Hao Junli, Ding Jie, Rutledge Gregory C
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Land Division, Defense Science and Technology Group, Fishermans Bend VIC 3207, Australia.
ACS Appl Mater Interfaces. 2022 Feb 16;14(6):8373-8383. doi: 10.1021/acsami.1c21391. Epub 2022 Feb 1.
To improve the flexibility of the fabric stacks used in protective clothing, shear-thickening fluids (STFs) have previously been incorporated into woven microfiber fabrics to enhance their impact resistance. However, the microfiber-STF composites can exhibit loss of the STF from the composite over time due to the large interstitial spaces between fibers, resulting in limited long-term shape stability. In this study, nonwoven mats of electrospun ultrafine fibers (UFFs) were used in place of woven microfiber fabrics to improve the STF retention within the fiber-STF composites by taking advantage of high specific surface area, small pore size, and large capillary force. The UFF-STF composite, comprising an electrospun polyamide (PA 6,6) UFF mat and a fumed silica (FS) STF, exhibited excellent shape stability with high breakthrough pressure and improved STF retention compared to composites based on conventional microfiber fabrics. The mechanical response of the composite is shown to depend on the rate of deformation. At strain rates lower than the shear-thickening threshold of the STF, the introduction of STF resulted in no stiffening or strengthening of fiber mats, allowing the composite to remain flexible. At high deformation rates above the onset of shear thickening, the incorporation of STF improved both the elasticity and the viscosity of the material. In addition, the shape stability and the mechanical properties of the composite were influenced by the STF viscosity and the UFF morphology. STF with high particle loading and UFF with small fiber diameter resulted in a more pronounced enhancement to membrane performance.
为提高防护服中织物叠层的柔韧性，此前已将剪切增稠流体（STF）掺入机织微纤维织物中，以增强其抗冲击性。然而，由于纤维间存在较大的间隙空间，微纤维-STF复合材料中的STF会随着时间的推移从复合材料中流失，导致长期形状稳定性有限。在本研究中，采用静电纺超细纤维（UFF）非织造垫代替机织微纤维织物，利用其高比表面积、小孔径和大毛细作用力来提高纤维-STF复合材料中STF的保留率。由静电纺聚酰胺（PA 6,6）UFF垫和气相二氧化硅（FS）STF组成的UFF-STF复合材料，与基于传统微纤维织物的复合材料相比，具有优异的形状稳定性、高突破压力和更高的STF保留率。结果表明，该复合材料的力学响应取决于变形速率。在应变率低于STF的剪切增稠阈值时，STF的引入不会使纤维垫变硬或增强，从而使复合材料保持柔韧性。在高于剪切增稠起始点的高变形速率下，STF的加入改善了材料的弹性和粘度。此外，复合材料的形状稳定性和力学性能受STF粘度和UFF形态的影响。高颗粒负载的STF和小纤维直径的UFF对膜性能的增强作用更为显著。
