本文研究了不同聚乙二醇（PEG2000）含量(0wt%~20wt%)的聚乳酸（PLA）膜的拉伸性能及阻隔性能，同时探究结晶老化过程对这些性能的影响。不同PEG含量的PLA膜在25 ℃和相对湿度50%环境中存放不同时间，测定其拉伸、透水和透氧特性。同时用扫描电镜揭示PLA膜的微结构。结果表明，PLA属于结晶较慢的部分结晶聚合物，而PEG可有效塑化PLA但同时也促进PLA结晶老化。PEG结晶以球粒状均匀分布在PLA基质内。在塑化和促进结晶两种效果共同作用下，含10 wt% PEG的PLA膜有较高的强度（拉伸应力和弹性模量分别为37.8 MPa，1721.4 MPa）和最大的断裂延伸率（63.75%）。PEG在最佳用量（10wt%）时，透氧性（OP）及透水性（WVP）最小，PLA和PEG的单纯结晶行为也使WVT和OP减小，而相分离会导致它们增大。添加10wt% PEG的PLA膜具有比较理想的膜拉伸性能和较低的WVP和OP渗透性以及一定的紫外线阻隔效果，适合应用于食品包装用膜。

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.

国家自然科学基金面上项目（31471628）；广州市珠江科技新星专项（201506010063）