Oxidized Polyacrylonitrile Fiber
Properties, Products and Applications
Alan Handermann (Zoltek Corporation, alan.handermann@zoltek.com)
BACKGROUND:
Oxidized polyacrylonitrile (OPAN) fiber, such as Pyron® fiber, is designed for cost-effective, flame and
heat resistant solutions in textile, industrial, aircraft and automotive markets.
The performance features of oxidized polyacrylonitrile fiber include:
•
Limiting Oxygen Index (LOI) values between 45 - 55
•
Unsurpassed flame and heat dimensional stability
•
Easy processability into yarns, wovens, knits & nonwovens
•
Soft, comfortable fabrics
•
Electrically nonconductive and excellent chemical resistance
•
No halogens and very low toxic gas emissions, upon flame exposure
The manufacturing process begins with polyacrylonitrile precursor fiber (PAN). The PAN precursor
fiber is solution spun and then processed through a high temperature oven, in air, to stabilize its
molecular structure.
PAN Precursor Fiber
Pyron (OPAN) fiber
Panex 35 (Carbon) fiber
After stabilization is complete, fiber finish is applied and the resulting fiber tow is pleated and boxed.
The tow can be further processed, through crimping and cutting, for the production of staple fiber,
which is baled for shipment. The management system, including the (scope of supply) production and
processing of Zoltek’s Pyron fiber has been certified to ISO 9001:2008 and AS9100C in accordance
with AS9104A.
FIBER PROPERTIES:
Oxidized polyacrylonitrile fiber is available as a
300,000 filament tow in various crimped and cut
staple lengths. Three denier sizes (1.7dtex, 2.2dtex
and 5.0dtex) and two different densities (1.37 g/cc
and 1.40 g/cc) are available. The Limiting Oxygen
Index (LOI) value is dependent upon fiber density.
Fiber cross-sections of a 1.7dtex fiber are shown in
the microphotograph.
Besides providing outstanding protection against
direct flame, OPAN fiber products exhibit low thermal
conductivity and make excellent thermal insulators.
Other fiber physical properties are listed below.
Standard Density
Density
1.37 g/cm3 (0.0495 lbs/in3)
LOI
Denier Diameter
Typical
Cut Lengths
Tenacity
Modulus
~55%
1.7dtex (1.5dpf) 2.2dtex (2.0dpf) 5.0dtex (4.5dpf) 1.7dtex (1.5dpf)
13µ (0.51mils) 15µ (0.59mils) 22.5µ (0.89mils) 13µ (0.51mils)
50mm (2.0”)
60mm (2.4”)
50mm (2.0”)
60mm (2.4”)
74mm (3.0”)
100mm (4.0”)
Staple
Crimp Level
Tow Count
60mm (2.4”)
18.5 – 23 cN/tex (2.1 – 2.6 gpd)
50mm (2.0”)
60mm (2.0”)
2.2dtex (2.0dpf)
15µ (0.59mils)
60mm (2.4”)
240 - 300 MPa (35 – 43.5 ksi)
575 – 690 cN/tex (65 – 78 gpd)
7.4 GPa (1.1 msi)
22 – 28%
0.0284 Kcal/(hr*m*°C)
0.0330 W/(m*°K)
0.229 (Btu*in)/(hr*sqft*°F)
(165 gsm x 4.4mm Pyron felt)
Carbon Content
Staple Moisture
Content
1.40 g/cm3 (0.0506 lbs/in3)
~45%
Elongation-toBreak
Thermal
Conductivity
High Density
~62%
13 +/-3% (yarn spinning)
11 +/-3% (nonwovens)
>3.0 crimps/cm (>7.6 crimps/inch)
300,000 filaments
OPAN fiber outperforms other heat and flame resistant fibers when it comes to direct flame exposure
and molten metal splash performance. OPAN fibers do not melt or burn and most importantly they
will not shrink; even after a 30 second 1250°C flame or molten metal drip exposure (see test set-up
and photos below). Besides maintaining dimensional stability, OPAN fiber also retains a soft hand
after being exposed to flame and it does this at a very economical price.
Typical Stress/Strain Tensile Strength Curve
Tenacity (gm/denier)
2.5
2.0
1.5
1.0
0.5
0.0
0.0
2.0
4.0
6.0
8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 24.0
Elongation (%)
FLAME COMPARISON TEST (30 second 1250°C flame exposure):
PYRON®
m-aramid
FR Polyester
TOXIC GAS GENERATION:
OPAN fiber has been evaluated, according to BSS 7229 for gas emissions during combustion and
found to generate very low levels of toxic gas. The chart below compares 1.37 g/cc density Pyron
fiber to other materials and the Airbus standard, for the toxic gas emission types tested.
