Blends of Poly(hydroxybutyrate) and Poly(ethylene succinate) Prepared in the Presence of Samarium

Abstract

Blends of the commercial biodegradable polymer poly(hydroxybutyrate) (PHB) with the oligomeric polyester poly(ethylene succinate) (PES) were prepared by melt processing in the presence of Sm(acac)₃. The occurrence of transesterification reactions during blend processing using the samarium catalyst was investigated. ¹H NMR analyses showed no evidence of transreactions, even using high content of catalyst (4 wt%), long reaction times and high temperatures (200°C). Under the drastic reaction conditions employed, chain degradation characterized by a significant decrease in the molecular weight (MW) of PHB has taken place. PHB/PES blends form immiscible systems in which the PHB crystallizes as large spherulites, but its crystallization is significantly influenced by the presence of PES, which does not crystallize at conditions in which the poly(hydroxyalkanoate) is crystallized.

Keywords:

• blends
• degradation
• PHB
• poly(ethylene succinate)
• transesterification

The authors wish to thank the CAPES and CNPq for financial support and PHB Industrial for the donation of PHB.

Notes

^a PES end groups.

Processing temperature: 170°C.

^a T_p: processing temperature.

^b Processing or thermal treatment time.

^c Nonprocessed sample.

^a Processing temperature: 170°C, t_p = processing time, Tc = crystallization temperature, X _c = degree of crystallinity, ΔH_m = melting enthalpy.

^b Sample not processed.