Soft, fully bio‐based poly‐hydroxyl thermosets based on catalyst‐free transesterification with decent re‐processability
Soft, fully bio‐based poly‐hydroxyl thermosets based on catalyst‐free transesterification with decent re‐processability
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DOI：
10.1002/app.52676
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发表时间：
2022-06
影响因子：
3
通讯作者：
Jie‐Jie Li;Shufen Zhang;Benzhi Ju
中科院分区：
文献类型：
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作者：
Jie‐Jie Li;Shufen Zhang;Benzhi Ju
大多数基于酯交换（TE）的玻璃化聚合物高度依赖于使用大量催化剂来促进交换反应以获得可再加工性，这带来了对人类健康或环境问题的额外担忧。在此，我们证明了具有软网络（低Tg）的TE玻璃化物，尽管不含催化剂或任何其他特殊设计，但仍然可以具有足够的动态性，易于再加工。本文合成了来自环氧大豆油（ESO）和生物二羧酸（DA）的完全生物基和无催化剂的热固性材料，并发现其具有良好的可再加工性。通过压缩重塑（10 MPa，160°C），ESO-DA热固性材料可在30分钟内修复可见缺陷，并在3小时内恢复机械强度。经过3次机械循环后，其机械强度与原始热固性材料相比几乎没有变化。应力松弛实验证实了在高温（≥150°C）下的网络重排以及材料的玻璃化流动。这些材料也能够在小压力下在没有溶剂的情况下焊接。最后，采用一种简单的熔融方法来调节回收的ESO玻璃体的机械强度。
Most of the vitrimers based on transesterification (TE) highly rely on the usage of large amounts of catalysts to promote exchange reactions to obtain re‐processability, which brings additional concerns on human health or environmental issues. Herein, we demonstrate that TE vitrimers with soft networks (lowTg), though free of catalysts nor any other special design, can be still dynamic enough to be easily re‐processed. In this paper, fully bio‐based and catalyst‐free thermosets from epoxidized soybean oil (ESO) and bio‐dicarboxylic acids (DA) were synthesized and found to possess decent re‐processability. By means of compressive remolding (10 MPa, 160°C), the ESO‐DA thermosets heal visible defects within 30 min and restore the mechanical strength within 3 h. Upon 3 times of mechanical recycling, the mechanical strengths remain nearly unchanged compared with those of pristine thermosets. Stress relaxation experiments confirm the network rearrangement at high temperatures (≥150°C) as well as vitrimeric flow of the materials. The materials are also capable of being welded without solvents under a small pressure. Lastly, a facile fusion method was employed to tune the mechanical strength of the recycled ESO vitrimers.