No abstract

Poly(3-hydroxybutyrate) (PHB) was plasticized with dioctyl (o-)phthalate, dioctyl sebacate, and acetyl tributyl citrate (ATBC). The thermal properties, mechanical properties, and melt flow ability were studied with differential scanning calorimetry, thermogravimetric analysis, a universal material testing machine, and a melt flow indexer. ATBC was revealed to be an efficient plasticizer, reducing the glass-transition temperature and increasing the thermoplasticization ability of PHB. We also blended poly(3-hydroxybutyrate-co-hydroxyhexanoate) (PHBHHx) and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3/4HB)] with PHB, ATBC, and antioxidant 1010 to overcome the brittleness of PHB and improve the melt flow stability of the materials. PHBHHx did little to improve the thermal processing but increased the fluidity of PHB, and P(3/4HB) toned the toughness of PHB. The addition of antioxidant 1010 enhanced the thermal stabilization of PHB.

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)/poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) blend films were prepared by solvent-cast method. The nonisothermal crystallization results showed that PHBV and P3/4HB are miscible due to a single glass transition temperature (T g ), which is dependent on blend composition. The isothermal crystallization results demonstrate that the crystallization rate of PHBV becomes slower after adding amorphous P3/4HB with 19.2 mol% 4HB, which could be proved through depression of equilibrium melt point (T C and 84 C, respectively. FTIR analysis showed that PHBV/P3/4HB blend films would maintain the helical structure, similar to pure PHBV. Meanwhile, with increasing P3/4HB content, the inter-and intrainteractions of PHBV and P3/4HB decrease gradually. Besides, a lower elastic modulus and a higher elongation at break were obtained, which show that the addition of P3/ 4HB would make the brittle PHBV to ductile materials.

Naturally amorphous biopolyester poly (3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) containing 21 mol % of 4HB was blended with semi-crystal poly(butylene succinate) (PBS) with an aim to improve the properties of aliphatic polyesters. The effect of PBS contents on miscibility, thermal properties, crystallization kinetics, and mechanical property of the blends was evaluated by DSC, TGA, FTIR, wide-angle X-ray diffractometer (WAXD), Scanning Electron Microscope (SEM), and universal material testing machine. The thermal stability of P3/4HB was enhanced by blending with PBS. When PBS content is less than 30 wt %, the two polymers show better miscibility and their crystallization trend was enhanced by each other. The optimum mechanical properties were observed at the 5-10 wt % PBS blends. However, when the PBS content is more than 30 wt %, phase inversion happened. And the two polymers give lower miscibility and poor mechanical properties.

The biodegradable behaviors of monofilament suture made from bacterial biopolyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) was investigated both in lipase solution and by implant into rat tergal muscles. Results showed that the monofilament suture lost its tensile strength gradually accompanied by decrease of molecular weight. The suture retained approximately 65% of its original strength after lipase degradation for 12 weeks, whereas the molecular weight decreased from 4.5 x 10(5) to 3.8 x 10(5). However, the crystallinity of the suture, after lipase degradation for 12 weeks, increased from 27 to 33%. This may ascribe to improve orientation arrangement of molecular chain in the monofilament after the fragment from amorphous regions dissolved in the buffer solution. The roughness of surface morphology increased with degradation. Rat implantation showed no remarkable tissue responses during in vivo degradation. Foreign body reactions were much milder than chromic catgut, which is one of the most common commercially available sutures.