Industrial Summit Technology
Technical Bulletin #ML-1-95
Industrial Sunnmit Technology • Parlin, N e w J e r s e y 0 8 8 5 9
PYRE-M.L. Wire Enamel
Introduction
Pyre-M.L. products are part of a family of materials
based on aromatic polyimides which are one of the most
thermally stable organic materials. These products include
Pyre-M.L. Wire Enamels, Pyre-M.L. Liquid " H " Enamels,
Pyre-M.L. Insulating Varnish, and Pyre-M.L. Thinner Table
1 describes these products and their associated codes/
grades.
During decades of commercial and military use,
Pyre-M.L. Wire Enamels have been recognized as having
the finest thermal stability, radiation resistance, solvent
resistance, cryogenic resistance, and electrical
properties of any enamel available. Precisely because of
these properties, Pyre-M.L. has been used in motors,
generators, transformers, and other apparatus which
operate continuously at temperatures up to 240°C.
Pyre-M.L. is also useful in heavy duty motors which, due
to temporary extreme overloads, acceleration torques, or
stalls, are subjected to even higher temperatures (up to
400°C) for limited periods (see Graph No. 1 ) . Its thermal
stability and very low tendency to give off volatile matters has led to its use in sealed relays designed for use in
vacuum. The almost absolute insolubility of Pyre-M.L. has
led to their use in hermetic refrigeration systems and certain liquid filled transformers. Pyre-M.L. products are U.L.®
approved.
Table 1
LIST OF PYRE-M.L. PRODUCT OFFERINGS
Cateaorv
1ST C o d e
Tech. Bull
Wire Enamel
RC-5019
RC-5057
RC-5069
RC-5083
ML-1-95
Insulating Varnish
RK-692
ML-2-95
Liquid " H " Enamel
RC-5097
ML-3-95
Thinner
T-8585
ML-4-95
Figure: - 1
O
O
-N-RNJ.
H
H
+ HjNRNHj-
Description of Product
Pyre-M.L. wire enamels are solutions of polyamic
acids formed by reacting aromatic diamines with aromatic
dianhydrides. Sometimes aromatic hydrocarbon or xylene
solvent is added as a diluent. The monomers used in PyreM.L. formulation and the accompanying reaction are shown
in figure 1. Various grades of Pyre-M.L. enamels with their
properties/specifications are described in Table 2.
Pyre-M.L. wire enamels can be applied to all sizes
of round, square, and rectangular wires by conventional
die coating techniques. They have also been applied to
irregular surfaces using other techniques such as spraying,
drop dispense, and brushing. Copper, aluminum, brass,
nickel, and chrome alloy have all been coated successfully.
Pyre-M.L. has also been used for coating glass served wire
and special hook up wires insulated with surface treated
Teflon® fluorocarbon resin.
When the enamel is baked it is converted to an inert
polyimide.
N-R
• •
-1 n
Page 1
Viscosity Stability
The viscosity, as manufactured, is not stable but
gradually drops by 35%, and then increases to gel. G e l a tion occurs in approximately 14 days at 120°F (49°C), 30
days at 1 0 0 T (38°C), and 90 days at 7 7 T (25°C). At 4 0 T
(4°C), it will not gel in one year. Hence, it is recommended
that Pyre-M.L. be stored under refrigeration conditions prior
to use. Pyre-M.L. is stored at 40°F in the Pyre-M.L.
manufacturing plant warehouse in Parlin, New Jersey,
USA. Storage in an unheated building may be acceptable
during winter. Viscosity measurements are strongly affected by temperature. S e e Graph No.2 for
temperature-viscosity conversion.
Moisture contamination has a detrimental effect on
viscosity stability, and hence, must be avoided. Allow all
chilled containers to reach room temperatures before
opening them to avoid moisture from condensing.
Graph No. 1
Thermal Life - Unvarnished PYRE-M.L.®
Coated Wire
lOO.OOQp-
lo.ooq -
CO
o
X
0)
1 ,ooq -
E
Properties of Magnet Wire Coated with PyreM.L. Enamel:
Thermal Properties
100
Tests made according to IEEE 57 or A S T M D2307
indicated that wire coated with Pyre-M.L. has a thermal life
of 20,000 hours at 243°C. This value was obtained with no
extrapolation. Samples aged at 200°C and 220°C show
no failures after 40,000 hours at which time the test was
discontinued. Again, refer to Graph No.1 which shows the
thermal life of wire coated with Pyre-M.L. based on data
from four different laboratories. Temperature V s . Weight
Loss is shown in Table 3. Wire coated with Pyre-M.L. is
suitable for use in Class H or 220°C insulating systems.
120
140
160 ISO 20O
2SO
300
350
40O
Temperature.°C
Graph No. 2
Effect of Temperature on Viscosity of
Pyre-M.L. Wire Enamel
Table 2
PYRE-M.L. PRODUCTS SPECIFICATION
I.S.T (USA) CORPORATION OFFERINGS
Code
RC-5019
RC-5057
RC-5069
RC-5083
Solicis(%)(1)
15.0-16.0
14.5-15.5
12.3-13.3
18.0-19.0
50-70
50-70
5-12
20-40
75-85
75-85
15
15-25
15-25
0
0
0
85
Viscosity
(Poise)(2)
Solvent System
NMP(%)
100
Aromatic
Hydrocarbon(%)
DMAC
0
Density
LBS/Gal
(+/-0.05)
9.11
8.80
8.72
8.57-8.67
KGS/Gal
(+/-0.05)
4.13
3.99
3.96
3.89-3.94
Temp.,-C
5
10
15
20
25
30
35
Note-(l) NEMA Test Method - 2gm/2hr/200°C Bake
(2) Measured at 25°C with Brookfield Viscometer #3 Spindle @ 12 R P M
Page 2
Table 3
by e x p o s u r e for 150 d a y s to F R E O N 116 (hexafiuor o e t h a n e ) F R E O N C 3 1 8 (octaflourocyclobutane),
or nitrogen at 300°F. C l a s s H dry type transformers
utilizing m a g n e t wire c o a t e d with P y r e - M . L . are in
commercial use.
Weight Loss at Elevated Temperatures
Hours At 220°C
2300
6900
13000
%Loss
3.3
4.8
5.6
Hours At 240°C
2300
6200
12500
%Loss
5.0
9.0
13.4
Hours At 260°C
2200
6500
11500
%Loss
10.5
23.2
27.1
Hours At 300°C
144
195
404
500
645
808
%Loss
4.1
5.1
7.0
8.3
8.3
8.3
Dielectric Liquid Resistance
L a b o r a t o r y tests indicate that m o d e r a t e l y or
thoroughly cured P y r e - M . L . has excellent resistance
to oil. H o w e v e r , P y r e - M . L . c a n be d e g r a d e d by water
at e l e v a t e d t e m p e r a t u r e s a n d p r e s s u r e s , it s h o u l d not
be u s e d at e l e v a t e d t e m p e r a t u r e s in s e a l e d s y s t e m s
c o n t a i n i n g a n y significant a m o u n t s of w a t e r or
materials s u c h a s p a p e r w h i c h d e c o m p o s e to water
without preliminary tests to s h o w that s e r v i c e will be
satisfactory. T h o r o u g h l y c u r e d wire p e r f o r m s best
under these circumstances.
Heat and Cold Resistance
a. Weight loss data from coated aluminum strip (in air)
at 5 minutes at 300°C shows:
Polyester
Epoxy
PYRE-M.L.
Electrical Properties
7.5%
1 6 . 5 % b a s e d on original film
weight
0.75%
b. R e t e n t i o n of e l o n g a t i o n (hours to 1% elongation)
o n h e a t a g i n g , (initial % E = 2 5 % )
T h e electrical properties are r e m a r k a b l y s t a b l e
over a wide range of t e m p e r a t u r e s a s illustrated in
Table 4.
T h e s e a r e d e s c r i b e d in Table 5
Refrigerant Resistance
Table 5
Sixty d a y s e a l e d tube tests at e l e v a t e d
temperatures in the p r e s e n c e of c o p p e r , iron,
a l u m i n u m , a n d either FREON® 12 or FREON® 2 2
refrigerants indicate that P y r e - M . L . is unaffected.
P y r e - M . L . w a s found to h a v e only 0 . 0 1 % e x t r a c t a b l e s
in F R E O N 12 a n d 0 . 0 2 % e x t r a c t a b l e s in F R E O N
22 b a s e d on the weight of the wire e n a m e l . T h e s e
favorable conditions h a v e b e e n c o n f i r m e d by reports
received from hermetic s y s t e m m a n u f a c t u r e r s .
Hours
Temperature
11
85
700
4500
752T(400°C)
6 6 2 T (350°C)
5 7 2 T (300°C)
4 8 2 T (250°C)
The mechanical properties of these polymer films
are excellent and are retained over a wide temperature
range. The zero strength temperature is 1472°F (800°C);
this is 270°F (150°C) above the melting point of aluminum.
The flex modulus, approximately 400,000 psi at ambient
temperature, increases by only 2 5 % when measured at
Dielectric Gas Resistance
Laboratory tests indicate that the electrical
properties of P y r e - M . L . are not significantly affected
Table 4
Dissipation Factor
Frequency
CES,
10^
103
10"
25!C
0.0025
0.0025
0.0030
150°C
.0062
.0056
.0048
175°C
.0180
.0072
.0061
200°C
>0.1000
>0.0177
>0.0101
225°C
>0.1000
0.1152
0.0207
250°C
>0.1000
0.5810
0.163
5.29
3.62
3.55
11.88
5.58
3.56
Dielectric Constant
102
103
10"
3
368
3.65
3.11
3.09
3.07
3.43
3.40
3.41
3.63
3.60
3.60
Pages
Table 8
-310°F (-190°C) a n d d e c r e a s e s by a b o u t 5 0 % w h e n
m e a s u r e d at 4 8 2 ° F (250°C).
