN blends were studied using DSC and a Rheovibron viscoelastomer. These blends were shown to be incompatible in the entire range of the LCP content. For the blends, the Tg and Tm were unchanged. The half time of crystallization for the LCP/PEN blends decreased with increasing LCP content. Therefore, the LCP acted as a nucleating agent for the crystallization of PEN. The dimensional and thermal stability of the blends were increased with increasing LCP content. In studies of dynamic mechanical properties, the storage modulus (E′) was improved with increasing LCP content and synergistic effects were observed at 70 wt% of LCP content. The storage modulus for the LCP/PEN 70/30 blend is twice that of PEN matrix and exceeded pure LCP.
A constitutive theory for polypropylene in cyclic deformation
Authors: Ariyama Takashi , Kaneko Kenji 
Published: December 2004

AbstractThe shape of the hysteresis loop has been studied for polypropylene subjected to different cyclic loadings. Cyclic tests were performed under different sets of cyclic strain amplitude and number of cycles, using a closed‐loop, electrohydraulic, servocontrolled testing machine. A constitutive theory is developed for the interpretation of loop shape behavior in terms of elastic, perfectly plastic materials of different yield strengths. The constitutive equation is based on a simple overlay model of bar elements. The calculated results agree well with experiments, which indicates the distictive shape of the hysteresis loop, termed a propelled‐like shape. The truss model reasonably explains the cyclic deformation behavior in polypropylene.
Modification and compatibility of epoxy resin with hydroxyl‐terminated or amine‐terminated polyurethanes
Authors: Wang Huei‐Hsiung , Chen Jung‐Chieh 
Published: December 2004

AbstractPhenolic hydroxyl‐terminated (HTPU) and aromatic amine‐terminated (ATPU) PU modifiers were prepared by reacting two different macroglycols (PTMG, polytetramethylene glycol, Mn = 2000, and PBA, Polybutylene adpate, Mn = 2000) with 4,4′‐diphenylmethane diisocyanate (MDI), then further coupling with two different coupling agents, bisphenol A or 4,4′‐diaminodiphenyl sulfone (DDS). These four types of PU prepolymers were used to modify the epoxy resin with 4,4′‐diamino‐diphenyl sulfone as a curing agent. From the experimental results, it was shown that the values of fracture energy, GIC, for PU‐modified epoxy were dependent on the macroglycols and the coupling agents. Scanning electron microscopy (SEM) revealed that the ether type (PTMG) of PU‐modified epoxy showed the presence of an aggregated separated phase, which varied between 0.5 μm and 4 μm in the ATPU (PTMG) and between 1 μm and 1.5 μm in HTPU (PTMG) modified system. On the contrary, the ester type (PBA) PU‐modified epoxy resin showed a homogeneous morphology and consequently a much smaller effect on toughening for its good compatibility with the epoxy network. In addition, it was found that the hydroxyl‐terminated bisphenol A as a coupling agent improved fracture toughness more than the amine‐terminated DDS because of effective molecular weight buildup by a chain extension reaction. The glass transition temperature (Tg) of modified epoxy resin as measured by dynamic mechanical analysis (DMA) was lower in PTMG‐based PU than in a PBA‐based PU series with the same weight of modifier.
Synthesis of poly(maleic anhydride) and its conformation in DMF
Authors: Kim Won Chae , Lee Dong Choo 
Published: December 2004

AbstractThe homopolymer of maleic anhydride was synthesized by free radical initiation and characterized. Molecular mass measurements of 14 selected fractions yielded Mw ranging from 1.1 × 104 to 14.7 × 104 g/ mol. Intrinsic viscosities obtained from the fractions in DME at 25°C were analyzed on the basis of the theory of Yamakawa et al. The persistence length was 2.3 ± 0.1 nm and ML was 600 ± 10 nm−1. The conformation of the poly(maleic anhydride) molecules in DMF is considered to be semiflexible.
Synthesis of copoly(ethylene terephthalate /imide)s and crystallization kinetics
Authors: Park Lee Soon , Lee Dong Chan 
Published: December 2004

AbstractCopoly(ehtylene terephthalate/imide)s (PETI) were prepared by melt polycodensation of bis(2‐hydroxyethyl)terephthalate (BHET) and imide containing comonomer, 4,4′‐bis[(4‐carbo‐2‐hydroxyethoxy)phthalimido]diphenylmethane (BHEI) with Sb2O3 as catalyst at 280°C under vacuum (∼ 1 mm Hg). The change of Tm with an increase of the BHEI repeat unit in the PETI copolymer was analyzed by the Flory equation. On isothermal crystallization, a longer induction time and a lower activation energy than for the PET homopolymer were observed with an increasing amount of BHEI repeat unit. The Avrami exponent, n, increased from 1.5 to 2.3 as the content of BHEI or crystallization temperature was increased. The Avrami rate constant K decreased with the increase of the BHEL unit. On nonisothermal crystallization, the Ozawa equation and Lawton plot were used to investigate the effect of BHEI units on the crystallization kinetics of PETI copolymers. From the change of the cooling crystallization function and the result of the Lawton plot, it was found that the BHEI unit effectively decreases the rate of crystallization.
Morphology and dynamic mechanical properties of nylon 66/ poly(ether imide) blends
Authors: Choi Kil‐Yeong , Lee Sung‐Goo , Lee Jae Heung , Liu Jingjiang 
Published: December 2004

AbstractThe morphology and dynamic mechanical properties of blends of poly(ether imide) (PEI) and nylon 66 over the full composition range have been invesigated. Torque changes during mixing were also measured. Lowertorque values than those calculated by the log‐additivity rule were ontained, resulting from the slip at the interface due to low interaction between the componeents. The particle size of the dispersed phase and morphology of the blends were examined by scanning electron microscopy. The composition of each phase was calculated. The blends of PEI and nylon 66 showed phase‐seoarated structures with small spherical domains of 0.3 ∼ 0.7 μm. The glass transition temperatures (Tgg) of the blends were shifted inward, compared with those of the homopolymers, which implied that the blends were partially imiscible over a range of compositions. Tg1, corresponding to nylon 66‐rich phase. This indicated that the fraction of PEI mixed into nylon 66‐rich phase increased with decreasing PEI content and that nylon 66 was rerely mixed into the PEI‐rich phase. The effect of composition of the secondary relaxations was examined. Both Tβ, corresponding to the motion of amide groups in nylon 66. and Tγ′, corresponding to that of either groups in PEI, were shifted to higher temperature, probably because of the formation of intermolecular interactions between the components.
Processabilities and mechanical properties of surlyn‐treated starch/LDPE blends
Authors: Kim Young Jin , Lee Hyang Mok , Park O Ok 
Published: December 2004

AbstractThe esterification of the hydroxyl group of starch with DuPont Surlyn was considered as pretreatment method of starch before blending with polyolefins. In treating starch with Surlyn, two different raction conditions were taken to optimize reaction conditions. First, the esterification reaction was carried out in 110°C xylene with oleic acid as a catalyst. Second, the reaction out in a 90°C mixture of deionized water and xylene with ceric ammonium nitrate(CAN) as an initiator. Starch granules would be swollen above the gelatinization temperature in water. In both cases starch was midified by Surlyn to have good compatibility with low‐density polyethylene (LDPE). The mechanical and theological properties were examined for blends of the treated starch and LDPE. This system may be one of the biodegradable polymer blends that sufficiently retain properties as a packaging film.