奈米顆粒懸浮液之流變行為及其液態裝甲之應用研究

Abstract

剪切增稠流體，為一種在高速剪切速率外力作用下，會產生黏度急速上升現象之非牛頓流體。此現象已開始應用於具備有防穿刺之功能性織物上，因此被稱之為液態裝甲，亦即在平日低速活動具備有輕柔衣著特性，於高速外力撞擊時，即刻產生流體黏度增高而硬度變硬現象之防護功能。目前液態裝甲主要是利用二氧化矽作為剪切增稠流體中之主要顆粒，但其液態裝甲之抗穿刺效果仍然極為有限，僅適用於極低速外力撞擊之應用。 近年來，非二氧化矽系統吸引研究學者強烈的興趣！在本研究中使用了三個非二氧化矽系統，包含聚合物（如聚苯乙烯），核殼型複合顆粒（聚苯乙烯/二氧化矽）和氧化鋁奈米顆粒作為分散相，應用在Kevlar纖維織布中。從實驗發現，將布料浸泡在核殼型複合顆粒（聚苯乙烯/二氧化矽）和氧化鋁奈米顆粒中的樣品，兩者都會在EN388穿刺實驗以及空氣槍彈道實驗中發現其耐衝擊之性質。然而，在手槍彈道測試中，這些樣品卻不具備此性質，其原因可能在於當樣品處於超高剪切速率 ( >300m/s )，將導致空蝕現象 (cavitation)。未來研究方向包括高分子奈米顆粒表面改性，分散液的選擇，以及更多有關於液態裝甲之應用。

SiO2 in PEG suspension solutions have been extensively studied to show their shear thickening behavior; i.e, the viscosity of the solution increases abruptly with the shear rate in the high shear regime. These solutions have also been applied to clothing and show great promise in the anti-stabbing property for liquid armor applications. Recently, non-SiO2 systems have attracted an intense research interest since great varieties of inorganic and/or organic nanoparticles are now available to use and further improvements for the bullet-proof vest are greatly needed. Given that these suspension systems have not been studied thoroughly yet. In this thesis, I investigate the rheological property of three different types of non-SiO2 solutions with pristine polystyrene (PS) nanoparticles, core/shell nanoparticles with PS cores and shells of SiO2, and Al2O3 nanoparticles. PS nanoparticles were used since the particles have good suspension stability over times due to their low density, while Al2O3 nanoparticles were chosen since they have relative high hardness. The application of these suspension solutions on KM2® Kevlar® fabrics as anti-stabbing clothes and as bullet-proof vest has also been evaluated. Novel core/shell nanoparticles were synthesized and stable dispersion solutions with volume fraction of 20~40% were prepared for viscosity measurement. PS/SiO2 core/shell nanoparticles were chosen in hopes that the effects of both high solution stability and good surface property with solvent can be synergistically obtained. Moreover, a convectional bullet-proof vest material, KM2® Kevlar® fabrics were impregnated with PS, PS/SiO2, SiO2 and Al2O3 suspension solutions in PEG (Mw=200). The impregnated fabrics were then tested with a sharp-tip puncture test using Instron and ballistic tests with air gun and pistol. The results demonstrated that KM2® Kevlar® fabrics impregnated with PS/SiO2, SiO2, and Al2O3 suspension solutions in PEG have enhanced EN388 anti-puncture performance, and an increased air gun ballistic penetration resistance. However, in pistol ballistic tests, significant reduced penetration resistance was observed. The reduction may result from the cavitation effect of the suspension solution in the fabric ahead of penetrating bullets due to ultra high shear rate, leading to degradation of bullet resistance. Future directions of the study include surface modification of nanoparticles, change of different dispersing liquid, and their STF property for liquid armor applications.