Temperature and physical-mechanical properties of thermoplastic materials based on polyhydroxybutyrate

Abstract

The temperature and physical-mechanical properties of polyhydroxybutyrate obtained during the cultivation of Azotobacter vinelandii N-14 bacteria strain, polylactic acid, poly(-caprolactone) and their blends were studied. Polymer samples in the form of films with a thickness of 50 m were cast on silicate glass plates applying 3% solutions of biopolymers in chloroform and subjected to heat treatment in an air thermostat at the temperature of 1100C for 20 minutes. It was found that the previous heat treatment of the studied biodegradable polymers increases their heat resistance which is evidenced by the shift of their thermal effects of melting to higher temperature area. It was determined that films based on polyhydroxybutyrate/polylactic acid/poly(-caprolactone) (20:55:25 wt.%) blend possesses improved mechanical properties. The film relative elongation at break increases from 3% to 46% for polyhydroxybutyrate and for the mixture, respectively. This is explained by the presence of poly(-caprolactone) polymers in above mixture. At the same time, despite the lower tensile strength characteristic which are typical of poly(-caprolactone), this value is higher for the polymer blends than for polyhydroxybutyrate (38.3 and 33.0 MPa, respectively). This is due to the high polylactic acid content (55%) in the polymer composition. The presence of poly(-caprolactone) (25%) in the blend improves the fluidity of its melt which will enable to reduce the temperature of product formation. The derived polymer mixture is recommended for the manufacturing of various packaging materials for food, agricultural and pharmaceutical products.