Note: Descriptions are shown in the official language in which they were submitted.
-` 2~22~;
--1--
,
44101 CAN 9A
ANTISTATIC COATING FOR sRusH ELEMENTS
~ACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to brushlike
materials that can be used for t:he treatment or
finishing of surfaces, or for the conveying of other
materials along a surface. The present invention
further relates to the use of coating compositions to
improve the performance of the brushlike materials.
2. ~ackground of the Art
srushlike materials have many different
utilit~es in industry. They can be used as finishing
tools to modify surfaces or to apply coating
compositions; they can be used as cushioning layers to
; 20 receive materials; they can act as vibratory transport
surfaces on conveyors, as well as providing other
functions. They can be used in the fcrm of mats,
belts, wheels, discs, rolls, and cylinders. Brushes
used for most of these purposes tend to provide a
surface of filaments essentially perpendicular to their
support layer. These filaments may be anchored by
~ embedment in the composition of the carrier layer, by
;~ an adhesive on the carrier surface, and/or by
mechanical attachment to the carrier surface as by a
; staple or loop. Where the brushes are used as
vibratory conveyors, the filaments are set onto the
carrier layer alt an angle, most or!all of the filaments ~ ~
tilting at about the same angle away from the - ~ -
;~ perpendicular, usually 5-40 away from the
perpendicular.
, '' .
- ` ~ 202220~
SUMMARY OF THE INVENTION
It has been found in the practice of the
present invention that the application of a
non-volatile, non-integral, electrically conductive
organic coating onto the surface of the fibers,
bristles or filaments of an industrial brush material
can improve its overall performance.
DSTAILED DESCRIPTION OF THE INVENTION
The present invention may be used on any
brush material which generally comprises a base with
extending bristles or filaments secured to the base.
The bristles or filaments may be secured by a wide
range of methods or constructions including adhesive
securement, tufting into the base, stapling folded over
filaments or bristles, and channel crimping of
filaments. The preferred construction i6 an adhesively
secured industrial brush construction. An industrial
brush construction consists of a base layer, a binder
layer and the bristles. The base and the binder may be
the same layer and the same material. The bristles are
preferably individually and uniformly embedded in the
binder such that they project upward and are generally
parallel to one another, but they may be formed by
bending single filaments and securing the filament at
the bend into the adhesive layer. The base layer and
the binder layer can be the same material or different
material and in general these layers are polymeric
materials. For example, the base layer can be a `~-
flexible resilient polymeric open cell foam or solid
film base, a polyester material, polyurethane, or a
nylon material.` In addition, a fabric, for example
made of cotton, nylon, metal, graphite or polyester can
be embedded into these polymeric materiais. The binder
layer is usually a semi-rigid polymeric material such
as a polyurethane, polyester, epoxy or nylon. In the
2~22
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case where the base and the binder layer are the ~ame,
it is preferable to use a polyurethane material. In
general the thickness of the base and binder layers can
range between 0.5 to 20 millimeters or 1 to 10
millimeters, preferably 2 to S millimeters. The larger
the diameter of the bristles, obviously the thicker the
binder layer is.
The fibers can be selected from many useful
types of fibers including the group consisting of:
nylon, polypropylene, polyester, polyethylene, metal
oxides, inorganic oxides, composition, and metallic
fibers. In some cases the fibers can be hollow, which
is well known in the brush art. In addition the
polymeric fibers may contain abrasive particles such as
those well known in the art like silicon carbide and
aluminum oxide. The particle size of these abrasive
particles will vary depending upon the application, but
in general they will range from 10 to 600 micrometers,
preferably 15 to 120 micrometers. If the fiber
contains the abrasi~e particles, the brush material
will typically produce a matte type finish on the
workpiece. If the fiber does not contain abrasive
part~cles, a glossy type finish will typically be
produced on the workpiece. The diameter of the fibers
can range from 0.01 to 5 millimeters, preferably 0.2 to
2.0 millimeter. The length of the fiber (above the
base surface), or trim length, can range from 2 to 260
millimeters, preferably 8 to 205 millimeters.
In some applications the fibers will be
nearly perpendicular to the binder layer, in other
applications such as conveyor systems, the fibers will
be placed at a specified angle or a specified tilt.
During the manufacture of the industrial
brush materials, the binder layer is extruded or
otherwise coated onto the base layer. I~ the base and
blnder arn the Aame, they can be extruded tcgether.
