Thermo-mechanical degradation and stabilization of poly(butylene succinate)

The thermo-mechanical degradation and recyclability of poly(butylene succinate) (PBS) have been investigated by means of consecutive extrusion cycles under different temperature profiles, in order to simulate reprocessing intensive conditions. Herein it was found that PBS, when reprocessed at temperatures higher than 190 °C, suffers from branching/recombination degradation reactions, resulting in extrudates of higher solution viscosity, and of bimodal distribution of molar masses. When typical stabilizers (Irganox® 1010, Irgafos® 168) were added, the thermo-mechanical degradation of PBS was significantly suppressed, revealing the radical character of the pertinent degradation reactions. The incorporation of stabilizers at the level of 0.1% efficiently maintained polymer properties through reprocessing, while the higher concentration of 0.5% had a negative impact on extrudates quality. On thermal properties basis, degraded and stabilized PBS exhibited similar melting and degradation points compared to virgin material, showing its possibility for mechanical recycling. However, the induced degradation resulted in accelerated melt crystallization and lower degree of crystallinity, which might be attributed to the nucleating effect of the formed branches. The addition of stabilizers restricted the increase of the melt crystallization rate, and the relevant melt behavior was found similar to virgin material.