bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of rubber‐matrix interfaces on the crystallization kinetics of isotactic polypropylene blended with ethylene‐propylene‐diene terpolymer (EPDM)
Authors: Wenig W. , Asresahegn M.
Published: December 2004

Blends of isotactic polypropylene with amorphous and slightly crystalline ethylene‐propylene‐diene terpolymer (EPDM), prepared by solution blending, have been investigated by optical microscopy and differential scanning calorimetry. Nucleation and crystallization kinetic parameters, such as nucleation rates, nucleation half times, Avrami‐exponents and spherulitic growth rates, have been determined. It has been found that the dispersion of crystalline EPDM in iPP is different from that of amorphous EPDM. Both EPDMs are incorporated into the spherulites, causing a decrease of the maximum growth rate of the iPP spherulites. The surface free energy of the iPP crystals is diminished on adding EPDM to iPP and is accompanied by a higher secondary nucleation rate. From the decrease observed in the Avrami exponent with increasing EPDM concentration in the blend, it has been concluded that nucleation becomes predominantly heterogeneous, as there is a proportional increase in the interfacial area between the two components.
Fibers from blends of PET and thermotropic liquid crystalline polymer
Authors: Mehta Sanjay , Deopura B. L.
Published: December 2004

Blends of poly(ethylene terephthalate‐Co‐p‐oxybenzoate), PET/PHB, with poly(ethylene terephthalate), PET, have been studied in the form of as‐spun and drawn fibers. DSC melting and crystallization results show that the PET is compatible with LCP and the crystallization of PET decreases by the addition of LCP in the matrix. Upon heating above the crystal melting temperature of PET, the blend shows good dispersion of LCP in the PET matrix. Wide angle X‐ray diffraction of drawn blended fibers show the possible formation of LCP oriented domains. The mechanical properties of drawn fiber up to 10 wt% LCP composition exhibit significant improvement in tensile modulus and tensile strength with values of 17.7 GPa and 1.0 GPa, respectively. Values of modulus are compared with prediction from composite theory, assuming the blend system as nematic domains of LCP. dispersed in PET matrix.
Sheet extrusion of in‐situ composites: Influence of processing parameters
Authors: Crevecoeur G. , Groeninckx G.
Published: December 2004

Unidirectional sheets were extruded of an in‐situ composite of thermotropic liquid crystalline Vectra B950 in a matrix of polyphenylene‐ether and polystyrene. Three important processing parameters were systematically varied: draw‐ratio, slit opening and extruder throughput. Morphology and mechanical properties of these films were determined, and qualitatively related to the processing conditions.
Analysis of residence time distribution in the extrusion process including the effect of 3‐D circulatory flow
Authors: Joo J. W. , Kwon T. H.
Published: December 2004

It is of great importance to accurately measure or predict the Residence Time Distribution (RTD) in designing extruders and/or in setting up a proper operating condition, because chemical reactions depend significantly on the RTD and temperature when chemical reactions take place during the extrusion process. A previous method to predict the RTD can analytically determine RTD, Residence Time Distribution Function f(t) and Cumulative Residence Time Distribution Function F(t), based on a simplified two‐dimensional velocity field in an extruder. However, this previous method cannot accurately take into account the three‐dimensional circulatory flow inside the extruder. The present paper suggests a new method to accurately determine the RTD taking into account the three‐dimensional circulatory flow and presents a new formula derived to calculate f(t). In order to demonstrate the applicability of the new method including the circulatory flow effect, RTD, f(t) and F(t) were calculated based on a three‐dimensional velocity field obtained via a quasi‐three‐dimensional finite element analysis. It was found that the previous method has a tendency to underestimate the RTD, owing to the neglect of the three‐dimensional circulatory flow in comparison with the new method.
Estimation of kinetic parameters associated with the curing of thermoset resins. Part II: Experimental results
Authors: Scott Elaine P. , Saad Zoubeir
Published: December 2004

This is a two‐part theoretical and experimental study on the estimation of the kinetic parameters associated with the curing of a thermoset epoxy resin. In Part II, the kinetic parameters associated with the curing of the bisphenol‐A‐diglycidylether/meta‐phenylenediamine (BADGE/mPDA) resin were estimated from both differential scanning calorimetry (DSC) and dielectric experimental data using a new estimation procedure described in Part I. The kinetic parameters estimated were the Arrhenius constants associated with a kinetic model used to describe the degree of cure. Isothermal experiments were performed using both experimental techniques at four different curing temperatures. The resulting estimates of the kinetic parameters were compared with results obtained from the same data using a linear regression method. The magnitude of the confidence intervals of the estimated parameters and the standard deviation of the model (based on the residual errors between predicted values of the degree of cure and experimental values) were used as criteria in the comparison of the results. From this comparison, it was concluded that the parameters estimated from DSC data using the new estimation procedure provided the estimates with the least variability and, consequently, the smallest errors associated with the kinetic model.
Effects of moisture and other contaminants in friction composites
Authors: Subramaniam N. , Blum Frank D. , Dharani L. R.
Published: December 2004

