Fraunhofer Institute for Applied Polymer Research, Division Biopolymers, Department Starch/Biotechnological Processes, Geiselbergstr. 69, 14476 Potsdam, Germany.
Carbohydr Polym. 2014 Feb 15;102:941-9. doi: 10.1016/j.carbpol.2013.10.040. Epub 2013 Oct 21.
The current study examined thermal and mechanical properties of fatty acid starch esters (FASEs). All highly soluble esters were obtained by the sustainable, homogeneous transesterification of fatty acid vinyl esters in dimethylsulfoxide (DMSO). Casted films of products with a degree of substitution (DS) of 1.40-1.73 were compared with highly substituted ones (DS 2.20-2.63). All films were free of any plasticizer additives. Hydrophobic surfaces were characterized by contact angle measurements. Dynamic scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) revealed thermal transitions (T(g), T(m)) which were influenced by the internal plasticizing effect of the ester groups. Thermal gravimetric analysis (TGA) measurements showed the increased thermal stability toward native starch. Tensile tests revealed the decreasing strength and stiffness of the products with increasing ester-group chain length while the elongation increased up to the ester group laurate and after that decreased. Esters of the longest fatty acids, palmitate and stearate turned out to be brittle materials due to super molecular structures of the ester chains such as confirmed by X-ray. Summarized products with a DS 1.40-1.73 featured more "starch-like" properties with tensile strength up to outstanding 43 MPa, while products with a DS >2 behaved more "oil-like". Both classes of esters should be tested as a serious alternative to commercial starch blends and petrol-based plastics. The term Cnumber is attributed to the number of total C-Atoms of the fatty acid (e.g. C6=Hexanoate).
本研究考察了脂肪酸淀粉酯（FASE）的热学和力学性能。所有高水溶性酯均通过脂肪酸乙烯酯在二甲基亚砜（DMSO）中的可持续均相酯交换反应获得。将取代度（DS）为 1.40-1.73 的产物浇铸薄膜与高取代度产物（DS 2.20-2.63）进行了比较。所有薄膜均不含任何增塑剂添加剂。通过接触角测量对疏水性表面进行了表征。动态扫描量热法（DSC）和动态机械热分析（DMTA）表明，热转变（Tg、Tm）受酯基团的内部增塑作用影响。热重分析（TGA）测量表明，与天然淀粉相比，产品的热稳定性有所提高。拉伸试验表明，随着酯基链长的增加，产品的强度和刚性降低，而伸长率增加到酯基月桂酸酯，然后降低。由于酯链的超分子结构，如 X 射线所证实的那样，最长脂肪酸的棕榈酸酯和硬脂酸酯变成了脆性材料。总结了 DS 为 1.40-1.73 的产品具有更多的“淀粉样”特性，拉伸强度高达 43MPa，而 DS>2 的产品则表现出更多的“油样”特性。这两类酯都应该作为商业淀粉共混物和石油基塑料的替代品进行测试。Cnumber 一词是指脂肪酸中 C 原子的总数（例如 C6=己酸酯）。
