Abstract:The tensile and barrier properties of polylactic acid (PLA) films with different polyethylene glycol (PEG) content (0wt%~20wt%) were investigated, and the effect of crystallization and aging process on these properties of the films were also evaluated. PLA films containing different PEG content were stored in conditions of 25 ℃ and 50% relative humidity for different times. Then, the tensile properties, water vapor permeability (WVP), and oxygen permeability (OP) of the films were measured, and the microstructure of each film was examined by scanning electron microscopy (SEM). The results showed that PLA was a polymer that crystallized partially and relatively slowly. PEG could effectively plasticize PLA and promote the aging and crystallization of PLA. PEG crystals were uniformly distributed in the PLA matrix and were spherical in shape. Under the combined effect of plasticization and promotion of crystallization, the PLA film with 10wt% PEG had a relatively high strength (tensile stress and elasticity modulus were 37.8 MPa and 1721.4 MPa, respectively) and the maximum elongation at break (63.75%). With the optimal amount of added PEG (10wt%), the minimum OP and WVP were obtained. The OP and WVP values were decreased by the simple crystallization behaviors of PLA and PEG and were increased by phase separation. In conclusion, PLA film containing 10 wt% PEG had satisfactory tensile properties and low OP and WVP, exhibited a certain effect on blocking ultraviolet (UV) rays, and was suitable for food packaging.
