Volume dependence of thermal conductivity and bulk modulus for poly(propylene glycol)

✍ Scribed by S. Peter Andersson; Ove Andersson

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 193 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(19980130)36:2<345::aid-polb13>3.0.co;2-h

✦ Synopsis

The thermal conductivity l and heat capacity per unit volume of poly(propylene glycol) PPG (0.4 and 4.0 kgrmol 01 in number-average molecular weight) have been measured in the temperature range 150-295 K at pressures up to 2 GPa using the transient hot-wire method. At 295 K and atmospheric pressure, l Å 0.147 W m 01 K 01 for PPG (0.4 kgrmol 01 ) and l Å 0.151 W m 01 K 01 for PPG (4.0 kgrmol 01 ). The temperature dependence of l is less than 4 1 10 04 W m 01 K 02 for both molecular weights. The bulk modulus has been measured in the temperature range 215-295 K up to 1.1 GPa. At atmospheric pressure, the room temperature bulk moduli are 1.97 GPa for PPG (0.4 kgrmol 01 ) and 1.75 GPa for PPG (4.0 kgrmol 01 ). These data were used to calculate the volume dependence of l, g Å 0 ͩ Ìl/l ÌV/V ͪ T . At room temperature and atmospheric pressure (liquid phase) we find g Å 2.79 for PPG (0.4 kgrmol 01 ) and g Å 2.15 for PPG (4.0 kgrmol 01 ). The volume dependence of g, (Ìg/Ì log V ) T varies between 019 to 010 for both molecular weights. Under isochoric conditions, g is nearly independent of temperature. The difference in g between the glassy state and liquid phase is small and just outside the inaccuracy of g of about 8%. The theoretical model for l by Horrocks and McLaughlin yields an overestimate of g by up to 120%.