The role of water and other contaminants like salt water, iso‐octane, and ethylene glycol on neat resin, composites, and friction materials have been investigated. The maximum solvent uptake and the diffusion coefficient of the solvent in these systems were determined and the experimental data was fitted to a Fickian model. The nature of the diffusion process was determined in each case and deviations from Fickian behavior were accounted for. For the neat resin and the composites, the diffusion coefficients of the liquids were of the order of 10−10 cm2/s. After exposure to these contaminants, mechanical properties of all the systems were determined and a general degradation in properties was found. The flexural strength and fracture toughness showed reduction in values while the flexural modulus was not affected.
Relating blow moldability to large amplitude oscillatory shear behavior
Authors: Giacomin A. J. , Jeyaseelan R. S. , Stanfill K. O.
Published: December 2004

The large amplitude oscillatory shear test has been used to discriminate subtle differences in nonlinear viscoelasticity between two high density polyethyene blow molding resins with different processability. Structural network theory was used to explain the subtle differences in terms of entanglement kinetics with remarkable accuracy. The resin with better shape retention characteristics in programmed parison blow molding was found to have a higher kinetic rate constant for molecular re‐entanglement.
Moldability studies for the reaction injection molding of polydicyclopentadiene
Authors: Ng Hendra , Manas‐Zloczower Ica , Shmorhun Mark
Published: December 2004

Moldability diagrams for the filling and curing stages of a dicyclopentadiene (DCPD) based reaction injection molding (RIM) system were established based on a simplified engineering approach. Initial monomer temperature and filling time are the critical parameters for the filling stage whereas in the curing stage, mold wall temperature and demold time proved to be the main processing variables. The physical and thermal properties of the molded samples were examined and the results indicate that such simplified moldability diagrams are sufficiently accurate to establish the processing conditions for the system under investigation.
Numerical simulation of fluid flow and heat transfer in a single‐screw extruder with different dies
Authors: Chiruvella Raman V. , Jaluria Y. , Abib A. H.
Published: December 2004

In a plasticating screw extruder, a polymer melt forms in the melting zone of the extruder. Pressurization of the molten polymer takes place in the melting and the metering sections so that the melt can flow through the restricted passage of the die and assume a desired shape. In a melt fed extruder, the throughput is governed by the pressure rise over the entire length of the extruder. The pressure developed in the screw channel may also be employed in rapid filling of molds, such as those in injection molding. When the geometry of the screw, the barrel temperature, and the die are selected, a unique set of operating parameters arise for a particular flow rate or screw speed. In the present study, numerical and analytical methods are used to calculate the transport in the extruder and the pressure drop in the die. An iterative numerical method based on solving the equations of motion and energy in the screw channel and a correction scheme to couple the die with the screw channel is discussed. The numerical algorithm is capable of handling an arbitrary variation of the viscosity of the polymeric fluid with the shear rate and temperature. The results obtained by simulating the fluid flow in the screw channel are compared with available numerical and experimental results in the literature, indicating good agreement. The performance characteristics of the extruder, for chosen thermal boundary conditions and screw geometry, are presented for different die geometries and different fluids. The important considerations that arise in the numerical simulation of the extrusion process are also discussed.
Cold‐drawing (necking) behavior of polycarbonate as a double glass transition
Authors: Zhou Z. , Chudnovsky A. , Bosnyak C. P. , Sehanobish K.
Published: December 2004

The thermomechanical behavior of poly(bisphenol A carbonate) (PC) undergoing cold‐drawing (necking) over a large range of temperature and strain rate has been studied. The cold‐drawing of PC has been described from a material particle perspective in terms of true stress and strain relationships. The isothermal draw stress is shown to be a material parameter, and the true stress‐strain behavior of necked material above the true drawing stress follows conventional treatment by rubber elasticity. Cold‐drawing is described as a double glass transition: first, a transition from an isotropic glass to an isotropic rubber at the yield point, then, on unloading after stretching of a rubbery mesophase, a transition from an oriented rubber to an oriented glass.
Solidification of thermoviscoelastic melts. Part I: Formulation of model problem
Authors: Bushko Wit C. , Stokes Vijay K.
Published: December 2004

The solidification of a molten layer of amorphous thermoplastic between cooled parallel plates is used to model the mechanics of part shrinkage and warpage and the buildup of residual stresses in the injection molding process. Flow effects are neglected, and a thermorheologically simple thermoviscoelastic material model is assumed. The equilibrium thermomechanical properties of the material and the shift function can be temperature‐ and pressure‐dependent. The model allows material to be added to fill the space created by the packing pressure applied during solidification; therefore, this model can be used to assess packing‐pressure effects in injection molding. The model also accounts for freeze‐off effects in which the cavity pressure is controlled by the solidification process and must therefore be determined as a part of the solution.
Effects of variable viscosity on the steady melting of thermoplastics during spin welding
Authors: Stokes V. K. , Poslinski A. J.
Published: December 2004

