http://www.acculam.com | Thermoset laminates are often referred to as “phenolics” and older trade names such as Bakelite, Textolite, Micarta, Phenolite, etc. You can get them in many grades and in sheet, tube, rod and molded forms. Industrial Laminate grades are differentiated by a variety of resin matrix binders that are reinforced by various fiber materials.

1. Industrial Laminates
“The Basics”
prepared by Michael Stacey • Accurate Plastics, Inc. • Yonkers, New York
In a comprehensive way, I have attempted to cover the basics of industrial laminates.
Thermoset plastic industrial laminates date back over 90 years, and much like
aspirin, industrial laminate is an old friend that continues to present new remedies
for today and tomorrow's toughest engineering headaches. Be sure to prescribe
industrial laminates to your customers...then call me in the morning. (wink!)
In 1906, Dr. Leo Bakeland experimented with
the polymerization of phenolic resins. He found
that by adding formaldehyde and heat, a chemical
cross linkage took place; thermoset plastics were
born. Soon after, it was discovered that cotton
cloth and paper materials could be impregnated
with this same mixture, semicured and then made
into a stack of sheets or wrapped around a mandrel and subsequently put into a hydraulic press
where heat and pressure could be applied. Full
polymerization took place rendering hard, dense,
reinforced thermoset plastics which today are
known as industrial laminates.
Simply put, thermoset plastics can be compared to cement, once cured they’re set, hence the
name thermoset. Thermoplastics can be compared
more to wax in-as-much as they can be remelted
and reshaped upon the reapplication of heat.
However, one key resulting difference is that thermoplastics lack the rigidity of thermoset laminates, as the tensile modulus of the following
materials indicate:
Graphite Epoxy
Steel
Aluminum
Glass Epoxy
Polycarbonate
(thermoset plastic)
(metal)
(metal)
(thermoset plastic)
(thermoplastic)
40,000,000 psi
30,000,000 psi
10,000,000 psi
5,800,000 psi
450,000 psi
Thermoset Plastic Industrial
Laminates
Thermoset plastic industrial laminates are
uniformly dense and structurally strong materials
that will not soften appreciably under the reapplication of heat. They are extremely durable plastics
that are lightweight and moisture resistant. They
are thermoset plastic resin impregnated reinforcing substrate materials that are cured under heat
and pressure to form solid shapes having high
mechanical and insulating properties. Industrial
laminates are available in sheet, rod, tube and
angle. Since these laminates are comprised of a
combination of materials, they are also referred to
as composites.
Thermoset plastic industrial laminates typically have a layered construction with no fewer than
two components:
The first is a reinforcing substrate such as
woven glass cloth, random glass mat, glass filaments, woven canvas cotton fabric, woven linen
cotton fabric, paper, woven aramid fabric, random
mat aramid, woven graphite fabric, random mat
graphite and others. The second is a thermoset
plastic resin binder that serves to adhere
Thermoset Laminate Layered Construction
T
TECHNICAL
REFERENCE
BL6
INDUSTRIAL
LAMINATES
•
Epoxy Grades
Melamine Grades
Silicone Grades
Polyester Grades
Phenolic
Paper Grades
Phenolic
Cotton Grades
•
Thermoset Industrial
Laminate
Properties
•
Manufacturing
Process
•
Applications
resin binder
reinforcing substrate
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Accurate
P L A S T I C S ,
the layers of reinforcing substrates to each other
to form a solid unit. Resin binders include epoxies, melamines, phenolics, polyesters, silicones
and others.
Unlike other groups of plastic materials, thermoset plastic industrial laminates have their own
standards which are published by NEMA
(National Electrical Manufacturers Association).
In concert with member manufacturers, NEMA
standards are set and “mininum values” published.
The most commonly used NEMA thermoset
laminate grades are as follows:
I N C.
Headquarters, Mfg.
