STATIC SHEAR MODULUS OF GAS-LIQUID FOAM DETERMINED BY THE PUNCH INDENTATION TEST

The punch indentation test was used to measure the static shear modulu s (mu) of shaving foam, Surface tension of the foaming liquid, the mea n foam cell diameter, and the volume fraction of the dispersed phase ( phi) were measured to determine the overpressure (Delta P) in foam cel ls, It was found that with increasing foam age mu decreased, reaching a steady value of similar to 0.18 Delta P when phi similar to 0.94. Th is is lower than the lowest values measured previously in gas-liquid f oams by nearly a factor of two. A possible reason could be reduced art ifacts and dynamic effects present in the previous measurements, This value agrees with values measured in oil-in-water emulsions (J. Colloi d Interface Sci. 112, 427, 1986). (C) 1996 Academic Press, Inc.