The steady melting of several amorphous and semicrystalline polymers during spin welding is analyzed by solving a simplified set of momentum and energy balance equations, assuming a shear‐rate and temperature‐dependent viscosity. A numerical model is developed for predicting the flow field and the temperature distribution in the molten film. It is shown that the steady melting rate of the thermoplastic solid is affected by the variable viscosity, by the pressure applied on the parts to be joined, and by a balance between the viscous heat generation in the melt and the convection of colder material into the molten film. The convection of heat in the outflow direction is shown to have a much smaller effect on the melting process.
A process model for nonisothermal photopolymerization with a laser light source. I: Basic model development
Authors: Flach Lawrance , Chartoff Richard P.
Published: December 2004

A mathematical model for a laser‐induced photopolymerization process has been developed. This model simulates important aspects of stereolithography, a rapid prototyping process used for the production of three‐dimensional plastic parts. The model consists of a set of coupled partial differential equations and considers irradiation, chemical reaction, and heat transfer in a small zone of material exposed to a stationary UV laser source. Numerical techniques are used for an approximate solution of the model equations, and the output includes spatial and temporal variations in the conversion of monomer to polymer, depletion of photoinitiator, and local variations of temperature in and around the region contacted by the laser light. Maximum conversions of approximately 60% and peak temperature rises of approximately 35° C were calculated for the cylindrical exposed region. Results have provided insights concerning laser dwell time, depth penetration, and the uniformity of polymer formed during the stereolithography process.
A process model for nonisothermal photopolymerization with a laser light source. II: Behavior in the vicinity of a moving exposed region
Authors: Flach Lawrance , Chartoff Richard P.
Published: December 2004

A mathematical process model that stimulates important aspects of stereolithography, a rapid prototyping technique used for the production of three‐dimensional plastic parts, has been developed. The model consists of a set of coupled partial differential equations and considers irradiation, chemical reaction, and heat transfer in a vat of photomonomer exposed to a moving UV laser source. Laser motion occurs in a straight line (vector path), and the model thus simulates the production of a single strand of plastic. Numerical techniques are used for approximate solution of the model equations, and output includes spatial and temporal variations in conversion of monomer to polymer, depletion of photoinitiator, and variations of temperature along the line of exposed material. The formation of a temperature wave that moves along the line of plastic is observed, together with the fact that the leading edge of the wave is steeper than the trailing edge, i.e., the material heats considerably faster than it cools. The maximum temperature of the wave reaches a pseudo–steady state after a short time. The results have provided useful information concerning the temperature at which the majority of the polymerization occurs; provided information on overall transient temperature behavior; allowed computer prediction of stereolithography working curves (cure depth and cure width vs. laser scan rate); and afforded a means for evaluating the amount of reaction that occurs in the dark period after light exposure.
Correlations between relaxation time spectrum and melt spinning behavior of polypropylene. 1: Calculation of the relaxation spectrum as a log‐normal distribution and influence of the molecular parameters
Authors: Fulchiron R. , Michel A. , Verney V. , Roustant J. C.
Published: December 2004

The linear viscoelastic behavior of commercial broad‐distribution polypropylenes is studied. The samples underwent different controlled peroxide degradation rates, so they exhibit different molecular distributions. The relaxation spectrum is obtained by assuming that it takes the shape of a Log‐Normal distribution. It is in agreement with the linear viscoelasticity theory by providing limiting values, contrary to other models. Moreover, the ratio τw/τn which takes place in this law is very useful to distinguish the synthesis differences of the samples when the Melt Flow Index alone cannot.
A study of creep and creep rupture of polycarbonate
Authors: Challa Sudarsana R. , Progelhof Richard C.
Published: December 2004

The creep characteristics of polycarbonate at elevated temperatures are investigated. The onset of glass transition temperature of polycarbonate is determined. An Arrhenius type relationship is used to describe the creep process and the concept of property retention index as applied to creep is discussed. An attempt is made to construct the master rupture curves for polycarbonate. The onset of glass transition temperature of polycarbonate was placed at around 110°C. It is concluded that the Arrhenius theory and the concept of property retention index are extremely useful in the construction of master rupture curves and that they require further investigation.
A flow model for non‐newtonian liquids inside a slot die
Authors: Yuan Sinh‐Luh
Published: December 2004

A one‐dimensional flow model for non‐Newtonian liquids inside a dual‐cavity slot die is presented. The model is capable of analyzing slot dies of any cavity shape, cavity taper, slot‐length variations, and slot‐gap variations. The proposed model incorporates a truncated‐power‐law model for the viscosity of non‐Newtonian liquids. According to flow models with power‐law approximation for liquid viscosity, the distribution of non‐Newtonian liquid through a slot die depends on the slot Reynolds number only. With our model, we find that the zero shear viscosity and the relaxation time of a non‐Newtonian liquid have large effects on its distribution. For non‐Newtonian liquids which are expected to experience shear‐thinning over portion of a slot die, it is concluded that a flow model with a truncated‐power‐law approximation for liquid viscosity be used to predict the liquid distribution from the die.
A polytetrafluoroethylene filled ultra‐high molecular weight polyethylene composite: Mechanical and wear property relationships
Authors: Silverstein M. S. , Breitner J.
Published: December 2004