18 Morris Place, Yonkers, NY 10705
Phone: 914-476-0700
Fax: 914 / 476-0533
www.acculam.com

2. Epoxy Grades
NEMA grades G10 and FR4 GlassCloth Reinforced Epoxy — natural color is
typically a yellowish to light
green. The most versatile allaround laminate grades are
continuous glass woven fabric
impregnated with an epoxy
resin binder. (Epoxy resins are
among the most versatile and
widely used plastics in the electronics field, primarily because
water absorption is virtually nil,
rendering it an outstanding insulator. Beyond
its electrical insulating properties, epoxy
resins exhibit superior adhesive properties
and great dimensional stability — shrinkage
is usually less than 1 percent). G10/FR4 has
extremely high mechanical strength, good
dielectric loss properties, and good electric
strength properties, both wet and dry. The
main difference between NEMA Grades G10
and FR4 is that FR4 is a fire retardant grade
of G10. Therefore, FR4 can be safely substituted where G10 is called out, while G10 can
never be substituted where FR4 is called for.
(G10 certifies to Mil-I-24768/2 GEE; FR4
certifies to Mil-I-24768/27 GEE-F.)
NEMA grades G11 and FR5 GlassCloth Reinforced Epoxy — natural color is
typically yellow green to
amber. This grade is similar to
G10/FR4 with the addition of
a higher operating temperature
and some improved mechanical strength at elevated temperatures. The main difference
between NEMA Grades G11
and FR5 is that FR5 is a fire
retardant grade of G11. Therefore, FR5 can
be safely substituted where G11 is called out,
while G11 can never be substituted where
FR5 is called for. (G11 certifies to Mil-I24768/3
GEB;
FR5
certifies to Mil-I-24768/28 GEB-F.)
Melamine Grades
NEMA grades G5 and G9
Glass-Cloth
Reinforced
Melamine — natural color is
typically a grayish brown.
These grades are composed of a continuous
glass woven cloth base impregnated with a
melamine resin binder. (Melamine resins,
once cured, are the hardest, most rigid and
abrasion
resistant
of the standard resins employed in the production of industrial laminates. However,
prolonged exposure to high temperature can
adversely affect its mechanical and electrical
strength properties. Arc resistance, however,
may remain unaffected despite excessive thermal exposure). Melamines are the hardest of
laminates, exhibiting good dimensional stability and arc resistance. It’s also caustic resistant. A key difference between NEMA
Grades G5 and G9 are that G9 is more resistant to the elements of the environment.
Thus, G9 can be safely substituted where G5
is called for. (G5 certifies to Mil-I-24768/8
GMG; G9 certifies to Mil-I-24768/1 GME.)
Polyester Grades
NEMA grade GPO-1 (tan color), GPO-2
(red color) and GPO-3 (red color) GlassMat Reinforced Polyester — These grades
are composed of random mat
(non-woven) fiberglass reinforcement held together by a
polyester resin binder. (Polyesters are versatile resins which
handle much like epoxies. Of
course, the basic resins are
chemically different. It’s their
physical application forms
which make them similar. Despite lower
costs, the important disadvantages of polyesters, as compared with epoxies, is lower
adhesion to most substrates, higher polymerization shrinkage, a greater tendency to crack
during cure or in thermal shock and greater
change of electrical properties in
a humid environment). GPO-2 offers superior arc resistance over GPO-1 while GPO-3
offers both arc and track resistance. (GPO-1
certifies to Mil-I-24768/4 GPO1; GPO-2
certifies to Mil-I-24768/5 GPO2 and GPO-3
certifies to Mil-I-24768/6 GPO3).
Phenolic Paper Grades
Accurate Plastics manufactures Acculam™ industrial
thermoset laminate sheet, rod, tube, angle and
channel.
Silicone Grade
NEMA grades G7 Glass-Cloth Reinforced Silicone — natural color is typically
cream to white. Composed of a continuous
glass woven cloth base impregnated with a silicone resin
binder, this grade has excellent
heat and arc resistance.