T h e retention of p h y s i c a l properties at low
temperatures, a s indicated, is exemplified by the results obtained with m a g n e t wire c o a t e d with P y r e - M . L .
e n a m e l in liquid helium at - 2 6 9 ° C (4°K). S a m p l e s of
2 5 - mil diameter wire w e r e c o o l e d to 4 ° K a n d s u b jected to a m a n d r e l b e n d . T h e radius at w h i c h failure
occurred on fonA/ard a n d r e v e r s e b e n d s is s h o w n in
Table 6. T h e superiority o v e r the materials tested is
clearly s h o w n .
T h e s e properties are d e s c r i b e d in details in T a b l e s
7,8, a n d 9.
Table 6
"Formvar"
Polyester
PYRE-M.L.
Filled TEFLON®
TFE-flourocarbon
Asbestos
Polyvinyl Chloride
11
85
700
4500
Failure Diameter In Inches
Forward Bend
Reverse Bend
3/4
1
1/2
3/4
O K at 1/8
O K at 1/8
1/2
1/2
1 3/4
752°F (400°C)
662°F (350°C)
572°F(300°C)
482°F(250°C)
1/2
1/2
1 3/4
Expansion
4.0x10-5'0C
5 . 5 x 10-5'oc
8-10X 10-5'oc
8.1
x 10-5'oC
5-9x
10-^'oC
Table 9
Coefficient of Thermal Conductivitv
Cal/sec/cm
PYRE-M.L
35x10-5
Silicon
35x10-5
Epoxy
5x10-5
Nylon
55x10-5
DELRIN
55x10-5
TEFLON
60x10-5
C/CM
Dependence of Properties on Degree of Cure
M a n y of the properties of wire c o a t e d with
P y r e - M . L . W i r e E n a m e l d e p e n d o n the d e g r e e to
w h i c h it is c u r e d . M a g n e t wire m a n u f a c t u r e r s a n d
u s e r s s h o u l d s e l e c t the p r o p e r d e g r e e of c u r e to give
the b a l a n c e of properties w h i c h b e s t m e e t s their
requirements.
Determining Degree of Cure
Table 7
Coefficient of Kinetic Friction
PYRE-M.L.
Graphite
T E F L O N TFE-flourocarbon
Linear Coefficient of Thermal
PYRE-M.L
T E F L O N TFE-flourocarbon
Nylon
DELRIN® acetal resin
Epoxy
0.17
0.18
0.04-0.09
The dissipation factor test is recommended for
controlling the degree of cure of wire in production, N E M A
Publication MW-1000 lists a limit of no greater than 0.006
for wire coated with Pyre-M.L. Other useful control tests
can be developed using weight loss at elevated
temperatures and crazing tendencies. These are shown in
Table 10.
Table 10
Properties of Heavy Build No. 18 (1.024mm) Wire Coated with PYRE-M.L.®
Degree of Cure
Dissipation Factor^
Dielectric Constant^
Weight Loss^
Crazing^
Crazing after
1/2hr.x150° C
Crazing after
1 hr. X 200° 0=
Flexibility^
IncomDiete
0.020
4.5
16%
Very Severe
Moderate
0.004
3.9
3%
Moderate
Thorough
0.0025
3.7
1.6%
Slight
Very Thorough
0.0015
3.2
1.3%
Very Slight
Severe
None
None
None
None
Borderline
2x
None
Passes
2x
None
Borderline
1x
None
Passes
1x
Inter-coat Adhesion
Unidirectional Scrape
Resistance (KG) (0.009")
G.E. Scrape
Dielectric Strength
Oil & Water Res.'
Flexibility
Dielectric Strength
Good
Good
Fair
Fair
_
40-70
8.5kV
1.02-1.17
15-35
12kV
1.06-1.27
20-40
11kV
1.19-1.50
25-45
11 kV
Poor
2kV
Good
7kV
Good
8.5kV
Good
5.5kV
1. Clean wires with soft clofn and bend into U shape. Dip wire in mercury. Connect one end of wire to t ge; place the other lead from the bridge in mercury. Make measurements at 25''C at 1000 cycles/sec
2. Weigh 70 grams of wire de-greased with acetone wet cloth. Bake 5 minutes at SOQ-C or 2 hours at 200''C. Cool for 2 minutes and weigh.
3. Wrap wires on 1x through 6x mandrels and dip N-methylpyrrolidone. Examine under lOx microscope. Many other solvents will give similar results.
4. As above, but bake coil for 30 minutes at 150"C before dipping in solvent.
5. Same as #4, but bake 1 hour at 200°C
6. Quick snap by NEMA Snap test and wrap on 1x and 2x mandrels.
7. Place NEMA twists in 7" (177.88mm) length of 3/4" (19.05mm) iron pipe. Add 50cc of transformer oil
and three drops of water. Seal pipe ends and age 88 hours at 200°C. Cool. Remove wires and measure dielectric strength and note flexibility.
Page 4
Comparison of Pyre-M.L. witli otlner Enamels
Table 11 (Continued)
T h e data in table 11 c o m p a r e P y r e - M . L . a n d
"Formvar" W i r e E n a m e l s a p p l i e d o n #18 C o p p e r wire.
T h e conditions u n d e r w h i c h the tests w e r e c o n d u c t e d
are defined in the footnotes. T h e results r e p r e s e n t
a v e r a g e v a l u e s for a n u m b e r of d e t e r m i n a t i o n s a n d
may vary s o m e w h a t from v a l u e s d e t e r m i n e d by other
methods.
lest
Application of P Y R E - M . L . :
Temperature^
A s mentioned before, Pyre-iVI.L. is a solution of
aromatic polyamic acid. The polyamic acid is then converted to an insoluble polyimide upon curing i.e. imidization. Water is formed during the cure.
G . E . Scrape
PYRE-M.L.
"TvDical Formvar"
15-35
60-80
scrapes
scrapes
1.3-1.5kg
1.02-1.17kg
Above 500°C
240°C.
Extractables^
Less than 0.1%
3.0-6.0%
Heat Shock^
P a s s e s to
Passes to
425°C
124°C
Poor
Fair
V. G o o d
Good
V. Good
Good
Poor
V. Good
Passes
Passes
P a s s e s 2x
P a s s e s 1x
Xylene
V. G o o d
V. Good
Cresylic Acid
V. G o o d
Poor
Carbon
V. Good
V. Good
Abrasion^
Unidirection
Scrape"
Cut Through
Solderability
Chemical
Resistance^
Material of Construction
5% Sulfuric
Pyre-M.L. Wire Enamels are weak acids, and
hence, will react with iron or mild steel. Therefore, all
equipment which come in contact with the enamel should
be made of stainless steel, polyethylene, polypropylene
or other appropriate material. The equipment include dies
used for removing excess enamel from the wire, coating
bath, rolls, reservoir for the enamel, pumps, filtration
equipment, etc. If iron is leached from the contact surface
into the enamel, the resulting dissolved iron has a detrimental effect on the enamel, and hence, the coated wire.
Acid
5% Hydrochloric
Acid
1% Potassium
Hydroxide
Quick Snap
Flexibility
Quick Snap Wind
on own diam.
...Solvent
Table 11
Resistance^
Comparison of the Initial properties of Wire Coated
with PYRE-M.L.® Wire Enamel and Another
Commercial Enamel
(applied on #18 copper wire) - 1.024mm
Tetrachloride
Naphtha
V. Good
V. Good
Test
PYRE-M.L.
"Typical Formvar"
Acetone
V. Good
V. Good
Thermal
220°c
105°c
Alcohol
V. G o o d
Good
Classification
Ethyl Acetate
V. Good
Fair
Build (diam.
0.0030 inch
0.0030 inch
Hexane
V. Good
Good
increase)
(0.076 mm)
(0.076 mm)
Transformer Oil
V. Good
Good
Crazing (solvent
P a s s e s if
Crazes, cracks
annealed
heal at150°C
Dry Dielectric
3400
2000
Strength^
volts/mil
volts/mil.
Wet Dielectric
1900
600
Strength^
volts/mil.
volts/mil.
Insulation
Infinite
Infinite
Stress)
FREON*22
Resistance^
Passes
Fails
The Pyre-M.L. described above is baked to a moderate
degree of cure.
Footnotes for Table of Initial Properties
Resistance
Dielectric
Constant
(100 cycles)^
3.9
3.71
(1000 cycles)
3.9
3.64
(100 cycles)'
0.0040
0.0275
(1000 cycles)
0.0040
0.0220
Dissipation
Factor
1. At room temperature and humidity
2. Standard NEIVIA twist. Soak in distilled water 24 hours, remove, clip loop, shake off excess water
and test.
3. Standard test, 700 grams load. At prevailing atmospheric conditions.
4. Indiana Technical College Unidirectional Scraper (0.009" needle).
5. ASTM D 1676
6. standard Soxhiet type equipment. Extraction with toluene for 12 cycles each lasting for 15
minutes followed by extraction with methanol for six cycles each lasting 20-25 minutes.
7. Wind on own diameter, then heat for one hour and examine for cracks.
8. Immerse in vanous reagents for 24 hours at room temperature. Examine for blistering, swell and
softening.
9. A. four days immersion in liquid FREON 22 at 60°C. Place in 120°C oven (immediately after
opening bomb) for 10 minutes. Observations made at 20x magnification. Mandrels of 1x, 3x, 5x
and strength all unaffected.
B. Stressed PYRE-M.L. placed in tube containing FREON and refrigerant oil. Held under pressure at 120°C. No evidence of film failure at six weeks.
+ If crazed, crazes will not heal. Annealing for 30 minutes to one hour at 175-200°C recommended.
„
Page 5
Table 12
Application Techniques
E x c e p t for the u s e of s t a i n l e s s steel or polyethylene equipment, P y r e - M . L . is a p p l i e d in m u c h the
s a m e m a n n e r a s " F o r m v a r " polyvinyl a c e t a l e n a m e l s .