'' ~
~ ~`
2~2V~
-4-
~fter or during the extrusion process, the fibers are
inserted, pres6ed, or adhered into or onto the binder
layer. Next the binder is cured and solidified to form
the completed article.
The industrial brush material can be used in
a wide variety of abrading and finishing appllcations.
The primary applications for the antistatic coating on
the industrial brush fiber material is conveying or
moving, cleaning and polishing. It has also been found
that the reduction in static charge results in a safer
work environment by diminishing the potential for
static sparks. In these applications the material
exhibits an increased use life, on the order of
magnitude of 6 months to over a year. In general, in
wood applications or conveying applications the static
:~ electricity build-up can result in serious problems for -
~`~ the customer. The antistatic coating has been more
successful in the above mentioned applications, than in
abrading applications where the bristles ordinarily
wear relatively fast. But some improvement is still
shown in these`environments.
he conveying or moving type applications is
best described as placing the industrial brush material
in segments in a horizontal bed. The preferred type o~
construction for this type of application is a
polypropylene ~iber with a twenty degree tilt. In
general static electricity is generated by the
workpiece traversing over the bristles. If the
industrial brush material is employed for conveyors for
electronic parts or light bulbs, the static electricity
can seriously damage these parts to the point where the
piece is worthless and has to be scrapped.
The second application is cleaning, which
entails defuzzing and removing dust from wood
workpieces, and cleaning dirt and oil o~f of metal,
wood or plastic workpieces. In these types of
-` 20222~
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applications, the cylinder brushes consist of bristles
made from nylon, polypropylene or nylon with abrasive
particles embedded therein. The static electricity i6
generated by the workpieces coming in contact with the
bristles. If enough static electricity is generated, a
spark could ignite the wood dust and create a serious
fire potential. Also in wood applications, the static
electricity causes dust to adhere to the bristles,
which in turn causes the entire brush to become clogged
with wood dust. In metal cleaning, the static
electricity causes the dirt and metal shavings to
adhere to the metal workpiece rather than being removed
from the workpiece by the brush.
The third major application is polishing, in
which the brush material is employed to impart a fine
finish on metal parts and in some cases can remove
light metal oxide build-up. This is typically a low
pressure application, pressure less than 34.5
Newton/square centimeter is generated at the interface.
The brush material is typically in the form of a
cylinder brush. The preferred industrial brush product
construction for this type of application consists of
nylon or polypropylene fibers. The static electricity
is generated by the interaction of the bristles with
the workpiece, usually a metal workpiece. Like above,
the static electricity results in the metal shavings
remaining on the workpiece rather than being removed by ~ ~
the brush. - -
The conductive coating composition of the
present invention has been referred to as
"nonvolatile". In the practice of the present ~ ~ -
invention this means that,`after evaporation of any
solvents, less than 2 percent by weight per week of the ~ ;
coating composition will evaporate off the surface of
an article at 25C and 40 percent relative humidity.
Preferably less than 1 percent by weight per week would
:
2 ~ 2 ~
--6--
evaporate and, more preferably, less than 0.1 percent
by weight per wee~ would evaporate at those
temperatures and conditions.
The greater the percentage of surfaceg of the
S fiber that are coated with the organic, conductive
coating compositions of the present invention, the
greater the general reduction in electrostatic
charging. This does not necessarily mean that greater
amounts of the coating composition better reduce the
10 electrostatic charging, but rather that it is important -
to insure the coating of as much surface areas as
possible on the brush. The coating composition should
- generally be applied so as to provide a dry (without
solvent) coating weight of between 0.5 (0.08 micrograms
per square centimeter) and 250 micrograms per square
inch ~40 micrograms per square centimeter) as an
average coating weight. secause the coating
composition will not necessarily spread uniformly over
the coated surface, or because of surface structure
variations ~such as embossed non-glare surface), it is
the average coating weight that must be considered in
this range. If less than this amount of material is
applied, insufficient antistatic protection will be
provided. If greater than this amount is applied, no
further antistatic protection is obtained, and an
undesirable, highly greasy appearance will be provided
to the coated article. Preferably a coating weight of
1-100 micrograms per square inch ~0.16 to 16 micrograms
per square centimeter) is used or more preferably 1-50
micrograms per square inch (0.16 to 8 micrograms per
square centimeter). In the most preferred practice of
the invention, 5-30 micrograms per square inch of the !
coating composition is used.
