bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study and finite element analysis of the injection blow molding process
Authors: Haessly W. P. , Ryan M. E.
Published: December 2004

A finite element numerical analysis of preform inflation associated with the injection blow molding process has been developed using a neo‐Hookean constitutive model. The analysis is capable of predicting final wall thickness distributions for axisymmetric mold geometries. Experimental studies were conducted on a Uniloy injection blow molding machine (Model 189‐3 and Model 122). A twelve ounce (355 mL) cylindrical bottle mold was instrumented with contact sensors, thermocouples, and pressure transducers. Visualization studies of the inflation process were performed using specialized tooling and high‐speed video cameras. The experimental studies provide justification for analyzing the deformation by means of a static elastic approach. The predicted wall thickness distribution is in reasonable agreement with the experimental data. Nonuniformities in the temperature distribution in the preform were found to have the most significant impact on the inflation behavior and the resulting wall thickness.
Anisotropy in injection‐molded ethylene‐propylene‐diene rubbers. Part I
Authors: Lavebratt Håkan , Stenberg Bengt
Published: December 2004

Anisotropy 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

Anisotropy 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

Water 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

Thermal 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.
Re‐examination of a proposed model for nonisothermal crystallization kinetics
Authors: Hammami Ahmed , Mehrotra Anil K.
Published: December 2004

This communication is a theoretical re‐examination of the model proposed by Choe and Lee for the nonisothermal crystallization kinetics of semicrystalline polymers.
Some relationships for the orientational drawing of polymers
Authors: Vlasov S. V. , Kuleznev V. N.
Published: December 2004

The 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

The 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

In 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

It 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

Rigid, 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

Mechanical 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.
Measurement of the J integral in polycarbonate using the method of caustics
Authors: Dhumne A. , Ravi‐Chandar K.
Published: December 2004

The nonlinear fracture behavior of polycarbonate is investigated. The feasibility of measurement of the J integral through the optical method of reflected caustics is demonstrated. Significant increase in the crack growth resistance during small amounts of crack extension is observed.
The relationship between structure and deformation behavior of sulfone polymers
Authors: Chiu Hsien‐Tang , Hwung Dao‐Shinn
Published: December 2004

The 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

The 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

Blends 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

The 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

Phenolic 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

The 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

Copoly(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

The 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

The 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.
Determination of relaxation time spectra by analytical inversion using a linear viscoelastic model with fractional derivatives
Authors: Friedrich Chr. , Braun H. , Weese J.
Published: December 2004

Recently, Friedrich proposed an empirical model for linear viscoelastic fluids corresponding to a constitutive equation with fractional derivatives [Phil. Mag. Lett., 66, 287 (1992)]. For this model, the relaxation modulus, the dynamic moduli, the relaxation time spectrum, and other material functions have been explicitly calculated as a function of the few parameters that characterize a viscoelastic fluid within this model. By fitting this model to experimental data, the model parameters can be determined and other material functions, in particular the relaxation time spectrum, can be calculated immediately. This paper reports to what extent this method, which may be called analytical inversion, is appropriate for the determination of relaxation time spectra. For that pupose, the spectra of a number of very different polymeric materials are determined with this method. The spectra calculated in this way are compared with the spectra obtained by nonlinear regularization. It turns out that the empirical model describes the linear viscoelastic properties of a variety of different materials with high accuracy. Keeping in mind that the determination of the relaxation time spectrum requires the solution of an ill‐posed problem, the agreement between the relaxation time spectra obtained by analytical inversion and by regularization is satisfactory for these materials.
An algorithm for analysis of polymer filling of molds
Authors: Voller V. R. , Peng S.
Published: December 2004

A numerical implementation of the Volume of Fluid (VOF) free surface technique, applied to a filling process governed by a potential flow, is introduced. The implementation is based on a finite element control volume space discretization and uses an implicit time integration. This allows for the accurate tracking of the filling front using large simulation time steps in molds with complex geometries. The approach is validated on comparision with the analytical solution for filling a one‐dimensional tube and with two‐dimensional results obtained with previously‐presented filling algorithms. Examples of the application of the approach in the analysis of structural resin transfer molding (SRTM) are presented. The capability of the method is demonstrated on predicting “race tracking” and “dry spotting” phenomena. The CPU requirement for a typical analysis is on the order of 1 to 20 s on pesonal computers.
Performance of reprocessed multilayer LDPE/nylon‐6 film
Authors: Nir M. M. , Ram A. , Miltz J.
Published: December 2004

