Processing and Characterization of Vitrimers

Polyethylene (PE) is one of the most widely used commodity plastics by volume. PE is versatile, lightweight, tough, is easy to process, and exhibits excellent chemical resistance. Some of the limitations of this material are its lower strength, poor dimensional stability at high temperature, and strong creep behavior. Cross-linked PE (XLPE) offers these properties with the sacrifice of not being recyclable due to its permanent cross-links. A new class of materials, called vitrimers, combine the properties of thermoplastics and thermosets: they behave like traditionally cross-linked materials at service temperature while being re-moldable and recyclable like thermoplastics when heated. Vitrimers are a type of covalent adaptable networks (CANs) materials that consist of dynamic cross-links that engage in thermoactivated exchange reactions as depicted in Figure 1. During the exchange reactions, the network can change its topology. Unlike permanent cross-linked materials, vitrimers can flow under the action of heat. Furthermore, the exchange reactions can provide shape memory, malleability, weldability, healing, and recyclability of thermosets.

Figure 1. Comparison between thermoplastics, thermosets and vitrimers

While significant focus has been placed on the development of vitrimer chemistry,  there is little understanding on how to process at scale. This research aims to enable industrial applications by understanding the processability, final part property, and structure-property relationship. This will allow the implementation of mathematical models to predict material properties and optimize processes.