Unraveling the cause for the unusual processing behavior of commercial partially bio‐based poly(butylene succinates) and their stabilization

Abstract

The commercially available partially bio‐based poly(butylene succinate) (PBS) and poly(butylene succinate‐co‐adipate) (PBSA) are subjected to prolonged and multiple extrusion cycles to investigate their thermal behavior. Empirically, both PBS and PBSA form branches at 190°C, with PBS possessing a higher tendency for branching than PBSA as studied by rheology and size exclusion chromatography (SEC). In each case, the branching is favored by fumaric acid moieties, making both PBS and PBSA susceptible to accelerated thermal oxidation. Indeed, the NMR signal attributed to fumaric acid disappears upon thermal processing of PBS and PBSA. Presumably, the bio‐based succinic acid used contains minor quantities of fumaric acid, yet still sufficient to cause this surprising processing behavior. The branching of both polymers is suppressed by stabilizers such as phenolic antioxidants, as proven by rheology and SEC. This is complemented by nuclear magnetic resonance (NMR), revealing that the fumaric acid signal is still well‐resolved in the stabilized processed samples.

Ternary blends of thermoplastic starch (TPS) with poly(lactic acid) (PLA) and poly(butylene succinate- co-adipate) (PBSA): design, processing and characterization of home compostable materials

“…Moreover, the study highlighted how at higher temperatures, branching occurred at the highest extent. Similar results were reported by (Hallstein et al, 2021) who clearly demonstrated branching phenomena in PBS and PBSA following extrusion cycles at 190°C. Such phenomena were associated to fumaric acid moieties detected both in PBS and PBSA, which disappear after extrusion processing thus suggesting reactions take place precisely in correspondence of fumaric acid moieties.…”

“…Such high values are presumably ascribed to the afore mentioned hyper-branching phenomena which affect PBSA during melt-processing, always causing viscosity increase, no matter what working conditions are set (Hallstein et al, 2021).…”

“…A further decomposition pahway was hypothesized, taking place through a hydrogen-transfer mechanism, followed by the production of succinic anhydride. The latter assertions were then contradicted in (Georgousopoulou et al, 2016) and more recently in (Hallstein et al, 2021). Georgousopoulou et al demonstrated how PBS, conversely to PLA, is subject to degradation phenomena following repeated extrusion cycles, related to branching/recombination reactions, thus causing a significant increase of the viscosity of the molten polymer, of the molecular weight and of the polydispersity index at equal final concentrations of carboxylic groups.…”

Co-Crystallization between Aliphatic Polyesters through Co-Inclusion Complexation with Small Molecule

“…The 1 H NMR spectra of the remaining structures were employed to detect the chemical compositions. As shown in Figure 7 , the characteristic nuclear magnetic resonance peak of the PBA at a chemical shift of 2.33 ppm still existed [ 33 ]. The mole ratios of the PBA/PBS in the THF-soaked blends were calculated based on the integrated areas of the two peaks at 2.33 ppm and 2.63 ppm, which increased with the initial feeding content of PBA, though much lower ( Table 1 ).…”

Sequential Infiltration Synthesis of Al2O3 in Biodegradable Polybutylene Succinate: Characterization of the Infiltration Mechanism

“…Furthermore, an analysis of PBS end groups was done assigning the hydroxyl end group CH 2 –OH of PBS at 3.7 ppm; the heteronuclear long-range correlations of this end group were not associated with the new formed alkyl- and alkoxy-groups, thus confirming the proposed PBS-TMA reaction mechanism of Scheme 1 . 44 , 45 To evaluate changes on the PBS microstructure as a function of the number of SIS, a quantitative analysis through 1 H experiments was performed. Data are reported in Figure S11 .…”