This research addresses the wear properties and processes of 10 vol% polytetrafluoroethylene (PTFE) filled ultra‐high molecular weight polyethylene (UHMWPE) composites and their relationship to mechanical properties. The addition of the PTFE micropowder results in a slight increase in modulus and a significantly lower strain at break. This is due to a quasi‐brittle failure mechanism. Crosslinking the UHMWPE reduces both the modulus and the ultimate properties. Polymer wear studies against SiC abrasive paper can be divided into initial and steady‐state processes. The initial wear, polymer‐SiC wear, is dominated by microcutting and the formation of a transfer film. A single‐pass wear rate (R1) can be derived from a power‐law description of the initial wear. The steady‐state wear eventually achieved, called polymer‐film wear, is dominated by sliding against a self‐generated. A steady‐state multiple‐pass wear rate (Rx) can be derived from a linear description of steady‐state wear. The relationships between the wear of UHMWPE and the wear of PTFE can be predicted through their ultimate and deformation properties and through an understanding of the wear mechanisms. These relationships cannot be used to relate composite and UHMWPE wear due to their different failure mechanisms. The lower Rx and coefficient of friction of the composite may be related to the PTFE flakes found on the worn and wearing surface. Crosslinking the UHMWPE yields little change in the worn and wearing surfaces and in Rx. The increase in R1 on addition of PTFE and decrease in R1 on crosslinking may be related to the respective increase and decrease in modulus.
Compatibility of poly(ethylene 2,6‐naphthalate) and poly(butylene 2,6‐naphthalate) blends
Authors: Yoon Kwan Han , Lee Sang Cheol , Park O Ok
Published: December 2004

Blends prepared from poly(ethylene 2,6‐naphthalate) (PEN) and poly(butylene 2,6‐naphthalate) (PBN) show only partial miscibility judged from their glass transition temperatures. Two distinct mechanical behaviors are observed: brittle for the blends < 20 wt% of PBN, while ductile > 20 wt% of PBN. The experimental modulus and strength values of the blends are within the predicted values according to Kleiner and Paul models, respectively. This means that PEN/PBN blends are somewhat compatible based on their tensile properties. Especially for 20 wt% of PBN blend, the high modulus and strength are observed. The viscosity of the blend is high, which may imply a somewhat entangled morphology in the amorphous state.
Multilayer rheology: A comparison of experimental data with modeling of multilayer shear flow
Authors: Carriere C. J. , Ramanathan R.
Published: December 2004

The rheological behavior of multilayer polyjeric structures has been investigated Measurements of the bulk viscoelastic properties via small‐amplitude oscilatory rheometry indicated that the shear viscosity is independent of both the numbe of layers (83 vs. 165) and the composition (30/70, 50/50, and 70/30 PC/PMMA by weight) within the limits of the data obtained. It is also apparent tha tthe shear viscosity is influenced strongly by the skin layer material. In additon, a model has been developed tha tcan be used to proedict the shear viscosity and shear stress ofa multilayer structure experiencing shear flow. The model predicts tha thte shear viscosity of a multilayer structure should be independent of the number of layers and strongly dependent on the material in the skin layer. These predictions are in agreement with experimental data.
Fundraising in the southern cone
Authors: Yoffe Daniel , Brunetti Renata M.
Published: December 2004

Fundraising in Latin America is making great strides, building on charitable roots and developing due to political and societal changes. Using the examples of Argentina and Brazil, the authors discuss current practices in philanthropy and fundraising.
New challenges to the third sector in a welfare state
Authors: Wells Lisa
Published: December 2004

The interdependence of the government and the third sector is an important characteristic of philanthropic expression in New Zealand. This chapter looks at what has influenced the development of fundraising practice and highlights some of the challenges.
Characterization of Synthetic‐Coal Char Particles using fractal dimension analysis
Authors: Ludlow Douglas K. , Vosen Wendy M.
Published: December 2004

The development and change of surface ruggedness in chars was studied at conditions typical in a pulverized coal furnace. The fractal dimension, a measure of surface ruggedness, of chars was measured using physisorption techniques. By adjusting the temperature encountered (1173 to 1773 K) and residence time (0.1 to 1.5 s) of the synthetic coal (sized to 46–106 μm diameter), chars at different stages of combustion were prepared in a laminar flow (drop‐tube) furnace. The particles were quickly cooled and quenched in an inert atmosphere. The samples were examined using a scanning electron microprobe, and their fractal dimensions were determined using gas physisorption. The adsorption data were used to test if the char surface was fractal on a molecular scale, to determine the fractal dimension, and to quantify changes in the fractal dimension during combustion. The fractal dimension of the unburned synthetic coal was approximately 2. The fractal dimension increased as high as 2.85 as the carbon matrix burned away and exposed mineral moieties. However, as combustion continued the carbon burned completely away leaving a mineral fly ash particle with a fractal dimension as low as 2.47.
Development of Agglomerate Size and Structure during spherical agglomeration in suspension
Authors: Müller Martina , Löffler Friedrich
Published: December 2004

During the spherical agglomeration process, a suspended solid is agglomerated by adding a binding liquid. First, mircoagglomerates or flocs are produced, which are compacted in the course of the process. Agglomerate size was evaluated by laser diffraction spectrometry, image analysis was used to determine the size and some adequately defined shape parameters calculated by Fourier analysis of the particle contour.

