1974 Volume 2 Issue 2 Pages 41-46
The present study is an experimental investigation of the effects of hydrostatic pressure on the capillary flow behavior of a polystyrene melt by using an Instron type rheometer with a two-stage capillary.
The results may be summarized as follows:
(1)The relations between the pressure losses in the first and second capillaries are given by the following equations
where, Δp1 and Δp2 are the pressure losses in the first and second stages, respectively, Δptot is the total pressure loss, which nearly equals the applied pressure p, and pn is the hydrostatic pressure induced by the second capillary. Since the sample is compressed in the first stage by the pressure pn, which is estimated by equation (b), it is possible to make an experimental study of the effects of hydrostatic pressure.
(2) The ratio of the viscosity coefficients for hydrostatic pressure flow to that for atmospheric pressure flow η′n/η′o is approximately given by the following equation.
where, K1 and N are material constants.
(3) The pressure loss due to the elasticity effect of the specimen at the capillary inlet, under the influence of the hydrostatic pressure, is given by the following eqution
where, ΔpE.0 is pressure loss at the capillary inlet under hydrostatic pressure, ΔpE.0 is that under stmospheric pressure, Δυ/υ0 is the volumetric strain, A and K2 are material constants.