Completely recyclable, lightweight, single Component Composite Material for Injection-Molded Components
Previously, polyethylene (PE) had to be reinforced with carbon or glass fibres in order to be used in lightweight construction. The need to add e.g. glass fibres to PE to improve its mechanical and tribological properties has made production and recycling more difficult and costly.
Polyethylene (PE) without such additives has a very good energy, environmental and cost balance. It can be recycled easily and almost infinitely often: used product is rasped, melted and formed into new components with consistently good quality.
In cooperation with the FMF Materials Research Center at the University of Freiburg and the polyolefin manufacturer LyondellBasell, the Fraunhofer IWM has produced and qualified a sustainable, all-PE single component composite. The reinforcing fiber structures are also made of PE and form during injection-molding.
Using a specific catalyst, the FMF pioneered the synthesis of a blend of PE with various chain lengths in the chemical reactor, including a fraction of ultra high molecular weight PE. These »reactor blends« form fibre-like nanostructures which reinforce the material. Due to the resulting mechanical properties of the material, it can be used in lightweight construction and is 100% recyclable. In the injection moulding process, the fibre structures are formed when high shear stresses occur in the injection moulding tool. In the 3D printing process, the fibre structures of the new material can also form in the nozzle. This allows the fibre alignment to be specifically adjusted during 3D printing.
An attractive combination of high stiffness, tensile strength and impact strength could be observed by FMF for the newly developed all-PE composites. The Fraunhofer IWM evaluated the behavior under crash loading (i.e. under high strain rates) and the tribological characteristics of the novel composites. Reactor blends with a suitable composition reach a similar wear resistance as poly(amides).
As a result, many new applications for this recyclable material are conceivable: in addition to light weight gear wheels in automobiles or for the food industry, it is also possible to produce nestling robot grippers which adapt to the shape of a part, medical orthoses or connectors.
Hees, T.; Zhong, F.; Koplin, C.; Jaeger, R.; Mülhaupt, R., Wear resistant all-PE single-component composites via 1D nanostructure formation during melt processing, Polymer 151 (2018) 47-55 Link
All-Polyethylene single Component Composite Material: Recyclable lightweight single Component Composite Material developed for Injection-Molded Components