Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University School of Chemical Technology, P.O. Box 16100, 00076 Aalto, Finland.
Carbohydr Polym. 2013 Jan 2;91(1):183-90. doi: 10.1016/j.carbpol.2012.08.032. Epub 2012 Aug 18.
Composites of poly(methyl methacrylate) (PMMA) and nanofibrillated cellulose (NFC) were prepared by solution blending and further processed by injection and compression molding. To improve adhesion at the PMMA/NFC interface, the nanofibrils were covalently grafted with PMMA. Formation of a percolating nanofibril network was observed between 1 and 5 wt.% of NFC by dynamic rotational rheometry in molten state. This observation was further supported by the behavior of glass transition temperature which decreased at low NFC concentrations but recovered above the percolation threshold, indicating a decreased mobility of the matrix polymer. This effect was more pronounced with ungrafted NFC, possibly due to a stronger network. The unmodified NFC induced a minor degradation of the molar mass of PMMA. As thin plates, the composites were transparent at low NFC concentrations but became partially aggregated at the highest NFC concentrations. Despite the continuous NFC network, tensile testing showed no improvement of the mechanical properties.
聚甲基丙烯酸甲酯（PMMA）和纳米原纤纤维素（NFC）的复合材料通过溶液共混制备，并通过注塑和压缩成型进一步加工。为了改善 PMMA/NFC 界面的粘附力，纳米原纤用 PMMA 进行了共价接枝。通过在熔融状态下的动态旋转流变仪观察到，在 1 至 5wt%的 NFC 之间形成了一个渗透的纳米原纤网络。这一观察结果得到了玻璃化转变温度行为的进一步支持，该温度在 NFC 浓度较低时降低，但在渗透阈值以上恢复，表明基体聚合物的流动性降低。这种效应在未接枝的 NFC 中更为明显，可能是由于网络更强。未经修饰的 NFC 导致 PMMA 的摩尔质量略有降解。作为薄片，复合材料在 NFC 浓度较低时是透明的，但在 NFC 浓度最高时会部分聚集。尽管存在连续的 NFC 网络，但拉伸测试显示机械性能没有提高。