The organic coating composition useful in the
practice of the present invention may be any
nonvolatile, or~anic, electrically conductive ~;
~ 20222~5
--7--
composition. It is highly preferred that the coating
is nonintegral or liquid as this provides the greatest
static reduction. By "nonintegral" it ~s meant that
the composition does not form a self-supporting solid
film when air dried, as it would be when present on the
surface of the brush. The term nonintegral therefore
excludes the provision of a solid, thermoplastic or
nonliquid conductive coating composition to the surface
of the brush. Useful conductive coating compositions
include the many antistatic agents and systems already
known in the art including long chain alkyl quaternary
amines, long chain alkyl quaternary phosphines,
fluorinated antistatic materials, low molecular weight
polymers or oligomers having pendant antistatic ionic
groups such as quaternary amine groups, and other
ionic, organic materials known for antistatic purposes
in the art. The preferred material according to the
practice of the present invention for use as an
antistatic coating composition is the composition of
2 U.S. Pat. No. 4,313,978. This particular composition
provides extremely long lasting and high efficiency ~ -
antistatic protection. That antistatic composition
comprises a fluorinated anionic surfactant which is an
amine salt of an acid containing a fluorinated organic
radical ~as defined herein) and an antistatic agent
which is an ionic salt of an amine. It has been found
that the combination of the fluorinated surfactant and
antistatic agent can provide a reduction in static
charging at very low application amounts.
The surfactants used in that preferred - `
composition of the present invention are anionic
fluorocarbon surfactants which are the aminé salts of
acids containing a fluorinated organic radical. The
preferred surractants may generally be depicted by the
35 formula: ~
.
` ~ 202220~
--8--
Rf--A--X Z
in which
R~ represent a fluorinated organic radical
~as defined herein~,
A represents a bond or a divalent linking
group,
x~ represents an acid anion, and
z~ represents a quaternary ammonium cation.
The fluorinated organic radical Rf is defined
as a radical which is saturated, aliphatic radical
having from 2 to 20 and preferably at least 3 carbon
atoms, the skeletal chain of which may be straight,
branched or, if sufficiently large, cycloaliphatic.
The skeletal chain may be interrupted by divalent
oxygen or trivalent nitrogen atoms bonded only to
carbon atoms provided the radical does not contain more
than one heteroatom, i.e., nitrogen or oxygen, for
~ every two carbon atoms in the skeletal chain the
-~ ~ radical being fully fluorinated with the exception that
it may contain hydrogen or chlorine atoms as
substituents provided that not more than one atom of
`~ either is present in the radical for each carbon atom.
Prefera~ly, the fluoroaliphatic radical iB a
perfluoroalkyl radical havinq a skeletal chain that is
straight or branched-
The fluorinated organic radical is linked tothe acid anion either by a direct bond or through the
divalent linkage A. Preferably the chain of the
linking group A is composed of carbon atoms although -~
heteroatoms, e.g., nitrogen or oxygen, may be present
provided they do not interfere with the ionic nature of
the~surfactant.i~ Preferred linking groupis are alkylene
groups.
Particularly suitable acid anions X~ include `
;~ ~ 35 carboxylic acid and sulfonic acid groups.
` ;:: `
--` 2~2~
Examples of suitable fluorinated organic
radical containing anions Rf-~-X- include 5 to 18
carbon atom perfluorinated alkyls such as
perfluoropentyl sulfonate and
perfluoro-octylcarboxylate.
The quaternary ammonium groups Z+ are derived
from the corresponding amine. Suitable amines include
aliphatic amines and aliphatic cyclic amines, which may
optionally be substituted with substituents whlch will
not affect the ionic nature of the surfactant.
Preferably the amines contain 2 to 12 carbon atoms.
Suitable amines include piperidine,
dimethylaminoethanol, morpholine, triethanolamine and
triethylamine.
Other suitable surfactants include those
containing 2 or more acid anions and quaternary ;
ammonium cations in which the acid anions are bonded
directly to the fluorinated organic radical or via one
or more linking groups. Preferably the fluorinated
20 organic radical is pendant although it may be present -; ~`
within the molecule as in the case of the amine salts
of (C2F4COOH)2 and (C2F4SO3H)2. Anionic surfactants
containing two or more fluorinated organic radicals may
also be used.
