Study On The Rheological Properties Of P(3HB-co-4HB) Copolymers And P(3HB-co-4HB)/PLA Blends

The rheological properties of microbially synthesized poly(3-hydroxybutyrate-co-4-hydroxybutyrate)s[P(3HB-co-4HB)] copolymers with varying comonomer(4HB) molar fraction and it blends with PLA, were systematically investigated in this paper. P(3HB-co-4HB) and PLA were melt blended using a HAAKE. The linear and non-linear shear rheological behaviors of P(3HB-co-4HB)s and its blends with PLA were systematically investigated by the plate rotary rheometer, capillary rheometer.etc. Shear viscosities dependence on temperature and copolymer compositions.The results show that:(1) the presence of 4HB increases the steric hindrance of the P(3HB-co-4HB) chains, thus resulting in increased segmental friction and entanglement density. The master curves of P(3HB-co-4HB) coincidence better.The results also show that P(3HB-co-4HB)/PLA blends is a kind of immiscible. The point of intersection of storage modulus(G’) and loss modulus(G") for P(3HB-co-4HB)/PLA melts was changed with mass fraction of P(3HB-co-4HB)(2) Temperature scanning curve of G’ of P(3HB-co-4HB) and P(3HB-co-4HB)/PLA blends occurs deviation, it shows that phase separation occurred, phase separation temperature of copolyesterare decreased as the 4HB unit ingceraseing.(3) The viscosity of P(3HB-co-4HB) and P(3HB-co-4HB)/PLA blends show typical shear thinned behavior. The rotary rheometer, capillary rheometer measured data can get larger range shear rate of viscosity changes.(4) G’and G" of P(3HB-co-4HB)/PLA blends increased with the mass fraction of PLA decreases. The viscosity of the PLA is less than P(3HB-co-4HB), the increased mass fraction of PLA results in a gradual decrease of the P(3HB-co-4HB)/PLA melt viscosity. but the mass fraction of PLA is about 20% wt, the viscosity of blends compared with pure P(3HB-co-4HB) was increased.