The shape analysis confirms the visual observations; the compaction of the flocs is expressed by the corresponding change of the shape parameters. The influence of several process parameters on changes in agglomerate shape can be described quantitatively and help to gain an insight into agglomeration mechanisms. The particle size distributions determined by image analysis and laser diffraction spectrometry hardly differ for fairly spherical flocs or agglomerates. Concerning the size distribution of the irregular flocs, laser diffraction spectrometry measures larger particles than image analysis.
Estimation of Analytical Procedures through Evaluation of analysis models
Authors: Barth P. , Zierath J.
Published: December 2004

The principles of the statistical valuation for the comparison of analytical procedures by evaluating model analyses are described. A computer program in FORTRAN I1 was developed and used for the evaluation of two process examples from the analytic field of explosives, i.e. determination of nitroglycerin and nitroglycol by means of gas chromatography.
Determining the Shelflife of Solid Propellants
Authors: Volk F.
Published: December 2004

While stored at various temperatures between 65°C and 90°C, several double base propellants with the Same composition differing only in the stabilizer, were aged artificially to the onset of autocatalytic decomposition. A correlation between the temperature and the storage period has been established for the results obtained at the respective temperatures.

Moreover, studies were carried out on the chromatographic analysis of stabilizer reaction products of the type occurring in particular in propellants with diphenylamine, 2‐nitrodiphenylamine, acardite I, acardite 11, and ethylcentralite as a result of storage at elevated temperatures due to reactions with the decomposition products of nitric acid esters.

It has been shown that continuing aging of the propellant gives rise to stabilizer reaction products which are quite characteristic of the respective aging condition. These reaction products may be used as a criterion for different stages of aging within the shelflife of solid propellants.
“Swedish Base Bleed” – increasing the range of artillery projectiles through base flow
Authors: Andersson K. , Gunners N. E. , Hellgren R.
Published: December 2004

The following article summarizes the development of the base flow technique in Sweden. Extensive theoretical and experimental studies have been made in cooperation between the Research Institute of National Defence (FOA) and the Swedish Naval Materiel Department (FMV‐M). Base Bleed gives a significant increase in range and reduces the dispersion. The increase in range is obviously depending on the volume made available for the unit. At firing tests an increase in range of 25% has been achieved due to the base flow effect.
Thermochemical Computations on Propellant Powder Gases at interior ballistic pressures and temperatures
Authors: Dürschner M. G.
Published: December 2004

The interaction of powder gas molecules in the interior ballistic pressure and temperature range does not allow the application of the Nobel‐Abel equation of state. An equation of state which correlates the thermodynamic variables pressure, specific volume, and temperature, and which meets to a high extent the physical facts, is the virial equation. Using an additive combined theorem for the virial coefficients, the equations for equilibrium in a chemically reacting gas composition without solid phase are derived by virtue of the virial equation as an equation of state. The internal energy and the enthalpy of the powder gases are given for the computation of the explosion temperature and the adiabatic flame temperature. For a numerical solution of this non‐linear system of equations, a combination of the gradient process and the Newton‐Raphson process (Such‐Weg‐Verfahren) is applied. Furthermore, the numerical results for different propellant powders are stated and discussed.
The Effect of Acoustic Field on the Thermal Conductivity of composite propellants
Authors: Ramachandran Lalitha , Gowariker V. R.
Published: December 2004

A study is conducted to determine the effect of acoustic field on the thermal conductivity of composite propellants based on poly‐ butadiene and polyurethane binders. The thermal conductivity of the propellant is determined by a specially designed equipment. The thermal conductivity measurements are made in steady state conditions and in an acoustic field of constant amplitude at various frequencies ranging from 1 kHz to 6 kHz and at different temperatures ranging from 30°C to 50°C. The results indicate that the thermal conductivities of the composite propellants increase when they are subjected to an acoustic field. The data obtained are presented in the paper. Since the burning behaviour of solid propellants is influenced also by its thermal conductivity, the present work may be of direct relevance in improving upon some of the existing burning rate and combustion models.
The Initiation of Tetryl by Small Charges of PETN
Authors: Dinegar R. H. , Millican M. S.
Published: December 2004

Explosion times of PETN pressings and PETN/tetryl assemblies have been measured as a function of the length and density of the PETN donor charge and the density of the tetryl acceptor. A charge length of about 3.5 mm is necessary for the PETN explosion wave to reach steady‐state velocity for the densities studied. The initiation of the tetryl pellet is related to the detonation velocity (and presumably peak pressure) as well as the pressure‐distance profile generated in the PETN explosion wave. Higher‐density tetryl charges appear to be more sensitive than lower.
Some theoretical considerations on Improving the Internal Ballistic Performance of Guns
Authors: Melchior E. , Witt W.
Published: December 2004

An improvement in internal ballistic performance is understood to mean an increase in muzzle velocity for the same weight of projectile and the same peak pressure. Using a thermodynamic model of the internal ballistics a possible method of achieving a significant improvement in performance is demonstrated based on optimizing the properties of the propellant in a charge of conventional design. An example of the application of the theoretical results is discussed.
The European Commission for the Standardization of the Tests of Explosives (changed since 1976: International study group for the standardization of the methods of testing explosives)
Authors: Ahrens H.
Published: December 2004

Since 1960 a group of experts, gathered on a voluntary basis, are working under the name of “European Commission for the Standardization of the Tests of Explosives” (Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen – Commission Européenne de Normalisation des Essais d'Explosifs).

