Fabrication and properties of lignin-reinforced self-healing polyurea elastomer
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摘要: 制备具有良好力学性能和室温下高效自修复性的高分子材料一直是一项艰难挑战。本文采用天然芳香基木质素作为增强相,通过两步法(聚脲反应及席夫碱反应)制备了一种木质素增强的自修复聚脲弹性体(T-L-PUA)。探讨了木质素添加量对T-L-PUA的热性能、紫外线(UV)阻隔性能及力学性能的影响并分析了其基于动态可逆亚胺键(C=N)的自修复特性及可回收性。结果表明:T-L-PUA的热稳定性随木质素比例增加有明显提升,其中残碳量较未加木质素样品(T-PUA)最多提升了16.6%。T-L-PUA在UV区(280~400 nm)的低透过率有助其实现UV阻隔功能。与T-PUA的平均透过率(41.6%)相比,所有T-L-PUA的平均透过率均在0.2%左右。木质素添加量为20%时力学性能最佳,相应T-L-PUA拉伸强度为12.44 MPa,较纯自修复聚脲弹性体提升了937%。T-L-PUA具有良好的自修复性,室温下修复48 h,T-L-PUA的拉伸强度及断裂伸长率的恢复效率分别在91%和92%以上。此外,T-L-PUA还可以通过热压回收和溶剂回收,重塑后力学性能基本保持不变。Abstract: The preparation of polymeric materials with good mechanical properties and efficient self-healing properties at room temperature has been a difficult challenge. Herein, a lignin-reinforced self-healing polyurea elastomer (T-L-PUA) was prepared by a two-step process (polyurea reaction and Schiff base reaction) using natural aromatic-based lignin as the reinforcing phase. The effects of lignin addition on the thermal, UV-blocking and mechanical properties of T-L-PUA were investigated and the self-healing property and recyclability based on dynamic reversible imine bonding (C=N) of T-L-PUA were analyzed. The results show that the thermal stability of T-L-PUA is significantly enhanced with the increase of lignin ratio, where the maximum increase of residual carbon is 16.6% compared with the sample without lignin. The low transmittance of T-L-PUA in the UV region (280-400 nm) helps to realize the UV-blocking function. Compared with the average transmittance of self-healing polyurea composite elastomer (T-PUA) (41.6%), the average transmittance of all T-L-PUAs is around 0.2%. The best mechanical property appears at 20% of lignin addition, and the corresponding tensile strength of T-L-PUA is 12.44 MPa, which is 937% higher than that of pure polyurea elastomer. T-L-PUA exhibits good self-healing properties. When T-L-PUA is repaired at room temperature for 48 h, the recovery efficiencies of tensile strength and elongation at break is above 91% and 92%, respectively. In addition, the T-L-PUA can also be recovered by the hot-pressing and solvent dissolution processes, and the mechanical properties remain largely unchanged after remolding.
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Key words:
- lignin /
- polyurea elastomer /
- self-healing property /
- imine bond /
- composites
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图 6 (a) T-PUA及T-L-PUA溶液的照片;(b) T-L2-PUA表面及截面的SEM图像;T-PUA及不同木质素含量T-L-PUA的拉伸应力-应变曲线(c)和杨氏模量及断裂伸长率(d)
Figure 6. (a) Pictures of the solutions of T-PUA and T-L-PUA; (b) SEM images of T-L2-PUA surface and section; Stress-strain curves (c), Young's modulus and elongation at break (d) of T-PUA and T-L-PUA with different lignin contents
图 7 (a) T-L2-PUA自修复试验过程的照片;(b) 修复0 h、1 h、5 h的T-L2-PUA表面超景深光学图像;(c) T-L-PUA的自修复机制示意图;修复12 h、24 h、48 h的T-L2-PUA拉伸应力-应变曲线(d)及恢复效率(e);(f) 不同木质素含量T-L-PUA修复48 h后的恢复效率
Figure 7. (a) Pictures of the self-healing test process of T-L-PUA; (b) Super depth-of-field optical images of surface of T-L2-PUA repaired for 0 h, 1 h and 5 h; (c) Schematic diagram of the self-healing mechanism of T-L-PUA; Tensile stress-strain curves (d) and recovery efficiencies (e) of T-L2-PUA repaired for 12 h, 24 h and 48 h; (f) Recovery efficiency of T-L-PUA with different lignin contents after 48 h healing
图 8 (a) T-L2-PUA热压回收前后的照片;(b) 热压循环回收后的T-L2-PUA的拉伸应力-应变曲线;(c) T-L2-PUA溶剂回收工艺;(d) 溶剂循环回收后的T-L2-PUA的拉伸应力-应变曲线
Figure 8. (a) Photographs of T-L2-PUA before and after hot-press recycling; (b) Tensile stress-strain curves of T-L2-PUA after hot-pressing cycle recovery; (c) Solvent recovery process of T-L2-PUA; (d) Tensile stress-strain curves of T-L2-PUA after solvent cycle recovery
表 1 T-L-PUA的样品命名
Table 1. Sample naming of T-L-PUA
Sample Mass ratio lignin∶(IPDI, PPG, TTD) T-L1-PUA 0.1∶1 T-L2-PUA 0.2∶1 T-L3-PUA 0.3∶1 T-L4-PUA 0.4∶1 表 2 T-PUA及不同木质素含量T-L-PUA的热性能结果
Table 2. Thermal properties of T-PUA and T-L-PUA with different lignin contents
Sample T5%/℃ T50%/℃ Tmax/℃ Rmax/(%·min−1) Ch/% T-PUA 285.5 343.8 366.4 11.300 2.800 T-L1-PUA 279.8 353.7 369.1 10.200 7.420 T-L2-PUA 268.9 359.7 372.1 10.000 11.630 T-L3-PUA 262.2 364.2 373.6 8.850 16.770 T-L4-PUA 261.6 369.5 376.0 8.710 19.430 Notes: T5% and T50%—Temperature corresponding to mass loss of 5% and 50%; Tmax—Temperature at the maximum rate of mass loss; Rmax—Maximum mass loss rate; Ch—Residual mass fraction. -
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