Multilayer LDPE/nylon‐6 films with an overall content of 71 wt% LDPE, 24 wt% nylon‐6, and 5 wt% PE‐based tie‐layer adhesive were reprocessed under both minimal and extensive mixing conditions. Thermal and mechanical properties, oxygen and water vapor permeability, and morphology of the reprocessed samples were determined. The modulus and yield stress of the reprocessed films fell between those of the pure homopolymers, whereas percent elongation at break and energy‐to‐break for all reprocessed films were less than those of the homopolymers. In minimally reprocessed film, layering of LDPE (low‐density polyethylene) and nylon‐6 was retained, whereas in extensively mixed samples, nylon‐6 domains were spherical and ranged from 0.2 to 7 μm. Minimally reprocessed film exhibited good O2 and H2O vapor barrier properties, whereas extensively‐mixed samples had poor barrier properties. Properties of well‐mixed blends prepared both with and without adhesive showed that 5 wt% adhesive did not compatibilize the LDPE and nylon‐6 components.
The current state of philanthropy in Mexico and Central America
Authors: Viesca‐Sada Adalberto
Published: December 2004

In Mexico and Central America, philanthropic activity has emerged as governments become less effective and support of societal needs by churches is not as prevalent as in earlier times.
Nongovernmental organization sustainability support in the Middle East
Authors: Mason Joan L.
Published: December 2004

This chapter provides one example of fundraising in a Middle Eastern country, Jordan, and exhibits the perceptions people have of volunteering, giving time and money, and the reality of corporate giving in the country.
Quick Optical Measurement of Particle Distribution in a Sedimentation Apparatus
Authors: Staudinger Gernot , Hangl Manfred , Pechtl Peter
Published: December 2004

The determination of the particle size distribution of a powder may last up to 14 hours with standard sedimentation techniques such as an Andreasen pipette.

If, in a photosedimentometer, not only the one sensor close to the bottom is incorporated but a number of sensors positioned at different heights, the time required for determining the particle size distribution of a powder may be reduced to 15 minutes. For each sensor there is an optimum location, which is determined both by the distance from the surface to the lowest and the highest sensor and by the number of sensors.

The instrument, equipped with three measuring sensors and a reference sensor is connected to a personal computer. The measured particle size distributions are reproducable with a standard deviation of less than 2%. Agreement with a Sedigraph or a sedimentation balance is about the same as the agreement of these two instruments with each other.

The time required for the determination of a particle size distribution of a quartz powder suspended in water with particle diameters from 1.5 to 60 μ is 15 minutes.
Fractal Differentiation Between Wear and Contaminant Particles found in mining machinery lubrication systems
Authors: Hancock David J. , Richards Michael J. , Adler Jeremy
Published: December 2004

This paper describes preliminary work carried out on the applicability of fractal geometry for differentiating between wear and contaminant particles found in mining machinery lubrication systems.

Coal dust, stone dust and roadstone dust from a granite quarry were used as the contaminant particles and the particles from two crushers, which had failed whilst in service, were used to provide the wear particles.

Two differing populations appeared with the wear particles having higher boundary fractals than the contaminant, but tending to spread across a wide range of fractal numbers, whereas the contaminants were lower and fairly tightly grouped.

The underfractal distributions of the two populations of particles, generate straight lines when plotted on Gaussian probability paper. This leads to the probability of being able to predict the distribution of particles, in fractal terms between wear and contaminant particles.
Size Measurement of Small Magnetic Particles
Authors: Sešelj Andreja
Published: December 2004

Many different methods for size measurement are known and since they differ in their physical principles, different results are also obtained. In the recent past, there were rapid developments in new measurement techniques and one can now quickly and routinely determine particle sizes in the very fine range. Smaller particle sizes, on the other hand, tend to increase the probability of agglomeration. The measurement of the particle sizes for magnetic materials is not well understood and this paper reports results regarding the size determination of very fine magnetic materials. Because of their dipole moment, these particles tend to agglomerate even more, which in turn causes certain difficulties during the measurements. Wet and dry laser measurement systems were compared and also magnetic materials with different permeabilities in order to establish the influence of individual factors on the measurement process and on the accuracy of the results obtained.
Relationships Between Particle Properties and Bulk Behaviour for some industrial powders
Authors: Hoffmann Alex C. , Finkers Hendrikus J. , Seegers Jacobus A.
Published: December 2004

