Page 251 - Handbook of Adhesives and Sealants

220 Chapter Six

Figure 6.7 Representative methods of vapor degreasing: (a) straight vapor cleaning, (b)
immersion vapor cleaning, (c) spray vapor cleaning, and (d) ultrasonic vapor cleaning.
Numbers represent the sequence in the processing steps. 20

High vapor density compared to air
Low heat of vaporization and specific heat in order to maximize
condensation and heat consumption
Chemical stability
Safe to operate
Low boiling point for easy distillation but high enough for easy con-
densation
Conformance to air pollution control legislation

Perchloroethylene and trichloroethylene are the most commonly
used of the vapor degreasing solvents. Although non-flammable, these
solvents are still toxic in both their liquid and vapor forms. Proper
ventilation and safety precautions must be taken. These solvents are
considered to have high boiling temperatures and are generally used
for metal parts contaminated with greases, oils, or processing lubri-
cants. Methylene chloride, Freon TF, Freon TA, and Freon TE are
generally used for temperature sensitive parts, particularly electronic
and delicate mechanical components and assemblies. These solvents
are considered to have low boiling temperatures. The temperature at