CONCENTRATION, ppm 4000 3000 2000 1000 Neoprene Foam FR Polyester Airbus Standard 0 CO Co+on HCN NOx TOXIC GAS Pyron 137 HCL TOTAL MOLTEN METAL COMPARISON TEST:
Molten
Aluminum
Felt Sample
75°
Angle
Molten Aluminum Test Set-up
535 gsm m-aramid felt
165 gsm OPAN felt
FIBER PROCESSING:
OPAN staple can be processed on all types of textile equipment. Suggested card processing
settings, for converting staple fiber into spun yarns are shown in Figure 1 below.
Flats to Cylinder 0.028” Back Plate Top: 0.022” Bottom: 0.022” Licker-­‐in 450-­‐550 rpm Front Plate Top: 0.034” Bottom: 0.017” Cylinder to Doffer 0.005” to 0.007” Licker-­‐in Cylinder 280 – 320 rpm Feed Plate to Licker-­‐in 0.034” Licker-­‐in to Cylinder FIGURE 1 0.007” Cylinder Screen Back: 0.034” Center: 0.034” Front: 0.187” OPAN fiber tow and staple can also be converted into many other product forms. Including:
needlepunched felts, stitchbonded felts, spunlace nonwovens, thermally bonded nonwovens, airlay
nonwovens, ring spun yarns, stretch-broken yarns, knit fabrics, woven fabrics and braided fabrics.
APPLICATIONS & END USES:
Various flame resistant fibers, suitable for blending with OPAN fibers to obtain particular end use
characteristics, are shown in the table below. In order to produce the best FR product three, four or
even more fibers can be blended to obtain the optimum price / performance solution for an end use.
FIBER
PROPERTY
Density, g/cc
Silica
polyamidepolybenzmodacrylic OPAN novoloid FR Viscose
PPS
melamine
m-aramid p-aramid p-aramid p-aramid polyimide PTFE
loaded
imide
imidazole
PROTEX PYRON KYNOL
LENZING PROCON BASOFIL
NOMEX TWARON TECHNORA KEVLAR
P84
TEFLON
viscose
KERMEL
PBI
1.37 1.62
1.37
1.27
1.52
1.34
1.40
1.34
1.38
1.44
1.39
1.44
1.41
2.10
1.4
1.40
Moisture
Regain, % @
20C & 65% RH
9 - 11
0.80
Breaking
Tenacity,
cN/tex (gpd)
11 - 17
(1.3-1.9)
29
(3.3)
Breaking
Elong., %
18 - 25
30
Initial Modulus,
cN/tex (gpd)
Limiting
Oxygen
Index, %
9.0
6.0
13.0
19 - 23
12 - 16
15 - 24
(2.1 - 2.6) (1.3 - 1.8) (1.7 - 2.7)
22 - 28
10 - 50
15 - 20
0.20
5.0
4.5
4.5
4.5
2.0
4.3
3.0
43
(5.0)
16
(1.8)
35
(4.0)
35 - 47
(4.0 - 5.3)
200
(23.0)
247
(28.0)
200
(23.0)
38
(4.4)
19.6
(2.0)
23.5
(2.7)
34.5
12 - 18
23
22 - 32
3.3
4.6
4.0
30
19
25 - 30
480
(55)
265
(30.0)
618 - 1060
(70 - 120)
5209
(590)
4900
(555)
127
(13)
400
(45)
575 - 690 260 - 350
(65 - 78) (29 - 40)
28 - 31
Decomposition 150 - 200
Temp., C (F) (302-392)
15.0
32 - 34
45 - 55
30 - 34
28
40
32
29 - 31
28 - 30
29
25
28 - 30
38
99
41
220
(428)
>450
(>842)
150
(302)
150 - 200
(302-392)
285
(545)
371
(700)
380 - 400
(716 - 752)
400
(750)
500
(932)
500
(932)
482
(900)
482
(900)
327
(621)
>500
(>932)
Acid
Resistance
Poor
Excellent
Good
Excellent
Poor
Excellent
Poor
Fair
Fair
Fair
Fair
Fair
Good
Excellent
Poor
Alkaline
Resistance
Poor
Excellent
Fair
Excellent
Poor
Excellent
Excellent
Poor
Poor
Poor
Poor
Poor
Good
Excellent
Good
Organic
Solvent
Resistance
Poor
Excellent
Excellent Excellent
Good
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Good
Excellent
Good
Bleach
Resistance
Poor
Excellent
Poor
Excellent
Poor
Excellent
Excellent
Poor
Poor
Poor
Poor
Poor
Abrasion
Resistance
Poor
Good
Fair
Poor
Fair
Fair
Good
Good
Good
Good
Good
Good
Ultraviolet
Resistance
Good
Excellent
Excellent
Good
Good
Good
Excellent
Good
Poor
Poor
Poor
Poor
Excellent
Good
Fair
Poor
Excellent
Good
Good
Poor
Excellent
Poor
Fair
Excellent
Excellent
Excellent
Poor
Poor
Excellent
Char Shrinkage Excellent
Excellent
Good
Char Strength
Poor
Poor
Good
Fair
Fair
Poor
Fair
Poor
Fair
Excellent
Excellent
Excellent
Poor
Poor
Good
Processing
Ease
Fair
Fair
Good
Good
Good
Fair
Fair
Good
Good
Fair
Fair
Good
Good
Fair
Good
Relative Price
*
**
**
**
***
***
***
****
****
*****
*****
*****
*****
******
*********
Various Pyron blended yarns, nonwovens, fabrics and
garments have been introduced into the FR market.
