immo!nvest – Die Plattform für Standorte und Immobilien

Tag: Forschende

  • New plastic protects against flames

    New plastic protects against flames

    Epoxy resins are resistant and versatile plastics. In combination with glass or carbon fibres, they are used, for example, to manufacture components for aircraft, cars, trains, ships and wind turbines. Such fibre-reinforced epoxy-based plastics have excellent mechanical and thermal properties and are much lighter than metal. Their weakness: they are not recyclable – at least not yet.

    Now Empa researchers led by Sabyasachi Gaan from Empa’s Advanced Fibers Laboratory have developed an epoxy resin-based plastic that is fully recyclable, repairable and also flame retardant – while retaining the favourable thermomechanical properties of epoxy resins. They have published their results in the Chemical Engineering Journal.

    Recycling epoxy resins is anything but trivial, because these plastics belong to the so-called duromers. In this type of plastic, the polymer chains are closely cross-linked. These chemical bonds make melting impossible. Once the plastic has hardened, it can no longer be deformed.

    The situation is different with thermoplastics, such as PET or polyolefins. Their polymer chains are close together but not bonded. Under the influence of heat, these plastics can be melted and formed into new shapes. The only problem is that due to the lack of cross-linking, their mechanical properties at elevated temperatures are generally not as advantageous as those of duromers.

    A new type of plastic
    The special epoxy resin that Empa researchers have developed in collaboration with national and international partners is actually a duromer – but unlike other duromers, it can certainly be melted like a thermoplastic. The key is the addition of a special functional molecule from the class of phosphonic acid esters to the resin matrix. “We originally synthesised this molecule as a flame retardant,” says Empa scientist Wenyu Wu Klingler, who co-invented the technology. However, the bond that the molecule forms with the polymer chains of the epoxy resin is reversible, i.e. it can be dissolved again under certain conditions. This loosens the cross-linking of the polymer chains so that they can be melted and shaped.

    Such materials, also called vitrimers, have only been known for about ten years and are considered particularly promising. “Today, fibre-reinforced plastics are practically impossible to recycle, except under extreme conditions that damage the fibres,” explains Wu Klingler. “Once they have had their day, they are incinerated or disposed of in landfills. With our plastic, it would be possible for the first time to put them back into the material cycle.”


    Their vision for the future, adds group leader Sabyasachi Gaan, is “a composite material in which the fibres and the plastic matrix can be completely separated and reused.” The researcher sees a particular advantage in carbon fibre-reinforced plastics, for example, as used in the construction of planes, trains, boats, cars, bicycles and more. “The production of carbon fibres requires a lot of energy and releases an enormous amount of CO2,” he explains. “If we could recycle them, their ecological footprint would be a lot better – and the price a lot lower.” In addition, valuable additives such as phosphorus could be recovered from the polymer matrix.

    Tailor-made material
    Fibre-reinforced plastics are not the only application for the new plastic. For example, it could be used to coat wooden floors, as a transparent, resistant layer that has good flame-retardant properties – and where scratches and damage can be “healed” again with a little pressure and heat.

    “We didn’t develop a single material for a specific purpose, but rather a toolbox,” Gaan explains. “The flame retardancy, recyclability and repairability are all there. We can optimise all other properties depending on the intended use.” For example, he says, flow properties are particularly important for the production of fibre-reinforced plastics, while exterior wood coatings must also be weather-resistant.

    To pursue these and other applications of the material, the researchers are now looking for industrial partners. The chances of commercial success are good: because in addition to all its other advantageous properties, the modified synthetic resin is also cheap and easy to manufacture.

  • A stove for safe wooden buildings

    A stove for safe wooden buildings

    A house fire does not always proceed in the same way. The combustible material catches fire, the temperature increases, the fire grows and spreads. The existing room volume, the fire load, the temperature and the oxygen concentration in the fire room influence its course. The latest acquisition by the Institute of Structural Analysis and Design at the Department of Civil, Environmental and Geomatic Engineering at ETH Zurich is intended to show how wooden structures behave in different fire scenarios. The knowledge gained will in turn help to expand the possible uses of wood as a safe and sustainable building material.

    Precisely simulating fire processes
    The furnace, which was specially developed for fire simulations, cost around 2.5 million Swiss francs including conversion measures, looks robust and is housed in the heating centre of the Hönggerberg campus. It is a metal cube reinforced with steel beams with a combustion chamber that is one metre high, one metre wide and just under 1.7 metres long. It is fired by 10 gas burners, half of which are mounted on each of the two long sides. They can heat the kiln to over 1,400 degrees. Several cameras outside the combustion chamber record the tests and the composition of the fire gases can also be analysed.

    “We can precisely adjust the temperature in the kiln and also the oxygen content,” Andrea Frangi explains proudly. Furthermore, the wooden components or other common building materials can be loaded with up to 50 tonnes during the tests. The professor of timber construction initiated the procurement of the fire simulator and helped determine its specifications. “The kiln allows us to simulate different fire histories and test their effect on wood structures.”

    Woodas a building material is sustainable and safe
    Timber construction is booming in Switzerland. And the buildings are growing. In Regensdorf, Zug, Winterthur and Zurich, high-rise timber buildings with heights of 75 to 108 metres are currently being planned or are already under construction. The fact that this is possible at all is also due to decades of research work, such as that carried out by Frangis Group in the fire simulator. New building products and technologies for connecting wooden components are also making ever larger and more unusual constructions possible.