(Silicone thermosetting resins are among the
best of all polymer materials in resistance to
temperature. Hence, silicone is broadly used
for high temperature electronic applications
requiring low electrical losses. Silicone isn’t as
strong as epoxies and phenolics upon aging at
lower temperatures but is stronger upon
aging over 400°F). G7 has extremely good
dielectric loss properties under dry conditions and good electrical properties under
humid conditions, although the percentage
of change is high. (G7 certifies to Mil-I24768/17 GSG.)
NEMA grades X, XX and XXX Paper
Reinforced Phenolic — natural color is
typically light tan to brown.
These grades are composed
of a paper base impregnated
with a phenolic resin binder.
(Phenolics are the oldest, bestknown general purpose thermoset resins. They are among
the lowest in cost and easiest to
process. Phenolics are quite adequate for a fair percentage of electrical applications. Generally speaking, they are not equivalent to epoxies in resistance to moisture,
humidity, dimensional stability, shrinkage and
retention of electrical properties in extreme
environments). The paper reinforced phenolic
has good electric strength properties with fair
mechanical strength and are outstanding for
use as template material and/or back-up material. A good rule of thumb in selecting a paper
grade is to remember the more X’s the better
the electrical properties, while the fewer X’s
represent superior mechanical properties. Paper
grades can be modified by adding plasticizers
to make them more conducive to part punching resulting in a P suffix added to the X designation, i.e., XP, XXP, XXXP. (Grade X certifies
to Mil-I-24768/12 PBM; grade XX to Mil-I24768/11 PBG and grade XXX to Mil-I24768/10 PBE).

3. Phenolic Cotton Grades
NEMA grades C and CE Canvas
Cotton-Cloth Reinforced Phenolic — natural color is typically light tan
to brown. C and CE grades are
composed of a continuous cotton woven cloth impregnated
with a phenolic resin binder.
(Phenolics are the oldest, bestknown general purpose thermoset resins. They are among
the lowest in cost and easiest to
process. Phenolics are quite adequate for a
fair percentage of electrical applications.
grade is composed of a continuous cotton
woven cloth impregnated with a phenolic
resin binder. This grade contains a fine weave
linen and, like the canvas phenolic; is known
for its mechanical properties. The finer weave
allows for machining more intricate details
than canvas grade, such as gear teeth, etc.
These grades are not recommended for primary electrical insulation, but grade LE
exhibits superior moisture resistance to
grades L, C and CE, and thus is an adequate
insulator for a fair number of applications.
(Grade L certifies to Mil-I-24768/15 FBI;
grade LE certifies to Mil-I-24768/13 FBE).
Generally speaking, they are not equivalent
to epoxies in resistance to moisture, humidity, dimensional stability, shrinkage and retention of electrical properties in extreme environments). These grades contain a medium
weave canvas and are known primarily for
their mechanical properties. These grades are
not recommended for primary electrical insulation. (Grade C certifies to Mil-I-24768/16
FBM; grade CE certifies to Mil-I-24768/14
FBG).
