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New epoxy resin resists flames and reduces waste

Aug 22, 2023 (Nanowerk Information) Epoxy resins are robust and versatile polymers. Together with glass or carbon fibers, they’re used, for instance, to fabricate elements for plane, automobiles, trains, ships and wind generators. Such epoxy-based fiber-reinforced polymers have wonderful mechanical and thermal properties and are a lot lighter than metallic. Their weak spot: They aren’t recyclable – not less than not but. Now Empa researchers led by Sabyasachi Gaan at Empa’s Superior Fibers laboratory have developed an epoxy resin-based plastic that’s absolutely recyclable, repairable and in addition flame retardant – all whereas retaining the favorable thermomechanical properties of epoxy resins. They’ve printed their findings within the Chemical Engineering Journal (“Recyclable flame retardant phosphonated epoxy based mostly thermosets enabled by way of a reactive strategy”). Recycling epoxy resins is something however trivial, as a result of these plastics are so-called thermosets. In this sort of polymer, the polymer chains are carefully crosslinked. These chemical crosslinks make melting inconceivable. As soon as the plastic has hardened, it will possibly not be reshaped. This isn’t the case for thermoplasts, resembling PET or polyolefins. Their polymer chains lie shut collectively however usually are not chemically linked to one another. When heated, these polymers could be melted and fashioned into new shapes. Nevertheless, due to the dearth of crosslinks, their mechanical properties at elevated temperatures are usually inferior to these of thermosets. flame retardant epoxy resin The brand new epoxy resin is flame retardant because of its phosphorus content material, as seen on this burn take a look at of an untreated MDF pattern (left) in comparison with a pattern coated within the new polymer. (Picture: Empa)

A brand new type of polymer

The distinctive epoxy resin that the Empa researchers have developed in collaboration with nationwide and worldwide companions is technically a thermoset – however in contrast to different thermosets, it may be reshaped like a thermoplast. The secret is the addition of a really particular purposeful molecule from the category of phosphonate esters into the brand new resin matrix. “We initially synthesized this molecule as a flame retardant,” says co-inventor of this know-how and Empa scientist Wenyu Wu Klingler. Nevertheless, the bond the molecule kinds with the polymer chains of the epoxy resin is dynamic and could be damaged underneath sure situations. This loosens the crosslinking of the polymer chains in order that they are often melted and reshaped. Such supplies, also referred to as vitrimers, have solely been identified for about ten years and are thought of significantly promising. “At present, fiber-reinforced composites usually are not recyclable in any respect, besides underneath very harsh situations, which harm the recovered fibers,” explains Wu Klingler. “As soon as they’ve reached the tip of their service life, they’re incinerated or disposed of in landfills. With our plastic, it will be doable for the primary time to convey them again into circulation once more.” “Our imaginative and prescient for the long run,” provides group chief Sabyasachi Gaan, “is a composite materials, through which each the fibers and the plastic matrix could be utterly separated and reused.” The researcher sees a chance in carbon-fiber-reinforced plastics particularly, as they’re generally used within the building of airplanes, trains, boats, automobiles, bicycles and extra. “The manufacturing of carbon fibers requires numerous vitality and releases an unlimited quantity of CO2,” he explains. “If we may recycle them, their environmental footprint could be rather a lot higher – and the worth rather a lot decrease.” Furthermore, the restoration of helpful components like phosphorus related to the matrix polymer could be doable. repairing epoxy resin Not normally doable for thermosets: The lower within the materials could be repaired by making use of warmth and strain. (Picture: Empa)

A fabric made to measure

Fiber-reinforced composites usually are not the one software for the brand new polymer. For instance, it might be used to coat picket flooring, as a clear, resistant layer that has good flame-retardant properties – and the place scratches and dents could be “healed” with a bit of strain and warmth. “We did not develop a single materials for a particular goal, however slightly a toolbox,” Gaan explains. “Flame retardancy, recyclability and repairability are a given. We are able to optimize all different properties relying on the supposed use.” For instance, he says, move traits are significantly vital for the manufacturing of fiber-reinforced plastics, whereas exterior wooden coatings also needs to be weather-resistant. To pursue these and different purposes of the fabric, the researchers at the moment are in search of industrial companions. The probabilities of industrial success are good: Along with all its different advantageous properties, the modified epoxy polymer can also be cheap and simple to fabricate.

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