Handbook of Solvents - George Wypych - ChemTech - Ventech!

15.1 Standard methods of solvent analysis 1069
ture. Measurements are made at a temperature selected from the range 21-99 o C. The instrument
is standardized by measuring the flow of a standard oil at both 37.8 and 50 o C.
In the bubble method, a standard viscosity tube is filled with a specimen liquid, the
temperature of liquid is equilibrated to 25 o C in a bath, the level of the meniscus is adjusted
to 100 mm line, cork is inserted to end on 108 mm line, sample is hold in thermostating bath
for another 20 min. Then the tube is inverted and the time for the bubble to flow from a mark
at 27 mm to 100 mm is measured.
15.1.35 VOLATILE ORGANIC COMPOUND CONTENT, VOC
Several terms are used in the paint industry to provide data on the VOC content of paints. 159
The percent of solids in paints is calculated either per unit weight or per unit volume. The
weight solids content is the weight of non-volatile materials divided by the total weight of
the coating. In practice, it is calculated by subtracting the total weight of volatile solvents
from the total weight of the coating and dividing the result by the total weight of coating.
The final result is multiplied by 100 to express it in percent. Percent of solids by weight is
calculated in similar manner.
A solvent, as defined by paint standards, is a volatile liquid that is incorporated primarily
for vehicle solvency and control of the application characteristics. The solvent content is
the calculated weight of solvents in a specific volume of paint. This definition is not equivalent
to the definition of VOC compound because it does include compounds which are excluded
by EPA (see more on this subject in Section 18.1).
Volatile organic compound by EPA definition means any compound of carbon, excluding
carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates,
and ammonium carbonate, which participates in atmospheric photochemical reactions. This
includes any such organic compound other than the following, which have been determined
to have negligible photochemical reactivity: methane; ethane; methylene chloride;
1,1,1-trichloroethane; 1,1,2-trichloro-1,2,2-trifluoroethane; trichlorofluoromethane;
dichlorodifluoromethane; chlorodifluoromethane; trifluoromethane; dichlorotetrafluoroethane;
chloropentafluoroethane; dichlorotrifluoroethane; tetrafluoroethane;
dichlorofluoroethane; chlorodifluoroethane; 2-chloro-1,1,1,2-tetrafluoroethane;
pentafluoroethane; 1,1,2,2-tetrafluoroethane; 1,1,1-trifluoroethane; 1,1-difluoroethane;
perchloroethylene; acetone; parachlorobenzotrifluoride; cyclic, branched, or linear completely
methylated siloxanes; and perfluorocarbon compounds which fall into these classes:
cyclic, branched, or linear, completely fluorinated alkanes; cyclic, branched, or linear, completely
fluorinated ethers with no unsaturations; cyclic, branched, or linear, completely fluorinated
tertiary amines with no unsaturations; and sulfur containing perfluorocarbons with
no unsaturations and with sulfur bonds only to carbon and fluorine. For purposes of determining
compliance with emissions limits, VOC is measured by the test methods in the approved
State implementation plan (SIP) or 40 CFR Part 60, Appendix A, as published in
(7/1/91) edition, as applicable.
Based on the above definition of VOC, the VOC content is calculated from a formula
by excluding from the total solvent content of the paint, the content of water and solvents
excluded by the above regulation. The following formula can be used for VOC calculation:
Wtotal solvents −Ww−Wexcluded solvents
VOC =
[15.1.1]
V −V −V
where:
Wtotal solvents
Ww paint w excluded solvents
total weight of solvents
weight of water present in formulation