The following is a short description of this activity, from its origin, up till now and for the future.
The Effect of Gritty Contamination on the Initiation of Explosives by Impact
Authors: Scullion H. J. , McCormack J.
Published: December 2004

In studies on the Rotter machine on the initiation of grit‐contaminated explosives by impact one can make use of the variable θ = 100 (F−Fmin)/Fmax where F = figure of insensitiveness. A virtually linear relationship then exists between the grit content (C %) and the reciprocal (or logarithm) of θ.
Über die Verwendbarkeit der neuen Methode der Sprengkapselprüfung nach Prior sowie der Prüfzünder PETN als Prüfnormal
Authors: Herrmann R.
Published: December 2004

Die von J. Prior vorgetragene Methode zur Sprengkapselprüfung wurde von uns neben der Bleiblockprüfung verwendet.

Die Veranlassung dazu war folgende: Der bisher verwendete Trauzl Bleiblock (250 mm hoch) ist umständlich in der Anwendung und für das Bedienungspersonal nicht frei von toxischen Wirkungen. Seine Mängel beim Anzeigeverhalten, die jetzt nach 50 Jahren bekannt sind, waren nur in zweiter Linie ausschlaggebend für einen Wechsel der Prüfmethode. Für das neue Verfahren läßt sich auch erst in 50 Jahren sagen, ob es besser ist. Zunächst hoffen wir es.

Die Bedingung für einen Wechsel der Prüfmethode: Eine neue Methode zur Bestimmung des Zündvermögens soll sich möglichst gut an die bisherige Methode anlehnen.

Das Ergebnis dieser Untersuchungen: Die von J. Prior vorgetragene Methode erfüllt diese Forderung, so daß wir sie unserer nationalen Behörde als neues Prüfverfahren für Sprengkapseln vorschlagen werden. Die Aussagefähigkeit entspricht der des Bleiblocks. Die Anzahl der jeweils durchzuführenden Versuche muß noch festgelegt werden, um eine gleichwertige Genauigkeit zu erhalten.

Als Prüfnormal an Stelle der Normalsprengkapsel Nr. 8 wird der Prüfzünder PETN 0.37 g vorgeschlagen. Auch hier muß die Übereinstimmung noch überprüft werden.
Ways of Reducing the Deflagration Tendency of ion‐exchanged permitted explosives
Authors: Glaskova A. P. , Zhadan S. N.
Published: December 2004

This work considers possible ways of reducing the deflagration tendency of ion‐exchanged permitted explosives based on new experimental data on the inhibition of ignition of methane‐air mixtures and on the cornbustion of condensed systems.

The mixtures contained the nitrates or perchlorates of the alkali metals as oxidizers together with ammonium chloride, oxalate, sulphate or phosphate as fuel. They had a zero oxygen balance. The effect of adding 12% of gelatinized nitroglycol was also investigated. The lower pressure limit and the burning rate were chosen as parameters to characterize the deflagration rendency. They were in a constant pressure bomb over the pressure range 0.1 MPa to 100 MPa using a method described previously.

It is shown that the lower pressure limit is higher and the burning rare lower for mixtures containing ammonium oxalate than for analogous mixtures but with ammonium chloride. The lower pressure limit is also higher for mixtures based on potassium perchlorate.

The calculated explosive characteristics and the burning parameters of the mixtures investigated arc reported. Reasons for the higher deflagration tendency of the mixtures containing ammonium chloride are discussed.
Mach‐Reflection of Detonation Waves in condensed high explosives
Authors: Müller F.
Published: December 2004

In a cylindrical arrangement as deviced by G. R. Fowles and W. M. Isbell for the generation of Mach‐reflection of shock waves in solids Mach‐reflection of detonation waves in condensed high explosives with different detonation velocities is investigated. The process is observed directly by flash x‐ray radiography. By means of this arrangement it is possible to generate via Mach‐reflection a plane detonation wave, the Mach‐disk. Characteristics and applications of the Mach‐disk are discussed.
A Numerical Study of Explosive Heating due to Projectile Impact
Authors: Chawla M. S. , Frey R. B.
Published: December 2004

A finite difference Eulerian computer code with some very useful Lagrangian features is employed to study the impact of a projectile on a heavily confined, inert, solid explosive. Temperature rise due to shock compression and plastic deformation in both the explosive and the metal confinement is estimated. It is concluded that in situations where the shock is weak and the explosive does not initiate shortly after the projectile impact, the possibility of it so doing, due to plastic deformation, at a later time cannot be discounted.
The assay of ammonium nitrate and ethylenediamine dinitrate
Authors: Selig W.
Published: December 2004

