bluuebunny/crossref_metadata_2025 huggingface dataset:
A state variable model for high strength polymers
Authors: Krempl Erhard , Bordonaro Christine M.
Published: December 2004

Displacement controlled experiments on nylon 66, poly(etherether ketone), and poly(ether imide) at room temperature suggest that nonlinear elastcity is not a good model for these polymers. Rather, qualitative evidence is presented that a state variable model shows promise. In this model, the rate of deformation is the sum of the elastic and the inelastic rates of deformation. The elastic rate of deformation is given by an objective formulation of Hooke's law, and the inelastic deformation is an increasing function of the overstress, the difference between the Cauchy stress and the equilibrium stress. The equilibrium stress is a state variable, and represents the stress that can be sustained at rest following deformation. Load controlled tests, intended to verify or falsify the model, show that the creep rate at the same stress level can be different on loading and unloading, and that the creep rate need not increase with an increase in creep stress level. These anomalous results can easily be explained by the introduction of the overstress concept, and by proper evolution of the equilibrium stress. They confirm the usefulness of the overstress concept for the modeling of these polymers.
Plastic behavior and deformation textures of poly(etherether ketone) under uniaxial tension and simple shear
Authors: Dahoun A. , Aboulfaraj M. , G'Sell C. , Molinari A. , Canova G. R.
Published: December 2004

Samples of poly(etherether ketone) (PEEK) were subjected to large plastic deformations under uniaxial tension and simple shear by means of a new video‐controlled testing method at constant true strain rate. The “equivalent” stress‐strain curves obtained under the two loading modes are close at the yield point, but diverge drastically at large strains, with a rapidly increasing hardening in tension and a moderate hardening under simple shear. X‐ray diffraction goniometry shows that these contrasting behaviors are associated with the different textures developed in the crystallite orientations. Under tension, the PEEK lamellae are progressively tilted in such a way that the chain axis becomes oriented parallel to the tensile axis; in the other mode, the final chain orientation is near to the shear axis. DSC analyses of deformed samples in both modes are carried out. The results show that the tension loading induces a fragmentation of the thin lamellae, while the shear mode generates less fragmentation. A quantitative model is presented that involves a composite approach: (i) the viscoplastic deformation of the crystalline lamellae, which is controlled by chain slip and transverse slip systems on planes parallel to the c axis, and (ii) the hyperelastic deformation of the amorphous phase, which depends on the affine unfolding of statistically distributed subchains. A discussion of the influence of the CRSS values on the stress‐strain curves and textures is developed by means of this model.
A constitutive model for the nonlinear viscoelastic viscoplastic behavior of glassy polymers
Authors: Hasan O. A. , Boyce M. C.
Published: December 2004

Two features of the glassy state of an amorphous polymer, which play a key role in determining its mechanical properties, are the distributed nature of the microstructural state and the thermally activated (temporal) evolution of this state. In this work, we have sought to capture these features in a mechanistically motivated constitutive model by considering a distribution in the activation energy barrier to deformation in a thermally activated model of the deformation process. We thus model what is traditionally termed the nonlinear viscoelastic behavior as an elastic‐inelastic transition, where the energetically distributed nature of inelastic events and their evolution with straining is taken into account. The thermoreversible nature of inelastic deformation is modeled by invoking the notion of strain energy stored by localized inelastic shear transformations. The model results are compared to experimental data for constant true strain rate uniaxial compression tests (nonmonotonic) at different rates and temperatures; its predictive capabilities are further tested by comparison with compressive creep tests at different stress levels and temperatures.
Solidification of thermoviscoelastic melts. Part II: Effects of processing conditions on shrinkage and residual stresses
Authors: Bushko Wit C. , Stokes Vijay K.
Published: December 2004

The solidification of a molten layer of thermoplastic between cooled parallel plates is used to model the mechanics of part shrinkage 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 model allows material to be added to fill the space created by the pressure applied during solidification, so that this model can be used to assess packing‐pressure effects in injection molding. Parametric results are presented on the effects of the mold and melt temperatures, the part thickness, and the packing pressure—the pressure applied during solidification to counteract the effects of volumetric shrinkage of the thermoplastic—on the in‐plane and through‐thickness shrinkages, and on residual stresses in plaque‐like geometries. The packing pressure is shown to have a significant effect on part shrinkage, but a smaller effect on residual stresses. Packing pressure applied later in the solidification cycle has a larger effect. Mold and melt temperatures are shown to have a much smaller effect. The processing parameters appear to affect the through‐thickness shrinkage more than the in‐plane shrinkage. While the results are presented in terms of normalized variables based on the properties of bisphenol‐A polycarbonate, they can be interpreted for other amorphous thermoplastics such as modified polyphenylene oxide, polyetherimide, and acrylonitrile‐butadiene‐styrene.
Low temperature melting behavior of CO2 crystallized modified PETs
Authors: Mensitieri G. , Del Nobile M. A. , Apicella A. , Guerra G. , Al Ghatta H.
Published: December 2004

