Studies On The Filling Modification Of Biodegradable Polyhydroxyalkanoates P3/4HB And PHB

At present the study on the application of biodegradable polymers has been more important. Two kinds of polyesters poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) , poly(3-hydroxybutyrate) with certain mechanical strength,heat molding and biocompatibility, has been paid more attention than other polymers. But high costs and narrow processing window has greatly limited the pplication of them.In order to reduce the production cost and improve its performance,several kinds of inorganic calcium carbonate particles and nano-silica particle were blend with P3/4HB and PHB respectively and were prepared into composites further. In the meantime, PHB-diol was grafted onto nano-silica and then were prepared into nano-composites with PHB.The characterizations were studied by universal testing machine(UTM), gel permeation chromatography (GPC), differential scanning calorimeter (DSC), thermogravimetic analyzer (TGA) and scanning electron microscopy (SEM), nuclear magnetic resonance (NMR) spectrum analyzer, Fourier transform infrared spectrometer (FTIR), polarizing microscope (POM), transmission electron microscopy (TEM) and so on.The results revealed that the thermal stability of P3/4HB was declined by mixing with CaCO₃ particles. Meanwhile, with increasing CaCO₃ content, the elongation at break, tensile strength and impact strength decrease gradually, But, a higher elastic modulus was obtained, which show that the addition of CaCO₃ would make the P3/4HB to brittle materials. The decrease of elongation at break, tensile strength and impact strength can be prevented by addition of P3/4HB which containing 20 mol % of 4HB However, compared with two other CaCO₃, P3/4HB/heavy CaCO₃ have the best mechanical properties and heavy CaCO₃ also with better dispersion. The NMR results show that PHB-diol were prepared successfully and the FTIR results revealed the PHB-diol were grafted onto the nano-silica surface successfully. The surface grafted nano-silica particles were well dispersed in PHB matrix than un-grafted SiO₂ particles and PHB/surface grafted nano-silica composites showed better mechanical properties than that of un-grafted SiO₂/PHB.