Suitability of Modified Supercritical Carbon Dioxide as Solvent for polar substances

As solvent supercritical carbon dioxide offers unique possibilities, like non-toxicity and therefore reduction of environmental pollution or access of low-temperature processing resulting in additional process safety. Therefore, knowledge to the influence of modifiers due to better solubility of polar substances is important for evaluating novel manufacturing techniques like the RESS- or GAS-process. Dynamic supercritical fluid extraction of PETN, nitroguanidine (NIGU) and RDX, respectively, with pure as well as with modified carbon dioxide indicated that all explosives except nitroguanidine were extracted though for RDX and 3-nitro-1,2,4-triazole the use of modifiers proved to be necessary. The results show the high capacity of modified supercritical carbon dioxide as a solvent in RESS- and GAS-processes.     

From Meso to Macro: Controlling Hierarchical Porosity in Supraparticle Powders

A drying droplet containing colloidal particles can consolidate into a spherical assembly called a supraparticle. Such supraparticles are inherently porous due to the spaces between the constituent primary particles. Here, the emergent, hierarchical porosity in spray-dried supraparticles is tailored via three distinct strategies acting at different length scales. First, mesopores (<10 nm) are introduced via the primary particles. Second, the interstitial pores are tuned from the meso- (35 nm) to the macro scale (250 nm) by controlling the primary particle size. Third, defined macropores (>100 nm) are introduced via templating polymer particles, which can be selectively removed by calcination. Combining all three strategies creates hierarchical supraparticles with fully tailored pore size distributions. Moreover, another level of the hierarchy is added by fabricating supra-supraparticles, using the supraparticles themselves as building blocks, which provide additional pores with micrometer dimensions. The interconnectivity of the pore networks within all supraparticle types is investigated via detailed textural and tomographic analysis. This work provides a versatile toolbox for designing porous materials with precisely tunable, hierarchical porosity from the meso- (3 nm) to the macroscale (≈10 µm) that can be utilized for applications in catalysis, chromatography, or adsorption.     

Characteristic Properties of an End Burning Grain with Smoke Reduced Ferrocene Containing Composite Propellant

Design, formulation and properties of an end burning grain are described which works for underwater propulsion operating at the level of 1200 N thrust for 20 s burning time. To avoid cavitational noise the formation of hot particles must be prevented. For this reason a smoke reduced composite propellant based on AP/HTPB with 86% energetic solids including 14% HMX and with 1% ferrocene derivative was adapted to grain size and motor configuration. For inhibition a pyrolytically stabilized polyurethane insulation was applied. The thermal insulation was made from a stiff high temperature resistant phenolic resin. The propellant exhibited a smooth burning behaviour with good processibility and mechanical properties. The desired performance was delivered at 120 bar operating pressure connected to 165 mm grain diameter and 93% thrust efficiency. Looking closer to the system it was found that part of the ferrocene derivative and plasticizer migrated from the propellant block to the inhibition layer. In the course of migration a small change of burning but a larger change of mechanical properties occurred in the boundary of the propellant. Despite these disadvantages burning times of 5 s and 10 s had been successfully realized with a case bonded configuration. For larger grain sizes, however, cracks occurred around the surface of the cylindrical propellant block. Calculation of the mechanical stresses which built up upon thermal shrinkage after curing and cooling showed values higher than the mechanical strength of the propellant could fit. These problems finally were overcome by a free standing grain. It led to a successful function of the motor for burning times of 20 s and more.     

Vorstellung eines Leitfadens zum Evaluieren der hygienegerechten konstruktiven Ausführung von Süßwarenmaschinen

Consumer protection is one of the most important criteria within industrial food production. The Machinery Directive and DIN EN 1672-2:2021-05 contain general requirements for hygienic design and cleanability of food processing machinery. Nevertheless, it happens that machines or equipment parts are used that are not suitable for the products to be processed. The consequences of this go as far as a public recall of products with a corresponding damage to the image of the food manufacturer. The working group of machine manufacturers and confectionery companies in the IVLV has dealt with the problem at the level of the association within the framework of a pre-competitive exchange and has developed a guideline for action as well as supporting forms for the procurement process of confectionery machines from the point of view of hygiene.