Differential scanning calorimetry (DSC) analysis has been performed on modified and commericial amorphous samples of poly(ethylene terephthalate) (PET) crystallized by high pressure carbon dioxide (CO2). Two endothermic peaks are present in the DSC scans of all the carbon dioxide‐treated samples. A qualitatively analogous behavior has been detected in the case of amorphous samples heat treated at temperatures slightly exceeding the glass transition temperature of virgin material. Wide angle X‐ray scattering analysis has confirmed the structural analogies between samples CO2 crystallized at 50°C and thermally crystallized slightly above Tg. A differential scanning calorimeter capable of working at high pressure of CO2 has been adopted in order to examine the effect of carbon dioxide on the crystallization temperature range.
Numerical simulation of blow molding—Viscoelastic flow analysis of parison formation
Authors: Tanoue Shuichi , Kuwano Yoshifumi , Kajiwara Toshihisa , Funatsu Kazumori , Terada Kousuke , Yamabe Masashi
Published: December 2004

The simulation of the parison formation process in blow molding has been studied. The flow field was divided into two regions, namely, the extrudate swell region near the die lip and the parison formation region after the exit swell. In the swell region, we predicted the swelling ratio and residual stress distribution for high Weissenberg numbers for steady planar well using the 1‐mode Giesekus model. In the parison formation region, the flow is assumed to be an unsteady unaxial elongational flow including drawdown and recoverable swell and is modeled using the 10‐mode Giesekus model. We calculated the time course of parison length and thickness distribution, and compare the calculation results of parison length with experimental data. It was found that the predicted values agreed rather well with the experimental values. The calculation results could especially predict the shrink‐back, which is the phenomenon where the parison length becomes shorter after the cessation of extrusion, and it was found tat this was caused by the recoverable swell of the parison, which depends on the tensile stress generation in the die. Various flow rates and die geometries were studied and confirmed the reliability and usefulness of the method.
Dynamics of uni and biaxial deformation and its effects on the thickness uniformity and surface roughness of poly (ether ether ketone) films
Authors: Cakmak M. , Simhambhatla M.
Published: December 2004

The uniformity of films and their surface roughness are of great importance in applications involving information recording (videotapes etc.). These properties of polymers processed with such film production techniques as tenter frame operations are not well understood. To understand the relationships between the process variables, such as stretching mode, rate of stretching, temperature of stretching, and material characteristics, melt cast amorphous PEEK films were subjected to systematic experiments involving variations of the process parameters. The results reveal that stress hardening in the stress strain curves plays an important role in defining the level of thickness uniformity and surface roughness. It the films are stretched in a way that they do not experience stress hardening, the resulting films were found to have significant variations in thickness, sometimes worse than those of precursor materials. In all cases, where films are subjected to substantial stress hardening, the above two parameters improved dramatically. This indicates that no matter what the stress response of the film, those films stretched to intermediate stretch ratios have poor thickness uniformity and surface quality. Once the stress hardening takes effect, the deterioration of the dimensional parameters was found to stop and reverse and ultimately reacha point in deformation space where the film quality was better than that of the original films. This is solely attributed to the stress hardening that allows the thinned sections of the films to sustain higher loads, thereby propagating the deformation to other underformed areas in the films, which in turn causes a “self‐leveling” effect. An important implication of this finding is that to obtain films of optimum thickness and surface quality, they need to be stretched beyond the (global) stress hardening point. Otherwise, less than desirable film quality may result.
Stress‐Strain curves for solid polymers
Authors: Kitagawa Masayoshi , Zhou Dexin , Qui Jianhui
Published: December 2004

In order to provide nw experimetnal facts required for constructing a nonlinear constitutive equationfor solid polymers, some tests wee conducted on amorphous pojymers of polycarbonate and poly(methyl methacrylate) and for a crystalline polymer of polyxymethylene under varous strain paths such as comprssion, torsion and combined tension‐torsion. It is shown that (1) the stress‐strain behavior for the strain paths without strain reversal is described well not only for amorphous polymers, but also for crystalline polymers by an overstess theory proposed by Krempl, and (2) at the strain paths wth stran reversal, the stress responses are considerably differetn from what is expected for the fstress responses of metals and their alloys.
Biopolyester melt behavior by torque rheometry
Authors: Melik D. H. , Schechtman L. A.
Published: December 2004

A torque rheometer method has been developed to evaluate the melt behavior of biopolyesters. The main features of this technique include: (i) a modified equipment configuration, so as to maintain the melt temperature within ± 1°C pf the set temperature after the first few minutes of polymer melting and thermal equilibration, and (ii) a kinetic equation that can be used to determine the melt behavior from the torque‐time data. Applying this methology to a poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerte) copolymer shows that the degradation kinetics follow Arrhenius behavior with temperature, that the degradation rate increases with increasing hear, and that the activation energy for random chain scission is independent of shear rate. This effect of shear on the degradation process may be a result of viscous heating. The degradation rate is increased because of the increased internal energy of the polymer chains as a result of the mechanical deformation. There is no evidence of direct mechanical degradation. Last, the viscosity values obtained with the torque rheometer are consistent with those obtained by capillary rheometry.
Comparisons of experimental data to indices of adhesion derived from dielectric models
Authors: Iwamoto N. E.
Published: December 2004

