Effects of combined humidity and temperature on the friction of non-compacted iron, copper and hydroscopic powders

Abstract

The effects of humidity and temperature on the interparticle friction of iron, copper, Portland cement and plaster of Paris powders have been investigated using a torsional apparatus. It is found that at ambient temperature (22 ± 2 °C), the interparticle friction of iron and copper powders, of a given particle shape, size distribution and size, first decreases then increases and again decreases with increasing humidity. At a constant relative humidity of ∼30%, the friction of iron and copper powders is relatively insensitive to temperatures up to ∼20 °C and then increases slowly but approximately linearly with increasing temperature. At 22 ± 2 °C, the interparticle friction of Portland cement and plaster of Paris powders increases gradually and then decreases with increasing humidity.