A Study on p-v-T Properties and Equation of State of the Polymer Alloys Polyphenylene Oxide (PPO)/Polystyrene (PS)

Abstract

A p-v-T device for determining the specific volume of solid and liquid polymer alloys as a function of pressure (up to 200MPa) and temperature (30-350°C) has been constructed. It is a plunger type which consists of a plunger, cylinder, heater and laser displacement meter. The measurement accuracy of the device was within ±2-3%. The p-v-T properties were determined by the isothermal testing method. We have discussed the effects of the mixing ratio on p-v-T properties of polymer alloys and the empirical equation of state. The empirical equation of state for amorphous polymers such as PPO, PS and its alloys is presented as follows:
v(p, T)=v_o(0, T_o)+(³∑_i=0A_iTⁱ+p¹∑_i=0B_iTⁱ+p²¹∑_i=0C_iTⁱ)
Here, v is specific volumes as a function of pressure and temperature, v_o is specific volume at atomospheric pressure (p=0) and room temperature (T_o). The A_i (i=0-3), B_i and C_i (i=0-1) are coefficients of the p-v-T characteristic each polymers. The values of these coefficients were determined by a least-squares fitting method. The specific volumes of solid and liquid amorphous polymers determined by the em. pirical eq. agree with the measured values to within 1.07% to 1.80% except for PPO. The volume strain K_v of the solid and molten polymer alloys changed irregularly depending on the mixing ratio. It is minimum when the mixing ratio is PPO/PS=20/80 weight percent.