A perspective of adhesion is offered using average property indices such as dielectric constant, dipole moment, and thermal conductivity. These indices have been derived by comparisons of dielectric theories of adhesion and cohesion with comparisons to experimental data found in the literature. For example, it was found that adhesion generally increases with increased dielectric constant, or with the inverse of the thermal conductivity, for metal substrates. It was also found that ranges in the experimental data found were primarily caused by changes in surface roughness, which meant that interaction densities were not predictable.
Effects of mixing porcedures on properties of compatibilized polypropylene/nylon 6 blends
Authors: Lee Jae‐Dong , Yang Seung‐Man
Published: December 2004

The paper consides the effects of compatibilization with maleic anhydride grafted polypropylene (PP‐g‐MAH) on the propertie of immiscible blends of polypropylene (PP) and nylon 6 (N6). We prepared the blends by three different mixing processes; single‐step blending, two‐step blending with reactive premixing, and two‐step blending with nonreactive premixing, to determine the effective mixiing process for fine morphological structure thermal stability, and mechanical properties. Dynamic melt reheological properties were measured to examine the modification of elastic properties by the compatibilizer. In addtion, thermal analysis was also carried out to detect the change in crystallization and thereby to probe the degree of compatibilizaton. The results show that compatibilized blends prepared by teh single‐step process exhibit improved phase morphology, thermal stability, and mechanical properties for dried conditions, compared with other blend types. Finally, the water absorption test indicates that the added compatibilizer yields enhanced water resistance in spite of the strong intrinsic hydrophilicity of N6. In particular, two‐step blending with reactive premixing is most effective in improving water resistance and reducing degradation of mechanical properties after moisture absorption.
Extrude distortion in the capillary/slit extrusion of a molten polypropylene
Authors: Kazatchkov Igor B. , Hatzikiriakos Savvas G. , Stewart Charles W.
Published: December 2004

Experiments were carried out in both sliding plate and capillary rheometers with a polypropylene resin to determine the conditions for the onset of slip, surface, and gross melt fracture. It was found that there was no distinction between surface and gross melt fracture, which is commonly observed in the case of polyethylenes. Furthermore, the flow curves determined by using capillaries having various diameters are diameter independent implying the absence of slip. However, experiments with slit dies having rough surfaces suggest wall slip. Further analysis has shown that the effect of viscous heating masks the detection of slip from the diameter‐dependency of the flow curves. The effect of a thin layer of fluoropolymer (Teflon PA, DuPont) on the critical shear stress for the onset of wall slip and melt fracture, as well as on the relationship between the wall shlip and the shear stress, were also examined. It was found that the presence of such layers increases the slip velocity, while it decreases the critical shear stress for the onset of slip.
Study of reaction injection molding of polyurethane microcellular foam
Authors: Park Hyeog , Youn Jae R.
Published: December 2004

Processing of microcellular foam was investigated for the feasibility of production of tough and lightweight polyurethanes. To increase the nucleation rate in a gas‐supersaturated resin, ultrasonic excitation was applied to the mixture of polyol(polyether‐based polyol) and isocyanate(diphenyl methane diisocyanate). A microcellular structure was produced by two sequential steps, i.e., supersaturationof the polyol resin with nitrogen gas at elevated pressure and ultrasonic bubble nucleation right after the impingement mixing of two components of the polyurethane system. Theoretical analyses based on nucleation theories were employed to predict the rate of nucleation in the gas‐supersaturated polyurethane. The rate of nucleatio in the resin was predicted by classical nucleation and cluster theories. In the experimental investigation, ultrasonic excitation was applied to increase the nucleation rate in the resin that had been saturated by nitrogen at a saturation pressure < 2.0 MPa.
Coefficients of dynamic friction and the mechanical melting mechanism for vinylidene chloride copolymers
Authors: Spalding Mark A. , Hyun Kun S. , Jenkins Steven R. , Kirkpatrick Donald E.
Published: December 2004

Previous research and this research indicate that the mechanical melting for poly(vinylidene chloride) copolymers (PVDC) is complex. Mechanical melting is defined as the melting (or devitrification) of a polymer when a significant portion of the thermal energy originates from a mechanical energy dissipative process. PVDC mechanically melted on a moving metal surface at temperatures of the test instrument that were considerably lower than the differential scanning calorimetry (DSC) onset melting temperature. PVDC formulated with low levels of high density polyethylene (HDPE), however, melted at metal temperatures near the DSC onset melting temperature. Two different mechanical melting mechanisms are proposed to explan the data, and the frictional data are discussed with respect to solids conveying in a single‐screw, plasticating extruder.
Sintering high performance semicrystalline polymeric powders
Authors: Brink A. E. , Jordens K. J. , Riffle J. S.
Published: December 2004