T e c h n i q u e s u s e d for coating different wire s i z e s are
a s follows:
Large Size Wires
R o u n d wires larger than about N o . 12 A W G
(2.05mm or .0808 i n c h e s diameter) a n d s q u a r e a n d
rectangular wire are usually c o a t e d o n vertical o v e n s
about 24ft. (7.3 meters) high. T h e best results h a v e
been obtained o n o v e n s w h i c h h a v e f o r c e d c o n v e c tion heat (up draft in the bottom a n d d o w n draft at the
top) s u p p l e m e n t e d by radiant heating p a n e l s n e a r the
bottom of the o v e n . A c c e p t a b l e wire c a n be p r o d u c e d
with other t y p e s of o v e n s .
T h e o p t i m u m o v e n operating t e m p e r a t u r e s
will have to be d e t e r m i n e d o n e a c h o v e n , but in a
two z o n e o v e n a bottom z o n e t e m p e r a t u r e of about
650°F (343°C) a n d a top z o n e t e m p e r a t u r e of a b o u t
900°F (482°C) will probably allow the most e c o n o m i cal coating s p e e d s . If a radiant p a n e l is u s e d , a p a n e l
temperature of 1000° F (538°C) h a s b e e n f o u n d to b e
best. Excellent a d h e s i o n h a s b e e n o b t a i n e d by curing the e n a m e l u n d e r t h e s e conditions to a d i s s i p a t i o n
factor of 0.002 at 1000 c y c l e s .
T h e d i e s u s e d for s q u a r e a n d r e c t a n g u l a r wire
should be m a d e of s t a i n l e s s steel. D i e s of a n y type
of design w h i c h h a v e g i v e n satisfactory results with
polyvinyl acetal type e n a m e l s will p r o b a b l y b e s a t isfactory for P y r e - M . L . , if they are m a d e of s t a i n l e s s
steel.
T h e two c o m m o n p r o b l e m s w h i c h h a v e b e e n
encountered in coating rectangular wire a r e lack of
a d h e s i o n a n d s m o o t h n e s s . A d h e s i o n is controlled
by the temperature at w h i c h the e n a m e l is c u r e d a n d
the d e g r e e of c u r e . A d h e s i o n is usually i m p r o v e d by
increasing wire metal t e m p e r a t u r e n e a r the bottom
of the o v e n . R a d i a n t heating p a n e l s are particularly
useful for improving a d h e s i o n . S m o o t h n e s s c a n be
improved by adjusting the die s i z e s or by slight r e d u c tions in the viscosity of the e n a m e l with N - m e t h y l - 2 -pyrrolidone. T h e o p t i m u m v i s c o s i t y will u s u a l l y be
the minimum viscosity w h i c h g i v e s a d e q u a t e c o r n e r
coverage.
Feet from
Bottom
A t y p i c a l o v e n pattern for a n 18ft. (5.5 meter)
laboratory vertical o v e n is d e s c r i b e s in Table 12.
Meters from
Bottom
Temp.,
"C
225
260
310
460
570
585
600
700
725
.3
.9
1.7
2.3
3.0
3.7
4.3
5.0
5.7
107
127
154
238
299
307
316
371
385
1
3
5
7
9
11
13
15
17
T h e o p t i m u m heat pattern for a n y particular
o v e n m u s t b e f o u n d experimentally. In g e n e r a l , the
b e s t results are o b t a i n e d by adjusting the temperature
in the bottom z o n e of the o v e n c o o l e n o u g h to prevent i m m e d i a t e blistering, but not e n o u g h to e v a p o rate sufficient s o l v e n t to p r e v e n t blistering in the top
z o n e . T h e top z o n e t e m p e r a t u r e is a d j u s t e d to give
adequate cure.
Fine Wires
P y r e - M . L . is u s u a l l y a p p l i e d to w i r e s s m a l l e r
then N o . 2 8 (0.0126 inch or 0 . 3 2 m m in diameter) o n
horizontal m a c h i n e s u s i n g s t a i n l e s s s t e e l roller d i e s .
To obtain s m o o t h wire it is u s u a l l y d e s i r a b l e to
dry p a s s fine wire o n c e through the o v e n before a p plying a n y e n a m e l . T h i s h e l p s r e m o v e a n y oil or dirt.
If n e c e s s a r y , P y r e - M . L . c a n b e r e d u c e d a b o u t 1 0 %
with either N M P or A r o m a t i c H y d r o c a r b o n for a p p l i c a tion to fine wire. T h e s o l v e n t s h o u l d b e a d d e d slowly
with g o o d agitation.
D e g r e e of C u r e
T h r e e round wire s a m p l e s w e r e c o a t e d u n d e r
different c o n d i t i o n s with a n 18ft. L . M . m a c h i n e . T h e
first s a m p l e is b a d l y u n d e r b a k e d , the d i s s i p a t i o n f a c tor is . 0 2 3 a n d the l o s s in w e i g h t of the c o a t e d wire
is 1 9 . 1 % of the w e i g h t of the c o a t i n g w h e n h e a t e d
for five m i n u t e s at 3 0 0 ° C . T h e s e c o n d s a m p l e is
c u r e d to the d e g r e e typical of m u c h of the c o m m e r c i a l
p o l y m i d e c o a t e d wire. T h e third s a m p l e is well c u r e d .
T h e results are d e s c r i b e d in T a b l e 13.
Table 13
Curing PYRE-M.L.
Medium Size Wires
W i r e s from about N o . 13 (0.072 inch or
1.83mm in diameter) to about N o . 2 8 (0.0126 inch or
0.32mm in diameter) are c o a t e d on either horizontal
or vertical m a c h i n e s . P h o s p h o r b r o n z e a n d s t a i n l e s s
steel dies are being u s e d c o m m e r c i a l l y .
Temp.,
»F
Temp.
°C
Speed
Ft/MIn
D.F.
at10^c.p.s.
Weight L o s s
5min at 300°C
55/315
55/370
135/515
35
25
25
.023
.004
.0015
19.1%
2.9%
1.4%
Page 6
T h e dissipation factor is related to the e n ergy n e c e s s a r y to realign the polar g r o u p s o n the
m o l e c u l e s e a c h time the field c h a n g e s . C h a n g e s in
dissipation factor therefore reflect the l o s s of c a r b o x y l
groups, a m i d e g r o u p s , w a t e r a n d N-methyl pyrrolidone during c u r e . D i s s i p a t i o n factor is the m o s t
precise w a y w e l<now for m e a s u r i n g d e g r e e of c u r e .
M a n d r e l w r a p test after q u i c k s n a p illustrate
the d e p e n d e n c e of flexibility o n d e g r e e c u r e . In c o n trast to most e n a m e l s , P y r e - M . L . h a s better flexibility
w h e n thoroughly c u r e d than w h e n u n d e r c u r e d . T h e y
are s h o w n in Table 14.
Temperature °C
Bottom
Top
310
315
315
315
315
465
465
465
465
488
Panel
Radiant
Speed
Ft./Min
Off
427
427
482
482
9
9
7
7
7
D.F. at
10^cps Adhesion
.0022
.0018
.0019
.0015
.0017
poor
poor
fair
fair
good
The most common types of ovens used for rectangular Pyre-M.L. coated wire have forced air convection
heat which is updraft in the bottom section of the oven
and down draft in the top section. The convection heat is
supplemented by electrically heated radiant panels near
the bottom of the oven. The solvents are catalytically
burned in the air stream after it has passed through the
bottom section of the oven.
Flexibility No. 18 AWG Wire
Snap & Wrap
.02
.004
.0015
Adhesion to No. 3 Square Wire
Recirculating G a s Ovens
Table 14
D.F. at 1000 c.p.s.
Table 16
2X-3X
2X
IX-2X
P a n e l s w e r e p r e p a r e d by c a s t i n g films (0.8-1.0
mils dry) o n a 22mil thick c o p p e r p a n e l . A l l p a n e l s
initially b a k e d at 10 minutes at 150°C to r e m o v e s o l vents before being g i v e n the b a k e a b o v e . A d h e s i o n
w a s tested with a s h a r p knife.
T h e a d h e s i o n to c o p p e r is a function of the
temperature of c u r e . E v e n u n d e r c u r e d P y r e - M . L .
c a n h a v e g o o d a d h e s i o n if it is b a k e d at a high t e m perature. All of t h e s e w i r e s h a v e thoroughly c u r e d
coatings, but the a d h e s i o n is i n f l u e n c e d by both the
d e g r e e a n d the temperature of c u r e .
S u b s e q u e n t e x p e r i m e n t s h a v e s h o w n that
radiant panel t e m p e r a t u r e s in the r a n g e of 5 3 8 ° C 593°C are e v e n better than the 4 8 2 ° C t e m p e r a t u r e
used above.
A d h e s i o n w a s d e t e r m i n e d after e l o n g a t i o n to
break, elongation of 3 0 % , a n d b e n d i n g o n a 1" m a n drel. All three tests g a v e identical results. V a r i o u s
a d h e s i o n results are s h o w n in T a b l e s 15 a n d 16.
Table 15
Data from a number of trial runs and demonstrations are shown in Tables 17 & 18. In several cases these
do not represent the optimum production conditions, but
rather the first set of conditions we could find to produce
acceptable wire.
All of the conditions shown in this table produced
wire with good inter-coat adhesion and adhesion to copper. For wire between 0.114 and 0.500 inch wide, between
.096 and .229 inch thick and having a cross-sectional area
between 1.3 x 10* square mils, the approximate speed is
given by the following expression:
Speed (ft./min.) =
4x10=
cross section area
(sq. mils)
Corner Coverage
Conventional universal wire enamel dies deposit
excessive enamel at the corners. The ideal combination
enamel and coating conditions allow just the right amount
of flow to leave the same thickness of enamel on the corners as there is on the flat surface, excessive flow leaves
the corners thin.