The antistatic agent used in the preferred ;-
compositions is an ionic salt of an amine. The
compounds have the property that they induce
conductivity to the surface upon which they are
applied. Suitable amines include those from which the
quaternary ammonium groups Z' are derived. The anionic ~-
portion of the antistatic agent may be chosen fro~ a
wide variety of`anionslincluding halide, sulfate, aryl ! '
sulfonate, aliphatic sulfonate, aryl carboxylate and -
~;~ aliphatic carboxylate. The anions may contain further
substi~uents pr~vidin~ they do not af~ct thc
` ~ antistatic properties of the compound, for example, the
2~227~
, , - 1 O - " '
presence of nitrogen atoms and highly fluorinated
radicals is undesirable in the anlon.
Specific examples of anions include:
C7H7SO3
SO4
Cl
CH3(CH2)8cO2
6 s 2
The fluorinated surfactant and antlstatic
agent may be derived from the same or different amines.
The compositions are preferably applled from
a single solution. Suitable solvents include lower
15 alcohols, e.g., ethanol and isopropanol, which may be ~ ~
diluted with a low boiling fluorocarbon. Preferably -
the solvent is chosen such that the fluorinated -~
surfactant and antistatic agent have substantially the
~same solubility so that the dried coating contains the
same ratio of constituents as in the applied solution.
I there is a substantial difference in the
solubilities, nonuniform coatings may result.
The ratio of fluorinated surfactant to
; antistatic agent in a composition depends upon the -;~
: 25 intended use. `~
The concentration of the solutions vary ;-
according to their intended use. Preferably the anion
molar percent of~the fluorinated organic radical i5 ,~
between 1 and 50%, preferably 1.8 and 47.9%, and most
` 30 preferably between 15 and 40 percent of the mixture of
~; ~the two ingredients. The present invention has been ; ;~
found to be independent of the specific antistatic
composition used, although some, of course, perform -`~
better than others because of their physical
propQrties-
::
`: ' '
202~20~
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The s~lutions can be applied to the brush
material by any conventional techniques such as roll
coating, spraying, brushing and immersing. After the
solution is applied it is dried to remove the volatiles
either at room temperature or at elevated temperatures.
The following examples will illustrate the
various embodiments.
~ .
Control Example
The control example was an untreated
sRUSHLONTM material, polypropylene fibers, with a
twenty degree tilt, part number 721B commercially
available from the 3M Company, St. Paul, MN.
Example 1
The following formulation was prepared 800
gram~ o FREON TF solvent from DuPont, 150 grams of
isopropyl alcohol, 50 grams of heptane, 0.44 grams of
deionized water, 0.026 grams of piperidinium toluene
sulfonate, 0.104 grams of piperidinium perfluoro-octyl
sulfonate and 0.1684 grams of STATICIDETM commercially
available from American Chemical Laboratories.
STATICIDETM is a humectant and consists of ethyl benzyl
ammonium chloride mixture with N-alkyl C12 to C16.
Example 2
:
The following formulation was prepared 800
grams of FREQNTM TF solvent from DuPont, 200 grams of
ethyl alcohol, 0.2 grams of CARBOWAxTM PEG 400
30 purchased from Union Carbide Corp., 0.32 grams of -
piperidinium toluene sulfonate and 1.28 grams of
piperidinium perfluoro-octyl sulfonate. The cARs
PEG 400 is a humectant and consist essentially of
polyethylene glycol.
r
! 2 0 2 2 2 ~ ~
-12-
Example 3
The following formulation was prepared 1000
grams of isopropyl alcohol, 1.6 grams of piperidinium
perfluoro-octyl sulfonate, and 0.4 grams o~
piperidinium toluene sulfonate.
Example 4
The following formulation was prepared 1000
grams of methyl alcohol, 0.8 grams of piperidinium -
toluene sulfonate and 3.2 grams of piperidlnium
perfluoro-octyl sulfonate and 4 grams of CARBOWAXTM PEG
400 purchased from Union Carbide Corp. The CARBOWAXTM
PEG 400 is a humectant and consist essentially of
polyethylene glycol.
Example 5
The following formulation was prepared 600
grams of ethyl alcohol, 400 grams of deionized water, ~ - -
~;~ 0.8 grams of piperidinium toluene sulfonate and 1.6
grams of piperidinium perfluoro-octyl sulfonate and
0.32 grams of CARBOWAXTM PEG 400 purchased from Union
Carbide. The CARBOWAXTM PEG 400 is a humectant and ~
consist essentially of polyethylene glycol. i~ ~-
In the previous examples, the piperidinium
25 salts were added first to the alcohol portion of the
solution, then the salts were dissolved into the
alcohol and finally the other components were added.