Poly(ether ether ketone) (PEEK) is high performance semicrystalline thermoplastic with a glass transition temperature of 143°C. The melting point (Tm) is quoted as 334°C. Because of its high thermal transitions, PEEK, requires high temperatures for processing, at least 370–400°C. It has been determined that under the recommended processing conditions PEEK can undergo branching and eventually crosslinks. An alternative to melt processing PEEK is to apply the powder metallurgy technique of sintering. This involves cold (room temperature) compaction of the polymeric powder, followed by pressure free sintering of the resultant green body. We have reported a process for preparing submicron PEEK particles, and the focus here is on the free sintering of these particles with emphsis on the effects of particle size, sintering temperature, and compaction pressure. The data is evaluated using the two particle model developed by Frenkel as well as the crack healing theory developed by Wool.
Processing and morphology of polystyrene/ethylene‐propylene rubber reactive and nonreactive blends
Authors: Scott Christ E. , Macosko Christopher W.
Published: December 2004

The difference between reactive and nonreactive polymer blends in terms of processing and morphology has been investigated. The glassy phases for the blends are an oxazoline functional polystyrene (PS‐Ox) and a similar non‐functional polystyrene (PS). The rubbery phases are an ethylene‐propylene rubber (EP) and a similar ethylene‐propylene rubber (EP‐MA) with 07% grafted maleic anhydride. In the case of PS‐Ox/EP‐MA blends, the oxazoline group may react with the grafted rubber functionality at the interface between the two immiscible components during blending to form a compatibilizing agent in‐situ. The nonreactive blends systems of PS‐Ox/EP and PS/EP‐MA were used for comparison to the reactive system. The blend components are rheologically matched to simplify the interpretation of the process and morphological data. The blends were prepared in a batch mixer with roller blades. The torque required for mixing was measured during the blending process. The torque traces for the reactive blends exhibited a peak in torque, attributed to the chemical reaction at the interface. The weight fraction of gel in the blends was used to measure the extent of reaction. It correlates well with the mixing torques and rheological properties. The nonreactive PS‐Ox/EP and PS/EP‐MA blends show poor interfacial adhesion between the two phases. In contrast, the reactive PS‐Ox/EP‐MA blends show excellent during annealing is also much greater for the reactive blends. Varying the functionality concentration in the PS phase shows that the dispersed phase rubber particle size is reduced by increasing the concentration of oxazoline in the matrix. Blends with no or small amounts of functionality in the PS phase exhibit yield behavior in tension. However, a level of concentration of reactive functionality may be reached where the material becomes brittle.
The leveling of thermosetting waterborne coatings. Part III: Leveling under controlled conditions
Authors: Kojima Shunji , Moriga Toshinori , Takenouchi Ken
Published: December 2004

Experiments on coated films of water borne, coatings (WBC) under controlled conditions (i.e., 25°C, 65% RH) were carried out to study the mechanism of leveling. Data in a companion paper imply that the development of the surface tension gradients plays an important role in promoting leveling. The stress due to surface tension gradients is found to be much greater than the stress introduced by hydrostatic pressure gradients in the film caused by surface tension and the free boundary curvature of the film. This reconfirms that the use of a co‐solvent, which evaporates faster than water, greatly accelerates the leveling of a WBC.
Study of the morphology and mechanical properties of polypropylene composites with silica or rice‐husk
Authors: Toro Patricio , Quijada Raúl , Murillo Omar , Yazdani‐Pedram Mehrdad
Published: December 2004

The mechanical, morphological behavior and water absorption characteristics of polypropylene (PP) and silica, or PP and rice‐husk, composites have been studied. The silica used in this study as filler was a commercial type produced from soluble glass or rice husks. The compatibilizing effect of PP grafted with monomethyl itaconate (PP‐g‐MMI) and/or with vinyltriethoxysilane (PP‐g‐VTES) as polar monomers on the mechanical properties and water absorption was also investigated. In general, a high loading of the studied fillers in the polymer matrix increases the stiffness and the water absorption capacity. This effect is more noticeable in the tensile modulus of the PP/silica composite with PP‐g‐VTES as compatibilizer. However, the increase of the rice‐husk charge as a natural filler in the PP matrix decreases the stiffness, and in the presence of PP‐g‐MMI as compatibilizer in PP/rice‐husk, the tensile modulus and water absorption of the composite were improved. The better adhesion and phase continuity in the PP/silica and PP/rice‐husk composites with different compatibilizers was confirmed by the morphological study. Copyright © 2004 Society of Chemical Industry
Plasma Deposition of Allylamine on Polymer Powders in a Fluidized Bed Reactor
Authors: Tatoulian Michaël , Brétagnol Frédéric , Arefi‐Khonsari Farzaneh , Amouroux Jacques , Bouloussa Otman , Rondelez Francis , Paul Alan John , Mitchell Robert
Published: December 2004

Summary: Thin films of plasma‐polymerized allylamine (PPAA) have been deposited onto polyethylene powders (PE) and polystyrene (PS) beads by using a low‐pressure 13.56 MHz plasma in a fluidized bed reactor. Chemical derivatization using a set of three different blocking agents has allowed quantitative measurement of the relative percentages of primary, secondary, and tertiary amines. Under optimized conditions, it is possible to incorporate up to 110 nmol of amine groups per gram of powder and with a selectivity of 75% for primary amines. Moreover, our data clearly show that for films deposited at 10 W the selectivity for primary amines is at a maximum, but this is at the expense of resistance to washing. A power of 20 W corresponds to an optimum value since both the amount of primary amines and the degree of resistance of the coating to solvents reach maximum values.

Distribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.

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Distribution of the primary (I), secondary (II), and tertiary (III) amine groups on plasma‐polymerized allylamine films deposited on polyethylene powders.
FTIR Plasma Phase Analysis of Hexamethyldisiloxane Discharge in Microwave Multipolar Plasma at Different Electrical Powers
Authors: Raynaud Patrice , Despax Bernard , Segui Yvan , Caquineau Hubert
Published: December 2004

Summary: In this paper, the gas phase composition of hexamethyldisiloxane (HMDSO) microwave plasma at 4 × 10−3 mbar and of the corresponding films were studied by FTIR spectroscopy under different power conditions. At low powers, species with a chemical structure very similar to that of HMDSO were observed in the gas phase, whereas the film essentially contained short [(CH3)2SiO]n‐like chains with a low branching rate and the end group Si(CH3)3. At higher powers, the chemical entities present in the gas phase contained several (SiO)x bonds, whereas the branching rate in the film increased with the amount of SiH, SiC and SiO bonds. The interpretation of these observations led to a proposal involving a chemical mechanism. In this mechanism, the increasing decomposition of HMDSO into by‐products, which themselves increasingly decompose as the power is raised, plays a determining role.

Comparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films.

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Comparison of FTIR plasma and deposit spectra showing the relationship between the HMDSO by‐products present in the plasma phase and the different functional groups and end groups present in the deposited films.
Dynamic Particle Size Analysis with Light Scattering Technique
Authors: Tüzün Ug̃ur , Farhadpour Farhad A.
Published: December 2004

The commercial forward light scattering equipment, Malvern analyser was used to determine the size distribution of two crystalline powders in the micron range dispersed in aqueous suspensions. The powders used represent two different forms of a micro‐porous crystalline adsorbent, silicalite [1]. Previous work by the authors [2], has established the partially absorbing nature of the silicalite crystals at visible wavelengths of the incident light. The theoretical analysis indicates that it is possible to obtain quite accurate size distributions in the (1–10 μm) size range providing measured values of the relative refractive index and the coefficient of absorptivity of the particles are used in the calculations. The present work illustrates the consistency with which the light scattering equipment can respond to changes in the measured size distributions as a function of a number of process parameters such as the solids loading in suspension, the period of agitation, and the intensity of agitation.
Cometary Dust Sizing: Comparison between optical and in‐situ sampling techniques
Authors: Crifo Jean François
Published: December 2004

We try to evaluate the level of confidence that can be placed in the optical methods available for sizing cometary dust (and, at the same time, deriving all its other characteristics). We use for this purpose the new informations provided by the in‐situ sampling of Comet Halley dust. We try to determine whether data from this origin are compatible with visible and I. R. spectra of this comet acquired from the Earth, and with earlier interpretations of such spectra. We find that, as happens frequently when remote sensing and local sampling techniques data can be compared, none of these techniques can claim to be fully satisfactory. In the case of cometary dust, current estimates based on optical sizing only may be much less accurate than precedingly assumed. Improvements in the observational approaches appear needed, as well as new laboratory investigations and theoretical developments to improve the capabilities of the optical studies of cometary dust.
Particle Trajectory Effects in Phase Doppler Systems: Computations and experiments
Authors: Gréhan Gérard , Gouesbet Gérard , Naqwi Amir , Durst Franz
Published: December 2004

The effects of the particle trajectories on phase Doppler measurements were explored numerically using generalized Lorenz‐Mie theory. Computations were performed for a commercial phase Doppler system and various schemes for elimination of the trajectory effects were examined. It is shown that these effects cannot be completely suppressed if the ratio of the two measured phase shifts from a single receiving unit is used to validate the measurements. On the other hand, the errors due to particle trajectories can be eliminated satisfactorily by employing an additional receiving unit, which allows one to detect the asymmetry of the scattered light pattern due to displacement of the particle trajectory from the centre of the measuring volume. A preliminary experimental evaluation of this method is presented and discussed.
Laser Diffraction – Unlimited?
Authors: Witt Wolfgang , Rüthele Stephan
Published: December 2004

Within the past 20 years, particle size analysis with laser diffraction (LD) has been subject to rapid development, extending the size range stepwise from 1–200 μm to about 0.1–3500 μm. The limits of LD are discussed in terms of light sources, the influence of the beam diameter, special Fourier optics and a new detector design.

It is shown that the size range is not only restricted by the wavelength of the laser and the transmission limits of the medium. Its extension is mainly related to improvements in the measurement of the angular intensity distribution. Influences from stability and flow dominate on the coarse side of the measuring range. On the fine side, the spatial extension of aerosols and the resulting demand for extended working distances can be covered only in a parallel laser beam. Extended Fourier optics in combination with an adapatable beam expansion technique and a detector with virtual borders between semicircular elements overcome the existing limits and extend the size range to a lower limit of about 0.05 μm and an upper limit above 10 mm.

The sensititivity limit of LD is approaching that of single particle counting techniques. For medical spray and inhaler applications, a 0.1% optical concentration can be converted to particle size distributions even for time‐resolved analyses with sample intervals of a few milliseconds.