NEMA grades L and LE Linen CottonCloth Reinforced Phenolic — natural
color is typically light tan to brown. This
THERMOSET INDUSTRIAL LAMINATE PROPERTIES
Minimum Values
G10, FR4
G11, FR5
G5, G9
G7
GPO 1
GPO 3
X
XX
XXX
C, CE
L, LE
glass cloth
epoxy
glass cloth
epoxy HT
glass cloth
melamine
glass cloth
silicone
glass mat
polyester
glass mat
polyester
paper
phenolic
paper
phenolic
paper
phenolic
canvas
phenolic
linen
phenolic
40,000
35,000
40,000
35,000
37,000
30,000
23,000
18,000
12,000
––
11,000
––
20,000
16,000
16,000
13,000
15,000
12,000
9,500
7,500
12,500
8,750
flatwise, PSI
edgewise, PSI
60,000
35,000
60,000
35,000
70,000
25,000
45,000
14,000
40,000
––
30,000
––
36,000
19,000
34,000
23,000
32,000
25,500
37,000
23,500
37,000
25,000
lengthwise, PSI
crosswise, PSI
55,000
45,000
55,000
45,000
55,000
35,000
23,000
20,000
23,000
––
20,000
––
25,000
22,000
15,000
14,000
13,500
11,800
17,000
15,000
15,000
13,750
Modulus of Elasticity in flex x10 -3
lengthwise, PSI
crosswise, PSI
2,700
2,200
2,700
2,200
2,500
2,000
1,400
1,200
––
––
––
––
1,800
1,300
1,400
1,100
1,300
1,000
950
850
1,050
850
Shear Strength, PSI
19,000
19,000
20,000
17,000
––
––
12,000
11,000
10,000
11,500
11,750
7
5.5
7
5.5
12
8
8.5
7.5
––
––
––
––
4
0.5
1.3
0.35
1
0.35
3.2, 2.3
1.9, 1.4
2.5, 1.8
1.1, 1
NEMA grades
reinforcements
resin binders
Properties
Tensile Strength
lengthwise, PSI
crosswise, PSI
Compressive Strength
Flexural Strength
IZOD Impact
flatwise, ft-lb/in of notch
edgewise, ft-lb/in of notch
Rockwell Hardness M scale
110
110
120
100
––
––
110
105
110
104
105
Specific Gravity
1.82
1.82
1.9
1.68
1.8
1.85
1.36
1.34
1.32
1.35
1.34
Coefficient of Thermal Expansion
cm/cm-°C x 10 -5
.9
.9
1
1
––
––
6
2
1.4
2
2
Water Absorption
.062” thick, % per 24 hrs
.125” thick, % per 24 hrs
.500” thick, % per 24 hrs
0.25
0.15
0.10
0.25
0.15
0.10
0.8
0.7
0.4
0.3
0.2
0.15
0.35
––
––
0.4
––
––
6
3.3
1.1
2
1.3
0.55
1.4
0.95
0.45
4.4, 2.2
2.5, 1.6
1.2, 0.75
2.5, 1.95
1.6, 1.3
0.9, 0.7
Dielectric Strength,volt/mil
perpendicular to laminations; short
.062” thick
.125” thick
500
400
500
400
400
350
400
350
370
––
400
––
700
500
700
500
650
470
200, 500
150, 360
200, 500
150, 360
Dissipation Factor
condition A, 1 megacycle
0.025
0.025
0.017
0.003
––
––
0.06
0.045
0.038
Dielectric Constant
condition A, 1 megacycle
5.2
5.2
7.12
4.2
––
––
6
5.5
5.3
Insulation Resistance
Condition: 96 hours at 90% relative
humidity (in megaohms)
200,000
200,000
10,000
200,000
––
––
––
––
––
––
––
2,000
1,600
1,700
650
––
––
700
800
950
1,800
1,600
Bond Strength, in lbs
Max Operating Temperature
approximate ° F continuous
sheet mil spec: Mil-I-24768 / _ _,
type
0.1, 0.055 0.1, 0.055
-, 5.8
-, 5.8
285
300
285
465
265
265
285
285
285
265
265
2, GEE
27, GEE-F
3, GEB
28, GEB-F
8, GMG
1, GME
17
GSG
4
GPO1
6
GPO3
12
PBM
11
PBG
10
PBE
16, FBM
14, FBG
15, FBI
13, FBE

4. MANUFACTURING FLOW CHART
Press
Shear
Resin
Sheet
B Stage�
Pallet
Base�
Mat’l
Tube
Dip Pan
Oven
Tube Roller
Manufacturing Process
Thermoset plastic industrial laminates are
identified in process by three stages A, B and
C stages:
A-stage refers to the key raw materials
described earlier – reinforcing substrates and
resin binders.
