Thermoplastic lignin esters as polymeric plasticizers for bioplastics

In this thesis, a sustainable and scalable process for modifying the structure of technical lignin to make it suitable for mixing with common bioplastics is studied. More specifically, this project deals with the development of a method of grafting fatty acids onto lignin. First, an updated state of the art concerning the processes for lignin production and its esterification is introduced and thoroughly discussed. Next, the materials and methods used to perform one-pot synthesis on lignin are described. The grafting process is initially optimized using a model reaction; afterwards, these conditions are adapted to technical lignin. The resulting process is also scaled up, overcoming unexpected issues due to mass and energy transfer. The modified lignins have been characterized through various thermal and analytical analyses (such as DSC, TGA and NMR), to provide a detailed description of their properties and structures. Finally, modified lignin was used to produce blends with commercial PLA as a proof of concept. As a matter of fact, this thesis is leading the basis for the fabrication of new-concepts materials based on plasticized lignin, aiming to conjugate sustainable industrially scalable processes and material performances.