Zoltek Whitepaper

Oxidized Polyacrylonitrile Fiber Properties, Products and Applications

By Alan Handermann, Zoltek Corporation alan.handermann@zoltek.com

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BACKGROUND:

Oxidized polyacrylonitrile (OPAN) fiber, such as Zoltek OX™ 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.

Zoltek OX™ (OPAN) fiber Zoltek PX35™ (Carbon) fiber

After stabilization, 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 OX™ fiber has been certified to ISO 9001:2008 and AS9100C in accordance with AS9104A.

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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 High Density

Density 1.37 g/cm3 (0.0495 lbs/in3) 1.40 g/cm3 (0.0506 lbs/in3)

LOI ~45% ~55%

Denier Diameter 1.7dtex (1.5dpf) ~13µ (0.51mils)

2.2dtex (2.0dpf) ~15µ (0.59mils)

5.0dtex (4.5dpf) ~22.5µ (0.89mils)

1.7dtex (1.5dpf) ~13µ (0.51mils)

2.2dtex (2.0dpf) ~15µ (0.59mils)

Typical Cut Lengths

50mm (2.0”) 60mm (2.4”)

50mm (2.0”) 60mm (2.4”) 74mm (3.0”)

100mm (4.0”)

60mm (2.4”) 50mm (2.0”) 60mm (2.0”)

60mm (2.4”) 74mm (3.0”)

Tenacity 18.5 – 23 cN/tex (2.1 – 2.6 gpd) 240 - 300 MPa (35 – 43.5 ksi)

Modulus 575 – 690 cN/tex (65 – 78 gpd) 7.4 GPa (1.1 msi)

Elongation-to-Break

22 – 28%

Thermal Conductivity

0.0284 Kcal/(hr*m*°C) 0.0330 W/(m*°K) 0.229 (Btu*in)/(hr*sqft*°F) (165 gsm x 4.4mm Zoltek OX™ felt)

Carbon Content ~62%

Staple Moisture Content

13 +/-3%

Staple Crimp Level

>3.0 crimps/cm (>7.6 crimps/inch)

Tow Count 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

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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.

FLAME COMPARISON TEST (30 seconds with 1250°C flame exposure):

Zoltek OX™ m-aramid FR Polyester

0.0

0.5

1.0

1.5

2.0

2.5

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

Te

na

cit

y (

gm

/de

nie

r)

Elongation (%)

Typical Stress/Strain Tensile Strength Curve

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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 Zoltek OX™ fiber to other materials and the Airbus standard, for the toxic gas emission types tested.

MOLTEN METAL COMPARISON TEST:

Molten Aluminum Test Set-up 535 gsm m-aramid felt 165 gsm OPAN felt

Zoltek OX™

Cotton

Airbus Standard

FR Polyester

Neoprene Foam

0

1000

2000

3000

4000

COHCN

NOxHCL

TOTAL

CO

NC

ENTR

ATI

ON

, p

pm

TOXIC GAS

Molten Aluminum

Felt Sample

75 Angle

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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.

Cylinder 280 – 320 rpm

Flats to Cylinder

0.028”

Cylinder to Doffer 0.005” to 0.007”

Front Plate Top: 0.034”

Bottom: 0.017” Back Plate Top: 0.022”

Bottom: 0.022”

Licker-in 450-550 rpm

FIGURE 1 Cylinder Screen

Back: 0.034” / Center: 0.034” Front: 0.187”

Licker-in to Cylinder

0.007”

Feed Plate to Licker-in 0.034”

Licker-in

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OPAN fiber tow and staple can also be converted into many other product forms. Including: needlepunched felts, stitch-bonded felts, spun lace nonwovens, thermally bonded nonwovens, air lay 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.

Various Zoltek OX™ 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, rayon's, 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.

FIBER

PROPERTY

Silica

loaded

viscose

modacrylic

PROTEX

OPAN

Zoltek

OX™

novoloid

KYNOL

FR Viscose

LENZING

PPS

PROCON

melamine

BASOFIL

polyamide-

imide

KERMEL

m-aramid

NOMEX

p-aramid

TWARON

p-aramid

TECHNORA

p-aramid

KEVLAR

polyimide

P84

PTFE

TEFLON

polybenz-

imidazole

PBI

Density, g/cc 1.62 1.37 1.37 - 1.40 1.27 1.52 1.34 1.40 1.34 1.38 1.44 1.39 1.44 1.41 2.10 1.4

Moisture Regain, %

@ 20C & 65% RH 9 - 11 0.80 9.0 6.0 13.0 0.20 5.0 4.5 4.5 4.5 2.0 4.3 3.0 15.0

Breaking Tenacity,

cN/tex (gpd)

11 - 17

(1.3-1.9)

29

(3.3)

19 - 23

(2.1 - 2.6)

12 - 16

(1.3 - 1.8)

15 - 24

(1.7 - 2.7)

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)

Breaking Elong., % 18 - 25 30 22 - 28 10 - 50 15 - 20 34.5 12 - 18 23 22 - 32 3.3 4.6 4.0 30 19 25 - 30

Initial Modulus,

cN/tex (gpd)

575 - 690

(65 - 78)

260 - 350

(29 - 40)

480

(55)

265

(30.0)

618 - 1060

(70 - 120)

5209

(590)

4900

(555)

127

(13)

400

(45)