The reproducibility of the sensor, with a standard deviation typically much less than 0.5%, is no longer the limiting factor. The reproducibility of the results is mainly dominated by the reproducibility of sampling, sample splitting, dispersion and the contamination of the optical path. The latter can be improved by the control of flow, especially for in‐line and inhaler applications.
Tomographic Imaging of Phase Distribution and Spatial Correlation of the fluidization dynamics in a fluidized bed
Authors: Wang Shijie , Dyakowski Tomasz , Xie Cheng‐Gang , Williams Richard A. , Beck Maurice S.
Published: December 2004

This paper describes the use of a capacitance tomography system for imaging gas bubbles in a fluidized bed in the vicinity of an air distributor plate. The results show how the solid concentration distribution varies as a function of time for three different flow regimes: bubbling, slugging and the transition to turbulent. Bubble shape, Length and coalesence can be observed. A method of spatial correlation to elucidate the bubble formation process is described.
Experimental Determination of the Response Envelope of fine limestone
Authors: Feise Hermann J. , Schwedes Jörg
Published: December 2004

Designing modern devices for bulk solids storage and handling requires an increasingly complex understanding of the handled bulk solids' mechanical behaviour. Models able to describe the behaviour of bulk solids can neither be formulated nor their parameters determined from common shear tests, since these do not contain sufficient information especially about the materials' stiffness characteristics. The paper describes the response envelope as a measure of the deformation resistance and its experimental determination from biaxial tests. It is shown that for fine limestone powder the stiffness in compression is only about 1/70 of the stiffness in expansion. The shape of the response envelope depends only on the ratio between the principal stresses at the stress state considered, whereas the size of the response envelope also depends on the stress magnitude.
Experimental Determination of Force using Gun Propellants of various grain sizes – comparison with thermodynamically calculated values
Authors: Jahnk H.
Published: December 2004

Since force is a parameter which is shape independent it is possible, and moreover advantageous, to use ground propellants for its experimental determination. These, due to their smaller grain size, give much shorter burning times than the unground propellants, which in turn reduces the pressure losses due to heat transfer to the containment vessel, and hence to a better agreement with theoretical values.

By using different grain sizes one can extrapolate to the force values at zero grain size and hence for zero burning time. These values are only on average about 2% less than the thermodynamically calculated values. Without extrapolation, as the present results show, one can expect a difference between the theoretical and experimental values of about 5%.

The conventional methods of determining force using closed vessels with volumes between 200 ml and 700 ml require a relatively large amount of sample material. The use of a ground powder allows the volume of the vessel to be reduced to 25 ml. This can be important when unknown foreign propellants have to be tested since these are usually only available in small quantities.
Determination of the Lifetimes of Gun Propellants using thin‐layer chromatography
Authors: Volk F.
Published: December 2004

A thin‐layer chromatographic method was developed in connection with the determination of the safe lifetimes of gun propellants. This method enabled the numerous stabilizer reaction products of diphenylamine and ethylcentralite, which were formed on storage, to be qualitatively analysed.

Since a correlation could be established between the temperature and the decomposition or formation of certain of these reaction products, it became possible to estimate the time of onset of autocatalytic decomposition of powders and solid propellants from an analysis of the material at much earlier times.
Die Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen (Ab 1976 geändert in: Internationale Studiengruppe zur Vereinheitlichung der Sprengstoffprüfmethoden)
Authors: Ahrens H.
Published: December 2004

Seit 1960 ist eine auf freiwilliger Basis zusammengetretene Gruppe von Experten tätig unter dem Namen „Europäische Kommission zur Vereinheitlichung der Sprengstoffprüfungen”︁ (European Commission for the Standardization of the Tests of Explosives – Commission Européenne de Normalisation des Essais d'Explosifs).

In dieser Mitteilung werden der Ursprung und die bisherige Aktivität sowie die beabsichtigte weitere Tätigkeit der Kommission kurz beschrieben.
Chemistry of Metal Benzylidene Picramates – benzylidene picramates of iron, cobalt and nickel
Authors: Srivastava R. S. , Agrawal S. P. , Bhargava H. N.
Published: December 2004

Ferrous, cobalt and nickel benzylidene picramates have been prepared by treating the corresponding aqueous sulphate and chloride solutions with sodium salt of 4′‐dimethyIaminobenzylidene‐2‐hydroxy‐ 3.5‐dinitroaniline. A metal: ligand ratio of 1:2 has been established in all these cases with the help of micro‐analysis and confirmed by spectrophotometric, colorimetric and magnetic susceptibility measurements. I.R. studies of metal benzylidene picramates show N + M coordination, where M is iron, cobalt or nickel. Explosive properties of these benzylidene picramates have also been studied and it was found that the thermal stability of these benzylidene picramates increases as the atomic radius of the metal decreases. Ferrous, cobalt and nickel benzylidene picramates increased as the atomic radius of the metal decreases.
A Rapid, Accurate Technique for Determining Densities of High Explosives
Authors: Lagus P. L. , Turner P. L. , Gaffney E. S.
Published: December 2004