The benefits gained by blending different fibers into
yarns and fabrics have been known for many years.
The overall performance synergies gained by
blending OPAN fiber with aramids, rayons,
modacrylics, cottons and/or nylons are of particular
interest for increasing abrasion and laundering
resistance, improving wickability, providing better
moisture management and increasing yarn and fabric
strength. Fiber blending provides many of these
benefits; while at the same time delivering the most
economical FR solution. Properly designed blends
have even been dyed into a spectrum of attractive
colors.
An example of one fiber blend solution, to help protect against the dual hazard threats of arc flash and
fire, is marketed by GSL Inc., under their Spentex® NGI label. Besides providing a range of colors,
these garments, are UL certified to NFPA 2112 and ASTM F1506 Hazard Risk Category 2 (HRC 2);
with 6 osy knits ATPV rated at 12.6 calories/cm2 and 6 osy twills ATPV rated at 9.3 calories/cm2.
Spentex NGI garments have 5x the flame protection, twice the durability, excellent wickability,
unsurpassed breathability, are very lightweight and require only normal laundering care; as compared
to other garments in this class.
Today, OPAN fiber is being processed around the world, as the key price/performance FR fiber for
many applications and end uses, including:
•
Aircraft, Rail, Bus & Marine Fireblocking Fabrics
•
Automotive Sound and Heat Insulation Packages
•
Brake and Friction Materials
•
Endless Needled Rollers and Seamless Belts
•
Fireservice and Arc Flash Balaclavas
•
Fireservice Thermal Liners
•
Flame Resistant and Arc Flash Baselayer Apparel
•
Flame Resistant Sleeves and Gloves
•
Industrial Heat and Flame Resistant Insulation
•
Oil, Gas and Utility “Dual Hazard” Arc Flash and FR
Apparel
•
Molten Metal Splash Apparel
•
Packing and Gasket Materials
•
Racing and Stunt Apparel
•
Welding Aprons, Spats, Gloves, Blankets, Torch Shields
and Curtains
CERTIFICATIONS AND TEST METHODS:
UL certifications have been obtained with several Pyron® based products. Many fabrics meet or
exceed industry standards, in each of the following end-uses, according to the test methods listed:
Aircraft Materials:
-
Federal Aviation Regulation (FAR) Section 25.853
-
ASTM E662-09 “Standard Test Method for Specific Optical Density of Smoke Generated by
Solid Materials”
-
ASTM E162-12a “Standard Test Method for Surface Flammability of Materials Using a Radiant
Heat Energy Source”
Electric Arc Apparel:
-
NFPA E-70 (2012) "Standard for Electrical Safety in
the Workplace”
-
ASTM F1506-10a "The Standard Performance
Specification for Flame Resistant Textile Materials for
Wearing Apparel for Use by Electrical Workers
Exposed to Momentary Electric Arc and Related
Thermal Hazards"
-
ASTM F1959 “Standard Test Method for Determining
the Arc Rating of Materials for Clothing”
-
BS EN 61482-1-2:2007 “Live working. Protective
clothing against the thermal hazards of an electric
arc. Test methods. Determination of arc protection
class of material and clothing by using a constrained
and directed arc.”
Fire Service Apparel:
-
NFPA 1975 (2009) “Standard on Station/Work
Uniforms for Emergency Services”
Industrial Fire Apparel:
-
NFPA 701 (2010) "Standard Methods of Fire Tests for Flame Propagation of Textiles and Films"
-
ASTM D6413 "Standard Test Method for Flame Resistance of Textiles (vertical test)"
-
NFPA 2112 (2012) "Standard on Flame Resistant Garments for Protection of Industrial
Personnel Against Flash Fire"
-
ASTM F1930-11 "Standard Test Method for Evaluation of Flame Resistant Clothing for
Protection Against Flash Fire Simulations Using an Instrumented Manikin."
