| Poly(hydroxyalkanoate)s (PHA) are natural polyesters produced by microorganisms as carbon and energy reserves. Generally, PHA exists in bacteria, alga and fungus, the contents varies from l%wt~30%wt. In some bacteria the PHA in the dry cell can be up to 70%wt by fermentation, but the cost is high. This class includes PHB (poly(3-hydroxybutyrate)) and PHBV (poly(3-hydroxybutyrate-co-3-hydroxyvalerate)) . These polymers present the advantages of biodegradability and biocompatibility over other thermoplastics with useful mechanical properties.The fermentation route to these materials leads to excellent stereochemical control and as a consequence, a complete isotactic[R] configuration polymer is produced. This structure results in very high levels of crystallinity to be achieved. These systems have been ideal models for polymer crystallization and morphological control.PHBV will degrade at the processing temperature, which is much lower than its acute thermal degradation temperature.As the material for chemical fiber, PHBV shows some special properties. When it was spun, the as-spun fiber was elastic and finally it would turn to be rigid. This change makes the processing difficult.It is found that PHBV(poly(hydroxybutyrate-co-valerate) will still thermal degrade at the temperature much more lower than the acute thermal degradation temperature. When it is heated at the temperature, the molecular weight will decrease as the time pass by. It is believed the 0 -elimination process.The SGR(Spherulite Growth Rate) of PHBV is related to crystallization temperature. With the increase of temperature, SGR increase first then decrease. Some sample's SGR will increase again at high temperature area. On the surface of PHBVspherulite, some concentric ring like patterns will occur. Based on the procedure of the formation of ring-like patterns, the possible mechanism is given. According to it, the concentric ring-like patterns are independent of the chemical structure and the crystal structure as well as the material of the carrier. But it is mainly dependant on the physical parameters such as volume shrinkage. And when PHBV crystallized, the HV content will be segregated, it will be accelerated when crystallization temperature is increased. DSC test shows, that if the sample crystallized at a low temperature, the result has a small peek, if it crystallized at a higher temperature, then the peek will divide into two peeks. It is believed related to the segregation of HV content.The apparent viscosity of PHBV will decrease quickly while the shear rate increase. While the temperature increases the flow curves move down, and it is showed that between 180℃ and 190℃ the influence of temperature on the flow behavior is smaller, and the influence of shear rate is smaller. While the content of HV increase, the flow curve move down and viscosity reduce.Based on former work, a special fiber processing equipment was designed and set up in the lab. The formation of fiber was researched, and finally some biomaterial fiber with some certain mechanic properties was got. The success of getting the fiber opens a new application field of this kind of biomaterial.In the work, it is founded to study the thermal degradation of the polymer by study the change of toque of micro twin screw extruder. And the spherulite growth rate of PHBV is studied and the factors, which influence the growth rate and the formula of spherulite growth rate, were discussed. A reasonable mechanism of the concentric ring like patterns on the surface of PHBV spherulite was given first. The segregation of HV content between cystal and amorphous parts was observed and the phenomena caused were discussed. It is the first time to get PHBV fiber by melt spinning in China. And the changes of fiber crystallization structure and orientation structure under force were studied.
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