A series of industrial powders, most of them organic, were characterized in terms of volumetric mean size, size distribution, density, particle shape, water rentention characteristics (under a series of controlled ambient relative humidities) and loosely packed and densely packed voidages (giving the compressibility). The behaviour of the powders in powder handling apparatus (a precision powder filler) was also determined. The minimum and maximum bulk densities of the powders were related to the properties of the individual particles by means of a semi‐empirical equation. The filling capacity of the powder handling apparatus was found to be related to the maximum bulk density of the powder while the filling accuracy turned out to be related to the compressibility of the powder. Knowing these interrelations made it possible to predict the powder behaviour in the handling apparatus directly on basis of the particle properties.
Ultrasonic Investigation of Mechanical Properties of Double Base Rocket Propellants
Authors: van der Schroeff J. A. , de Boer R. S.
Published: December 2004

For a series of double base rocket propellants and for poly‐ methylmethacrylate (PMMA) the longitudinal and transverse sound wave velocities are measured at a frequency of 0.351 MHz in t h e temperature range of −40°C to +60°C. The relations between these acoustic properties and mechanical properties are given and the principal independent elastic constants are calculated. With increasing temperature these constants of the propellants decrease gradually, which points to a softening of the material. This is important for the functioning of the propellant grains in the rocket motors.
Consideration to the Mass Distribution of Fragments by natural‐fragmentation in combination with preformed fragments
Authors: Held M. , Kühl P.
Published: December 2004

The empirical formula for the distribution of fragments from rotationally‐symmetric, cylindrical warheads can be extended to the case high explosive shells. The parameters arising from this can be determined by fitting the measured results to the theoretical values. In this work possible methods of performing such a fitting procedure are discussed.
Studies of the Combustion of Solid Propellants at High Pressures
Authors: Grune D.
Published: December 2004

To determine burning velocities of solid propellants at high pressures, a new type of manometric bomb of 0.1 1 volume has been designed. Tightening is provided by a cartridge section from a 30 mm HS 831 steel case. 3 0 to 50 ms after the maximum, the pressure is automatically released by erosion of a 1 mm nozzle, this time lag being given by the electric igniter placed before the nozzle and by blocking it for a short time.

The bomb has been applied to measure pressures p in a range up to 7000 bar as a function of loading density A for a double base propellant. The curve p(A) shows a change of slope at about 5000 bar for which explanation is still lacking.
La Commission Européenne de Normalisation des Essais d'Explosifs (changé depuis 1976: Groupe d'Etude International pour la Normalisation des Essais d'Explosifs)
Authors: Ahrens H.
Published: December 2004

Depuis 1960 un groupe d'experts, réunis de leur propre gré, travaillent sous le nom de „Commission Européenne de Normalisation des Essais d'Explosifs„ (European Commission for the Standardization of the Tests of Explosives, Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen).

Le suivant est une courte description de cette activité depuis son origine, jusqu'à présent et pour l'avenir.
Environmental Testing of Caseless Ammunition
Authors: Schmitt D.
Published: December 2004

Caseless ammunition is subjected to considerable loading both prior to and during use in the weapon. In order to be able to assess the suitability of the ammunition whilst still at the development stage, the types of loading which might occur were analyzed and test methods for their laboratory simulation compiled. A small calibre caseless ammunition developed at ICT was tested on this basis. It was concluded that the simulated loadings had no detrimental effect on the ammunition.
The rapid determination of nitrogen in Primary and Secondary Explosives using the Merz Method
Authors: Söntgerath H.
Published: December 2004

The rapid determination of nitrogen in explosives is basically possible using the Heraeus automatic Mikrorapid N as developed by Merz. The combustion of the substance takes place in pure oxygen and the nitrogen is determined volumetrically. However, when sodium and lead azides are analyzed in this way the residues of sodium and lead strongly attack the quartz of the combustion tube. In order to achieve the longest possible service life of the combustion tubes a joint investigation with BASF AG was undertaken to test other tube materials (e. g. steels, nickel, Alsint, Phythagoras) in addition to quartz. Pythagoras proved to be the most suitable material for the combustion of all explosives at 950° C in the same tube. For the determination of sodium azide a quartz finger (according to Merz) can be inserted in the tube which, at 500° C, collects the sodium residues.
Correlation of Specific Impulse and Ignition Delay in Liquid Rocket Propellants
Authors: Kishore K. , Sunitha M. R.
Published: December 2004

Theoretically there seems to be a linear dependence between specific impulse and the ignition delay in liquid bipropellant systems. It has been observed that the plot of specific impulse versus mixture ratio of various systems based on red fuming nitric acid oxidizer show a maximum. The ignition delay versus mixture ratio plot of the same systems on the other hand show a minimum at a mixture ratio which corresponds to the maximum specific impulse. Thus, the mixture corresponding to maximum performance of a liquid bipropellant system could be qualitatively predicted from the ignition delay measurements.
Ein modifiziertes Lagrangesches Modell der Innenballistik
Authors: Heinz C. , Hensel D.
Published: December 2004