Ammonium nitrate and ethylenediamine dinitrate in a composite have been determined by potentiometric titration with standard base after reaction with formaldehyde. Ethylenediamine dinitrate yields two breaks, while ammonium nitrate exhibits only a single potentiometric break. Both components can therefore be resolved. The first potentiometric break is a measure of the ethylenediamine dinitrate content, while the second break is a measure of the sum of the components.
High‐speed photographic studies of impact on thin layers of emulsion explosive
Authors: Krishna Mohan V. , Field J. E. , Swallowe G. M.
Published: December 2004

A photographic study, at microsecond framing rates, has been made of the impact behaviour of thin layer samples of emulsion explosives. The experiments were performed using a drop‐weight apparatus with transparent anvils. The effects of incorporating aluminium granules (∼100 μm in size) and glass microspheres (50 μm to 150 μm diameter) in the emulsion matrix were also studied. It was possible to record the flow of the emulsion both with and without additives. Of particular interest were observations of the onset and development of crystallization in the layer. In no case was there evidence for initiation of explosion.
Smoke generators. IV. The ignition of loose powder mixtures of pyrotechnic white smoke compositions containing hexachloroethane and silumin in sealed tubes
Authors: Hartley F. R. , Murray S. G. , Williams M. R.
Published: December 2004

A small sealed tube has been used to study the reaction between hexachloroethane and silumin, which is important in certain types of smoke generating pyrotechnics. Standard amounts were heated at 483 K in a 12−cm3 tube. Products identified were aluminium chloride and tetrachloroethylene. The effects of added oxides were noted. Zinc oxide, magnesium oxide and cupric oxide inhibited the reaction. Ferric oxide accelerated the reaction and stannous oxide, zirconium dioxide and titanium dioxide seemed to have little effect. Other substances found to inhibit the reaction were ammonium chloride, water and ortho‐chloroaniline. Pentachloroethane was found as a product when water was present indicating the formation of pentachloroethyl radicals.
Smoke generators. V. Thermochemical investigation of pyrotechnic white smoke compositions containing hexachloroethane and silumin
Authors: Hartley F. R. , Murray S. G. , Williams M. R.
Published: December 2004

Simultaneous differential thermal analysis with thermogravimetric analysis has shown that the inhibition of the ignition of silumin‐hexachloroethane smoke generators by zinc oxide is not due to the adsorption of hexachloroethane vapour on zinc oxide. Analysis of this and previously reported evidence suggests a free radical mechanism for the reaction of aluminium with hexachloroethane. Zinc oxide inhibits this by competition for radicals.
Thermal Decomposition of Energetic Materials XXIV. A comparison of the crystal structures, IR spectra, Thermolysis and impact sensitivities of nitroguanidine and trinitroethylnitroguanidine
Authors: Oyumi Y. , Rheingold A. L. , Brill T. B.
Published: December 2004

The crystal structure of trinitroethylnitroguanidine (TNENG) was determined by X‐ray diffraction for comparison with nitroguanidine (NGu). Pertinent crystal parameters are: orthorhombic, Pbca, a = 14.611 (7) Å, b = 11.973 (5) Å, c = 11.452 (5) Å, V = 2003 (2) Å3, Z = 8, D(calcd) = 1.758 g/cm3, R(F) = 6.30%, R(wF) = 6.58%. A hydrogen bonded network like that present in NGu is largely responsible for the lattice cohesion of TNENG. The IR spectrum of the condensed phase using slow thermolysis, and the gas phase using slow and fast thermolysis, suggests that parallel CN and NN bond fission reactions take place in both TNENG and NGu. The calculated and experimental values of the impact sensitivity of TNENG and NGu are compared. We conclude that the impact sensitivity and the thermal decomposition of TNENG are dominated by the characteristics of the C(NO2)3 group. The intermolecular hydrogen bonding that may desensitize nitroguanidine to impact has essentially no stabilizing effect on TNENG.
Emissionspectroscopy of Boron Ignition and Combustion in the range of 0.2 m̈m to 5.5 m̈m
Authors: Eisenreich N. , Liehmann W.
Published: December 2004

Boron particle combustion is retarded by initial presence of an oxide coating. In current boron ignition models, oxygen is assumed to desolve in the oxide and diffuse to the B/B2O3 interface for reaction. One method to observe the reaction of boron with its surrounding atmosphere is the time resolved emission spectroscopy we applied in the range of 0.2 m̈m to 5.5 m̈m for different burning processes.

In one experiment boron powder was burned in oxygen atmosphere initiated by an efficient pyrotechnic device. The energy transfer by the hot gases led to a glowing phase of the boron particles which then changed to a high temperature combustion and ended in a further glowing phase. The two glowing phases emitted continuous emission spectra, while the burning phase emitted the bands of BO and BO2.

