Yan Tingzi, Chen Depei, Zhao Baijin, Jiang Xiaodong, Wang Lian, Li Yongjin
College of Material, Chemistry and Chemical Engineering, Key Laboratory of Organosilicon Chemistry and Material Technology, Ministry of Education, Hangzhou Normal University, Hangzhou 311121, China.
Jiangsu Boiln Plastics Company Limited, Zhangjiagang 215626, China.
Polymers (Basel). 2022 Sep 4;14(17):3672. doi: 10.3390/polym14173672.
The incorporation of montmorillonite (MMT) into Nylon 6 can endow advantages like improved mechanical strength and thermal stability, making Nylon 6/MMT a possible ideal alternative for Nylon 66. However, the relationship between the microstructure and physical properties of nylon 6/MMT nanocomposites is unclear so far due to the complicated system, including the highly asymmetric geometry of the exfoliated MMT layer and the complicated interaction between MMT layers and entangled nylon 6 chains. Herein, we focus on two processes, namely the impact of MMT on the solidification procedure during molding and the toughness-brittleness transition during the tensile stretch, in order to elucidate the structure-property relationship of nylon 6/MMT composites. We firstly studied the solidification process of nylon 6/MMT with bending height experiments. The results showed that the solidification process occurs prior to the crystallization of nylon 6, indicating that a physical crosslinked network rather than a crystalline structure is the reason for the solidification process. Furthermore, the solidification speed has a step change at around 2 wt% MMT content, indicating that the MMT percolation network is related to the transition. We further studied the influence of MMT inclusion on the mechanical properties, and found the tensile strain at break showed a similar step change at around 2 wt% MMT content, which further confirms the existence of an MMT percolation network above 2 wt% MMT content. It was generally believed that the main effect of MMT on nylon 6 is the nanofiller enforcement; we found that the percolation effect of the highly asymmetric 2-D nanofiller plays a central role in influencing the mechanical properties and solidification behavior during molding.
将蒙脱石（MMT）加入尼龙6中可赋予其诸如提高机械强度和热稳定性等优点，使尼龙6/MMT成为尼龙66可能的理想替代品。然而，由于体系复杂，包括剥落的MMT层高度不对称的几何形状以及MMT层与缠结的尼龙6链之间复杂的相互作用，尼龙6/MMT纳米复合材料的微观结构与物理性能之间的关系目前尚不清楚。在此，我们聚焦于两个过程，即MMT对成型过程中凝固过程的影响以及拉伸过程中的韧脆转变，以阐明尼龙6/MMT复合材料的结构-性能关系。我们首先通过弯曲高度实验研究了尼龙6/MMT的凝固过程。结果表明，凝固过程在尼龙6结晶之前发生，这表明物理交联网络而非晶体结构是凝固过程的原因。此外，凝固速度在MMT含量约为2 wt%时发生阶跃变化，表明MMT渗流网络与该转变有关。我们进一步研究了MMT的加入对力学性能的影响，发现断裂拉伸应变在MMT含量约为2 wt%时呈现类似阶跃变化，这进一步证实了MMT含量高于2 wt%时存在MMT渗流网络。一般认为MMT对尼龙6的主要作用是纳米填料增强作用；我们发现高度不对称的二维纳米填料的渗流效应在影响成型过程中的力学性能和凝固行为方面起着核心作用。