    Until 2004, only one- to two-storey buildings with a load-bearing structure made of wood were permitted in this country. From 2005, the limit was six storeys, and since 2015 there has effectively been no upper limit. “The planned high-rise buildings are certainly lighthouse projects,” says Frangi. “But for mid-rise buildings, wood has long since established itself as a building material and convinces with a good price-performance ratio, sustainability and safety.” The latter may be surprising, but while steel beams can deform in the event of a fire and thus become unstable, timber structures can retain their structural integrity for longer.

    The load-bearing capacity of a wooden beam in case of fire is essentially determined by its size. If the beam burns, about four centimetres of the wood are converted into charcoal per hour on the sides exposed to the fire. Possible weak points are connecting elements and constructional details. In order to expand the possible applications of modern timber construction, Andrea Frangi and his team want to further research the burning behaviour of timber components and connections under realistic conditions. “The construction sector causes a large proportion of climate-damaging emissions. With our research, we can help to ensure that even more of the renewable and CO2-storing resource wood is used as a building material,” Frangi is convinced.

  • Switzerland-wide premiere: Fire tests on wall-bound green façade

    Switzerland-wide premiere: Fire tests on wall-bound green façade

    Green facades can contribute to improving the microclimate in the city, support heat regulation in the building and promote biodiversity. However, there is still a large knowledge gap with regard to fire behaviour. In order to close this gap, researchers from the Institute of Timber Construction, Structures and Architecture IHTA at the Bern University of Applied Sciences BFH have carried out two fire tests on wall-mounted green facades.

    The test arrangement consisted of a multi-storey external wall element with two full and two only partially formed storeys. In the lower part of the wall element, the researchers placed a fire chamber that was open to the front. This allowed them to simulate the escape of flames from a window as it occurs after the so-called flash-over – the sudden development of a small fire into a large fire. The tests were carried out on the premises of the Dynamic Test Center of the BFH-TI in Vauffelin as closely as possible to the test specifications for exterior wall cladding systems of the Association of Cantonal Fire Insurers VKF (2016).

    Based on the results, it is possible to evaluate the fire behaviour of wall-bound green façades for buildings of medium height and to optimise the construction of external wall cladding systems for approval. The tests were part of a multi-year research project.

  • Five technologies on the way to net zero

    Five technologies on the way to net zero

    The TA-Swiss study aims to inform policy-makers and the public about the opportunities, limits and risks of different methods for CO2 extraction and storage. Aspects such as feasibility, climate effectiveness, costs, resource consumption and impacts on the environment and population were considered.

    The five technologies are:

    • the storage of CO2 as biomass in forests and the use of wood
    • storage in the form of humus in the soil and the use of plant carbon
    • capture and storage of CO2 from biomass combustion (BECCS)
    • removal from the air and storage (DACCS)
    • the accelerated weathering of demolition concrete and rock (carbonation)

    Each of the five NETs was assessed based on the current state of knowledge and with the help of expert interviews. Potential opportunities, risks, synergies and conflicts were identified and considered from a system perspective. Based on this, general and specific, technology-related options for action and recommendations were derived and reflected on together with selected stakeholders.

    The most important general recommendations of the study
    In order for NET’s contribution to the net-zero target to be implemented in an environmentally and socially compatible manner, politics and society should address the issue at an early stage. This requires in particular that the public is involved in shaping the conditions of use of NET by means of fact-based and comprehensible information.

    There is a need for an overarching strategy for the use of limited resources, such as renewable energy, water, biomass and soil, and for financing for the development and implementation of NET.

    Further research is needed to determine the potential of the different technologies.

    It must be possible to record the amount of CO2 removed from the atmosphere in the long term in a transparent and simple way to create a reliable assessment framework and avoid counting the same CO2 more than once.

    The minimum period of CO2 fixation from which a technology or NET project is recognised in terms of the Climate Strategy should be reflected.

    NETs can only be used as a supplement to the priority reduction of greenhouse gas emissions when achieving the net zero target. Therefore, it is important that separate targets apply to the reduction of CO2 emissions and to CO2 removal.

    Switzerland currently has a pioneering role in the development of NET. This competitive advantage should be further strengthened by promoting the relevant research and development, as well as demonstration projects.

  • BFH researchers develop sustainable binder for wood-based materials

    BFH researchers develop sustainable binder for wood-based materials

    The sustainability of wood-based materials such as plywood or wood fibreboard is largely determined by the binder used. Formaldehyde-based binders, as they are mainly used today, are responsible for the majority of CO2 emissions from wood-based materials. Moreover, their formaldehyde emissions are often considered problematic. Research into the development of mineral binders has therefore been going on for several years, including at BFH. Compared to a formaldehyde adhesive, these binders have almost 80 percent lower CO2 emissions. A new mineral binder for the production of wood-based materials is being developed by researchers at the BFH’s Institute of Materials and Wood Technology IWH in a recently launched Innosuisse project. In the project, the researchers are working together with the Swiss company Omya International AG, a leading global supplier of calcium carbonate minerals.

    Less than 20 per cent binder
    The development by BFH and Omya International AG is initially intended for the production of mineral-bonded plywood. The finished boards are to contain less than 20 per cent binder and have the mechanical properties of conventionally produced plywood for interior use. The binder should be able to be cured with heat, which will enable a fast manufacturing process and thus make the product competitive.