Es wird cin modifiziertes Lagrangesches Modell der Innenballistik mitgeteilt. Dieses hat gegenüber dem bestehenden Lagrangeschen Modell den Vorteil, daR es genauer ist und daR es als Ausgangsnäherung fur ein iteratives Verfahren benutzt werden kann.
Untersuchung der Detonationsschwaden verschiedener Explosiv‐ und Sprengstoffe
Authors: Volk F.
Published: December 2004

In einem Sprengkessel wurden verschiedene Mengen an Nitropenta, Hexogen, Tetryl, Polyvinylnitrat und Ammonit 1 sowohl in Argon‐ Atmosphäre als auch unter Luft zur Detonation gebracht. Die hierbei gebildeten Reaktionsschwaden wurden gaschromatographisch analysiert. Der Gehalt an Stickoxiden wurde unter Verwendung eines NOx‐Chemolumineszenz‐Analysators ermittelt.

Es zeigte sich, daß bereits eine geringe Menge Luft (4 Vol.%) in der Inertgasatmosphäre den NO‐Gehalt der Detonationsschwaden deutlich erhöht. Eine noch stärkere Bildung von NO wird beim detonativen Zerfall der Explosivstoffe in Luft beobachtet.

Die experimentellen Ergebnisse werden diskutiert und mit Resultaten verglichen, die unter Verwendung eines thermodynamischen Rechenprogrammes erhalten wurden.
Testing of Low‐Sensitivity Explosives from the safety point of view
Authors: Wollert‐Johansen P.
Published: December 2004

The world's explosive industry is changing. New non‐nitroglycerin explosives of different sensitivities and physical characteristics are being developed. Many slurry explosives are mixed and pumped at elevated temperatures, and powder explosives will often be exposed to higher than ambient temperatures in the process equipment. explosives? Is it possible that different fractions of a powder explosive have different sensitivities? Which test methods can we use to evaluate sensitivity? Will the results tell us something we can apply in practical safety evaluations of explosives and process equipment? These are some of the questions we have asked. In this note some results from our work on sensitivity testing are reported. What effect has temperature on the sensitivity of “insensitive” explosives? Is i t possible that different fractions of a powder explosive have different sensitivities? Which test methods can we use to evaluate sensitivity? Will the results tell us something we can apply in practical safety evaluations of explosives and process equipment? These are some of the questions we have asked. In this note some results from our work on sensitivity testing are reported.
Empfindlichkeit der Sprengstoffe gegenüber Zündern und Zündstärke von Zündern als unsymmetrisch‐reziproke Größen
Authors: Ahrens H.
Published: December 2004

Im Bereich chemisch einheitlicher detonationsfähiger Stoffe können auf Grund experimenteller Ergebnisse die Empfindlichkeit der Sprengstoffe gegenüber Zündern (z. B. als Ergebnisse von Versuchen mit MeGkapseln) einerseits und die Zündstarke von Zündern andererseits eindeutig und allgemein als reziproke Größen aufgefaßt werden. Auf der Seite der Sprengstoffe spielt in diesem Zusammenhang als Variable neben bestimmten Sprengstoff‐Eigenschaften die globale Dichte der Sprengkörper eine ausgeprägte Rolle. Der Dichteeinfluß auf die Zündempfindlichkeit verhalt sich dabei gerade umgekehrt wie der Dichteeinfluß auf die durch den reziproken kritischen Durchmesser festgelegte Detonationsempfindlichkeit.

Geht man auf der Seite der Sprengstoffe zu heterogenen Zwei oder Mehrkomponenten‐Mischungen über, wobei es sich um Komponenten verschiedener Reaktivität (ggf. einschließlich inerter Komponenten) handelt (Gewerbliche Sprengstoffe), dann findet sich die reziproke Beziehung im Sinne einer Unsymmetrie mehr oder weniger verändert. Entscheidend dafür ist in erster Linie die Art, Menge und strukturelle Einordnung der hochsensiblen Komponente.

