Recyclable and Creep Resistant Polyethylene – through Transient Cellulose Networks

“Plastics enhance almost every aspect of human life from food consumption to medical care and even energy production. However, the often superficial use of plastics means that a large fraction of this versatile class of materials is not recycled but, instead, burned for energy recovery, buried as waste in landfills, or worst case simply discarded leading to polluted oceans etc. There are two types of plastic: (1) thermoplastics, which can be reprocessed and reused, and (2) thermosets, where an internal network prevents reshaping through heat or shear. This means that in particular recycling of thermosets can only be done with great difficulty. Many plastics, including in many cases polyethylene, must be crosslinked to be suitable for certain applications, which transforms an initially thermoplastic material into a thermoset. Approaches that avoid crosslinking would enhance the recyclability of some of the most common plastics, which is a prerequisite to develop a truly circular economy. This project will establish a new concept that can be used as an alternative to crosslinking. The new concept entails the use of cellulose as a reinforcing agent that prevents creep of a molten polymer matrix, which alleviates the need for crosslinking. At the same time, the material remains thermoplastic, and thus can be recycled. We will develop this concept with focus on polyethylene, the most widely used commodity polymer, which today must be crosslinked to be suitable for a wide range of medical and electrical applications. Our final aim is to demonstrate that cellulose composites can be used as a melt creep-arresting additive for polyethylene resins that are in use today. We anticipate that our new concept, i.e. the use of a cellulose material as an alternative to crosslinking chemistry, opens up a new design principle for plastics with a high degree of recyclability. Ultimately, our approach may allow to considerably expand the versatility of the most common type of plastic used today, improving the recyclability of polyethylenes and opening up new application areas where superior creep resistance is required.”