Crystallization, Morphology, and Enzymatic Degradation of Polyhydroxybutyrate/Polycaprolactone (PHB/PCL) Blends

✍ Scribed by Deliani Lovera; Leni Márquez; Vittoria Balsamo; Antonieta Taddei; Cristina Castelli; Alejandro J. Müller

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 587 KB
• Volume: 208
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200700011

✦ Synopsis

Abstract

Two types of mixtures were prepared by solution blending: high molecular weight polyhydroxybutyrate (PHB)/poly(ε‐caprolactone) (PCL) and PHB/low molecular weight chemically modified PCLs (mPCL). The morphology, crystallization, and enzymatic degradation of the blends were studied by differential scanning calorimetry, polarized light optical microscopy, scanning electron microscopy, ^1^H NMR, and weight loss measurements. In addition, enzymatic degradation studies were performed by an exposure to Aspergillus flavus. High molecular weight PHB/PCL blends were found to be immiscible in the entire composition range. Phenomena such as PCL fractionated crystallization and a decrease in PHB nucleation density were detected. When PHB was blended with mPCLs, the blends were partially miscible; two phases were formed, but the PHB‐rich phase exhibited clear signs of miscibility through a depression of both the T~m~ and the T~g~ of the PHB component (which was stronger with lower molecular weight mPCL), and an increase in the growth rate of PHB spherulites in the blends as compared to neat PHB or to the PHB component in the PHB/PCL blends. The biodegradation by a exposure to A. flavus showed that the blends are synergistically attacked in comparison to the homopolymers. Two factors may influence the improved degradation rate of the blends: the dispersion of the components and their crystallinity that was reduced in view of the fractionated crystallization and impurities transfer. In the case of the PHB/mPCL blends, the increased miscibility between the components caused a reduction in the degradation rate.

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