Untersuchung des Prall‐ und Druckverhaltens feuchter γ‐Al2O3‐Granulate

The material behavior of dominant elastic‐plastic γ‐Al₂O₃ granules has been experimentally studied by means of quasi static compression tests and dynamic impact tests until fracture. The obtained distributions of breakage velocity and specific breakage energy are compared. Thus, velocity‐dependent influences at stressing like viscous behaviour can be derived. Additionally, the influence of particle size and moisture content are investigated.     

Einfluss des Bindemittels und der Feuchtebeladung auf die Festigkeit von Zeolith 4A‐Granulaten

A comprehensive analysis of the material behavior and the strength of (temporary binder) binderless and binder containing zeolithic molecular sieves in granular form is presented. The material behavior has been studied using single granule uniaxial compression tests until primary fracture. The received force‐displacement curves have been approximated using the Hertz and the Tomas model, respectively. The rate independent micro‐mechanical properties and specific fracture characteristics are presented.     

Einfluss der Feuchtebeladung bei der Druckbeanspruchung von Granulaten

The material behavior of γ‐Al₂O₃‐, zeolite 4A‐ und sodium benzoate granules at compression has been experimentally studied. The material behavior has been found to be dominant elastic, elastic‐plastic and dominant plastic. Additionally, the influence of moisture content on the material behavior has been investigated. The force‐displacement curves have been approximated using suitable mechanical models.     

Druck‐ und Bruchverhalten von γ‐Al2O3‐Granulaten

The material behaviour of dominant elastic‐plastic, spherical γ‐Al₂O₃‐granules at compression until primary breakage has been experimentally studied. The influence of particle size and moisture content on the compression behaviour was also investigated. The mechanical properties of the granules can be determined using the recorded force‐displacement curves. Additionally, the specific fracture energy distribution and the distribution of the equivalent impact velocity at fracture can be derived from the force‐displacement curves.     

Numerische und analytische Beschreibung der mechanischen Eigenschaften quasi‐tetraederförmiger Agglomerate

Quasi tetrahedral agglomerates consist of four primary particles, from which three primary particles generally form a base area on which the fourth primary particle is arranged centrally; in the regular case the primary particles having equal radii. The coordinates of the centers of the primary particles are derived for agglomerates exhibiting equal primary particles (regular tetrahedron) and primary particles of different radii (inclined tetrahedron). Moreover, an analytical model for elastic contact deformation is derived on the basis of the Hertz model. Subsequently, tetrahedral agglomerates are modeled using the discrete element method and the compression test between two rigid plates is simulated and compared with experimental results.     

Compression Behavior of Moist Spherical Zeolite 4A Granules

The material behavior of elastic‐plastic zeolite 4A granules has been experimentally studied using compression tests. The influence of particle size and moisture content has been investigated. Furthermore, the specific fracture energy distribution and the distribution of the equivalent breakage velocity at impact on a rigid target have been determined.     

Influence of Moisture Content on the Compression Behavior of Granules

The material behavior of γ‐Al₂O₃, zeolite 4A, and sodium benzoate granules during compression has been found to be dominant elastic, elastic‐plastic, and dominant plastic. Additionally, the influence of moisture content on this material behavior has been investigated. Typical force‐displacement curves were approximated using suitable mechanical models.     

Mechanische Eigenschaften zyklisch be‐ und entfeuchteter Zeolithgranulate

The production of zeolite granules varies in the amounts of binder content and different drying/activation temperatures. Here, the influence of moisture content and cyclic moisture loading and unloading on the mechanical properties like the strength of three different types of zeolite granules has been studied by uniaxial compression tests. The force‐displacement curves and scanning electron microscopy pictures of the granule and fracture surfaces show that with increasing number of moistening‐drying cycles, a continuous decrease in the strength of granules take place due to non‐regenerative damage of the structure.     

An Experimental Study on Binderless Briquetting of Low‐Rank Coals

The potential of binderless briquetting as a means of transforming low‐rank coals into low moisture high grade solid fuel products has been studied. Using two dried low‐rank coals, binderless briquettes with high mechanical strength have been successfully produced through mechanical compression. An increase in heating value was achieved as a result of moisture reduction in the briquettes compared to as‐received coals. The residue moisture content in the briquettes had a predominant effect on briquetting characteristics and there existed an optimum moisture content for the maximum briquettes strength. The chemical structure and wettability of binderless briquettes were analyzed using FTIR and contact angle measurement. The results showed that hydrophobicity and chemical structure significantly affected the briquette properties.     

