App. Note 10 - Enviromental Impact
What are the prospects for restrictions on contact cleaning solvents?
The individual service manager is not generally aware of the large
amounts of cleaning solvents that are used in the electronics industry.
Setting aside those that are used in "closed" systems (where release of
solvents to the atmosphere is minimized or virtually eliminated), hundreds
of thousands of gallons of cleaning solvents are use each year in the electronics
industry. The environmental impact of these is considerable, as a substantial
portion of them evaporate into the air.
Not only do solvents present a potential hazard to human health in the
workplace, they often combine with other chemicals, forming layers of often-phototropic
smog. While few solvents have the potential impact of the chlorofluorocarbons,
they are nevertheless of considerable concern to environmental authorities
and concerted efforts are underway to limit their use. A measure of things
to come are California (and other States) restrictions on the amount of
solvents permitted in paints and other coatings, and strict regulations
governing processes which have the potential to release any solvents into
the atmosphere (such as compressed-air based paint spraying).
Manufacturers and service organizations operating coast-to-coast are
finding it increasingly difficult to cope with the numerous and differing
standards as to what an acceptable cleaning solvent and its permissible
level of usage. This makes the use of "centralized stores" purchasing,
with its attendant economies, quite hard to manage. Indeed what may be
legal in one area of a state may well be banned in another area of the
very same state.
What is Stabilant 22?
Stabilant 22 is a virtually non-toxic liquid polymer that is
applied to electromechanical contacts, and then left in place. Unlike a
cleaner it is not "hosed" on the connector and wiped off. Very little must
be used as a coating of less than 0.5 to 1 mils in thickness are usually
sufficient to treat the connector.
Unlike cleaners, Stabilant 22 is an initially non-conductive
material that, under the action of an electric field gradient, switches
to a conductive state. This gradient designed so that the switching action
takes places only within the mating contacts and NOT between adjacent contacts.
Thus there is no leakage, and the material can be used to coat an entire
connector at a single application.
Generally, Stabilant 22 imparts the reliability of a soldered joint
to an electromechanical contact without forming a physical bond.
Does the action of Stabilant 22/22A/22E deteriorate with age?
Stabilants have been in some field trial applications for over
fifteen years now, without showing any sign of reduced effectiveness. The
material has a high molecular weight and a very low vapor pressure, thus
it is not prone to evaporation.
Once again let us emphasize the point that unlike some other contact
treatments containing oils, Stabilant 22 will not cross-link when
exposed to certain materials such as high sulfur brass, or when used on
connectors having elastomer or most plastic components with accelerant
and curing agents, or when used on contacts where cross-link promoting
agents are present in the environment. The phenomena of "varnishing" does
not occur with Stabilant 22.
In what forms is the material available?
The material is available as a concentrate, Stabilant 22 or in a solvent-diluted
form, as Stabilant 22A or Stabilant 22E (either with isopropanol
or ethanol), The diluted material has 4 parts of solvent to 1 part of Stabilant
22 by volume, and is much thinner, and therefore easier to apply to contacts
such as socketed IC's.
Some end users prefer to buy larger quantities and use industrial syrettes
to apply the material onto connections. Camel's hair or sable brushes can
be used to brush it on card-edge connectors. Cards can also have their
edge connectors dipped into the dilute material.
What is meant by a piece of electronic equipment's solvent burden/year?
Solvent burden/year is the average amount of cleaning solvent used
per year to keep a piece of electronic equipment operating over its useful
How did the use of Stabilant 22A or Stabilant 22E change the solvent burden/year?
In the trial use of a solvent to clean contacts in an older computer,
we found that it took about 20 mL of an isopropanol-perchloroethylene based
material to clean a 100-contact card-edge connector. Even though some was
left on the wiper used, it too evaporated. The equipment became erratic
in operation four months later, and the contacts had to be re-cleaned.
In the proceeding year, the same approximate pattern had been repeated
to the point where we could safely say that the annual solvent usage for
that set of contacts was about 60 mL. The next time that we had the equipment
malfunction we used 2mL of Stabilant 22A which released 1.6 mL of
isopropanol to the atmosphere. No further service was needed for three
and a half-years, (the equipment was sold in working order), thus the solvent
burden of that connector was about 0.46 mL/year. This is a reduction in
solvent burden of 130:1.
Had the concentrate (Stabilant 22) been used there would have
been no solvent burden as the vapor pressure of that material is very low
and virtually no evaporative losses take place.
Do Stabilants contain any Ozone Depleting Chemicals?
Stabilants do not contain any ODC's such as CFC'S, HCFC's or
Trichloroethylenes, nor are such chemicals used in their manufacture.
How about materials that cannot be imported to or sold in some areas?
Neither the Stabilants themselves, nor any of the inks used
on their labels or packaging, contain Lead, Cadmium or Hexavalent Chromium.
Other factors in the use of Stabilants:
Neither Stabilant 22, Stabilant 22A, or Stabilant
22E, are subject to the TSCA (Toxic Substance Control Act) nor are
they reportable under SARA Title 111.
What about disposal of Stabilant material or Stabilant-treated equipment?
As noted, Stabilants are not a chelating agents and thus will
not cause heavy metals to become concentrated in effluents. And while there
is no evidence of toxicity to marine or littoral life, we recommend, subject
to local ordinances, that surplus or contaminated Stabilant materials be
destroyed by incineration.
- Halogen content: 0 ppm (ug/g
- Sulfur content: 0 ppm (ug/g)
For United States end-users:
Stabilant 22 is not a hazardous waste when discarded as defined
Stabilant 22 is not a halognated solvent when spent as defined
The total Organic Carbon Content (TOC) of Stabilant 22 is 28%
As the useful life of the Stabilants is generally well in excess
of five years, the reduction solvent burden when using either the isopropanol
diluted Stabilant 22A or the ethanol-diluted Stabilant 22E,
could be as much as 200:1, by volume alone, for the connector in a piece
of electronic equipment.
Granted that the Mean Time Between Failure of 4 months is much shorter
than a typical MTBF for most electronic equipment, the amount of solvent
used was also minimized by careful application. While even a 50:1 reduction
in solvent burden is worthwhile, the total elimination of solvent burden
by the use of the concentrate Stabilant 22 is even more significant,
22 is not a chelating agent, a matter of concern to both those industries
producing heavy metal waste, and to the Nuclear power generating industry.
As Stabilant 22 contains no solvents and has an exceptionally
low vapor pressure, it is technically not subject to the various rules
and regulations governing coatings such as paints and varnishes, and in
California's Southwest, the amounts of isopropanol or ethanol (as a solvent)
involved in the use of Stabilant 22A or Stabilant 22E, are
so small, on a daily basis that there is generally no problem in obtaining
a letter of exception from the appropriate agencies. As Stabilant 22A
or Stabilant 22E are not packaged in quantities sufficient to be
affected the various acts it does not require special labeling in California.