Nonstop Monomer-to-Aramid Nanofiber Synthesis with Remarkable Reinforcement Ability,Macromolecules

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Nonstop Monomer-to-Aramid Nanofiber Synthesis with Remarkable Reinforcement Ability
Macromolecules ( IF 5.1 ) Pub Date : 2019-01-17 00:00:00 , DOI: 10.1021/acs.macromol.8b02391
Jun Mo Koo _{1,

2} , Hojun Kim ₁ , Minkyung Lee ₁ , Seul-A Park ₁ , Hyeonyeol Jeon ₁ , Sung-Ho Shin ₁ , Seon-Mi Kim ₁ , Hyun Gil Cha ₁ , Jonggeon Jegal ₁ , Byeong-Su Kim ₃ , Bong Gill Choi ₄ , Sung Yeon Hwang _{1,

5} , Dongyeop X. Oh _{1,

5} , Jeyoung Park _{1,

5}

Affiliation

Aramid nanofibers (ANFs), typically produced by exfoliating aramid microfibers (Kevlar) in alkaline media, exhibit excellent mechanical properties and have therefore attracted increased attention as nanoscale building blocks. However, the preparation of aramid microfibers involves laborious and hazardous processes, which limits the industrial-scale use of ANFs. This work describes a facile and direct monomer-to-ANF synthesis via an as-synthesized intermediate low-molecular-weight poly(p-phenylene terephthalamide) (PPTA) without requiring the environmentally destructive acids and high-order shearing processes. Under the employed conditions, PPTA immediately dissociates and self-assembles into ANFs within a time period of 15 h, which is much shorter than the time of 180 h (not including the Kevlar preparation time) required for the Kevlar-to-ANF conversion. Interestingly, the fabricated ANFs exhibit nanoscale dimensions and thermoplastic polyurethane (TPU) reinforcing effects similar to those of Kevlar-derived ANFs; i.e., a 1.5-fold TPU toughness improvement and a maximum ultimate tensile strength of 84 MPa are achieved at an ANF content of only 0.04 wt %. Remarkable reinforcement ability investigated by comprehensive analytical data comes from ANFs, which disturb ordered hydrogen bonding in hard segments and induce strain hardening along the elongation pathway. Thus, the developed approach paves the way to industrial-scale production of ANFs and related nanocomposites.

中文翻译：

具有不凡增强能力的不间断单体到芳族聚酰胺纳米纤维合成

芳族聚酰胺纳米纤维（ANFs）通常是通过在碱性介质中将芳族聚酰胺超细纤维（Kevlar）剥落而生产的，具有出色的机械性能，因此作为纳米级构建基块引起了越来越多的关注。然而，芳族聚酰胺微纤维的制备涉及费力且危险的过程，这限制了ANF在工业规模上的使用。这项工作描述了通过合成后的中间低分子量聚（p-对苯二甲酰对苯二甲酰胺（PPTA），而无需破坏环境的酸和高阶剪切过程。在使用条件下，PPTA立即在15小时内解离并自组装为ANF，这比凯夫拉尔向ANF转化所需的180小时（不包括凯夫拉制备时间）短得多。有趣的是，所制造的ANF表现出纳米级尺寸，并且热塑性聚氨酯（TPU）的增强效果与Kevlar衍生的ANF相似。即，在仅0.04重量％的ANF含量下，实现了1.5倍TPU韧性的改善和84MPa的最大极限抗拉强度。综合分析数据研究得出的惊人增强能力来自ANF，这会扰乱硬段中有序的氢键，并导致沿延伸路径的应变硬化。因此，开发的方法为ANFs和相关纳米复合材料的工业规模生产铺平了道路。

更新日期：2019-01-17

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