Adiiesion to Panels
Minutes
0.5
1.0
2.0
5.0
2.0
8.0
20.0
Temperature
Adhesion
D.F.
400°C
Excellent
.017
.007
.004
.003
.06
.02
.011
200°C
Poor
Insufficient
Flow
Ideal
Flow
Excessive
Flow
Insufficient flow ("dog bone") can be corrected by
lowering the viscosity, by decreasing the volatility of the
solvents and thinners, by decreasing the temperature in the
bottom oven, or by decreasing speed.
Page 7
Table 17
Table 19
Radiantly Heated Ovens
Overload Resistance
(NEMA Method)
The data below show conditions used on three
radiantly heated ovens.
Oven Type
2 Ft/10=
Polyimide
13.70-17.70
TeslLl
Test 2
TestJ
Polyamide-imide
8.06-10.01
electric
indirect
electric
Polyester
3.34 - 5.87
Formvar
2.27 - 6.31
2.85 - 5.48
gas
Oven Might
20 ft.
20 ft.
10 ft.
Nylon/Formvar
3ft
-
.
3100C
Selected data from:
5 ft.
-
313°C
-
6 ft.
288°C
-
400"C
10 ft.
343°C
432°C
377°C
15 ft.
400°C
466°C
x
-
493°C
x
.040 X .
.200
10.5
098 x
.300
10
.070 X
.190
4.5
8
6
10
3.2
2.5
4.5
Temperature
17 ft.
Wire Size
Speed (ft./min.)
No. of Coats
Build-width
(mils)
5.7
Build-thickness
(mils.)
Dielectric
Table 20
Overload Resistance
(Essex Method)
Minutes
5.5
8.0
30 amp.
3.5....amp
>5
1.32
Polyvinyl Formal
1.57
.83
Nylon/Formal
1.70
.90
Polyester
1.75
.90
Nylon/Polyester
1.06
Polyimide
4.1
4.0
8.0
"Overload Test" by W. W.Pendleton of Anaconda Wire &
Cable given at N E M A Magnet Wire Committee Presentation, Insulation Conference, Chicago, October 17,1967.
Polyester-imide
1.70
.92
Strength (kv)
Amide-imide/
2.50
1.08
Type of Dies
Polyester
Enamel Code
cone
universal
universe
RC-5057
RC-5019
RC-501
52
63
Viscosity
(poises)
Selected data from;
"Magnet Wire Temperature at Overload Conditions" by
E.W. Daszewski of Essex Wire Corperation, Proceeding of
Seventh El Conference, p. 137.
28
Table 18
Production Trials Recirculating Gas Ovens Rectangular Wire
Wire Sizes
(Inches)
.229 X
.100 X
.114 X
.229 X
.114x
.096 X
.170 X
.060 X
.170 X
.140 X
.229
.500
.228
.229
.114
.229
.270
.210
.250
.280
Area
Sq. Mils.
x10*
Speed
Ft./
Min.
Coats
5.23
5.00
2.60
5.23
1.30
2.87
4.59
1.26
4.24
3.92
7
8-1/2
10
7
11-V2
13-1/2
8
16
8
11
6
6
6
6
6
8
8
4
8
8
Build
Thickness
Build
Width
Bottom
Air°C
Top
Air°C
Radiant
Panel
°C
Viscosity
at 25°C
3.8
4.4
4
2.6
4.5
4.5
5.0
5.0
2.0
5.0
5.0
5.0
4.0
316
316
316
316
316
343
280
232
277
277
488
488
488
482
482
493
480
538
450
450
482
482
455
455
455
565
470
577
550
550
60
60
30
30
30
12
60
32
14
14
-
-
-
2.0
6/5
-
Dielectric
strength
(KV)
6.5
5.0
-
7.5
5.2
3.5
7.3
3.5
4.0
Pages
;
F l o w is a l s o controlled by the c r o s s s e c t i o n of
the bare copper. T h e greater the radius of the corner,
the l e s s the t e n d e n c y to flow a w a y from it. S h a r p corners, burrs, a n d abrupt c h a n g e s in curvature are hard
to coat.
Enamel Circulation and Application
:
i
i
P y r e - M . L . wire e n a m e l s h o u l d b e p u m p e d ,
filtered a n d recirculated with a n all s t a i n l e s s s t e e l
s y s t e m . C o n t a m i n a t i o n with iron c a n l e a d to g e l a tion, rough wire a n d d e c r e a s e d t h e r m a l stability of the
coated wire.
k
I
i
I
T h e most c o m m o n d i e s a r e s t a i n l e s s steel
m o d e l s of the universal g r o o v e d pin d i e s . T h e d i s c
type of die c o v e r e d by G . E.'s patent # 2 , 8 7 5 , 7 2 5 is
a l s o u s e d in production.
:
;
!
[
j
[
!
O u r e x p e r i e n c e h a s b e e n that the preferred
groove s i z e is 15 mils. If the width of the wire is m o r e
than three times the t h i c k n e s s it m a y be n e c e s s a r y to
limit the build on the e d g e s by using g r o o v e - l e s s die
pins on the e d g e s on s o m e of the c o a t s . T h i s s h o u l d
not be don on the first coat. A n i n c r e a s e in both width
and t h i c k n e s s of at least 0.5 mils is preferred o n the
first coat to promote g o o d a d h e s i o n a n d prevent o x i dation of the copper.
Smoothness
O c c a s i o n a l l y o n e e n c o u n t e r s a ripple or "ora n g e p e e l " in the s u r f a c e of the e n a m e l w h e r e o n e or
more of the d i e s is applying a thick film. T h i s s o m e times results in periodic "globs" or e v e n blisters at or
near the c o r n e r s . T h i s c a n be c o r r e c t e d by r e d u c i n g
the film t h i c k n e s s with s m a l l e r die g r o o v e s , r e d u c i n g
the surface t e n s i o n with "flow agent" or h y d r o c a r b o n
thinners, or by lowering the viscosity.
Streaks
C o n v e n t i o n a l d i e s a p p l y e n a m e l in s t r e a k s . If
the e n a m e l d o e s not flow to a uniform film o n the first
coat, there will be s t r e a k s c a u s e d by the oxidation
of the c o p p e r w h e r e the first c o a t is thin. W i t h r e l a tively transparent e n a m e l s , this streak a p p e a r a n c e
is not hidden by the s u b s e q u e n t c o a t s . It is not c l e a r
whether the objection to t h e s e s t r e a k s is b a s e d o n
engineering or aesthetic r e a s o n s , but they a r e difficult
to correct without a b a n d o n i n g the c o n v e n i e n c e of
universal d i e s .
With conventional d i e s , the s t r e a k s c a n b e
minimized, but usually not e l i m i n a t e d , by r e d u c i n g the
viscosity a n d a p p l y i n g a full wet c o a t o n the first p a s s .
Blistering
Blistering is generally due to insufficient heat or
too much heat in the bottom of the oven. It is, of course,
a function of film thickness, any condition such as excessive corner coverage, rippling, irregular jerking of the wire,
excessive variation, etc. which causes localized areas of
excessive film thickness will exaggerate blistering.
Ovens which lack heat capacity in their bottom
section can usually be run faster with RC-5069, which
contains a fairly volatile hydrocarbon diluent than with the
pure N-methyl pyrrolidone type enamel such as RC-5019.
In contrast, short ovens with plenty of bottom zone heat
capacity will run fastest with RC-5019.
Blistering is caused much more readily by convection heat, which skins over the wet film, than by radiant
heat, which tends to heat from the metal.
Curing blistering is usually easy if one is willing to
accept slower coating speeds. Otherwise it involves the
careful selection of the solvents and oven pattern to optimize speed. On modern, high-heat capacity equipment,
blistering will ultimately limit the speed.
Precipitation
If the polyamic acid polymer in Pyre-M.L. is cured
to the polyimide before sufficient solvent is evaporated to
lead to film formation, the polyimide will precipitate from
solution as a yellow powder. This is frequently encountered when one attempts to cure thick films rapidly. When
encountered, it is usually caused by excessive heat at the
bottom of the oven. A s with blistering, this phenomenon is
a function of thickness, and it is exaggerated by poor flow,
jerky wire movement, and vibrations which lead to localized
thick films.
Pyre-M.L. tends to craze or crack when coated
wire is first bent and then dipped in solvent or varnish. This
tendency is dependent on the degree of cure. Crazing
may be prevented by stress relieving the enamel with heat
after the wire is bent or wound into a coil. We recommend
stress relief for all coils before varnishing or de-greasing.
S e e Table 21.
Table 21
Solvent Crazing
Stress Relief
D.F.
atlO^c.p.s.
.01
.004
.002
_
None
30 min./
150° C
60 min./
220° C
Severe
Moderate
Slight
Slight
None
None
None
None
None
Page 9
TEST
Varnishing Magnet Wire Coated with P Y R E - M . L .
Twisted pairs of 18HIVIL s e a l e d in iron pipe
with 50g of 1 0 C oil a n d 3 d r o p s of w a t e r for 88 h o u r s
at 200°C. Twists tested i m m e d i a t e l y for r e m o v a l .
Pyre-M.L. Insulating Varnishes RK-692 is recommended for use with magnet wire coated with Pyre-M.L.
(See Bulletin ML-2 95) This varnish has outstanding
thermal stability and mechanical and electrical properties.
They maintain their strength and electrical properties at
temperatures above 250°C.
Oil filled transformers normally o p e r a t e b e l o w
150°C. T h i s is a n a c c e l e r a t e d s c r e e n i n g test to s e l e c t
materials or further evaluation in t r a n s f o r m e r i n s u l a tion s y s t e m s . T h o r o u g h c u r e i m p r o v e s oil a n d w a t e r
resistance. T h e results a r e s h o w n in T a b l e s 2 2 a n d
23.
