2.2. Reprocessing
PBS was subjected to five successive extrusion cycles in a Haake
Rheomex twin-screw co-rotating extruder (L/D ¼ 25, d ¼ 16 mm).
Reprocessing temperature was set at 190, 200 and 210 C at constant
rotation speed of 100 rpm. After each extrusion cycle, the
extrudates were cooled in water bath, pelletized in 3 mm pellets
and dried at 80 C for 5 h.
Multiple extrusion was carried out on neat PBS, as well as on
samples containing the stabilizers. To examine the effect of storage
and drying on reprocessing and to “simulate” typical storage
environmental conditions, PBS sample was exposed for two weeks
to 50.0 ± 3.5% RH environment [52] at fixed temperature of 25 C. It
was then dried (80 C, 5 h) (prePBS: preconditioned PBS) and reextruded
according to the aforementioned procedure. The prepared
PBS formulations and pertinent degradation conditions are
presented in Table 1.