Steinbeis experts develop process for purifying and activating basalt fibers
Melt basalt and it creates a material consisting of several minerals called basalt fiber. These minerals are primarily of natural volcanic origin, or in technical terms: They are geogenic. Unlike glass fiber and carbon fiber material, basalt fibers can be produced using processes that save resources. The supply is also practically limitless. Compared to CFRPs and GFRPs (carbon fiber-based/glass fiber-based reinforced plastics), the life cycle of basalt fibers from extraction to recycling requires much less energy in production, and the process is also much less demanding in technological terms. To make more use of these advantages in material production, the Steinbeis Innovation Center for Intelligent Functional Materials, Welding and Joining Techniques, Implementation has been working on a new process for producing basalt fiber thermoplastic tapes. The project is part of an initiative backed by the ZIM, the governmental innovation program for small and medium-sized business.
Basalt fiber-based reinforced composites (BFCs) containing thermoplastic matrix materials are beneficial to resource-efficient lightweight construction, offering advantages not just in terms of the material itself, but also with respect to processes and engineering. Until now, this potential has scarcely been exploited. Previously, the properties of basalt fiber were not stable due to the geogenic extraction process, and this material has not yet found widespread application in industry. Recent advancements in material analysis now make it possible to inexpensively and quickly analyze the heterogeneous composition of individual basalt rocks and thus enable commercially viable batch production with uniform fiber quality. Only now is it possible to apply the outstanding material properties of basalt fiber to specific technologies in ways that allow production to be safeguarded over an extended period of time. As a result, there is comparatively little information on the different ways to use basalt fiber technology for material reinforcement purposes, especially when it comes to the design of boundary layers between the fibers and the surrounding matrix, although the same applies to the surface reactions of basalt fibers.
Comparison of a lateral section of fibers with matrix materials: a) with plasma treatment b) without plasma treatment
“Our research at the Steinbeis Innovation Center Intelligent Functional Materials, Welding and Joining Techniques, Implementation based in Dresden has involved pursuing a number of avenues,” explains Dr.-Ing. habil. Khaled Alaluss, co-director of the center. “We designed technology models and methods for splaying fibers, and in parallel to this we developed a process for cleaning and activating the basalt fiber surface. Both parts of this research fed into the resulting overall process for producing the basalt fiber thermoplastic tapes.” The researchers first focused on establishing the technological foundations required for running simulations on basalt fiber tapes, also looking at a selection of preconfigured components. The experts also conducted a series of tests to develop, examine, and optimize different ways to clean and activate the basalt fiber filaments. This involved a variety of treatment processes, which were evaluated in terms of effectiveness using an assessment system developed for laboratory measurements. The Steinbeis experts then worked alongside project partners to integrate suitable processes into laboratory equipment. As a result of the project, the experts have now created an experimental setup for producing BFC tapes.
Oleg Nuss, who has been conducting the research for Steinbeis, explains the details: “The basis we took for development was an approach involving overlaying chemical binding energy with polarized covalent bonding mechanisms. To raise electron bonding, plasma arcs have to be used to add binding energy to the desired purification effects.” To achieve this, laboratory-scale experiments were carried out on purification and activation. This revolved around a specially developed method for analyzing the results, looking at the angle of contact, the direction of strands, and speed. The final step was to put the findings into practice. The results were handed on to the Institute for Lightweight Engineering and Polymer Technology (ILK), the partner in Dresden that has been developing the production technology. For the project team, this involved investigating a variety of plasma processing configurations and different process parameters for producing the basalt fiber thermoplastic tape. Once combined with plasma treatment, the process was much more stable, delivering throughput rates of between 1.0 and 2.0 m/min. The experiments involved producing several hundred meters of basalt fiber thermoplastic tape, and the project partners at the ILK used this to develop a demonstration plant. Comparisons showed that without the plasma treatment, it would not have been possible to produce untreated basalt fiber thermoplastic tapes or set up the demonstration plant within a reasonable time frame, let alone with a sensible volume of materials.
Using basalt fiber thermoplastic tapes made with fibers that had already been plasma-treated allowed the researchers to produce a homogeneous fiber layer with parallel strands. “The basalt fiber thermoplastic tapes that have already been produced clearly show the positive effects of plasma treatment: The tapes that haven’t been plasma treated have significantly inferior mechanical bonds, such that the tapes already start to break down into individual fragments when they’re rolled or even undergo simple handling – especially along the fibers,” highlights Prof. Dr.-Ing. Gunnar Burkner, who is also a director of the Steinbeis Innovation Center. It was not even possible to conduct a simple bending test with unidirectional clamping – the tapes were clearly not stiff enough. The results are better after subjecting the basalt fibers to plasma treatment. The fibers are meshed better into the material matrix, and this improves the bond between the matrix and the fibers. Tapes offer an extremely effective mechanical bond and with this, excellent stiffness properties. Analysis of the results clearly shows that using plasma treatment simplifies basalt fiber processing and improves process stability, now making it possible to produce basalt fiber thermoplastic tapes for industrial applications.
Associate Prof. Dr. habil. Khaled Alaluss, Oleg Nuss, Prof. Dr.-Ing. Gunnar Bürkner
Steinbeis Innovation Center Intelligent Functional Materials, Welding and Joining Techniques, Implementation (Dresden)