Chemical and optical mixing characterization of a dynamic inline mixer

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Chemical and optical mixing characterization of a dynamic inline mixer

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Reactive molding of elastomeres in 3D-printed molds for robotic actuators

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Reactive molding of elastomers in 3D-printed molds for robotic actuators

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Study of the particle formation and morphology of single mannitol-water droplets depending on the drying conditions

In chemical, pharmaceutical and food processing industry, spray processes have a wide range of applications, especially in the production of tailor-made powder products of defined characteristics from solutions or suspensions. The effects of process parameters (e.g. temperature and relative humidity) on the drying kinetic of a droplet and the properties of the resulting particles are largely based on experience. Still there is a lack of information on the fundamentals of particle formation. To close this gap numerical simulations as well as single droplet experiments were carried out under various conditions. This study concerns the influences of relative humidity, drying temperature and mass fraction on the solid layer formation and on the particles of single droplets consisting of mannitol-water solutions. An acoustic levitator (Fig 1 a)) was used to carry out the single droplet experiments. By means of a camera and a light source shadowgraphy was used to analyze the droplet drying kinetic and the development of the droplet respectively. Raman spectroscopy was used to analyze the polymorphism[1] of oversaturated mannitol-water droplets (relative humidity above 10 %). Using a thin thermocouple (150 µm) the particle temperature was recorded. Typical drying curves showed a continuous decrease of the droplet surface area until the solid layer was formed. The progress of the droplet temperature during the evaporation depends on the increase of the mannitol concentration at the droplet surface and start crystallization. Numerically, the unsteady, one-dimensional mass and energy diffusion equations for spherically symmetric droplets were solved accounting for the occurrence of the solid layer formation. Moreover, the influence of the air humidity on the solid layer formation and the droplet temperature evolution was investigated experimentally and validated by simulations. It was shown that an increase in the humidity of the drying air leads to a delayed solid layer formation[2] and a decrease of the final particle porosity whereas a higher mannitol concentration and a higher temperature have a contrary effect. The validity of the numerical model concerning the time instance of the solid layer formation and the progress of the droplet temperature was confirmed. Using the numerical model the drying of a single droplet was successfully simulated. Additionally a morphology map for the obtained particles from the single droplet experiments was developed. Please click Additional Files below to see the full abstract

Lunar Exploration Orbiter (LEO): Providing a Globally Covered, Highly Resolved, Integrated Geological, Geochemical and Gephysical Data Base of the Moon

The German initiative for the Lunar Exploration Orbiter (LEO) originated from the national conference “Exploration of our Solar System”, held in Dresden in November 2006. Major result of this conference was that the Moon is of high interest for the scientific community for various reasons, it is affordable to perform an orbiting mission to Moon and it insures technological and scientific progress necessary to assist further exploration activities of our Solar System. Based on scientific proposals elaborated by 50 German scientists in January 2007, a preliminary payload of 12 instruments was defined. Further analysis were initated by DLR in the frame of two industry contracts, to perform a phase-zero mission definition. The Moon, our next neighbour in the Solar System is the first choice to learn, how to work and live without the chance of immediate support from earth and to get prepared for further and farther exploration missions. We have to improve our scientific knowledge base with respect to the Moon applying modern and state of the art research tools and methods. LEO is planed to be launched in 2012 and shall orbit the Moon for about four years in a low altitude orbit

Scale-up of Emulsion Polymerisation up to 100 L and with a Polymer Content of up to 67 wt%, Monitored by Photon Density Wave Spectroscopy

The scale-up process of the high solid content (up to 67 wt%) emulsion polymerisation of vinyl acetate and Versa®10 from 1 L over 10 L to 100 L was investigated. An emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester in a molar ratio of 9:1 was carried out in a starved-fed semi-batch operation. As a radical source, a redox initiator system consisting of L-ascorbic acid, tert-butyl hydroperoxide and ammonium iron (III) sulphate was used. The process parameters, such as the required stirring speed and heat dissipation, were determined and adjusted beforehand via reaction calorimetry to ensure a successful scale-up without safety issues. In addition, the emulsion polymerisation was monitored inline by Raman (qualitative monomer accumulation), as well as Photon Density Wave spectroscopy (particle size and scattering coefficient) and temperature measurements. The data provided by Raman spectroscopy and temperature measurements revealed mixing difficulties due to an insufficient stirring rate, while the inline measurement with Photon Density Wave spectroscopy offered an insight into the development of the product properties. It proved to be reliable and precise throughout the entire scale-up process, especially compared to conventional offline methods, such as dynamic light scattering or sedimentation analysis by means of a disc centrifuge, both of which encountered issues when using higher polymer contents

Scale-up of Emulsion Polymerisation up to 100 L and with a Polymer Content of up to 67 wt%, Monitored by Photon Density Wave Spectroscopy

The scale-up process of the high solid content (up to 67 wt%) emulsion polymerisation of vinyl acetate and Versa®10 from 1 L over 10 L to 100 L was investigated. An emulsion copolymerisation of vinyl acetate and neodecanoic acid vinyl ester in a molar ratio of 9:1 was carried out in a starved-fed semi-batch operation. As a radical source, a redox initiator system consisting of L-ascorbic acid, tert-butyl hydroperoxide and ammonium iron (III) sulphate was used. The process parameters, such as the required stirring speed and heat dissipation, were determined and adjusted beforehand via reaction calorimetry to ensure a successful scale-up without safety issues. In addition, the emulsion polymerisation was monitored inline by Raman (qualitative monomer accumulation), as well as Photon Density Wave spectroscopy (particle size and scattering coefficient) and temperature measurements. The data provided by Raman spectroscopy and temperature measurements revealed mixing difficulties due to an insufficient stirring rate, while the inline measurement with Photon Density Wave spectroscopy offered an insight into the development of the product properties. It proved to be reliable and precise throughout the entire scale-up process, especially compared to conventional offline methods, such as dynamic light scattering or sedimentation analysis by means of a disc centrifuge, both of which encountered issues when using higher polymer contents

Tough, Stretchable, and Thermoresponsive Smart Hydrogels

Self-healing, thermoresponsive hydrogels with a triple network (TN) were obtained by copolymerizing N-isopropyl acryl amide (NiPAAm) with polyvinyl alkohol (PVA) functionalized with methacrylic acid and N,N′-methylene bis(acryl amide) crosslinker in the presence of low amounts (<1 wt.%) of tannic acid (TA). The final gels were obtained by crystalizing the PVA in a freeze-thaw procedure. XRD, DCS, and SEM imaging indicate that the crystallinity is lower and the size of the PVA crystals is smaller at higher TA concentrations. A gel with 0.5 wt.% TA has an elongation at a break of 880% at a tension of 1.39 MPa. It has the best self-healing efficiency of 81% after cutting and losing the chemical network. Step-sweep strain experiments show that the gel has thixotropic properties, which are related to the TA/PVA part of the triple network. The low amount of TA leaves the gel with good thermal responsiveness (equilibrium swelling ratio of 13.3). Swelling-deswelling loop tests show enhanced dimensional robustness of the hydrogel, with a substantial constancy after two cycles