Fibre and Particle Engineering Laboratory, University of Oulu, PO Box 4300, Oulu FI-90014, Finland.
Department of Chemistry, University of Oulu, PO Box 3000, Oulu FI-90014, Finland.
Carbohydr Polym. 2015 Nov 20;133:524-32. doi: 10.1016/j.carbpol.2015.06.090. Epub 2015 Jul 10.
Nanocellulosic materials with good thermal stability are highly desirable for applications, such as reinforcement and filler agents in composites. In the present work, phosphonated cellulose was utilized to obtain nanocelluloses with good thermal stability and potential intumescent properties. Phosphonated cellulose was synthetized from birch pulp via sequential periodate oxidation and reductive amination using a bisphosphonate group-containing amine, sodium alendronate, as a phosphonating reagent. After high-pressure homogenization, bisphosphonate cellulose nanofibres or nanocrystals were obtained, depending on the initial oxidation degree. Nanofibres had a typical diameter of 3.8nm and length of several micrometers, whereas nanocrystals exhibited a width of about 6nm and an average length of 103-129nm. All nanocelluloses exhibited cellulose I crystalline structures and high transparency in water solutions. Phosphonated nanocelluloses exhibited good thermal stability and a greater amount of residual char was formed at 700°C compared to birch pulp and mechanically produced, non-chemically modified NFC.
具有良好热稳定性的纳米纤维素材料在复合材料的增强和填充剂等应用中非常理想。本工作利用磷酸化纤维素制备具有良好热稳定性和潜在膨胀性能的纳米纤维素。磷酸化纤维素通过桦木浆的顺序高碘酸盐氧化和还原胺化反应，使用含有双膦酸酯基团的胺（阿仑膦酸钠）作为磷酸化试剂合成。高压均质化后，根据初始氧化度得到双膦酸酯纤维素纳米纤维或纳米晶体。纳米纤维的典型直径为 3.8nm，长度为数微米，而纳米晶体的宽度约为 6nm，平均长度为 103-129nm。所有纳米纤维素均表现出纤维素 I 晶体结构，在水溶液中具有很高的透明度。磷酸化纳米纤维素具有良好的热稳定性，与桦木浆和机械制备的非化学改性 NFC 相比，在 700°C 下形成的残炭量更大。
