Investigation of Phase Separation in Biopolymer Blends

1 Poly((3-Hydroxybutyrate)(PHB)/Poly(L-Uctic Acid)(PLA) Blends 

Polymer blends of PHB and PLA have previously been analyzed by several research groups, using a wide variety of methods [7-9]. In the following, the application of transmission FT-IR and Raman imaging will be discussed as an alternative approach to providing a better understanding of the chemical and physical properties of these blends. 

Based on the spectra measured with the FT-IR, FT-NIR and Raman instruments of samples with various mechanical and thermal pretreatments, and under different experimental conditions, images have been derived by exploiting the spectral differences of the blend components. 

PLA 60/40 wt% blend, PLA contents of 33 and 71wt% were calculated for the PHB-rich and PLA-rich phases, respectively. 

In FT-IR polarization spectroscopy two spectra are generally recorded, with the electric vector of the radiation polarized parallel (E ) and perpendicular (Ex), respectively, to a reference direction (e.g., the drawing direction) of the anisotropic sample being investigated. Based on a uniaxial orientation geometry from these experimental data, the intensity of any absorption band, independent of anisotropy, can be expressed by the stmctural absorbance Aq, which can be calculated by Eq. (22.3)  

The blending of different polymers is a frequently used technique in industrial polymer production to optimize the material properties. The biodegradable polymer poly(3-hydroxybutyrate) (PHB) [50, 51], for example, which can be produced by bacteria from renewable resources, has the disadvantage of being stiff and brittle. The mechanical properties of PHB, however, can be readily enhanced by blending with another biopolymer, poly(lactic acid) (PLA) [52]. For the preparation of 

PHB) (b) FT-IR transmission spectrum of a PHB/PLA (50 50wt%) blend film. (Reproduced with permission from Ref. [57] 2008, ACS Publications.) 

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