In the cases where the deionized water was used, it was ~-
added last to the formulation.
Next, three 5 cm by 10 cm BRUSHLONTM samples
per~example wer~e cut and the entire BRUSHLONTM sample
was immersed into the various solutions. The excess
solution was gently shaken off then placed to dry
overnight with the fibers up.
The residual charge for each example was
measured using a Monroe Electrostatic Fieldmeter placed
. ~
r~~~ 2 ~ ~ 2 ~ ~ ~
-13-
2.54 cm from the sample. The residual charge is a
measure of how conductive a material is prior to any
static electricity being generated. Then a fresh
carpet segment for each test sample (100% nylon, 1.25
cm loft, multistrand, 12.5 cm by 28 cm in area) was
rubbed 10 times against each BRUSHLONTM sample to
generate a static charge. Immediately, another
reading, the electrostatic charge, was taken in the
same manner as the residual charge was measured for
each sample. The electrostatic charge measures how
resistant the BRUSHLONTM material was to static
electricity. The results can be found in Table 1, each
reading represents an average of three samples.
Table 1
Residual Charge Electrostatic Charge
Example tvolts) (volts)
Control 5 2710
1 3.5 265
2 10 130
3 6.5 255
20 4 1.5 70
It can be concluded from the above data that the
formulations of the Examples significantly reduce the
amount of static charge build-up on the BRUSHLON M ~ :
material-
.
Example 6
A BRUSHLONTM material (a polypropylene fiber, 20degree tilt, part number 721B available from 3M Company,
St. Paul, MN) had an antistatic coating applied that
consisted of by;~weight~94~ ethyl alcohol, 0.4% piperidinium
toluene sulfonate, 1.6% piperidinium perfluoro-octyl
sulfonate, 2~ CARBOWAXTM PEG 400 purchased from Union
Carbide Corp. and 2% STATICIDETM purchased from American
Chemical Laboratories.
-` 20222~
-14-
The treated ~RUSHLON M material was employed by
an independent third party under a confidential disclosure
agreement as a conveyor means for radio circuit boards for
four months and 10 days. If there is static electricity
generated as these boards move across the BRUSHLON~M
material, the static electricity seriously damages the
boards, to the point that some of them are unusable. On
average about 1000 boards/week are transported across this
conveyor system and on average two percent of the boards
would be lost due to the static electricity problem.
Prior to this invention, the third party utilized
3M~s BRUSHLON~M material as a conveyor means, but sprayed
the bristles on average anywhere from once a day to once a
week with STATICIDETM to prevent static build-up. The
third party has stated that the STATICIDE~M coating had
never lasted more than one week. The present invention was
employed for four months and ten days without any damage to
any of the circuit boards.
70 Example 7 -;~
In this example, various BRUSHLONTM wheels
(available from 3M Company) having a 21 cm inner diameter
and was approximately 31 cm in width were utilized. All of
the wheels contained nylon fibers that were approximately
3.18 cm in length-
Wheel A had 0.041 cm diameter fibers andcontained the non volàtile organic treatment of this
invention. The non volatile organic treatment contained by
weight 90~ deionized water, 10 ethyl alcohol, 0.2%
polyethylene glycol and 0.2~ Harlow Salts. The Harlow
Salts consisted of 80%,by weight piperidinium I !
perfluoro-octyl sulfonate and 20~ by weight piperiddinium
toluene sulfonate. The organic treatment was mi~ed by
first fully dispersing the Harlow salts into the ethyl
alcohol, then the polyethylene gly~ol was added~ followed
by teh de~oni~ed water. The organic treatment wa~
- 2 ~
-15-
continuously mixed throughout the preparation. The organic
treatment was then applied to the brush by spraying and the
excess organic treatment drained of of the brush. The
brush then sat ~or a few days to allow the treatment to
dry.
Wheel B had 0.041 cm diameter fibers and
contained the STATICIDETM treatment. The STATICIDE~M
treatment (American Chemical Laboratories) consisted of by
weight 0.13~ n-alkyl (60% C14, 30~ C16, 5~ C12 and 5~ C16)
dimethyl benzl ammonium chlorides, 0.13% n-alkyl (68% C12,
32% C14) dimethyl ethyl benzl ammonium chlorides and 99.84%
inert lngredients. The STATICIDET treatment was applied
to the brush in the same manner as Wheel A.
