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Stuttgart, Germany

Pieter R.,Hoffmann Mineral GmbH
Polymers Paint Colour Journal | Year: 2012

Calcined Neuburg siliceous earth, available as Silfit Z 91 (untreated) or as Aktifit AM (surface-modified), has great potential as an extender of TiO 2 in various paint applications. Its high colour neutrality, its ability to increase opacity as well as abrasion resistance, its tendency to initially matte coatings while maintaining gloss levels after accelerated weathering, all these properties combined, make this product - which is made by exposing the naturally occurring mineral to 1000°C -a 'hot item' in its best sense. That it sells for significantly less than half the current price of TiO 2 is merely the icing on the cake. Source

Friedrich K.,University of Kaiserslautern | Friedrich K.,King Saud University | Knor N.,Hoffmann Mineral GmbH | Almajid A.A.,King Saud University
Mechanics of Composite Materials | Year: 2012

It has been demonstrated in recent years that the tribological performance of polymer-based composites can be greatly improved by incorporating, besides such classical tribofillers as short carbon fibers and lubricating graphite flakes, additional ceramic nanoparticles into the polymeric matrix. However, due to the large surface area and high adhesion forces, nanoparticles exist not as separate particles, but as their agglomerates. To achieve the desired improvements, it is necessary to split up these agglomerations and to distribute them as single particles in the polymeric matrix. In the present paper, this is demonstrated for two different thermoplastics used frequently as matrices for polymeric tribomaterials (polyamide 66, PA66, and polyetheretherketone, PEEK). Processing by twin-screw extrusion allowed us to incorporate titanium dioxide (TiO 2) nanoparticles of different size (15 and 300 nm). The production of a highly filled masterbatch and its multiple extrusion and dilution resulted in a very good deagglomeration, which improved its performance considerably. In regard to particle size, the 15-nm particles showed a significantly greater improvement in the mechanical properties of polymer-based composites than the 300-nm ones. Enhancements in the stiffness, strength, and toughness could be achieved in many cases. The scanning electron microscopy confirmed these results. The final set of results obtained illustrates how the nanoparticles improve the tribological behavior of PA66 and PEEK compounds used in various industrial applications. © 2012 Springer Science+Business Media, Inc. Source

Schneider S.,University of Cambridge | Jager M.,Lindenstr. 53 | Kroh A.,Natural History Museum Vienna | Mitterer A.,Hoffmann Mineral GmbH | And 5 more authors.
Acta Geologica Polonica | Year: 2013

With approximately 100 species, the invertebrate macrofauna of the Neuburg Kieselerde Member of the Wellheim Formation (Bavaria, southern Germany) is probably the most diverse fossil assemblage of the Danubian Cretaceous Group. Occurring as erosional relicts in post-depositional karst depressions, both the Cretaceous sediments and fossils have been silicified during diagenesis. The Neuburg Kieselerde Member, safely dated as Early Cenomanian to Early Turonian based on inoceramid bivalve biostratigraphy and sequence stratigraphy, preserves a predominantly soft-bottom community, which, however, is biased due to near-complete early diagenetic loss of aragonitic shells. The community is dominated by epifaunal and semi-infaunal bivalves as well as sponges that settled on various (bio-) clasts, and may widely be split into an early bivalve-echinoid assemblage and a succeeding sponge-brachiopod assemblage. In addition to these groups we document ichnofauna, polychaete tubes, nautilids and bryozoans. The fauna provides evidence of a shallow to moderately deep, calm, fully marine environment, which is interpreted as a largescale embayment herein. The fauna of the Neuburg Kieselerde Member is regarded as an important archive of lower Upper Cretaceous sea-life in the surroundings of the Mid-European Island. Source

Heckl S.,Hoffmann Mineral GmbH | Knor N.,Hoffmann Mineral GmbH
Kunststoffe International | Year: 2011

The novel calcined Neuburg Siliceous Earth (Aktifit AM, surface treated) from Hoffmann Mineral GmbH, Neuburg a.d.Donau, Germany, is predicted to open up further possibilities for the above-mentioned applications. Silfit Z 91 is a naturally occurring mixture of amorphous and cryptocrystalline silica and lamellar kaolinite that has been thermally treated. Aktifit AM is an activated Silfit Z 91, whose surface has been modified with aminosilane. Charpy impact strength is determined according to DIN EN 179-1 on the unnotched standard test sample in the edgewise impact direction. This property profile, together with the excellent processing behavior of calcined siliceous earth, characterized by a low proportion of grit, good dosability and good wetting and dispersion behavior, offers clear advantages over competitor fillers. Source

Oggermuller H.,Hoffmann Mineral GmbH | Reiter S.,Hoffmann Mineral GmbH
PPCJ Polymers Paint Colour Journal | Year: 2014

Titanium dioxide and calcium carbonate were partially replaced with Neuberg siliceous earth under constant pigment volume concentration while working with a water-based white road paint. Different wet thicknesses were applied to black/white contrast cardboards with the aid of an applicator with doctor blade. After drying with relative humidity, the dry film thicknesses were determined and the color value measured over the black and white underground. To increase the early rain resistance so that no changes of the film surface can be observed after precipitations. The replacement of 40% TiO2 and 12.5% NCC with SilFit Z91 leads to an improvement of the abrasion resistance by 15%. Source

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