PHB In Blends Research Articles

Crystallization and crystalline dynamics of poly(3-hydroxybutyrate) / poly(4-vinylphenol) polymer blends studied by low-frequency vibrational spectroscopy

Composition- and temperature-dependent far-infrared (FIR), terahertz (THz), and low-frequency Raman spectra of poly(3-hydroxybutyrate) (PHB)/Poly(4-vinylphenol) (PVPh) polymer blends were measured to investigate the effects of PVPh in PHB crystallization. FIR, low-frequency Raman, and wide angle X-ray diffraction (WAXD) studies revealed that PVPh reduces the crystallinity of PHB in blends without a significant change in the crystal structure. The FIR and low-frequency Raman spectra divided the blends into three categories: high-ordered crystalline, less-ordered crystalline, and amorphous. A new peak was observed at 135 cm−1 in the FIR spectra of the PHB/PVPh blends, which may be assigned to the less-ordered crystalline phase of PHB, predicting the inter-molecular hydrogen-bond interactions of PHB/PVPh. The intensity ratio of the peaks at 97 and 82 cm−1 changed with the blending ratio variations owing to the crystalline dynamics of PHB. Deformation of the PHB helical structure occurred first, followed by weakening of the intra-molecular hydrogen-bond within PHB. Shifts of several peaks were observed in the FIR and low-frequency Raman spectra, suggesting that the intra-molecular hydrogen-bond (CO⋯H-C-) within PHB weakened with temperature. The novelty of the present study is to demonstrate that low-frequency vibrational spectroscopy is very sensitive to monitor changes from the intra-molecular hydrogen bonding to inter-molecular hydrogen bonding between PHB and PVPh.

Effect of poly(vinyl acetate) (PVAc) on thermal behavior and mechanical properties of poly(3-hydroxybutyrate)/poly(propylene carbonate) (PHB/PPC) blends

To assess the compatibility of blends of synthetic poly(propylene carbonate) (PPC), with a natural bacterial poly(3-hydroxybutyrate) (PHB), a simple casting procedure of blend was used. poly(3-hydroxybutyrate)/poly(propylene carbonate) blends are found to be incompatible according to DSC and DMA analysis. In order to improve the compatibility and mechanical properties of PHB/PPC blends, poly(vinyl acetate) (PVAc) was added as a compatibilizer. The effects of PVAc on the thermal behavior, morphology, and mechanical properties of 70PHB/30PPC blend were investigated. The results show that the melting point and the crystallization temperature of PHB in blends decrease with the increase of PVAc content in blends, the loss factor changes from two separate peaks of 70PHB/30PPC blend to one peak of 70PHB/30PPC/12PVAc blend. It is also found that adding PVAc into 70PHB/30PPC blend can decrease the size of dispersed phase from morphology analysis. The result of tensile properties shows that PVAc can increase the tensile strength and Young’s modulus of 70PHB/30PPC blend, and both the elongation at break and the tensile toughness increase significantly with PVAc added into 70PHB/30PPC.