Table 22
Cure vs. Oil & Water Resistance
D.F.
at lO^c.p.s.
Dielectric Strength (KV^
Initial
Final
.01
.004
.002
9.3
11.5
10.8
2.4
7.0
8.5
Table 23
Transformer Fluid Resistance
Varnished Twists
18 HML
PYRE-M.L
10.0 K V
9.2 K V
11.2 K V
Oil
Oil & Water
Askeral
VARNISH "X"
12.2 K V
8.3 K V
10.2 K V
T h i s wire had a dissipation factor of a b o u t
.004 before v a r n i s h i n g . Test c o n d u c t e d a s a b o v e .
Major Advantages of P Y R E - M . L . :
T h e r m a l Stability
Overload Resistance
C h e m i c a l Inertness e x c e p t alkali
Radiation Resistance
Uses for P Y R E - M . L . :
Transformers
Hermetic Motors
Traction Motors
Appliances
P o w e r Tools
Mine Motors
Aircraft W i r e
Aerospace Wire
G a s Chromatograph Capillaries
Semi Conductor Coating
Alignment Coating
Instrument/Sensor Wire Coating
Insulating systems employing wire coated with
Pyre-M.L. with certain silicone, epoxy, and phenolic varnishes are in commercial use and are giving satisfactory
results. Certain commercially available varnishes degrade
the thermal stability of wire coated with Pyre-M.L. according to laboratory results. All systems should be thoroughly
tested before commercial use.
Wire coated with Pyre-M.L. should be heated for
30 minutes to one hour at 175°C to 200°C after winding
and before varnishing to relieve stresses in the film and
to prevent crazing of the wire enamel by the varnishing
solvents.
Safety and Handling Procedures
While we are not aware of any health problems
attributed to the use of this and related products during the
past 20 years, good industrial hygiene should be practiced.
Pyre-M.L. wire enamels and varnishes should be handled
in well-ventilated areas, eye contact must be prevented,
and skin contact should be minimized.
The TLV for Xylene is 10Oppm (ACGIH). If ventilation is not adequate to maintain work place air concentrations below this level, N I O S H / M S H A approved respirators
should be worn. Eye protection and Neoprene gloves
should be used.
Animal tests have shown that these materials are
only slightly toxic when ingested. They do cause skin irritation after prolonged or repeated contact, and any inadvertent skin contamination should be promptly washed off with
water. In the event of eye contact, flush immediately with
water for 15 minutes and s e e a physician.
The solvents typically used with Pyre-M.L. are
extremely flammable and must be kept away from sparks,
open flame, or other sources of ignition. Although we have
not run tests, we would predict the by-products of combustion would be toxic by inhalation.
Waste disposal of Pyre-M.L. should be carried out
in an E P A approved incinerator. Under these conditions,
there is enough oxygen present that toxic by-products are
minimized. The disposal of Pyre-M.L. must comply with
Local, State and Federal regulations.
F D A Status
Pyre-M.L. products are not F D A approved. I.S.T.
neither warranties these products nor sanctions their usage
in medical applications unless explicitly approved.
Page 10
ustrial Summit Technology
Technical Bulletin #ML-2-95
Industrial S u m m i t Technology • Parlin, N e w J e r s e y 0 8 8 5 9
PYRE-M.L. INSULATING VARNISH - RK-692
Introduction
P y r e - M . L . products a r e part of a family of m a terials b a s e d o n a r o m a t i c p o l y i m i d e s w h i c h a r e o n e
of the most thermally stable o r g a n i c m a t e r i a l s . T h e s e
products include P y r e - M . L . W i r e E n a m e l s , P y r e - M . L .
Liquid " H " E n a m e l s , P y r e - M . L . Insulating V a r n i s h , a n d
P y r e - M . L . Thinner. Table 1 ( s e e p a g e 1) d e s c r i b e s
these products, a s s o c i a t e d c o d e / g r a d e , a n d M L T e c h nical Bulletin number.
Table 24
PYRE-M.L. PRODUCTS SPECIFICATION
Code
Solids (%)(1)
RK-692
11.5-12.5
Viscosity
6-10
(Poise) (2)
Solvent System
R K - 6 9 2 is a high temperature v a r n i s h d e v e l o p e d for u s e in conjunction with P y r e - M . L . e n a m eled wire. It is a solution of a r o m a t i c p o l y a m i c a c i d in
N-methyl pyrrolidone. T h e p o l y a m i c a c i d is p r o d u c e d
by reacting the a r o m a t i c d i a m i n e with the a r o m a t i c
dianhydride. T h e application p r o c e s s i n v o l v e s drying
of the solvent from the solution followed by curing a n d
baking of the p o l y a m i c a c i d left b e h i n d . During the
latter p r o c e s s , water is r e m o v e d , a n d the p o l y a m i c
acid turns into p o l y m i d e film. T h e film s o f o r m e d is
m e c h a n i c a l l y tough, c h e m i c a l l y inert, thermally s t a b l e ,
and radiation a n d c r y o g e n i c resistant. It a l s o h a s
excellent electrical insulating properties w h i c h r e m a i n
essentially u n c h a n g e d o v e r a w i d e r a n g e of t e m p e r a tures for e x t e n d e d time p e r i o d s . R e f e r to T e c h . B u l l e tin M L - 1 - 9 5 for a detailed d e s c r i p t i o n of t h e s e properties. P y r e - M . L . products a r e U.L.® a p p r o v e d .
Product Properties
N M P (%)
Xylene (%)
15-25
Density
LBS/Gal
(+/-0.05)
8.59
KGS/Gal
(+/-0.023)
3.90
Note - (1) N E M A Test Method - 2gm/2hr. /200°C B a k e
(2) Measured at 25°C with Brookfield Viscometer #3 Spindle @ 12 R P M .
B. Dried F i l m
T h e major properties of the v a r n i s h e d film a r e d e s c r i b e d below:
(1)
Thermal Stability - excellent
Expected life at 220°C over 100,000 hours
Expected life at 240°C over 25,000 hours
Expected life at 300°C over 1,000 hours
(2)
Electrical properties - excellent from -250°C to +250°C
temperature. Electric strength exceeds 3000 volts per
mil dry, and 1500 volts per mil when wet. It remains
essentially the same over this entire temperature range.
Dissipation factor (about .003 at 100 cycles at room temperature) increases only slightly and dielectric constant
(about 3.8 at 100 cycles at room temperature) actually
drops as the temperature is raised to 300°C. Insulation
resistance is infinite when dry and 5x10^ megahms after
boiling 10 minutes in water
A . Liquid V a r n i s h :
P y r e - M . L . V a r n i s h is a c o a t i n g solution w h i c h
is converted into polyimide film by the a p p l i c a t o r s .
T h e s e product p r o p e r t i e s / s p e c i f i c a t i o n s a r e d e s c r i b e d
in Table 2 4 . T h e s e meet the c o m m e r c i a l a n d military
specifications required by the industry.
75-85
Page 11
Radiation R e s i s t a n c e - v e r y g o o d .
( E x p o s u r e to 3 , 0 0 0 m e g a r a d s of e l e c t r o n s
c a u s e d only minor cinanges in electrical a n d
physical properties.)
R e p r e s e n t a t i v e v a l u e s for thermal conductivity
are:
PYRE-M.L.
Silicone
Epoxy
TEFLON®
fluorocarbon
35 X ^Q-^ c a l / ( s e c ) (Cm^) ( ° C / C M )
3 5 X 10-^ c a l / ( s e c ) (Cm^) ( ° C / C M )
5 X 1 0 - 5 c a l / ( s e c ) (Cm^) ( ° C / C M )
6 0 X 1Q-' c a l / ( s e c ) (Cm^) ( ° C / C M )
S t o r a g e in a n u n h e a t e d building m a y b e
a c c e p t a b l e w h e r e winters a r e c o l d . V i s c o s i t y m e a s u r e m e n t s a r e strongly affected by t e m p e r a t u r e .
S e e G r a p h N o . 2 ( p a g e 2) for t e m p e r a t u r e - v i s c o s i t y
c o n v e r s i o n . Refrigeration is highly r e c o m m e n d e d for
l o n g e r s h e l f life.
M o i s t u r e c o n t a m i n a t i o n h a s a detrimental
effect o n v i s c o s i t y stability a n d m u s t b e a v o i d e d . A l low all chilled c o n t a i n e r s to r e a c h r o o m temperature
before o p e n i n g to a v o i d w a t e r c o n d e n s a t i o n .
Table 25
(5)
(6)
L i n e a r coefficient of thermal e x p a n s i o n :
PYRE-M.L.
4X105/°C
TEFLON®
5.6X105/°C
Epoxy
5to9X105/°C
Coefficient of K i n e t i c friction:
PYRE-M.L.
0.17
Graphite
0.18
TEFLON
0.04 to 0.09
(7)
S o l v e n t a n d Oil R e s i s t a n c e - e x c e l l e n t
(8)
Flame Resistance - excellent
(The dried film will not p r o p a g a t e f l a m e a l though the v a r n i s h s o l v e n t s a r e f l a m m a b l e . )
(9)
B o n d Strength by helical coil m e t h o d o n
PYRE-M.L.:
25°C
125°C
150°C
200°C
300°C
(10)
after 4 w e e k s
6
6
6
6
3
to
to
to
to
to
8
8
8
8
5
lbs.
lbs.
lbs.
lbs.
lbs.
Weight Loss:
300°C
after 3 w e e k s
1%
C . Properties of R K - 6 9 2 V a r n i s h a r e a s indicated in
Table 2 5 .