Limiting Oxygen

Index, %28 - 31 32 - 34 45 - 55 30 - 34 28 40 32 29 - 31 28 - 30 29 25 28 - 30 38 99 41

Decomposition

Temp., C (F)

150 - 200

(302-392)

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 Good

Alkaline Resistance Poor Excellent Fair Excellent Poor Excellent Excellent Poor Poor Poor Poor Poor Fair Excellent Fair

Organic Solvent

ResistancePoor 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 Excellent

Abrasion Resistance Poor Good Fair Poor Fair Fair Good Good Good Good Good Good Excellent Good

Ultraviolet Resistance Good Excellent Excellent Good Good Good Excellent Good Poor Poor Poor Poor Excellent Good Fair

Char Shrinkage Excellent Poor Excellent Good Good Poor Excellent Poor Fair Excellent Excellent Excellent Poor Poor Excellent

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 1 2.5 3 3.5 4.5 4.5 4.5 4.5 - 5.5 4.5 - 5.5 9 - 12 9 - 12 10 - 13 14 - 15 18-22 75 - 80

CARBONCOMFORT™ FR HENLEY

6 opsy Spentex NGI Arc Rating: 13 cal/cm2

HRC Level 2 UL Certified to NFPA 2112

NFPA 70E Compliant

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An example of a proprietary fiber blend solution, to help protect against the dual hazard threats of arc flash and flash fire, is marketed by National Safety Apparel, Inc., under their CARBONCOMFORT™

garment brand name. 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 opsy knits ATPV rated at 13 calories/cm2 and 6 opsy twills ATPV rated at 9.3 calories/cm2. CARBONCOMFORT™ 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 Zoltek OX™ based products. Many fabrics meet or exceed industry standards, in each of the following end-uses, according to the test methods listed:

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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”

CARBONCOMFORT™ FR Button Down Shirt 6 opsy Spentex NGI, Arc Rating: 9.3 cal/cm2, HRC Level 2

Flash Fire: UL Certified to NFPA 2112 Arc Flash: NFPA 70E Compliant

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- California Administrative Code, Title 19, Section 1237

- ASTM E800-07 “Standard Guide for Measurement of Gases Present or Generated During Fires”

CARBONIZED ZOLTEK PX35™ FELTS:

100% Zoltek OX™ felts can be used as a precursor material for carbonization into Zoltek PX35™ felts. These felts typically have a carbon content of ~95% and are electrically conductive. Applications include: ultrahigh temperature furnace insulation, composites, high-temperature acid gas filtration, battery electrodes for energy storage and other high performance applications.

Properties of Zoltek PX35™ carbonized felt 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

0.027 Kcal/(hr*m*°C) 0.031 W/(m*°K)

0.22 (Btu*in)/(hr*sqft*°F)

Thermal Conductivity

@ 550°C

0.061 Kcal/(hr*m*°C) 0.071 W/(m*°K)

0.49 (Btu*in)/(hr*sqft*°F)

Specific Heat @ 23°C

0.18 cal/(gm*°C) 0.74 joule/(gm*°C)

0.18 Btu/(lb*°F)

Specific Heat @ 550°C

0.40 cal/(gm*°C) 1.68 joule/(gm*°C)

0.40 Btu/(lb*°F)

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CARBONIZED ZOLTEK PX30™ FABRICS:

100% Zoltek OX™ woven and knit fabrics, made with stretch-broken yarns, can be used as a precursor material for carbonization into Zoltek PX30™ 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, battery storage electrodes and other high performance applications where a drapeable, very thermally stable, very high carbon content fabric is desired.

Properties of several of the Zoltek PX30™ 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 237 gsm 7.0 opsy 288 gsm 8.5 opsy 246 gsm 7.3 opsy

Yarn Count (warp x fill)

177 x 177 (yarns/10cm)

45 x 45 (yarns/in)

114 x 114 (yarns/10cm)

29 x 29 (yarns/in)

150 x 150 (yarns/10cm)

38 x 38 (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

Zoltek OX™ 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 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 lbs/in3

1.77 g/cm3 0.0639 lbs/in3

Oxidation Rate

1% per hour @ 500°C (932°F)

Ongoing developments of new and improved Zoltek OX™ staple, tow, felt and fabric products, along with carbonized Zoltek PX35™ felt and Zoltek PX30™ fabrics, enable textile and industrial suppliers

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and end users, to commercialize flame resistant, high performance product solutions to meet the increasingly stringent requirements of these diverse markets.

About Zoltek: Zoltek Companies, Inc., a global leader in the production of industrial grade carbon

fiber, develops low-cost carbon fiber and carbon fiber intermediate products for use in automotive

parts, wind turbine blades, thermoplastic compounding, offshore drilling, civil engineering, marine, and

various other commercial products. In 2014, Zoltek joined the Toray Group – a relationship that has

advanced the company’s technology, strengthened its technical and financial resources, and

positioned it for further growth and development as the global leader in carbon fiber. To learn more,

please visit www.zoltek.com. For more information about Toray Group please visit www.toray.com.

Note: “Zoltek OX™”, "Zoltek PX35™" and "Zoltek PX30™" are registered trademarks of Zoltek

Corporation, a subsidiary of Toray Group.

“CARBONCOMFORT™“ is a registered trademark of National Safety Apparel, Inc.

Contact: Alan Handermann Zoltek Corporation 3101 McKelvey Road Bridgeton, MO 63044 Phone: +1 (314) 291-5110 Email: sales@zoltek.com