Hydrophobicity modification of woven cotton fabric by hydrophobic fumed silica coating

Water repellency of woven cotton fabric was achieved by coating with the aqueous dispersion containing organosilane agent (HDTMS) and fumed silica. The coating agents were applied using padding method and then followed by batching the coated fabric at the ambient temperature for 24 h to allow the condensation reaction between HDTMS silanol group and fumed silica silanol group, rendering silica particles hydrophobic. An ultrasonicator was employed to prepare the homogenous coating dispersion. The water repellency evaluated by water contact angle determination which showed the contact angle over 110° was obtained with low amount of applied HDTMS of 1 wt%. The effect of fumed silica addition on an increase in fiber surface roughness geometry showed the influential result in improving the water contact angle. From durability to washing test, the hydrophobic coatings evidenced from SEM and ATR/FTIR remained adhering to fiber surface, indicating the durability. After washing, the coating on the fabric with fumed silica addition appeared to be scatter particles which made a contribution to the higher contact angle value when compared to sheet-like layer coating in case of HDTMS coating alone.     

Boundaries of Correlation Adjustment with Applications to Financial Risk Management

Abstract

In recent years, stress testing has become a regulatory requirement for risk assessment in financial institutions. To perform stress testing in multi-asset case, adjusting the correlation matrix to an extreme level is an important process. With a larger matrix, it is more difficult to choose the right correlation coefficients such that the newly adjusted correlation matrix is still valid. In this article, we present a systematic way to obtain the boundaries of a correlation matrix for both single stress and multiple stress cases, which can help determine how much the correlation should be adjusted in the first place.