Handbook of Solvents - George Wypych - ChemTech - Ventech!

14.2 Aerospace 853
Table 14.2.1. Total releases of solvents by the aerospace industry. [Data from ref. 1]
Solvent Amount, kg/year Solvent Amount, kg/year
benzene 62,000 methyl ethyl ketone 995,000
bromotrifluoromethane 750 methyl isobutyl ketone 47,000
n-butyl alcohol 7,000 methyl tetr-butyl ether 550
sec-butyl alcohol 10,000 tetrachloroethylene 285,000
cyclohexane 400 1,1,1-trichloroethane 781,000
1,2-dichlorobenzene 600 trichloroethylene 429,000
1,1-dichloro-1-fluoroethane 10,000 trichlorofluoromethane 1,800
dichloromethane 314,000 toluene 414,000
isopropyl alcohol 1,000 xylene 103,000
methanol 21,000
ture difference), UV radiation (substantially higher during flight), mechanical abrasion due
to the high speed of travel, exposure to salt in the atmosphere, exposure to higher level of acids
and sulfur dioxide, and exposure to de-icing fluids during winter. 2,3 These unusual conditions
should be considered in conjunction with the mechanical movement of the coating
caused by rapid changes in temperature and the flexing of aircraft elements because of
changes in pressure and severe load variations on wings. 2 In addition, because of their size,
aircrafts must often be painted at low temperatures which requires a coating that will cure at
these temperatures without leaving entrapped volatiles. These could evaporate in the low
pressure conditions at high altitude and cause the formation of voids where corrosion could
start. These factors make the design of an effective coating system a severe technological
challenge.
Coatings are used by the aerospace industry both for OEM and maintenance purposes.
In each case surface cleaning and preparation is required. A paint stripping operation is
added to the task in maintenance repainting. Coatings are applied by spraying, brushing,
rolling, flow coating, and dipping. Depending on the method of application, the rheological
properties of coatings must be adjusted with solvents and, in some cases, with water. An alternative
method of viscosity adjustment involves heating the coatings to lower its viscosity
by increasing its temperature. This reduces solvent usage. Solvents are also used for equipment
cleaning.
In addition to paints, sealants are also used. Sealants are mostly based on polysulfides,
containing solvents as discussed in the previous section. Also, non-structural adhesives
containing solvents are used as gaskets around windows and for carpeting.
Paint removal is accomplished by either chemical or blast depainting.
Dichloromethane is the most common solvent used for this application. Aerospace industry
estimates that 15,000 to 30,000 different materials are used for manufacturing some of
which are potentially toxic, volatile, flammable, and contain chlorofluorocarbons. Some of
these substances may result in air emissions, waste-waters, and solid waste.