Role of monomer sequence in the crystallization and rheology of PBAT

Poly(butylene adipate-ran-terephthalate) (PBAT) is a typical biodegradable aliphatic−aromatic polyester. It has been widely used as compost bags, packaging films, and agricultural mulching films because of its complete biodegradability, good processability and mechanical properties, and low water vapor permeability. In this work, we showed that a small difference in the monomer ratio of the BT (butylene terephthalate) and BA (butylene adipate) units of PBAT would lead to significant differences in the continuous sequential block distributions as determined by the high-resolution NMR tests and the first-order Markovian model. As a result, macroscopic properties, such as crystallization behaviors, phase separation behaviors, and rheology, are greatly affected. A PBAT sample with a higher BA content and, consequently, a longer continuous BA block sequence has a lower crystallization temperature, a weaker concentration fluctuation at elevated temperatures, and a stronger strain hardening in melt elongation.