Modulating the rheological response of shear thickening fluids by variation in molecular weight of carrier fluid and its correlation with impact resistance of treated p-aramid fabrics

The present study deals with the effect of molecular weight of carrier fluid on the rheological behaviour of shear thickening fluid (STF) and impact energy absorption by treated p-aramid fabrics. High molecular weight polyethylene glycols (HMW-PEG: 1000, 3000 and 6000 g mol^?1) were individually added to a mixture of PEG 200 and PEG 600 to prepare ternary mixtures of carrier fluids. Increase in average molecular weight of the carrier fluid via addition of PEG 1000 and PEG 3000 enhanced the dilatant behaviour of STF. On the other hand, addition of PEG 6000 led to a rheological response inferior to that obtained via addition of PEG 3000 owing to solidification of the former at room temperature resulting in fusion of silica particles. However, an inverse relation was observed between the rheological behaviour of HMW-PEG based STFs and impact resistance of p-aramid fabrics treated with them. The diminution in impact energy absorption occurred due to lubrication effect caused by long polymer chains of HMW-PEG. On the other hand, fusion of solidified PEG 6000 and silica particles created rough microstructures over the yarn surface, which enhanced inter-yarn friction, resulting in improved impact energy absorption.