Nano from nature

Looking at Neuburg Siliceous Earth, a naturally occurring nanostructured filler material, whose specific particle structure imparts coatings with very good mechanical and chemical resistances, while being easy to incorporate into the formulation.

The extraction of natural mineral fillers has been pursued for more than 200 years. During this period, the requirements placed on such fillers, and consequently the products themselves, have changed considerably. With respect to product consistency, purity and functional properties, functional fillers have to respond to ever higher and more stringent demands.

In connection with innovations in paints and coatings, there is often reference made to “nanotechnology”. In this context, quite frequently, products and materials are proposed which – in view of a missing, generally accepted definition – do not really deserve this designation. In theory, an ultrafine natural mineral filler with a mean grain size <1 µm could be called a nano filler, which would mean “nano from nature”. Neuburg Siliceous Earth, with primary particles of way below 500 nm, would easily fit into this category. There do not exist uniform rules yet, but from scientific publications it can be concluded that only products with grain size distributions <100 nm should be considered as nano materials. The majority of natural mineral fillers do not meet such a requirement.

However, from a technical application standpoint, it is often not of critical importance whether or not a material can be called a nano filler. It is rather the total (eventually composite) particle structure observed on the nanometer scale which gives rise to specific technical application effects in coatings. This refers not only to dispersion, stability and rheology, but also to flattening, elasticity, hardness, wear resistance and corrosion protection.

The particle structure of Neuburg Siliceous Earth offers an outstanding example of such a situation. The image covers an area about 12 µm wide. Distinctly visible is the natural fusion of the kaolinite particles of rather conventional appearance with a corpuscular quartz. The particular character of Neuburg Siliceous Earth lies in the fact that the corpuscular quartz consists of a high number of aggregated, partly dispersible primary particles which rarely exceed a size of 200 nm. On the other hand, in this functional filler the kaolinite is found in a state that indicates it has already been subjected to extensive delamination.

The combination of these two particle phenomena as created by nature gives rise to a number of beneficial properties in paint and coatings systems which very often cannot be matched the same way by other natural or synthetic fillers, including the so-called nano fillers – and this is without including costs.

Another advantage: because of its fine particle size and the rounded grain shape of the quartz portion, Neuburg Siliceous Earth only exhibits very low abrasivity vis-à-vis dispersion aggregates and processing equipment.

In view of the mineral hardness of the quartz, the coatings formulated with Neuburg Siliceous Earth offer outstanding abrasion and scratch resistance. These are important reasons for Sillitin and the surface treated Aktisil to be used in wear resistant parquet floor coatings. In addition, the flattening action of Neuburg Siliceous Earth allows for the elimination of additives otherwise intended for such effects.

The fine particle quartz also has a positive influence on the resistance against chemicals, which is why the siliceous earth is eminently suitable as a functional filler for use in chemically resistant and anti-corrosion coatings.

The natural combination of corpuscular quartz and lamellar kaolinite ensures rapid incorporation and excellent dispersion – in particular, in aqueous systems – along with a basically low sedimentation tendency. Plus, if a sediment is formed, it will be easily redispersed. This way, Neuburg Siliceous Earth can also serve as a functional filler to “stabilise” coarser particle size fillers.

The good integration of the filler into the polymer network leads to excellent mechanical properties.

This effect of good “integration” into the polymer network can be further enhanced by a surface treatment (e.g., with silanes). By modifying the filler surface, the compatibility with the polymer is increased which leads to outstanding rheological properties as well as good mechanical characteristics and excellent resistance against abrasion and chemicals.

The effects enumerated confirm that the properties of coatings cannot be improved with synthetic nanofillers only. In fact, nature has developed some “natural nano-structured fillers” that make it possible to develop high quality coating formulations with very good performance.

Hoffmann Mineral is an innovative filler specialist whose products are based on Neuburg Siliceous Earth, which the company extracts, improves and distributes. The company’s know-how and production plant are also used for third-party toll conversion.

The company prides itself on a century of supplying Siliceous Earth products, while continuously developing materials for a variety of applications. Customer orientation, innovation and strict quality management are key factors in Hoffmann’s market position.
Distribution is worldwide, with 36 agents in 31 countries representing the company. Sales have increased during the last 10 years in the European and CEE market.

Find out more: www.hoffmann-mineral.com