DALLA BETTA GROUP S.R.L.

BASALTO

Other Specialties

Basalt has always been used since ancient times for its hardness to pave roads and, as a fill, in construction. More recently it has also been used in the production of anti-abrasive coatings and paving tiles by molding from the melt. In fact, in recent decades, it has been discovered that basaltic rocks are not all chemically identical and that those with certain chemical compositions have some physical characteristics that make them suitable for the extrusion of useful continuous filaments of various diameters (9/13µm). In 1923, the Parisian Paul Dh© was the first to obtain a patent for the production of basalt filaments; after the Second World War, researchers from France, Germany, Great Britain, Italy and mainly the USA continued with the first attempts at extruding basalt. Only in the 1950s and 1960s in Moscow and Prague were the first significant results obtained and in the following decade, interest, also motivated by the extensive existing deposits, resumed also in the north-west of the United States. In the same years, the Soviet Ministry of Defense also showed interest in the potential of this technology for military and aerospace applications. Research was thus focused in the important center of Kiev: the development was successful but the technology was kept secret except for some brief, small publications. Research institutes and production plants were clearly off limits. Only in the 1990s, this technology was declassified and this allowed the start of civil use. The technological process for producing basalt fiber is based on four fundamental steps: - an initial pre-treatment of the basaltic rock - a furnace melting process to obtain continuous fibers - a continuous "spinning" treatment - "weaving" or other, more specific processes to obtain other final shapes for specific applications To produce basalt fiber, it is necessary to bring the rock above the melting temperature (about 1400 °C) in order to guarantee an adequate viscosity for spinning. To do this, a furnace of refractory material is used. The melt is then extruded through a matrix containing multiple bushings to produce continuous basalt threads. These threads are wound on a bobbin, an operation that also has the task of stretching the fibers in order to reduce their diameter and increase their mechanical properties. Although quite similar to glass fibres, basalt fibres have superior mechanical properties but require a higher temperature to be spun, making the production process more energy-intensive.

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