An improved gas comparison pycnometer has been developed, based on precise differential pressure measurements coupled with a sample volume compensator. Using helium gas, volumes of solid and powdered explosives can be measured to a precision approaching one part in lo4. Coupled with a precise mass measurement, these volumes allow densities with an uncertainty of ∼± 0.002 g/ml to be inferred. Measurements performed on various explosives have allowed assessment of the purity and homogeneity of individual samples. It is also possible to infer void percentage or porosity in pressed explosive pellets.
5,6,7‐Trihydro‐5,7‐diphenyl‐thiazolo[3,2‐b]‐s‐triazin‐3 (2h)‐one as a stabilizer for the double base propellant
Authors: Soliman Adly Abdel‐Wahid
Published: December 2004

5,6,7‐Trihydro‐5,7‐diphenyl‐thiazolo [3,2‐b]‐s‐triazin‐3(2H)‐one (C17H15N3OS) is used as a stabilizer for the double base propellant and gave good results with the stability tests. The samples were stored for 12 days at 100° C and were extracted by different suitable solvents. The column partition chromatography helped in separation of 5,6,7‐trihydro‐5,7‐(2‐nitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐ 5,7‐(4‐nitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐5,7‐(2,2′‐dinitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3(2H)‐one; 5,6,7‐trihydro‐5,7‐(4,4′‐dinitrodiphenyl)‐thiazolo[3,2‐b]‐s‐triazin‐3 (2H)‐one with their different percentages.
Versuche zur Detonationsübertragung von Wettersprengstoffen mit Ionenaustausch in natürlichem Einschluß
Authors: Scholz F. , Meerbach H.
Published: December 2004

Die Detonationsübertragung von selektiv detonierenden Wettersprengstoffen hängt in besonderer Weise von dem Einschluß der Ladesäule ab. Obwohl es für eine standardisierte Prüfung notwendig ist, eine einheitliche Prüfapparatur zu erstellen, dürften Versuche zur Detonationsübertragung unter praktischen Einschlußbedingungen doch von erheblichem Interesse sein.

Zur Tagung der Europäischen Kommission 1972 war ein kurzer Beitrag vorgelegt worden, der sich mit der Detonationsübertragung verschiedener Wettersprengstoffe mit Ionenaustausch in Bohrlöchern in der Kohle und im Karbongestein über ein Hindernis von Acetatscheiben hinweg befaßte. Diese Arbeiten wurden fortgesetzt, wobei besonders eine Kombination von Luftabstand und Hindernis aus Acetatscheiben in Betracht gezogen wurde.
Setback Testing of ANFO and Water‐Based Explosives
Authors: Listh O.
Published: December 2004

In a setback simulator a gunpowder charge is used to drive a heavily confined sample of explosive against a stationary plunger. The pressure on the sample, the sample velocity, and the acceleration of the sample are recorded. The results found show that the degree of confinement of the sample is an important test parameter. The results for civil AN‐based explosives show that water gels containing sensitizers are easier to initiate than the military explosive Comp. B, whereas non‐cap‐sensitive slurries could not be initiated in this test. There was no obvious difference in sensitivity between water gels with or without aluminium content. Contrary to this, ANFO containing aluminium showed a higher sensitivity than did pure ANFO. Critical pressures on the sample were in the range of 0.04 GPa‐0.14 GPa, and the corresponding sample velocities ranged from 8 m/s to 27 m/s. Sample decelerations when hitting the plunger were in the range of 30 m/s2‐80 km/s2.
Methode zur Bestimmung des Zündvermögens von Sprengkapseln und Sprengzündern
Authors: Prior J.
Published: December 2004

Es wird über eine Prüfmethode der Fa. Dynamit Nobel AG berichtet, bei der mit einer einzigen Prüfmischung die gesamte Skala der Zündstärken der technisch verwendeten Sprengkapseln und Sprengzünder erfaßt werden kann. Der Aufbau der Prüfanordnung, das Herstellen des Prüfsprengstoffs und der Prüfladung werden beschrieben, Versuchsergebnisse werden diskutiert.
Strength Testing of Explosives by Underwater Detonation
Authors: Bjarnholt G.
Published: December 2004

Shock wave energy and bubble energy for different explosives have been measured in underwater experiments. A method to determine bubble energies in cases where the free water surface and bottom boundary disturb the bubble oscillation has been developed. The shock energy loss when the primary shock wave travels from the charge to the gage resulting in heating of the surrounding water has been estimated by correlation with data derived from detonation calorimeter experiments for some explosives. Comparison of the measured total expansion work with data from thermodynamic computer calculations show good agreement for many oxygen balanced explosives, but poor agreement for explosives with a large oxygen deficit. For explosives of the ANFO type there is a considerable effect on expansion work by booster size, charge size, and shape.
Recent Work on Deflagration at SMRE
Authors: Murray W. L. , Godwin D. W. , Smith D. T.
Published: December 2004

