Strong Nanocomposite Reinforcement Effects in Polyurethane Elastomer with Low Volume Fraction of Cellulose Nanocrystals
Strong Nanocomposite Reinforcement Effects in Polyurethane Elastomer with Low Volume Fraction of Cellulose Nanocrystals
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DOI：
10.1021/ma200318k
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发表时间：
2011-06-14
期刊：
影响因子：
5.5
通讯作者：
Berglund, Lars A.
中科院分区：
文献类型：
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作者：
Pei, Aihua;Malho, Jani-Markus;Berglund, Lars A.
通过在聚氨酯预聚体制备过程中加入纤维素纳米微晶（CNCs），制备了拉伸强度和断裂伸长率均较好、模量显著提高的聚氨酯/纤维素纳米复合材料。这种聚氨酯的纳米结构由单独的纳米纤维素晶体共价键合，并特别与硬聚氨酯（PU）的微区，其特征在于通过傅立叶变换红外光谱和透射电子显微镜。动态力学分析表明，纳米复合材料的储能模量和热稳定性得到了显著提高。这是由于软基质中的CNCs增强和由于CNC-PU分子相互作用而增加的弹性体网络的有效交联密度的组合。拉伸试验表明，纳米复合材料具有较高的拉伸强度和断裂应变。特别地，仅掺入1重量%的纤维素纳米晶体，分别实现了拉伸强度的8倍增加和断裂应变的1.3倍增加。这种高强度表明，CNC在高应变下强烈取向，并且还可以诱导协同PU取向效应，从而有助于显著的强度增强。本发明的弹性体纳米复合材料优于常规橡胶材料和用微晶纤维素、碳纳米管或纳米粘土增强的聚氨酯纳米复合材料。
Polyurethane/cellulose nanocrystal nanocomposites with ultrahigh tensile strength and stain-to-failure with strongly improved modulus were prepared by adding cellulose nanocrystals (CNCs) during the preparation of prepolymer. The nanostructure of this polyurethane consisted of individualized nanocellulose crystals covalently bonded and specifically associated with the hard polyurethane (PU) microdomains as characterized by Fourier transform infrared spectroscopy and transmission electron microscopy. The storage modulus and thermal stability of the nanocomposites were significantly improved as measured by dynamic mechanical analysis. This was due to a combination of CNCs reinforcement in the soft matrix and increased effective cross-link density of the elastomer network due to CNC-PU molecular interaction. Tensile test revealed that the nanocomposites have both higher tensile strength and strain-to-failure. In particular, with only 1 wt % of cellulose nanocrystals incorporated, an 8-fold increase in tensile strength and 1.3-fold increase in strain-to-failure were achieved, respectively. Such high strength indicates that CNCs orient strongly at high strains and may also induce synergistic PU orientation effects contributing to the dramatic strength enhancement. The present elastomer nanocomposite outperforms conventional rubbery materials and polyurethane nanocomposites reinforced with microcrystalline cellulose, carbon nanotubes, or nanoclays.