Viscosity Stability
Insulating Varnish Properties
Physical Properties
RK-692
Elongation at 25°C
10-25%
Tensile Strength at 25°C
(lO^psi)
15
Weight Loss
50 hours at 300°C
150 hours at300°C
3.3 hours at 400°C
3.3 hours at 450°C
1%
1%
11%
20%
Bond Strength (lbs.)*
Initial at 25°C
Initial at 180°C
at 25°C after 2 wks. at 300°C
at 180°C after 2 wks. at 300°C
at 25°C after 4 wks. at 300°C
at 25°C after 3 wks. at 260°C
at 180°C after 3 wks. at 260°C
6-9
6-8
3-5
5-7
3-5
Temp, up to which dissipation factor
is essentially constant
300°C
Temp, at start of decomposition
in air by thermal gravimetiric analysis
(12°C/min. rate of rise)
540550°C
Film thickness applied per coat
(panel dipped at 4 in/min at 25°C)
(in mils)
1.0
Dielectric Constant (25°C 100 cps)
3.5
Dielectric Strength (kV/mil)
4.0
Viscosity, a s m a n u f a c t u r e d , is not s t a b l e but
gradually d r o p s by 3 5 % , a n d then i n c r e a s e s to g e l .
Gelation o c c u r s in a p p r o x i m a t e l y 14 d a y s at 120°F
(49°C), 30 d a y s at 100°F (38°C), a n d 9 0 d a y s at
77°F (25°C). At 4 0 ° F (4°C), it will not gel in o n e year.
P y r e - M . L . is stored a t 4 0 ° F in the P y r e - M . L . m a n u f a c turing plant w a r e h o u s e in Parlin, N e w J e r s e y , U S A .
Page 12
Process
Small Servo Units
Application Procedure
P r e h e a t the w o u n d unit 1/2 hour or l o n g e r at
175° to 2 0 0 ° C to relieve s t r e s s e s that m a y h a v e b e e n
d e v e l o p e d in the P y r e - M . L . e n a m e l o n the wire during
winding.
Pyre-M.L. Varnish may be successfully a p plied by b r u s h , v a c u u m i m p r e g n a t i o n , total i m m e r sion, end turn dipping, a n d roll o v e r m e t h o d s d e p e n d ing on the s i z e of e q u i p m e n t b e i n g v a r n i s h e d a n d
customer preference.
S t a i n l e s s steel e q u i p m e n t is r e c o m m e n d e d ,
but inert or polyethylene plastic type lining of c o n t a i n ers will suffice.
T h e key to the s u c c e s s f u l u s e of P y r e - M . L .
V a r n i s h is to r e m o v e the s o l v e n t before p o l y m e r c o n v e r s i o n . Insufficient solvent r e m o v a l c a n be d e t e c t e d
after the fact by the p r e s e n c e of o p a q u e y e l l o w film
or yellow powder. T h i s m e a n s that the p o l y m e r w a s
converted to its final insoluble, infusible form before
the formation of a film. A d e q u a t e film formation t a k e s
place only by the e v a p o r a t i o n of the s o l v e n t from a
solution of the u n c o n v e r t e d polymer.
1.
2.
3.
4.
5.
6.
7.
1.
2.
3.
4.
5.
S o l v e n t r e m o v a l will b e facilitated by the u s e
of well ventilated, f o r c e d c o n v e c t i o n o v e n s .
6.
B e s t results are o b t a i n e d by p r e h e a t i n g the
units before v a r n i s h i n g a n d allowing the heat form the
m a s s to drive off most of the s o l v e n t before s u b j e c t i n g
the unit to further b a k e s in the 100°C - 1 5 0 ° C r a n g e
and final b a k e s at 2 1 5 ° C - 2 3 0 ° C .
R e d u c e o n e part R K - 6 9 2 with 2-3 parts
T-8585 Solvent.
P r e h e a t unit to 175°C - 2 0 0 ° C to relieve
stresses.
C o o l to b e l o w 150°C.
I m m e r s e w h i l e hot in v a r n i s h until bubbling
s t o p s ( a p p r o x i m a t e l y o n e minute).
Drain a n d a l l o w s o l v e n t to f l a s h . H o l d for 15
m i n u t e s after all e v i d e n c e of s o l v e n t flashing is
no l o n g e r v i s i b l e .
B a k e 1 h o u r at 100°C.
B a k e 1 h o u r at 150°C - R e - d i p for o n e minute
if n e c e s s a r y after 1 5 0 ° C b a k e . R e p e a t s t e p s
4 , 5, a n d 6.
B a k e 1 h o u r at 2 1 5 ° C or higher.
P r e h e a t unit to 1 7 5 ° C - 2 0 0 ° C to relieve
s t r e s s e s , t h e n c o o l to b e l o w 150°C.
I m m e r s e w h i l e hot in v a r n i s h until bubbling
s t o p s ( a p p r o x i m a t e l y 3-5 minutes).
D r a i n a n d a l l o w s o l v e n t to f l a s h . H o l d for at
least 1/2 h o u r after all e v i d e n c e of s o l v e n t
f l a s h i n g is n o l o n g e r v i s i b l e .
B a k e 2 h o u r s at 100°C.
B a k e 2 h o u r s at 150°C - R e d i p for o n e minute
if n e c e s s a r y after 1 5 0 ° C b a k e . R e p e a t s t e p s
3, 4 , a n d 5.
B a k e 2 h o u r s at 2 1 5 ° C or higher.
T h e 1 0 0 ° C b a k e m a y b e e l i m i n a t e d if w i n d i n g s
are not tight.
W h e n P y r e - M . L . e n a m e l e d c o n d u c t o r s are
present in the unit being v a r n i s h e d , the w i n d i n g s
s t r e s s e s s h o u l d be relieved by a n n e a l i n g the c o n d u c tors at t e m p e r a t u r e s of 175°C to 2 0 0 ° C for at least 1/2
hour.
1.
2.
3.
If units are being v a r n i s h e d by m e a n s other
than total i m m e r s i o n or e n d turn d i p p i n g , for e x a m p l e
spraying, temperature of the v a r n i s h e d unit s h o u l d be
limited to b e l o w 100°C to prevent b u b b l i n g of the film.
Units of sufficient m a s s to provide 9 0 ° C - 100°C heat
removal from v a r n i s h will tend to b e c o m e t a c k free in
a relatively short time.
4.
5.
P r e h e a t to 1 7 5 ° C - 2 0 0 ° C to relieve s t r e s s e s .
C o o l d o w n to 1 0 0 ° C .
R o l l o v e r in v a r n i s h at a p p r o x i m a t e l y 5-1 Orpm
for five m i n u t e s . D r o p or r e m o v e p a n from
h e a t radiating from unit. C o n t i n u e rotating unit
until t a c k free.
B a k e 3 h o u r s at 150°C.
B a k e 2 h o u r s at 2 1 5 ° C or higher.
In a c o n t i n u o u s o p e r a t i o n , the P y r e - M . L . V a r n i s h in
the t a n k s s h o u l d b e m a i n t a i n e d at a t e m p e r a t u r e
w h i c h will i n s u r e stability with relationship to c o n s u m p t i o n or the addition of f r e s h material. In s o m e
c a s e s cooling may be necessary.
Typical cure p r o c e d u r e s for units e m p l o y i n g
the P y r e - M . L . s y s t e m - conductor, c o a t e d fabric a n d
varnish are a s follows: A l l t e m p e r a t u r e s are metal
temperatures. T h e length of time required to get the
unit to temperature must be c o n s i d e r e d .
Page 13
With periodic v a r n i s h a p p l i c a t i o n s , a r r a n g e ments s h o u l d be m a d e to s e a l up a n d store the v a r nish under refrigeration while not in u s e ( s e e " V i s c o s ity Stability").
to maintain w o r k p l a c e air c o n c e n t r a t i o n s b e l o w t h e s e
levels, N I O S H / M S H A a p p r o v e d respirators s h o u l d be
w o r n . E y e protection a n d N e o p r e n e g l o v e s s h o u l d be
used.
P y r e - M . L . V a r n i s h m a y be a p p l i e d to s u r f a c e s
by spray, dip, roller coat, or b r u s h . O n e s p r a y c o a t
will give a p p r o x i m a t e l y 0.2 mil (0.0051 m m ) dry film.
If heavier films are d e s i r e d , t h e s e m a y b e a p p l i e d by
multiple coats with a 5 to 15 minute b a k e at 150°C
between c o a t s to r e m o v e solvent. W h e n d e s i r e d
thickness is o b t a i n e d , the w h o l e structure c a n b e
given the final high temperature b a k e n e c e s s a r y for
conversion to polyimide.
A n i m a l tests h a v e s h o w n that t h e s e materials
are only slightly toxic w h e n i n g e s t e d . T h e y d o c a u s e
s k i n irritation after p r o l o n g e d or r e p e a t e d contact, a n d
a n y inadvertent s k i n c o n t a m i n a t i o n s h o u l d b e
promptly w a s h e d off with water. In the e v e n t of e y e
contact, flush i m m e d i a t e l y with w a t e r for 15 minutes
and s e e a physician.
Film t h i c k n e s s of 0.5 mil (0.0127 m m ) per c o a t
m a y be applied by dip, roll coat, or brush with little
or no thinning. Multiple c o a t s m a y b e a p p l i e d with
complete solvent r e m o v a l b e t w e e n c o a t s at 100°C to
150°C for 5 to 15 minutes. A final high t e m p e r a t u r e
cure m a y then be g i v e n the c o m p l e t e film.
These suggested baking equivalents m a y be
u s e d a s a guide for determining the c u r e b a k e o n
P y r e - M . L . coating:
6 0 minutes
3 minutes
1 minute
at 2 0 0 ° 0
at 300° C
at 4 0 0 ° 0
T h e s e b a k e s represent minimum c u r e . A n a d e q u a t e
baking s c h e d u l e for a particular application s h o u l d b e
determined by experiment.
T h e s o l v e n t s typically u s e d with P y r e - M . L .
are e x t r e m e l y f l a m m a b l e a n d must b e kept a w a y
from s p a r k s , o p e n f l a m e , or other s o u r c e s of ignition.