Rückschlüsse auf die Aussagekraft verschiedener Verfahren Zündstarke‐Messung an Zündern und auf die Frage der Schaffung durch Absolutangaben definierbarer Skalen fur Initiierungs‐Sensibilität und Zündstarke werden dargelegt.
Utilisation de la Méthode par Immersion pour la Détermination de l'Energie dans les Gaz d'Explosion
Authors: Fossé C.
Published: December 2004

C'est par une simple mesure seismographique que l'on obtient la période de pulsation de la bulle gazeuse formée sous l'eau lors de l'explosion et en résultant par calcul l'énergie dans les gaz d'explosion. Les énergies dans les gaz d'explosion pour quelques explosifs industriels sont évaluées.
The Propagation of Blasts from Solid Explosives to two‐phase media
Authors: Oved Y. , Eidelman Sh. , Burcat A.
Published: December 2004

The aim of this investigation is to determine the influence of the energy release from a combustible two‐phase media on the blast wave generated by an explosive charge, during the first stages of the process. For this purpose ball charges of “Composition B” were detonated in air, in pure nitrogen containing suspended solid particles of carbon, and in pure oxygen containing particles of aluminum and carbon. The blast wave's velocity was measured in all the media using fast frame camera 300,000 f.p.s. and streak photography at 2 mm/μs. The influence of release or absorption of energy by the medium was investigated by comparing experiments done in inert media with those conducted in combustible media while other parameters are kept constant.

Kozorezov's triple isentrope model was compared to the results, and good agreement is found. The article contains detailed information on the experiments and the calculations performed.
Etude par Résonance Magnétique Nucléaire Impulsionnelle de la Plastification du Nitrate de Polyvinyle
Authors: Michaud C. , Arnaud B. , Adenis J. C. , Marechal E.
Published: December 2004

La Résonance Magnétique Nucléaire Impulsionnelle permet l'étude de systèmes constitués de plusieurs phases de mobilités différentes. Nous présentons ici une application de cette technique à l'examen du phénomène de plastification du nitrate de polyvinyle au phtalate de dibutyle. Dans ce matériau, on met ainsi en évidence les phases suivantes:

polymère rigide,

polymère mobile,

plastifiant rigide,

plastifiant mobile.

Ces différentes phases sont suivies quantitativement en fonction du taux de plastifiant et de la température.
Thermoanalytical Determination of Tetrazene in Primer Mixtures
Authors: Krien G.
Published: December 2004

The heat of decomposition allows the quantitative determination of tetrazene in primer mixtures by DSC or DTA. The standard deviation of the method is 0.02 mg if the content in tetrazene is in the range of 0.1 mg to 1.5 mg. The confidence interval of a measurement is 0.03 mg tetrazene. This is sufficient for control measurements in view of the large variations introduced during sampling of tetrazene in small amounts of primer. The low weight required by the method (2 mg or more) enables the determination of tetrazene in friction compositions of a detonator or in percussion caps. This is important when malfunctions have to be analyzed.
Structure moléculaire des derivés nitrés aromatiques. III. Effet de la corrélation électronique sur le calcul des états singulets à l'équilibre et hors d'équilibre, le long de la liaison CNO2; analyse de populations de charges sur le groupe CNO2
Authors: Odiot S. , Blain M. , Leclercq J. M. , Leclercq J. , Fliszar S. , Boileau J. , Fleury G.
Published: December 2004

Les distributions électroniques de charges dans les états singulets du nitrobenzène, des meta‐ et para‐dinitrobenzènes et du 1,3,5‐trinitrobenzène ont été calculées en fonction de la vibration de valence totalement symétrique du ou des groupements CNO2 par calcul CNDO/S avec IC incluant mono et biexcitations. L'effet de la corrélation électronique sur le niveau fondamental calculé en STO‐3 G et les états excités est pris en considération.
Nitramine Solid Rocket Propellants with Reduced Signature
Authors: Klöhn W. , Eisele S.
Published: December 2004

Solid rocket propellants containing nitramine are considerably superior to doublebase propellants, both as regards their performance and mechanical properties. The pressure exponent of non‐modified nitramine propellants is n ≥ 0.9. The possibility of changing the burning rate or, respectively, the pressure exponent has, however, only been realisable to a restricted extent up till now in propellants with an increased nitramine content. In the following propellant system containing nitramine, the effects of ammonium perchlorate on burning behaviour are studied:

ammonium perchlorate (AP)

hexogen (RDX)

nitroglycerin (NG), or trimethylolethane trinitrate (TMETN)

polyurethane binder (PU)

AP concentrations already as great as 10% produce considerable changes in the burning behaviour of the propellants described above. It is possible to reduce the pressure exponent by the addition of ammonium perchlorate from n ≥ 0.9 to n ≤ 0.65. The burning rates may also be influenced with AP concentrations ≤ 20% and by varying the AP particle size by the factor of 2. All the propellants prepared were easily castable and showed exceptionally good viscoelastic properties (strain at break εR > 200%) in the temperature range between −40 °C to + 50 °C. The thermal chemical stability is not influenced negatively in any way by the combination of nitric acid esters and ammonium perchlorate.