Another experimental setup was used to feed boron particles in a hot oxidizing atmosphere provided by a propane/air flame which flew into a combustion chamber. Herein the reaction of boron was recorded with high speed cinematography and time resolved emission spectroscopy. The flame contained a small amount of background radiation and we could identify emitted bands of BO, BO2, HBO2, CO and CO2.
Penetration Cutoff Velocities of Shaped Charge Jets
Authors: Held M.
Published: December 2004

The maximum depth of penetration, Pmax, of a shaped charge jet can theoretically be calculated from 5 quantities for the purely continuous, or for the initially continuous and then particulated, or for the fully particulated penetrating jet. These quantities are the distance Z0 of the target plate from the virtual origin, the value of γ (i.e. the square root of the ratio of target to jet density), the jet tip velocity vj,0 the efficient residual velocity vj,min, and the particulation time tp.

Instead of calculating the individual values of vj,min for the individual depths of penetration Pexp at various standoff distances, this quantity can quite simply be read from the standoff diagram by means of the penetration cutoff lines‐ a so‐called Standoff/Cutoff‐diagram ‐, using the experimentally determined depth of penetration Pexp. The penetration cutoff lines are lines which start at the virtual origin and which represent the ideal increment in depth of penetration per jet velocity interval in the standoff diagram, the abscissas of this line corresponding to the jet tip velocities.

The methods are demonstrated and explained, using the results of three firings with one type of shaped charge as an example. The shots were made at 6, 12, and 24 calibers standoff distance, and the cratering history was also determined in these trials.
Shaped Charge Jet Heating
Authors: Racah E.
Published: December 2004

A one‐dimensional theoretical model of shaped charge jet heating is developed. The model includes heating due to the shock wave transferred to the liner by the explosive detonation wave and due to the plastic work performed during liner collapse and jet elongation. Results calculated by a one‐dimensional shaped charge computer code using this model fall within the lower bound of the experimental range.
Computations of ESR coupling constants in organic radicals. III. Nitro Derivatives of the Benzyl Radical
Authors: Hameka H. F.
Published: December 2004

We compute the ESR coupling constants and the geometries of ten nitro derivatives of the benzyl radical. We consider the three mononitrobenzyls, the six dinitrobenzyls and 2,4,6‐trinitrobenzyl. The computations are based on the use of the Gaussian 82 Program Package with the STO‐3G basis set. There are no experimental data available.
The Mott Fragmentation Model and the Vpl break‐up parameter
Authors: Hirsch Eitan
Published: December 2004

It is shown that the Mott fragmentation model and the Hirsch formula for the shaped charge jet break‐up time complete one another to yield a unified model. This model is consistant with the microscopic picture of internal flow splitting in the metal, into shear bands undergoing a strain larger than the average and the metal between them which undergoes a strain which is smaller than the average. This splitting reduces the deformation energy dissipated by the metal while elongating. It corresponds to the splitting of the stress versus strain characteristics of the metal into the isothermic and adiabatic curves as measured by Johnson and Cook. The parameter Vplwhich describes the break‐up process according to the Hirsch model, is identified with the expression (dσm/ϱ)1/2 where dσm is the difference in yield strength between the isothermic and adiabatic curves where the adiabatic characteristic becomes a maximum. The comparison with available experimental measurements of this prediction shows a very encouraging agreement. The weak dependence of Vpl on the strain rate on the one hand and the observed increase of the jet break‐up time in slowly elongating jets on the other hand are also explained using energy considerations. The recent recovery of jet particles by Zernow yields supportive evidence of the proposed theory which may be extended to all semi steady metal plastic flow phenomena. The final break‐up, according to this model is due to the separation between the two sides of shear bands where the slide motion went on during the whole deformation process.
Gun Muzzle Blast and Flash
Authors: Klingenberg G.
Published: December 2004

Gun muzzle blast and flash phenomena are of importance since they are associated with the formation of large overpressures and intense muzzle flash. About 30% of the chemical energy released from the propellant used in a conventional gun is converted into kinetic energy of the projectile. The remaining energy is mainly contained in the propellant gas‐particle mixture which escapes from the muzzle of the gun in a few milliseconds. The sudden discharge produces a blast wave because of the rapid displacement of air originally surrounding the gun. In addition, these gases are generally fuel‐rich and mix with air turbulently entrained from the surroundings. Combustion of this mixture causes gun muzzle flash, usually associated with the formation of a secondary blast wave. The design of solid propellant charges, gun performance, muzzle attachments and chemical flash suppressants is guided by the need to keep the above hazards to safe limits. In this paper, blast and flash phenomena are characterized using data of recent investigations and showing illustrative examples of their development.
A New Method Rapidly Measuring Nitroglycerin in the coating of the rocket propellant
Authors: Kong Yang‐Hui , Liu Zi‐Ru , Yin Cui‐Mei , Wu Cheng‐Yun
Published: December 2004

In this paper an application of thermogravimetric‐derivative thermogravimetric analysis (TG‐DTG) to the measurement of the nitroglycerin (NG) in thc coating of the rocket propellant was developed. In comparisons with gas chromatography (GC) and weight method (WM), TG‐DTC has been confirmed to he even more available to measure rapidly migration of NG in thc coating. The new method is accurate to within ± 0.5% and its standard deviation is O.1. The method is of actual significance in respect of thc investigation of the migration regularity of plasticizer, the selection for coating materials and the prediction of service life of the solid propellants.