聚乳酸/聚己二酸丁二醇酯-对苯二甲酸双连续相共混物薄膜的SiOx憎水界面生成与阻水研究

To relieve the energy dilemma and the environmental pollution, the applications of biodegradable Polylactic acid (PLA) in the packaging and agricultural mulch has become an inevitable trend. However, poor moisture barrier property greatly restricts the application of PLA. Hence, the project using the manipulation of structure and morphology to form hydrophobic SiOx network in the interface between bicontinuous phase PLA/poly adipic acid butyl glycol ester-terephthalic acid (PBAT) to improve the water vapor barrier properties of the blend membrane. This project intends employing synergistic control of the structure, reactivity and molecular weight of PSZ to facilitate the phase separation and interfacial distribution of PSZ in PLA/PBAT matrix. The PLA/PBAT film with bicontinuous phase fine structure will be obtained by compound adjustment of viscosity and blend ratio of PLA/PBAT. With the help of infiltrated moisture, the PSZ located in the interface between PLA and PBAT phase transform into SiOx network. On the base of the research of the distribution of PSZ and the morphology of PLA/PBAT, the factors that affecting the distribution and mechanism of action of the PSZ will be proved, the forming conditions of bicontinuous phase fine structure of PLA/PBAT in the presence of PSZ will be obtained. By the investigation of moisture adsorption and permeability of composite membrane with different SiOx network, the plasticizing behavior and permeation mechanism of moisture in SiOx-PLA/PBAT film will be revealed, which provides guidance for the preparation of biodegradable film with high moisture barrier property.

为缓解能源危机和环境污染，聚乳酸（PLA）在包装及农用地膜中的使用已成为必然。然而，较差的水汽阻隔性能严重制约了PLA的应用。为此，本项目提出通过调控PLA/聚己二酸丁二醇酯-对苯二甲酸（PBAT）双连续相精细结构并在其界面形成完整的阻水SiOx网络，以提高共混薄膜的水汽阻隔性能。本项目拟采用综合调整PSZ微观结构、反应基团及分子量实现PSZ在PLA/PBAT的界面分布，通过调控组成比和黏度比获得PLA/PBAT双连续相精细结构，借助渗入的水汽与PSZ的反应使PSZ转化为SiOx阻水网络。通过PSZ分布情况及PLA/PBAT相态结构变化研究，探讨影响PSZ分布的因素及其作用机制，探明PSZ-PLA/PBAT双连续相精细结构的形成机制。通过对含有SiOx网络的复合薄膜水汽吸附及渗透性研究，探明水汽在SiOx-PLA/PBAT薄膜中的增塑行为及渗透机理，为制备高水汽阻隔性降解薄膜提供理论指导。

通用塑料薄膜，特别是可生物降解型塑料薄膜较差的水汽阻隔性能严重制约着其在包装及农用地膜中的广泛应用，为此本项目提出了通过共混体系的相态结构调控而形成双连续相的精细结构，并在连续相的界面处构建完整的阻水网络，从而实现复合薄膜的高水汽阻隔特性。首先研究了能形成致密阻水层SiOx的陶瓷前驱体的制备，获得了粘度可调的PSZ合成工艺参数。其次研究了第三相材料在两元塑料共混体系内的迁移及运动规律，并在塑料薄膜共混体系中构建了不同类型的阻水汽层，如内部集中取向分布阻隔层、隔离结构阻隔层、表面SiOx涂覆层及SiOx与大片层填料混合阻隔层等。在此基础上分析和探讨了氧气及水汽在上述类型的共混薄膜中的渗透和传播机制。结果发现通过PSZ所形成的SiOx层能有效提高塑料薄膜的疏水性，可使复合薄膜的表面水接触角提高到150o左右，从而有效降低了塑料薄膜对水润湿及渗透特性；通过塑料共混体系的特性、含量及加工参数调节可有效调控阻隔层的结构与形态；阻隔层的完整性及连续性是影响复合薄膜阻气和阻水性的关键参数，表/界面致密的SiOx层和内部高度取向的片层填料结合是高阻气及阻水的理想结构。本项目还将所获得的相态结构调控成果拓展到电磁屏蔽及导热领域，通过调控电磁及导热填料在塑料基体内的形态及分布，获得电磁屏蔽及导热率兼顾的塑料复合薄膜。这些研究为塑料（特别是可降解塑料）在高阻隔包装材料、农用地膜、电磁屏蔽及电子封装等方面的应用提供了理论基础和实践经验。