Reconfigurable Shape Memory and Self-Welding Properties of Epoxy Phenolic Novolac/Cashew Nut Shell Liquid Composites Reinforced with Carbon Nanotubes
Reconfigurable Shape Memory and Self-Welding Properties of Epoxy Phenolic Novolac/Cashew Nut Shell Liquid Composites Reinforced with Carbon Nanotubes
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DOI：
10.3390/polym10050482
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发表时间：
2018-05-01
期刊：
影响因子：
5
通讯作者：
Ando, Shinji
中科院分区：
文献类型：
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作者：
Kasemsiri, Pornnapa;Lorwanishpaisarn, Narubeth;Ando, Shinji
传统的形状记忆聚合物(SMPS)可以记住它们的永久形状。然而，由于永久的化学或物理交联网络，这些SMP无法重新配置其原始形状以获得所需的几何形状。为了克服这一限制，人们开发了可以通过键交换反应(Bers)重新配置的新型SMPS。本研究制备了多壁碳纳米管(CNTs)增强的环氧酚醛酚醛树脂(EPN)和生物腰果壳液(CNSL)的聚合物复合材料。得到的复合材料具有形状记忆和自焊接性能，其形状可以通过BERS进行重构。用变温傅里叶变换红外光谱和动态力学分析研究了它们的形状记忆机理。当碳纳米管含量为0.3wt%时，EPN/CNSL复合材料的形状固定度和形状恢复率最高。此外，还观察了近红外光辐照引起的形状记忆行为。所有样品在5次循环中均表现出较高的形状恢复率，接近100%，并且随着碳纳米管含量的增加，形状恢复率显著缩短。形状重构和应力松弛的能力影响了重塑样品的光致形状记忆性能。此外，应力松弛对自焊性能也有影响。碳纳米管阻碍应力松弛，导致粘结断裂能(G(C))降低。而EPN/CNSL复合材料的G(C)值与环氧玻璃体相当。这些结果表明，EPN/CNSL复合材料结合了热致和光致形状记忆、形状重构和自焊接等材料设计概念，有望成为先进智能材料应用的可行方法。
Conventional shape memory polymers (SMPs) can memorize their permanent shapes. However, these SMPs cannot reconfigure their original shape to obtain a desirable geometry owing to permanent chemically or physically crosslinked networks. To overcome this limitation, novel SMPs that can be reconfigured via bond exchange reactions (BERs) have been developed. In this study, polymer composites consisting of epoxy phenolic novolac (EPN) and bio-based cashew nut shell liquid (CNSL) reinforced by multi-walled carbon nanotubes (CNTs) were prepared. The obtained composites exhibited shape memory and self-welding properties, and their shapes could be reconfigured via BERs. Their shape memory mechanisms were investigated using variable-temperature Fourier transform infrared spectroscopy and dynamic mechanical analysis. The EPN/CNSL composite containing 0.3 wt % CNTs showed the highest shape fixity and shape recovery ratio. Furthermore, shape memory behavior induced by irradiation of near-infrared (NIR) light was also observed. All samples showed high shape recovery ratios of nearly 100% over five cycles, and increasing the CNT content shortened the recovery time remarkably. The ability of shape reconfiguration and stress relaxation affected the photo-induced shape memory properties of reshaped samples. Additionally, the self-welding properties were also influenced by stress relaxation. The hindrance of stress relaxation caused by the CNTs resulted in a decrease in adhesive fracture energy (G(c)). However, the G(c) values of EPN/CNSL composites were comparable to those of epoxy vitrimers. These results revealed that the material design concepts of thermal- and photo-induced shape memory, shape reconfiguration, and self-welding were combined in the EPN/CNSL composites, which could be feasible method for advanced smart material applications.