Chlorobenzene evaporation rate

Volatilization. Even though the vapor pressure of PCBs is very low, small amounts of spilled PCBs will slowly evaporate into the overlying air (evaporation rate is about 4.8 x 10 to 7.8 X 10 g/m /h) (NRC, 1979). This can happen for spills on both water and soils. Calculations of average mass losses through evaporation could be computed for many spills. As for PCB mixtures that contain chlorobenzenes and mineral oils, the lighter components consisting mainly of chlorobenzenes and mineral oils will evaporate first, leaving behind the thicker PCBs. The evaporation rate is dependent on the wind speed and temperature. However, the net result of volatilization is the removal or transference of PCBs from one environmental compartment to another without any net loss from the environment. 

Another important consideration is the boiling point (BP) of the solvents. The BP determines how quickly the solvent evaporates and thereby the formation rate for polymer and fullerene domains. Polymer domains that equilibrate slowly in high BP solvents tend to be more crystalline (thermodynamic product) whereas low BP solvents evaporate quickly and yield mixed amorphous films (kinetic product). When spin-coating at 1,000 rpm, a 20 mg/mL solution of 1 1 P3HT PCBM condenses to a film in 1-3 s when processed with CHCI3 (BP = 61°C), 5-10 s when processed in chlorobenzene (BP = 132°C), and the film remains wet after 60 s when processed with 1,2 dichlorobenzene (BP= 182°C) (Moule, personal observation) [70]. The change in structural order in P3HT is observed in a red shift of the absorption spectrum and formation of a clearly defined vibronic structure [71]. 

---