Processing stability of polyhydroxybutyrate (PHB)

The aim of this thesis was to observe and to evaluate the effects of selected additives on stabilization of two poly-3-hydroxybutyrates - Biomer and Hydal. In the experimental section of the thesis,the physical properties of pure polymers, polymers with mixture of polylactid acid, boron nitride and Citroflex 4A as well as the samples with five different additives which were added to this mixture, were meassured. Whilst processing the samples, the torque inside of the kneader was recorded. Tensile strength, Young´s modulus and relative extension were evaluated using tensile tests. Next, the differential scanning calorimetry was used to determine the melting points and their changes in comparison to the pure polymers. To evaluate the thermooxidative stability, method of induction periods was used, where the amount of time needed for degradation to make the material brittle was observed and recorded. These methods determined the the Stabilizer 9000 (Raschig) as the most suitable, owing to its better thermooxidative stability and considerable relative extension. As for DHT-4A on the other hand, it was proven that within P3HB it supports degrading processes, which devaluate the processing properties of this material even more. Amongst the other additives no significant influence on the material was observed and the changes of properties were attributed to the mixture of PLA and the other substances