The paper gives an account of recent work at the Safety in Mines Research Establishment (SMRE) aimed at developing a test of high discrimination for examining the deflagration characteristics of permitted explosives that are designed to be very resistent to deflagration. Experience with an existing apparatus in which an explosive contained in a tube is subjected in the presence of coal dust to the detonation products from a charge of the same explosive is reviewed. More recently experiments have been made using an apparatus of the Audibert‐Delmas type in which an igniter is used to initiate burning in a primer consisting of explosive mixed with coal dust, and the subsequent burning of the adjoining charge of explosive, which may be surrounded by a sheath of coal dust, is followed by measuring the temperature and pressure of the gases in the containing tube. Various possible test arrangements and criteria for assessing the propensity of an explosive to deflagrate are discussed.
Role of Additives in Combustion Waves and effect on stable combustion limit of double‐base propellants
Authors: Kubota N.
Published: December 2004

The effect of additives on the flame structures and the burning rates of double‐base propellants have been examined by means of photographic observations and temperature profile measurements. The additives used for this study are lead salicylate (PbSa, 2%), nickel (Ni, 1%), ammonium perchlorate (AP, 30%), and cyclotetramethylene tetranitramine (HMX, 30%). The addition of PbSa increases the burning rate, but does not improve the flame temperature characteristics. The addition of Ni increases the flame temperature significantly at pressures below 30 atm. The Ni acts as a catalyst to promote the flame reaction while it does not act as a burning rate modifier. The additions of AP and HMX increase the thermal performance of the propellant system, however, the HMX does not improve the stable combustion limit of the rocket motor at low pressures. The addition of Ni or AP is found to increase the flame temperature at pressures below 30 atm, and the stable combustion limit is lowered to below 3 atm.
Relation entre la Structure Electronique et la Sensibilité au Choc des Explosifs Secondaires Nitrés‐Critère Moléculaire de Sensibilité. I. Cas des Nitroaromatiques et des Nitramines
Authors: Delpuech A. , Cherville J.
Published: December 2004

Résumé

Cet article est le premier d'une série où l'on tente d'établir une relation entre la sensibilité au choc des explosifs secondaires nitrés et leur structure électronique. On y met en évidence, dans le cas des nitroaromatiques et des nitramines, le rǒle privilégié lors de la génération de la détonation d'une liaison R–NO2 de la molécule. L'examen des modifications subies par la distribution électronique de cette liaison après absorption d'énergie permet de définir un paramètre parfaitement corrélé à l'échelle des sensibilités expérimentales. La validité de ce paramètre en tant que critère de sensibilité accrédite, a posteriori, l'existence avant la détonation d'un état excité.
Predicting High Explosive Detonation Velocities from their composition and structure
Authors: Rothstein L. R. , Petersen R.
Published: December 2004

A simple, empirical linear relationship between detonation velocity at theoretical maximum density and a factor, F, that is dependent solely upon chemical composition and structure is postulated for a gamut of ideal explosives. The explosives ranged from nitroaromatics, cyclic and linear nitramines, nitrate esters and nitro‐nitrato aliphatics to zero hydrogen explosives, carbonless explosives and hydrogen rich explosives. Of the 64 explosives evaluated, 95% had calculated detonation velocity values within 5% of experimental and 98% within 7%. Only nitromethan varied grossly (−; 13%) from calculated velocity and the absolute error for all explosives is ±2.3%.
Thermal Decomposition Process of HMX
Authors: Kimura J. , Kubota N.
Published: December 2004

The thermal decomposition of HMX has been investigated using thermoanalytical techniques and infrared spectroscopic study at both above and below its melting point. The weight loss phenomenon that occurs as the temperature is elevated at a constant heating rate has been clearly separated into four elementary processes which are induction period, sublimation, first order solid phase reaction, and highly exothermic liquid phase reaction by plotting them against the logarithm of the heating rate versus the reciprocal temperature. Hydroxymethyl formamide has been shown to be a major product of the liquid phase decomposition, which suggests that the decomposition of HMX in the liquid phase should be initiated by the N‐N bond scission but not by the C‐N bond scission.
The Preparation of Hexanitrobibenzyl from TNT with sodium hypochlorite
Authors: Gilbert E. E.
Published: December 2004

A parametric study of the Shipp‐Kaplan procedure shows promise for the use of reduced amounts of cheaper mixed solvent systems, the use of lower quantities of more concentrated hypochlorite, and elimination of the aging period. Use of methanol as the sole reaction solvent at 50°C shows promise; methanol with a hydrophobic cosolvent gave crude HNBB of high purity. Only a slight improvement in yield was obtained; under no conditions did it exceed 82%.
Effect of initial particle size on the DDT of pressed solid explosives
Authors: Price D. , Bernecker R. R.
Published: December 2004

The effect of the initial particle size on the deflagration to detonation transition (DDT) of pressed, confined explosives has been studied. The explosives examined were ground tetryl, RDX, picric acid, waxed RDX, and waxed HMX. The ground tetryl was studied over the range of 61%−90% theoretical maximum density (TMD); most of the rest of the comparisons were made at 70% TMD. It was found that the initial particle size (or particle size distribution) δ affected the predetonation column length ℓ, the relative time to detonation, and even the apparent mechanism of DDT. Available data in the literature in conjunction with the present results indicate that the curves ℓ versus %TMD at constant δ, and ℓ versus δ at constant %TMD both exhibit a minimum.