B-stage refers to the product produced
when reinforcing substrates and resin binders
are brought together but not cured. The reinforcing substrate is unwound from a large
master roll and dipped into a bath of liquefied resin binder. The reinforcing substrate
becomes either saturated, as is the case with
absorbent papers and cotton cloths, or coated, as is the case with glass and graphite
cloths. Once the wet resin binder is joined
with the reinforcer substrate in this method,
it is slowly drawn through a long conveyorized oven where the liquefied resin binder is
dried. The result leaves dry semicured resin
binder in and/or on the reinforcing substrate.
Once joined and dried in this fashion, the
product is referred to as B-stage or prepreg,
and the process described is called B-staging,
prepreging or treating.
C-stage refers to sheet, rod, tube, angle or
other in their “cured stage.”
• Sheets — B-stage is sheeted into plys
then laid on top of each other into predetermined stacks that will render a given thickness. These stacks are placed into the
hydraulic laminating press between two flat
surfaces and pressure is applied. While under
pressure, heat is introduced to begin the bake
cycle. The resin in the B-stage product is reactivated by the heat to a sticky state which
moves slowly, filling and bonding the layers
together until it eventually hardens and cures.
Once plys bond to each other and cure they
are referred to as C-stage laminate sheet and
the process described is called laminating or
pressing.
• Rods — the B-stage is convolutely
wrapped under tension onto itself, much like
a roll of paper towels is wound. Once the Bstage is rolled to form a rod, it is placed into
a laminating press which has upper and lower
half round mold cavities. When the two half
round molds close and meet each other a full
round is formed. The size of the mold cavity
determines the diameter of the finished rod.
Once pressure is applied, the layers are
pressed together filling all voids. Similar pressures and heat cycles employed for making
sheet are used. When the layers bond to each
other and cure, they are referred to as C-stage
laminate rod or rolled and molded rod.
• Tubes — rolling tubes are nearly identical to rolling rods with the exception that a
steel rod called a mandrel is employed to size
and form the inside diameter of the tube. Bstage rolled tubes are usually placed into an
oven chamber as opposed to a press. Tube
bake cycles compare to those of sheet and rod.
Once cured, the center mandrel is extracted.
The final cured product is referred to as Cstage laminate tube or rolled tube.
• Angles — this process is nearly identical
to that of sheets except the mold cavities are
“V” shaped rather than flat surfaces. The final
cured product is referred to as C-stage laminate angle or molded angle.
• Other shapes — once cured, the end
product is referred to as C-stage.
APPLICATIONS
FOR THERMOSET
INDUSTRIAL
LAMINATES
Industrial laminates are used in the
following industries:
• Electronics
• Electrical
• Machinery
• Automotive and Trucking
• Metal Finishing
• Aviation
• Chemical
• Home Appliance
• Textile
Of these, the largest markets are
electrical and electronics, where
thermoset industrial laminates
provide strong reliable insulators
for applications in :
• Relays
• Bus Bars
• Standoffs
• Washers
• Arc Shields
• Vanes
• Test Board
• Panels
• Sockets
• Coils
• Fuses
• Motors
• Generators
• Gaskets
• Transformers
• Circuit
• Condensers
Boards
You Know�
It’s Right...�
When It’s�P L A
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New York
Accurate
S T I C S ,
18 Morris Place, Yonkers, NY 10705
Phone: 914-476-0700 • Fax 914-476-0533
TM
• Switches
• Terminal Strips
These laminates, as a group, are
the hidden work horses in many
industrial applications.
I N C.
West Virginia
PO Box 2287, Weirton, WV 26062
Phone: 914-476-0700 • Fax 304-723-1625
Massachusetts
33 Tech Park Drive, Falmouth, MA 02536
Phone: 914-476-0700 • Fax 508-457-9275