A l t h o u g h w e h a v e not run tests, w e w o u l d predict the
b y - p r o d u c t s of c o m b u s t i o n w o u l d b e toxic by i n h a l a tion.
W a s t e d i s p o s a l of P y r e - M . L . s h o u l d be c a r ried out in a n E P A a p p r o v e d incinerator. U n d e r t h e s e
c o n d i t i o n s , there is e n o u g h o x y g e n present that toxic
b y - p r o d u c t s are m i n i m i z e d . T h e d i s p o s a l of P y r e M . L . m u s t c o m p l y with L o c a l , S t a t e a n d F e d e r a l r e g u lations.
F D A Status
P y r e - M . L . p r o d u c t s a r e not F D A a p p r o v e d .
I.S.T. neither w a r r a n t i e s t h e s e p r o d u c t s nor s a n c t i o n s
their u s a g e in m e d i c a l a p p l i c a t i o n s u n l e s s explicitly
approved.
Packaging
S t a i n l e s s steel t a n k s a n d other c o n t a i n e r s a r e
r e c o m m e n d e d for application of this v a r n i s h . P o l y ethylene lined c o n t a i n e r s are a l s o a d e q u a t e . T h e
varnish s h o u l d be kept out of c o n t a c t with mild s t e e l ,
brass, copper, a n d a l u m i n u m a l l o y s c o n t a i n i n g o v e r
1/2% c o p p e r to avoid p o l y m e r d e g r a d a t i o n . T h e s t a tus of other a l u m i n u m a l l o y s is still doubtful.
Safety and Handling P r o c e d u r e s
W h i l e w e are not a w a r e of a n y health problems attributed to the u s e of this a n d related p r o d u c t s
during the past 2 0 y e a r s , g o o d industrial h y g i e n e
should be practiced. P y r e - M . L . wire e n a m e l s a n d
v a r n i s h e s s h o u l d be h a n d l e d in well-ventilated a r e a s ,
e y e contact m u s t b e p r e v e n t e d , a n d skin c o n t a c t
should be m i n i m i z e d .
T h e T L V for X y l e n e is l O O p p m ( A C G I H ) . A n d
while the A C G I H h a s not b e e n e s t a b l i s h e d a T L V for
n-methyl-pyrrolidone, 1ST h a s e s t a b l i s h e d a n internal
e x p o s u r e limit of 2 5 p p m . If ventilation is not a d e q u a t e
Page 14
Industrial Summit Technology
Technical Bulletin #ML-3-95
Industrial S u m m i t Technology • Parlin, N e w J e r s e y 0 8 8 5 9
PYRE-M.L. - LIQUID "H" ENAMEL - RC-5097
Introduction
P y r e - M . L . products a r e part of a family of m a terials b a s e d o n a r o m a t i c p o l y i m i d e s w h i c h a r e o n e
of the most thermally stable o r g a n i c materials. T h e s e
products include P y r e - M . L . W i r e E n a m e l s , P y r e - M . L .
Liquid " H " E n a m e l s , P y r e - M . L . Insulating V a r n i s h , a n d
P y r e - M . L . Thinner. Table 1 ( s e e p a g e 1) d e s c r i b e s
these products a n d their a s s o c i a t e d c o d e s / g r a d e s .
Liquid " H " E n a m e l (also k n o w n a s R C - 5 0 9 7 )
w a s d e v e l o p e d for top coating insulated airframe a n d
a e r o s p a c e wires. R C - 5 0 9 7 is a solution of a r o m a t i c
polyamic acid in N-methyl pyrrolidone. T h e p o l y a m i c
acid is p r o d u c e d by reacting a n a r o m a t i c d i a m i n e with
an aromatic dianhydride. T h e application p r o c e s s
involves drying of the solvent from the solution followed by curing a n d baking of the p o l y a m i c a c i d left
behind. During the latter p r o c e s s , w a t e r is r e m o v e d
and the p o l y a m i c a c i d turns into p o l y i m i d e film. T h e
film s o formed is m e c h a n i c a l l y t o u g h , c h e m i c a l l y inert,
thermally stable, radiation a n d c r y o g e n i c resistant.
It a l s o h a s excellent electrical insulating properties
which remain essentially u n c h a n g e d o v e r a w i d e
range of temperature for e x t e n d e d time p e r i o d s .
Refer to T e c h . Bulletin M L - 1 - 9 5 for a detailed d e s c r i p tion of t h e s e properties. P y r e - M . L . products a r e U.L.®
approved.
Description of Product
P y r e - M . L . Liquid " H " is a coating solution
which is converted into polyimide film by the a p p l i c a tor. T h e product properties a r e d e s c r i b e d in Table
27. T h e specifications stated herein a p p l y to R C 5097 u s e d for top coating airframe a n d a e r o s p a c e
wires either for c o m m e r c i a l u s e s or in c o m p l i a n c e
with military u s e s s u c h a s called out in Military s p e c s
MIL W - 8 1 3 8 1 . Frequently, c u s t o m e r s will p i g m e n t
R C - 5 0 9 7 for color c o d i n g or c o s m e t i c r e a s o n s . T h e
procedure for facilitating pigmentation is d e s c r i b e d in
A p p e n d i x I.
Table 27
PYRE-M.L. PRODUCTS SPECIFICATION
Code
RC-5097
Solids(%)(1)
10.5-11.5
Viscosity
(Poise)(2)
105-135
Solvent System
NMP(%)
75-85
Aromatic Hydrocarbon(%)
Density
LBS/Gal
(+/-0.05)
KGS/Gal
(+/-0.023)
Note:
15-25
8.64
3.92
{1) N E M A Test Method - 2gm/2hr./200°C Bake
(2) Measured at 25°C with Brookfield Viscometer #3 Spindle @ 6 R P M .
Viscosity Stability
The viscosity a s manufactured, is not stable but
gradually drops by 3 5 % , and then increases to gel. Gelation occurs in approximately 14 days at 120°F (49°C),
30 days at 100°F (38°C), and 90 days at 77°F (25°C). At
40°F (4°C), it will not gel in one year. Hence, it is recommended that Pyre-M.L. be stored under refrigeration
conditions prior to use. Pyre-M.L. is stored at 40°F in the
Pyre-M.L. manufacturing plant warehouse in Parlin, N J ,
U S A . Storage in an unheated building may be acceptable during winter Viscosity measurements are strongly
affected by temperature. S e e Graph No. 2 (page 2) for
temperature-viscosity conversion.
Moisture contamination has a detrimental effect on
viscosity stability, and hence, must be avoided. Allow all
chilled containers to reach room temperatures before opening them to avoid moisture from condensing.
Page 15
Safety and Handling Procedures
W h i l e w e a r e not a w a r e of a n y health problems attributed to the u s e of this a n d related p r o d u c t s
during the past 2 0 y e a r s , g o o d industrial h y g i e n e
should be practiced. P y r e - M . L . wire e n a m e l s a n d
v a r n i s h e s s h o u l d be h a n d l e d in well-ventilated a r e a s ,
eye contact must b e p r e v e n t e d , a n d skin c o n t a c t
should be m i n i m i z e d .
T h e T L V for X y l e n e is l O O p p m ( A C G I H ) . A n d
while the A C G I H h a s not e s t a b l i s h e d a T L V for
n-methyl-pyrrolidone, 1ST h a s e s t a b l i s h e d a n internal
e x p o s u r e limit of 2 5 p p m . If ventilation is not a d e q u a t e
to maintain work p l a c e air c o n c e n t r a t i o n s b e l o w t h e s e
levels, N I O S H / M S H A a p p r o v e d respirators s h o u l d b e
w o r n . E y e protection a n d N e o p r e n e g l o v e s s h o u l d b e
used.
A n i m a l tests h a v e s h o w n that t h e s e materials
are only slightly toxic w h e n i n g e s t e d . T h e y d o c a u s e
skin irritation after p r o l o n g e d or r e p e a t e d contact, a n d
any inadvertent skin c o n t a m i n a t i o n s h o u l d b e
promptly w a s h e d off with water, in the e v e n t of e y e
contact, flush with w a t e r for 15 m i n u t e s a n d s e e a
physician.
T h e s o l v e n t s typically u s e d with P y r e - M . L .
are extremely f l a m m a b l e a n d m u s t b e kept a w a y
from s p a r k s , o p e n f l a m e , or other s o u r c e s of ignition.
Although w e h a v e not run tests, w e w o u l d predict the
by-products of c o m b u s t i o n w o u l d b e toxic by i n h a l a tion.
W a s t e d i s p o s a l of P y r e - M . L . s h o u l d be c a r ried out in a n E P A a p p r o v e d incinerator. U n d e r t h e s e
conditions, there is e n o u g h o x y g e n p r e s e n t that toxic
by-products are m i n i m i z e d . T h e d i s p o s a l of P y r e M.L. must c o m p l y with L o c a l , S t a t e a n d F e d e r a l r e g u lations.
FDA Status
P y r e - M . L . products are not F D A a p p r o v e d .
I.S.T. neither warranties t h e s e products nor s a n c t i o n s
their u s a g e in m e d i c a l a p p l i c a t i o n s u n l e s s explicitly
approved.
ustrial Summit Technology
Technical Bulletin #ML-4-95
Industrial S u m m i t Technology • Parlin, N e w J e r s e y 0 8 8 5 9
PYRE-M.L. THINNER - T-8585
Introduction
Shelf Life
Pyre-IVI.L. products are part of a family of
materials b a s e d o n a r o m a t i c p o l y i m i d e s w h i c h a r e
one of the most thermally stable o r g a n i c m a t e r i a l s .