Wheel C had 0.051 cm diameter fibers and
contained no antistatic treatment.
The above discussed three brushes were tested
according to the following procedure. Each brush was
installed on a Timesavers (Minneapolis, MN) conveyorized
brush machine. The brush rotated at approximately 900
20 revolutions per minute. The conveyor belt contained a ~ ;
particle board workpiece which was abraded by the brush.
'rhe conveyor belt operated at 9.2 meters/minute. The
interference between the ends of the bristles and the
workpiece was 0.11 cm. After thirty minutes, in which the
workpiece was in contact with the brush wheel, the `
workpiece was removed. The purpose of this thirty minutes
~; was to generate heat and static electricity which is
typically seen in industrial brush applications. Next, the
workpiece was passed underneath the brush three more times,
each time the electrical charge on the brush was measured.
The measurement~was taken approximately 2.54 cm from the
bristles using a Model 255 Digital Stat-Arc electrostatic
` field meteL while the brush rotated. Then the workpiece
was passed underneath the brush for a ourth time and the
electrical charge on the workpiece was measured. The
results can be found in ~ables 1 and 2. ~he valuès are
: '
` ~2~2~
-16-
based upon the highest readings. The test was stopped once
the charge on the brush exceed 9000 volts.
Table 1
5 Electrostatic Charge on the Brush Wheels
Time Wheel A Wheel B Wheel C
minutes volts volts volts
720 4100 1-3,400
380 9960
790 :~
120 1170
150 1070 ::
180 1780
210 2110 .
1 5
: : Table 2
; Electrostatic Charge on the Workpiece
Workpiece WorkpieceWorkpiece ~:
From From From ..
:~ Time Wheel A Wheel BWheel C
minutes volts volts volts
~:; 30 7800 4800 880
5820 4600
2590 B680
120 6430
150 B230
~ : 180 7840 .
:: : 210 5960
: ~ It was concluded from the above data that the brush of the
: invent!lon (Wheei A) had significantly less static charge ~ ~ia
than the prior art brushes. It appeared that the Wheel B
~: (STATICIDE~M treatment) wore off or evaporated rather
35 quickly and th~ voltago re3ding approached Wheel C. It wa~ ~
' ~ `' .-
~ i` 20222~
-17- ;
also noted that as the static charge corresponding to the
workpiece decreased, the static charge corresponding to the
brush increased. It is known in the art that the static
charge corresponding to the brush wheel is more significant
than the static charge correspondinq to the workpiece.
Example 8
Various BRUSHLONTM segments ~available from 3M
Company), 5.1 cm by 12.7 cm and having 0.030 cm dlameter by
2.2 cm length polypropylene fibers with a 20 degree tilt to
them were utilized in this example. Segment A contained
the organic treatment of the invention and this treatment
was applied in the same manner as Wheel A (Example 7).
Segment B contained the STATICIDETM treatment and this
lS treatment was applied in the same manner as Wheel B
(Example &). Segment C did not contain any treatment.
The segments were then tested according to the
following procedure. A nylon carpet piece was held
; stationary and the segment-was pulled across the carpet by
hand to generate static charge. Then, after a number of
strokes which were listed in Table 3, the static charge in
volts were measured. The static charge values are an
average of five different BRUSHLONTM samples for each
segment. The segment was placed in a vertical slot and the
field and the field meter was placed 90 degrees from the
brush segment. The field meter was the same as the one
described above. A new piece of carpet was used every 50
strokes. Additional for the 50 strokes, the same piece of
carpet was used for segments A through C, although for each
brush segment a different area of the carpet was rubbed. ~
1: ' ' ' . .
~ '' ;"~
~ 202~205
,
- 18 -
.
Table 3
Electrostatic~Charge on the Carpet
Voltage of Voltage of Voltage of
Strokes Segment A ~ment B, Segment C
0 50 ljQ 3500
4500
00 225 175 3700
150 300 225 2750 ~.
200 275 3~)0 2700
0 250 250 300
300 275 250
350 300 350
400 250 225
450 800 750
500 300 225
550 800 750 ~ `
~:; 600 1050 950
650 1450 900
` : : 700 1250 750
~ ~:
'` `~ ~: '
~ ~ 25
.` : ~ .
:
`~ ~ 30
' ` ", ' '' ,:
~ ~ :
,~
, :~