-
ASTM F2700-08 “Standard Test Method for
Unsteady-State Heat Transfer Evaluation of Flame
Resistant Materials for Clothing with Continuous
Heating”
Molten Metal Apparel and Accessories:
-
ASTM F955-07 “Standard Test Method for
Evaluating Heat Transfer through Materials for
Protective Clothing Upon Contact with Molten
Substances”
Welding Materials:
-
DIN EN ISO 22007-2:2012-04 “Plastics: Determination of thermal conductivity and thermal
diffusivity - Part 2: Transient plane heat source (hot disc) method”
-
California Administrative Code, Title 19, Section 1237
-
ASTM E800-07 “Standard Guide for Measurement of Gases Present or Generated During Fires”
CARBONIZED PANEX® 35 FELTS:
100% Pyron® felts can be used as a precursor
material for carbonization into Panex® 35 felts.
These felts typically have a carbon content of
~95%
and
are
electrically
conductive.
Applications include: ultrahigh temperature
furnace
insulation,
composites,
hightemperature acid gas filtration, battery energy
storage
and
other
high
performance
applications.
Properties of a these carbonized fabrics are
shown below. Other areal felt weights and
thicknesses can also be produced.
SI Units
US Units
Carbon Content
~95%
~95%
Processing
Temperature
1400°C
2552°F
Roll Width
98.0 cm
38.6 inches
Areal Weight
1035 gsm
30.5 opsy
Thickness
10.5 mm
0.413 inches
Felt Density
0.10 g/cm3
0.0037 lbs/in3
Roll Length
50.0 m
54.7 m
Thermal
Conductivity
@ 23°C
Thermal
Conductivity
@ 550°C
Specific Heat
@ 23°C
Specific Heat
@ 550°C
0.027 Kcal/(hr*m*°C)
0.22 (Btu*in)/(hr*sqft*°F)
0.031 W/(m*°K)
0.061 Kcal/(hr*m*°C)
0.49 (Btu*in)/(hr*sqft*°F)
0.071 W/(m*°K)
0.18 cal/(gm*°C)
0.74 joule/(gm*°C)
0.18 Btu/(lb*°F)
0.40 cal/(gm*°C)
1.68 joule/(gm*°C)
0.40 Btu/(lb*°F)
CARBONIZED PANEX® 30 FABRICS:
100% Pyron woven and knit fabrics, made with stretch-broken yarns, can be used as a precursor
material for carbonization into Panex® 30 fabrics. These fabrics typically have a minimum carbon
content of 99% and are electrically conductive.
Applications include: carbon friction composites,
activated carbon fabrics, fuel cells and other
high performance applications where a
drapeable, very thermally stable, very high
carbon content fabric is desired.
Properties of several these carbonized fabrics
are shown below; others can also be produced.
Property
Plain Weave (PW03)
SI
US
Plain Weave (PW06)
SI
US
Satin Weave (SW06)
SI
US
Knit Fabric (KF07)
SI
US
Carbon
Content
99% min.
99% min. 99% min.
99% min. 99% min.
99% min. 98% min. 98% min.
Areal
Weight
115 gsm
3.4 opsy
7.0 opsy
8.5 opsy 246 gsm 7.3 opsy
237 gsm
288 gsm
Yarn Count 177 x 177
45 x 45 114 x 114
29 x 29 150 x 150
38 x 38
(warp x fill) (yarns/10cm) (yarns/in) (yarns/10cm) (yarns/in) (yarns/10cm) (yarns/in)
Knit Construction
Average
Thickness
0.41 mm
0.016 in
0.67 mm
0.027 in
0.89 mm
0.035 in
0.89 mm
0.040 in
Roll Width
81 cm
32 in
109 cm
43 in
109 cm
43 in
57.2 cm
22.5 in
Typical
Roll Length
73.2 m
80 yd
36.6 m
40 yd
36.6 m
40 yd
14.6 m
16 yd
Pyron Yarn
Count
2/30 Nm
2/27 wc
2/18 cc
2/11.3 Nm
2/10 wc
2/6.7 cc
2/11.3 Nm
2/10 wc
2/6.7 cc
Fiber
Density
1.75 g/cm3
0.0632
lbs/in3
1.75 g/cm3
0.0632
lbs/in3
1.75 g/cm3
0.0632
0.0639
1.77 g/cm3
lbs/in3
lbs/in3
Oxidation
Rate
2/11.3 Nm
2/6.7 cc
2/10 wc
1% per hour @ 500°C (932°F)
Ongoing developments of new and improved Pyron® staple, tow, felt and fabric products, along with
carbonized Panex felt and fabrics, enable textile and industrial suppliers and end users, to
commercialize flame resistant, high performance product solutions to meet the increasingly stringent
requirements of these diverse markets.
is a registered trademark of Zoltek Corporation
is a registered trademark of Zoltek Corporation
Spentex® is a registered trademark of GSL, Inc. in the U.S.
The content of this white paper does not necessarily reflect the view or opinion of Advanced Textiles Source or the Industrial Fabrics Association International.