Simulation der auf van der Waals Wechselwirkungen beruhenden Haftkräfte zwischen rauen Partikeln und glatten Wänden in gasförmiger Umgebung

A computer program is presented that can be used to calculate adhesion force distributions of irregularly shaped particles. Basis is the calculation of the single interactions between the involved atoms respectively molecules of the contact partners and overlapping these to a resultant whole interaction. The example of roughness shows that extremely bimodal distributions can arise for identical particles.     

Synthesis,Crystal Structure,and Thermal Behavior of 3‐(4‐Aminofurazan‐3‐yl)‐4‐(4‐nitrofurazan‐3‐yl)furazan (ANTF)

The energetic material 3‐(4‐aminofurazan‐3‐yl)‐4‐(4‐nitrofurazan‐3‐yl)furazan (ANTF) with low melting‐point was synthesized by means of an improved oxidation reaction from 3,4‐bis(4′‐aminofurazano‐3′‐yl)furazan. The structure of ANTF was confirmed by ¹³C NMR spectroscopy, mass spectrometry, and the crystal structure was determined by X‐ray diffraction. ANTF crystallized in monoclinic system P2₁/c, with a crystal density of 1.785 g cm⁻³ and crystal parameters a=6.6226(9) Å, b=26.294(2) Å, c=6.5394(8) Å, β=119.545(17)°, V=0.9907(2) nm³, Z=4, μ=0.157 mm⁻¹, F(000)=536. The thermal stability and non‐isothermal kinetics of ANTF were studied by differential scanning calorimetry (DSC) with heating rates of 2.5, 5, 10, and 20 K min⁻¹. The apparent activation energy (E_a) of ANTF calculated by Kissinger's equation and Ozawa's equation were 115.9 kJ mol⁻¹ and 112.6 kJ mol⁻¹, respectively, with the pre‐exponential factor lnA=21.7 s⁻¹. ANTF is a potential candidate for the melt‐cast explosive with good thermal stability and detonation performance.     

Rubber content effect on scratch behavior in acrylonitrile‐styrene‐acrylate copolymers

The scratch behavior of butyl‐acrylate rubber‐modified styrene‐acrylonitrile thermoplastics is investigated following the ASTM D7027 linearly increasing normal load test methodology. The critical normal loads at the onset of the major transitions along the scratch path, such as groove formation, scratch visibility, microcrack formation, and plowing, are reported and quantitatively analyzed. It is found that the scratch resistance generally deteriorates with increasing butyl‐acrylate rubber content, and is strongly related to the tensile and compressive yield stresses of the blends. Microscopy investigation indicates that a rubber content of up to 30 wt % in a styrene‐acrylonitrile copolymer (SAN) does not alter the scratch‐induced damage mechanisms, but only reduces the critical onset loads for the observed damage transitions. The present finding suggests that addition of rubber causes reductions in modulus, tensile, and compressive yield stresses, thus leading to deterioration in scratch resistance. It appears that the improvement in ductility for SAN after the rubber toughening does not benefit scratch resistance. Implication of rubber toughening on scratch behavior of polymers is discussed. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Rheological investigation of polyamide 6 TiO2‐ and BaSO4‐nanocomposites

Commercially available TiO₂ and BaSO₄ nanoparticles were incorporated in polyamide 6 (PA 6) via twin screw extrusion. The primary particle size of nanoparticles was 15 nm and 20 nm. The compounds were manufactured via multiple extrusion and dilution processing steps. The dispersion of the nanoparticles in the matrix was investigated by scanning electron microscopy and image analysis, micro‐tomography, and transmission electron microscopy. The rheological properties were determined via plate–plate‐rheometer. It was found that for TiO₂ fillers a threefold extrusion process is sufficient to realize a dispersion index of 94.4%. BaSO₄ fillers were hardly dispersible, ending up with a maximum dispersion index of 71%. Deagglomeration does not lead to a change in rheological properties but the number of extrusion steps decreases the rheological properties. A good particle‐matrix interaction leads to higher moduli and viscosity. The remaining agglomerates seem to act as defects decreasing the energy absorption of the respective compounds. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011