Li Fenfen, Zhang Caili, Weng Yunxuan, Diao Xiaoqian, Zhou Yingxin, Song Xinyu
College of Chemistry and Materials Engineering, Beijing Technology and Business University, Beijing 100048, China.
Beijing Key Laboratory of Quality Evaluation Technology for Hygiene and Safety of Plastics, Beijing Technology and Business University, Beijing 100048, China.
Materials (Basel). 2020 Jul 6;13(13):3024. doi: 10.3390/ma13133024.
Graphene oxide(GO)/polylactic acid (PLA) nanocomposite, prepared using a solvent-free melt mixing processing, is investigated as a potential oxygen barrier packaging film in this work. In order to disperse GO homogeneously in PLA matrix, hydrophobic silane coupling agent, i.e., γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560), is used to modify the graphene oxide sheets. The modified GO is able to be well bonded to the PLA due to the formation of covalent bonds between the epoxy groups of KH560 and the carboxyl and hydroxyl terminal groups of PLA. Furthermore, the thermal stability of GO is enhanced due to the long alkyl side chain of KH560, which could also increase the crystallinity of PLA. As a result, the crystallinity of PLA is significantly improved because of the linear KH560 chains, which can act as nucleating agents to improve the crystallization. The KH560-GO helps to reduce the O permeability of KH560-GO/PLA composite films via a dual-action mechanism: (1) providing physical barrier due to their native barrier properties, and (2) by resulting in higher degree of crystallinity. The as-prepared KH560-GO0.75/PLA is able to exhibit ca. 33% and ca. 13% decrease in the than the neat PLA and GO0.75/PLA film, respectively. Finally, the mechanical properties and impact fractured surfaces indicate that the increase in the tensile strength and elongation at break value of KH560-GO/PLA are due to the strong interfacial adhesion and the strong bonding between the epoxy group of KH560-GO and hydroxyl and carboxyl acid terminal groups of PLA matrix.
本文采用无溶剂熔融共混工艺制备氧化石墨烯（GO）/聚乳酸（PLA）纳米复合材料，并将其作为潜在的氧气阻隔包装薄膜进行研究。为了使氧化石墨烯均匀分散在聚乳酸基体中，使用疏水性硅烷偶联剂γ-（2,3-环氧丙氧基）丙基三甲氧基硅烷（KH560）对氧化石墨烯片进行改性。由于KH560的环氧基团与聚乳酸的羧基和羟基端基之间形成了共价键，改性后的氧化石墨烯能够与聚乳酸良好结合。此外，KH560的长烷基侧链增强了氧化石墨烯的热稳定性，这也可以提高聚乳酸的结晶度。结果，由于线性的KH560链可以作为成核剂来改善结晶，聚乳酸的结晶度显著提高。KH560-GO通过双重作用机制有助于降低KH560-GO/PLA复合薄膜的氧气透过率：（1）由于其固有的阻隔性能提供物理阻隔；（2）通过导致更高的结晶度。所制备的KH560-GO0.75/PLA相比纯聚乳酸薄膜和GO0.75/PLA薄膜，氧气透过率分别降低约33%和约13%。最后，力学性能和冲击断裂表面表明，KH560-GO/PLA的拉伸强度和断裂伸长率的增加是由于KH560-GO的环氧基团与聚乳酸基体的羟基和羧基端基之间有很强的界面附着力和强结合力。
