Feasibility of Solid-State Postpolymerization on Fossil- and Bio-Based Poly(butylene succinate) Including Polymer Upcycling Routes

Fossil-based and true bio-based poly(butylene succinate) (PBS) prepolymers were synthesized and submitted to solid-state polymerization (SSP) in the proximity of the polyester melting point (T-m), for reaction times up to 29 h under flowing nitrogen. SSP acted as a postcrystallization process, imparting an increase of the PBS melting point up to 126 degrees C from a starting T-m of 112-114 degrees C. Adding a precrystallization step prior SSP even resulted in a 2.5 times increase of the initial MW and a T-m shift up to 128 degrees C. Furthermore, the effect of most critical process parameters on the SSP feasibility and effectiveness was assessed, so as to launch an appropriate operation profile. End-group imbalance turned out to be the most significant key parameter for PBS polymerizability, and various attempts were made toward correcting it. Finally, SSP was examined as a PBS recycling technique and efficiently revived hydrolyzed PBS structures.