T h e s e products include P y r e - M . L . W i r e E n a m e l s ,
P y r e - M . L . Liquid " H " E n a m e l s , P y r e - M . L . Insulating
Varnish, a n d P y r e - M . L . Thinner. Table 1 ( s e e p a g e
1) d e s c r i b e s t h e s e products, their a s s o c i a t e d c o d e s /
g r a d e s , and M L T e c h n i c a l Bulletin n u m b e r s . P y r e M.L. products are U.L.® a p p r o v e d .
Three year shelf life is recommended for T-8585
from unopened containers. Frequent opening and closing
of the T-8585 containers will lower its shelf life.
Description of Product
Materials of Construction
P y r e - M . L . T h i n n e r (T-8585) is a mixture of
N-Methyl-Pyrrolidone a n d a r o m a t i c h y d r o c a r b o n
solvents in an 8 0 / 2 0 ratio. T h i s product w a s d e s i g n e d
to meet the "thinning" n e e d s of P y r e - M . L . c u s t o m e r s .
For thinning, stainless steel 316, H D P E ,
polypropylene, or other suitable material of construction is
required for the mixing equipment and the contact
surfaces.
Application of P Y R E - M . L . Thinner:
Safety and Handling Procedures
T - 8 5 8 5 is a d d e d on a n a s n e e d e d b a s i s , to
P y r e - M . L . e n a m e l s or v a r n i s h e s to lower their
viscosities a n d / o r s o l i d s . T h e a m o u n t of T - 8 5 8 5
required d e p e n d s u p o n the extent of v i s c o s i t y / s o l i d s
reduction d e s i r e d . F o r reducing viscosity, T - 8 5 8 5
amount is estimated using past e x p e r i e n c e or running
a small pilot in the laboratory. F o r r e d u c i n g % s o l i d s ,
T-8585 a m o u n t is c a l c u l a t e d by using the following
formula:
W h i l e w e a r e not a w a r e of a n y health probl e m s attributed to the u s e of this a n d related products
during the p a s t 2 0 y e a r s , g o o d industrial h y g i e n e
s h o u l d b e p r a c t i c e d . P y r e - M . L . wire e n a m e l s a n d
v a r n i s h e s s h o u l d b e h a n d l e d in well-ventilated a r e a s ,
e y e contact m u s t b e p r e v e n t e d , a n d skin contact
should be minimized.
T-8585 to be a d d e d (in L b s . per 100 lbs. of P y r e - M . L . )
= (old solids in %) x 100 / (new s o l i d s in %) - 1 0 0 .
If both the solid a n d v i s c o s i t i e s n e e d to be
lowered, then lower the s o l i d s using the a b o v e
formula. R e c h e c k the n e w viscosity. If it is still high,
then lower it by running a pilot or estimating from the
past e x p e r i e n c e .
T h e thinner must be m i s s e d thoroughly with
P y r e - M . L . prior to u s e .
Storage Conditions
Unlike Pyre-M.L. wire enamels or varnishes,
refrigeration is not required for Pyre-M.L. Thinner T-8585.
Room temperature storage is adequate.
T h e T L V for x y l e n e is l O O p p m ( A C G I H ) . A n d
while the A C G I H h a s not e s t a b l i s h e d a T L V for
n-methyl-pyrroiidone, 1ST h a s e s t a b l i s h e d a n internal
e x p o s u r e limit of 2 5 p p m . If ventilation is not a d e q u a t e
to maintain w o r k p l a c e air c o n c e n t r a t i o n s b e l o w t h e s e
l e v e l s , N I O S H / M S H A a p p r o v e d respirators s h o u l d be
w o r n . E y e protection a n d N e o p r e n e g l o v e s s h o u l d b e
used.
A n i m a l tests h a v e s h o w n that t h e s e materials
are only slightly toxic w h e n i n g e s t e d . T h e y do c a u s e
s k i n irritation after p r o l o n g e d or r e p e a t e d contact, a n d
a n y inadvertent s k i n c o n t a m i n a t i o n s h o u l d be
promptly w a s h e d off with water. In the event of e y e
contact, flush with w a t e r for 15 m i n u t e s a n d s e e a
physician.
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The solvents typically used with Pyre-M.L. are
extremely flammable and must be kept away from sparks,
open flame, or other sources of ignition. Although we have
not run tests, we would predict the by-products of combustion would be toxic by inhalation.
Waste disposal of Pyre-M.L. should be carried out
in an E P A approved incinerator Under these conditions,
there is enough oxygen present that toxic by-products are
minimized. The disposal of Pyre-M.L. must comply with
Local, State and Federal regulations.
FDA Status
Pyre-M.L. products are not F D A approved. I.S.T.
neither warranties these products nor sanctions their usage
in medical applications unless explicitly approved.
Appendix I
COLORING LIQUID H POLYIMIDE WIRE ENAMEL
Introduction
Safe Handling Practices
P o l y m i d e j a c k e t e d wire, i n s u l a t e d witti Teflon®, c a n be c o l o r e d by three m e t h o d s - t o p c o a t s ,
s h o w through, a n d pigmentation. T h e natural c o l o r of
cured Liquid H is y e l l o w d e p e n d i n g o n c o a t t h i c k n e s s
and curing conditions. If the p o l y i m i d e is no m o r e
than o n e or two mils thick, the color of the Teflon® will
s h o w through although it will be distorted toward a m ber by the polyimide. B l u e s a n d white are particularly
affected. P i g m e n t i n g the Liquid H p r o d u c e s c o l o r s
that are unaffected by coating t h i c k n e s s , are m o s t d u rable a n d l e s s e x p e n s i v e than t o p c o a t s a n d retain the
printing, potting a n d thermal properties of the b a s e
polyimide. B l u e s a n d whites c a n n o t b e r e a d y by this
route.
The organic solvents used in Liquid H are combustible. Keep away from heat and oven flame. Use only
with adequate ventilation and avoid breathing vapors. Skin
contact should be avoided. Exposed areas should be
flushed with water immediately. Wash hands thoroughly
after handling. Keep container closed.
Rubber gloves resistant to the solvents used with
Liquid H can be purchased from Richmond Rubber C o m pany, 618 East Leigh Street, Richmond, Virginia. Specify
"Will-Guard" No. 64.
S o m e of the pigments used to color Liquid H are
highly toxic. The manufacturer's suggestions for handling
them should be learned and followed.
Description of the Process
Storage and Handling
M o s t pigments suitable for coloring Teflon®
will perform well in Liquid H. A color c o n c e n t r a t e will
first be m a d e in N-methyl-2-pyrrolidone. T h i s is d o n e
by blending the ingredients to m a k e a 2 0 % (weight)
pigment mixture a n d grinding 2 4 hours in a ball mill
for five minutes in a h o m o g e n i z e r . T h e resulting c o l o r
concentration s h o u l d then be s c r e e n e d through a 2 0 0
m e s h s i e v e to r e m o v e a n y large particles.
Liquid H is p i g m e n t e d by a d d i n g o n e or m o r e
color c o n c e n t r a t e s a n d stirring with a suitable p r o p e l ler type mixer. S i n c e the natural p o l y i m i d e c o l o r is
s o intense, a high pigment loading is n e e d e d to get
r e a s o n a b l e c o l o r s . T h e highest loading attempted
w a s 3 0 % ( b a s e d o n the final product). A t high l o a d ings the polyimide b e c o m e s brittle; w e d o not s u g g e s t
loadings b e y o n d 2 0 % without e x t e n s i v e testing. C o n centrate addition to Liquid H s h o u l d be d o n e while the
polymer is being stirred to get the best mixing effect.
B e c a u s e Liquid H is s o v i s c o u s , a o n e h o u r mixing
time should be a l l o w e d to e n s u r e h o m o g e n o u s b l e n d
and the mixing e n e r g y s h o u l d b e ten h o r s e p o w e r
per hundred gallons. S a m p l e color formulations are
shown in Table 2 8 . T h e y are c a l c u l a t e d to p r o d u c e
2 8 % pigment in the final product.
C o a t i n g with p i g m e n t e d Liquid H is the s a m e
a s the natural product e x c e p t the v i s c o s i t y is slightly
lower. A d d i n g color c o n c e n t r a t e s r a i s e s both s o l i d s
level and N M P content. Liquid H is 1 2 % s o l i d s a n d
the concentration 2 0 % . N o c h a n g e in coating build
should be noticed. T h e stripping die d i a m e t e r will remain at 6-10 mils larger than the wire for 1/4 mil build
per p a s s . T h e o v e n profile s h o u l d b e 2 5 0 ° F at the bottom to 4 5 0 ° F at the top a n d the wire r e s i d e n c e time
will remain at one to one and one quarter minutes per pass.
Pigmented Liquid H should be stored below 70°F.
It must be kept in closed containers, free of moisture.
S o m e pigments may tend to settle after prolonged storage
and will require reconstitution immediately before use.
Table 28
LIQUID H COLOR FORMULATIONS
P a r t s by W e i g h t
YELLOW
Liquid H 301 (12% solids)
White Cone. (20% TiPure R-900 in N M P ) *
BROWN
100
15
Liquid H 301
White Cone. (20% TiPure R-900 in N M P )
Brown Cone. (20% Ferro Brown V 5 1 0 2 in N M P ) * *
ORANGE
100
5
10
Liquid H 301
Orange Cone. (20% Ferro Orange in N M P )
White Cone. (20% TiPure R-900 in N M P )
RED
100
10
5
Liquid H 301
Red Cone. (20% Ferro Red V 8 8 4 5 in N M P )
White Cone. (20% TiPure R-900 in N M P )
BLACK
100
14
1
Liquid H 301
Orange Cone. (20% Ferro Black V 3 0 2 in N M P )
PURPLE
100
10
Liquid H 301
Red Cone. (20% Ferro Red V8845 in N M P )
Blue Cone. (20% Ferro Blue V3285 in N M P )
100
14
1
"TiPure" Is a Du Pont Registered Trademark
' "Ferro is a Ferro Corporation Trademark
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