A Rheological Consideration of Needle Penetration of Waxes

Abstract

Depth of penetration have been measured continuously from time to time by the use of a penetrometer of the type JIS K 2530 with some modification. Velocity of penetration was determined by graphycally differentiating the curve correlating the depth with time. Shearing stress at the osculating plane of the apex of needle of the penetrometer reduces with increase of the depth. As the results, relation of the velocity and the shearing stress can be correlated in a figure. By extrapolating the correlating curve to the point at which the velocity is zero, yield value of waxes can be easily determind. It was found that needle penetration number usually used as an index of hardness pf waxes inversely proportional to the 0.6 power of the yield value. Consequently, the needle penetration number can be employed as an quantitative index of the hardness of waxes.